Towards Sustainable Development of Tidal Areas

Towards Sustainable Development of Tidal Areas

International Commission on Irrigation and Drainage

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Towards Sustainable Development of Tidal Areas

International Commission on Irrigation and Drainage

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© All right reserved. No part of this book may be reproduced electronically or by printing or photocopying or mimeographing or translated into any other language without the permission in writing of the International Commission on Irrigation and Drainage (ICID).

October 2010

Sponsoring ICID National Committees/Committee Korean National Committee on Irrigation and Drainage (KCID) Japanese National Committee, ICID (JNC-ICID) ICID-Chinese Taipei Committee (CTCID)

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Membership of Working Group on Sustainable Development of Tidal Areas (WG-SDTA)

(October 2010)

Dr. Park Sang Hyun

Chairman (Korea) (E-mail : [email protected]; [email protected])

Ir. Henk P. Ritzema

Vice-Chairman (The Netherlands) (E-mail : [email protected])

Dr. Ruey-Chy Kao

Secretary (Chinese Taipei) (E-mail : [email protected])

Prof. Cai Lingen

China (E-mail : [email protected], [email protected])

Dr. Indreswari Guritno

Indonesia (E-mail : [email protected])

Dr. E.J. James

India (E-mail : [email protected])

Dipl. Ing. Bernd Probst

Germany (E-mail : [email protected])

Mr. Ueda Kazumi

Japan (E-mail : [email protected])

Mr. Teoh Weng Chaw

Malaysia (E-mail : [email protected])

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CONTRIBUTORS

Chapter 1. Introduction Editors: Henk Ritzema, Wageningen University and Research Centre, Wageningen, The Netherlands (Email: [email protected]) Jonathan Simmm, HR Wallingford, UK (Email:[email protected]) Affiliated contributors: Cao Zhi Hong, Ph.D., Institute of Soil Science, Chinese Academy of Sciences, Nanjing, China, Dr. V.M. Yagnik, M.E, Ph.D., Gujarart Engineering Research Institution, Vadodara (Gujarat), India Man Mohan Singh, B.E (Civil), Vadodara Irrigation Circle, New Kothi Building, Vadodara (Gujarat), India Kazumi Ueda, Advisor of NTC Consultants Inc., Japan (Email: [email protected]) Kim Ju Chang, M.Sc., Dongshin Engineering & Consultants Co., Seoul, Korea (Email: [email protected]) Chapter 2. Planning Framework for Managing Tidal Area Development Editor: Park, Sang Hyun, Ph.D., ISAN Corporation, Anyang, Korea (Email: [email protected]) Subchapter authors: Shigetaka Taniyama, Ph.D., President of Japanese Society of ICID, Hon., Saitama, Japan (Email: [email protected]) Kim Hyung Joong, Ph.D., Rural Research Institute, KRC, Ansan, Korea (Email: [email protected]) Lee Deog-Bae, Ph.D., National Academy of Agricultural Science, RDA, Suwon, Korea (Email: [email protected]) Joong-Dae Choi, Ph.D., Kangwon National University, Chuncheon, Korea (Email: [email protected]) Kim Seong Joon, Ph.D., Konkuk University, Seoul, Korea (E-mail: [email protected]) i

Kim Hong Sang, Ph.D., Korea Rural Economic Institute, Seoul, Korea (Email: [email protected]) Masaharu Kuroda, Ph.D., Kyushu-Kyoritsu University, Kitakyushu, Japan (Email: [email protected]) F.G.J. de Jager, Fugro, Hydraulic Engineering Division, Nieuwegein, the Netherlands (Email: [email protected]) J.D. Stoop, Fugro, Hydraulic Engineering Division, Nieuwegein, the Netherlands (Email: [email protected]) C.J.J. Zimmerman, Ministry of Transport, Public Works and Water Management, Delft, the Netherlands (Email: [email protected]) Eisaku Shiratani, Ph.D., Dept. of Rural Environment, National Institute of Rural Engineering, Tsukuba, Japan (Email: [email protected]) Affiliated contributors: Lim Jong Wan, Ph.D., Sunjin Engineering and Architecture Co., Seoul, Korea (Email: [email protected]) IM Sang Bong, Ph.D., Rural Research Institute, KRC, Ansan, Korea (Email: imsb@ekr. or.kr) Chapter 3. Tidal Area Features and Natural Processes Editor: Ruey-Chy Kao, Tainan Hydraulics Laboratory, National Cheng Kung University, Taiwan (Email: [email protected]) Subchapter authors: Chan-Ji Lai, Ph.D., Professor, Tainan Hydraulics Laboratory, National Cheng Kung University, Taiwan (Email: [email protected]) Wen-Son Chiang, Ph.D., Tainan Hydraulics Laboratory, National Cheng Kung University, Taiwan (Email: [email protected]) Hwa Chien, Ph.D., Institute of Hydrological & Oceanic Sciences, National Central University, Taiwan (Email: [email protected]) Ping Chen, Tainan Hydraulics Laboratory, National Cheng Kung University, Taiwan (Email: [email protected]) Jiang-Ping Wang, Ph.D., Department of Live Sciences, National Cheng Kung University, Taiwan (Email: [email protected]) Chia-Yang Tsai, Ph.D., Changhua Environmental Protection Union, Taiwan (Email: [email protected]) Indreswari Guritno, Ph.D., Senior expert for the Coordinate Ministry of Economy for Infrastructure Development, Jakarta, Indonesia (Email: indreswari.guritno@ gmail.com) ii

Assistance: Chun-Yi Liu, Assistant, National Cheng Kung University, Taiwan (Email: [email protected]) Chapter 4. Engineering for Sustainable Development of Tidal Areas Editor: Kazuaki Hiramatzu, Professor, Faculty of Agriculture, Kyushu University, Japan (Email: [email protected]) Subchapter authors: Kiichiro Tanaka, Director of Tanaka R & D Technical Office (Email: [email protected]. ne.jp) Shiomi Shikasho, Taiyo Consultants Co., Ltd., Japan (Email: [email protected]) Manabu Shimaya, Penta-Ocean Construction Company, Japan (Email: [email protected]) Affiliated contributors: G. P. van de Ven (Netherlands) Ken Mori, Professor, Faculty of Agriculture, Kyushu University (Japan) Manabu Shimaya, Penta-Ocean Construction Company (Japan) Lee, Haeng-Woo, Ph.D., Ministry for Food, Agriculture, Forestry and Fisheries, Korea (Email: [email protected]) Jacobus Hofstede, Schleswig-Holstein State Ministry for the Interior, Coastal Defense Division, German Shiomi Shikasho, Fukuoka, Japan Ken Mori, Faculty of Agriculture, Kyushu University, Japan Manabu Shimaya, Penta-Ocean Construction Company, Japan Chapter 5. Tidal Reclamations and Their Impacts on Natural Processes Editors: Bernd Probst, Schleswig-Holstein State Ministry of Agriculture, Kiel, Germany (Email: [email protected]) Jo Jin Hoon, Ph.D., Rural Research Institute, KRC, Ansan-si, Korea (Email: jjhjo @ekr.or.kr) Subchapter authors: Reinhard Dieckmann, Professor, University of Applied Sciences Kiel, Department of Civil Engineering, Germany (Email: [email protected]) Thomas Tischler, Research and Technology Center Westcoast, Germany, Hafentörn 1 D-25761 Büsum, phone: +49 (0) 4834 / 60 42 07, fax: +49 (0) 4834 / 60 42 99 (Email: [email protected])

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Atsushi Marui, Graduate School Student, Graduate School of Bioresource and Bioenvironmental Sciences, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka, 812-8581, Japan (Email: [email protected]) Yoshisuke Nakano, Professor, Faculty of Agriculture, Kyushu University, Japan Tamotsu Funakoshi and Tomokazu Haraguch, Assistant Professor, Faculty of Agriculture, Kyushu University, Japan Koji Inosako, Associate Professor, Faculty of Agriculture, Tottori University, 4-101 Koyama-Minami, Tottori 680-8550 Japan T. Akae and H. Nukumizu, Faculty of Environmental Science and Technology, Okayama University, Tsushima-naka 3-1-1, Okayama, Japan K. Nagahori, Professor Emeritus, Okayama University, Japan Lee, Deog-Bae, Ph.D., National Institute of Agricultural Science and Technology, RDA, 249 Seodun-dong, Suwon, Korea Chapter 6. Towards an Integrated Decision Support Framework Editors: Jonathan Simm, HR Wallingford, UK (Email: [email protected]) Henk Ritzema, Wageningen University and Research Centre, Wageningen, The Netherlands (Email: [email protected])

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FOREWORD In front of you is the Handbook “Towards sustainable development of tidal areas”. The Handbook has been prepared by the Working Group on Sustainable Development of Tidal Areas (WG-STDA) of the International Commission on Irrigation and Drainage (ICID). The initiative to establish this Working Group was taken in 2001 by the Korean National Committee of ICID. It was officially established in 2002 under the chairmanship of Park, Sang Hyun, PhD. Over the past eight years, WG-STDA has held several workshops, seminars and meetings in order to prepare the Handbook in a very good cooperation of the specialists of the various densely populated countries, like Bangladesh, China, India, Indonesia, Japan, Korea, and Taiwan as well as from Germany, Great Britain, Malaysia and the Netherlands where the development of tidal areas plays an important role. Tidal areas exist all over the world along the coasts. Generally they are by their nature sensitive areas with a high ecological value. Due to their physical conditions and environmental value they are basically unsuitable for development. However, due to the in many cases strategic location there is often a tremendous pressure to develop these areas for various types of land use. We therefore may observe on the one hand a rapid population growth, significant increase in agricultural exploitation, as well as in urbanization and industrialization in tidal areas. On the other hand there is an increased need to prevent further environmental degradation and to protect areas with a high environmental value. Therefore there is an urgent need for integrated sustainable development and management of such areas. Although we are all concerned about the impacts of climate change - none the less for tidal flood prone areas - due to the developments as listed above an increasing number of worlds’ population is living and working in the tidal areas. Population growth is especially taking place in the urban areas in the emerging and least developed countries, a significant part of it in the tidal areas. Especially in tidal areas in South and East Asia we may observe a very rapid growth of urban areas. Think for example of the growth of cities like Bangkok, Jakarta, Manila and Shanghai from 1 – 2 million people in the 1970s to more than 10 million at present. There are no indications that this tendency will change. In the rural areas we may observe improvements in agricultural production and an increase in the value of crops, farm buildings, water management facilities and infrastructure. Due v

to urbanization and industrialization and the improvement in the standard of living the value of property, buildings and infrastructure has significantly increased and will further increase in future. In order to cope with the growth for new urban areas very often reclamation has taken place of lowlying areas in the neighborhood of the existing urban area. From a water management and flood protection point of view this implies removal of storage area, increase in urban drainage discharges and in the need for adequate urban drainage and flood protection in a river basin context. Therefore we may observe at quite some places a significant increase in damage and to a certain extent as well in casualties when flooding occurs. In addition there are quite some land reclamation projects in the foreshore coastal area, predominantly for urban and industrial expansion, airports and to a limited extent generation of tidal energy. One can think of the reclamations along the west coast of Malaysia, the expansion of Rotterdam harbor, the airports of Hong Kong, Osaka and Incheon, etc. While so many issues are at stake integrated development and management approaches will be needed. However, many countries are struggling to develop the appropriate policies, planning and implementation mechanisms. Therefore the initiative to prepare the Handbook was vey appropriate and timely and the result is most welcome. In the Handbook the reader can find the features of tidal areas, the natural processes, the planning framework, engineering aspects with respect to water management and flood protection, impacts of reclamation on natural processes, recommendations with respect to decision making and envisaged long-term changes in land use, land subsidence and impacts of climate change. All the material has been brought together by the specialists and government officials of the countries where the development and management of tidal areas plays an important role. Therefore the Handbook presents a good overview of the state of the art with respect to the relevant aspects. It is intended to be used for policy makers, specialists, designers, and those who are involved in planning, preparation, implementation and management of tidal areas. I like to use this opportunity to sincerely congratulate Dr. Park, Sang Hyun, the editors and the authors with the result. Although the Handbook is considered to be the final product of the Working Group, I hope that the Working Group can continue with its valuable work, while in future the tidal areas will only become more important and the challenges to develop and manage these areas in a sustainable way under the pressures of population growth, urbanization and industrialization in densely populated countries, especially in South and East Asia, will continue to play a major role.

Prof. Bart Schultz, Ph.D., M.Sc. President Honoraire ICID Chairman Editorial Board Irrigation and Drainage vi

PREFACE Historically, development of tidal areas has contributed to the supply of food for human beings, as well as disaster prevention. The development was carried out in small scale without giving much damage to the nature, however, present large scale development is blamed for environmental disruption. Therefore, sustainable development of tidal areas became important to meet the needs of human and nature simultaneously. There are three aims of sustainable development of tidal areas (SDTA), such as optimal use of land and water resources, disaster prevention, and preservation of biodiversity for present and future generation. Well-managed paddy fields, irrigation canals and freshwater reservoirs have excellent functions as wetland to provide habitats for birds, fishes and worms throughout the year. There still remain problems to cope with the disaster caused by the Typhoon and Tsunami near the tidal areas. Improved environment through sustainable development of tidal areas will contribute not only to agriculture but also to traffics, tourism, industries and amenity. Consequently, the willingness of public sectors, farmers, enterprisers and other stakeholders should be integrated for Sustainable Development of Tidal Areas. Based on this view, ICID Working Group on Sustainable Development of Tidal Areas (WGSDTA) has been launched in Montreal Congress 2002. The Main activities of WG-SDTA are to publish a Handbook on SDTA to be used as a Guideline for engineers and decision makers. Since 2002, WG-SDTA has organized International Workshops on SDTA during every ICID Council Meeting, and the results have been included in the ICID Handbook titled Forward Sustainable Development of Tidal Areas. For the publication of the Handbook, our Working Group leaders, Ir. Jonathan Simm and Dr. Henk Ritzema, prepared the Nine Principles and Indicators to be adopted in each Chapter and Position paper on SDTA has been circulated among all the National Committees through ICID Central Office. Consequently, valuable papers and information have been arrived from well experienced experts in ICID National Committee of China, Germany, Great Britain, India, Indonesia, Malaysia, Japan, Korea, Taipei Chinese, and the Netherlands Especially Japanese National Committee, Korean National Committee and Taipei Chinese Committee had organized interim meeting to discuss the publication plan and these Committees vii

provided publishing cost of the Handbook. I deeply appreciate their contribution to the publication of the Handbook. I express grateful thanks and appreciation to all the Chapter editors, authors and other great supporters, Dr. Shigetaka Taniyama, Prof. Bart Schultz and Elder Kim Ju Chang for their passionate contributions to prepare the Handbook on SDTA. Finally, I express my gratitude to ICID Central Office for their efforts and cooperation in the course of publication.

Park, Sang Hyun, Ph.D. Chairman ICID WG-SDTA

Working Group meeting on SDTA in ICID Montreal Sept. 2002

Working Group Contributors on SDTA in ICID Kuala Lumpur, Sept. 2006

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TABLE OF CONTENTS Contributors Foreword Preface

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Chapter 1. Introduction 1.1 ICID Working Group on Sustainable Development of Tidal Areas 1.2 Historical Context 1.3 Towards Sustainable Development of Tidal Areas 1.4 Objectives, Readership and Structure of the Manual

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Chapter 2. Tidal Area Features and Natural Processes 2.1 Introduction 2.2 Physical Feature, Landforms and Sediment Transport 2.3 Physical Processes 2.4 Chemical Features 2.5 Biological Features 2.6 Case Studies 2.7 Summary

33 37 47 56 68 84 89

Chapter 3. Planning Framework for Managing Tidal Area Development 3.1 Multifunctional Role of Tidal Reclaimed Areas 3.2. Land Use Planning 3.3 Conservation of Habitat and Biodiversity 3.4 Irrigation and Drainage Planning 3.5 Catchment Flood Management Planning 3.6 Water Quality Management Planning 3.7 Economic Issues on Tideland Reclamation 3.8 Management and Institutional Context

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Chapter 4. Engineering for Sustainable Development of Tidal Areas 4.1 Dike and Final Closure 4.2 Water Facility and Water Management System 4.3 Diversion Channel and Estuary Management 4.4 Filling-up Reclamation of the Tidal Area and Artificial Shores

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Chapter 5. Tidal Reclamations and Their Impacts on Natural Processes 5.1 Introduction 5.2 Impacts on the Morphology 5.3 Impacts on the Tidal Dynamics 5.4 Impacts on the Environment and Ecosystems 5.5 Impacts on the Groundwater in Embanked Areas 5.6 Impacts on the Groundwater in Embanked Areas Chapter 6. Towards an Integrated Decision Support Framework 6.1 Principe 1 - Integrated Multi-functional Approaches 6.2 Principle 2 - Holistic Engagement with Social, Economic and Environmental Issues 6.3 Principle 3 - Management of Risk and Uncertainty and Adaptation to Change 6.4 Principle 4 - Enabling Methods and Means

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CHAPTER 1

Chapter 1. Introductiion

INTRODUCTION EDITOR: HENK RITZEMA (THE NETHERLANDS), JONATHAN SIMM (UK)

1.1 ICID Working Group on Sustainable Development of Tidal Areas The International Commission on Irrigation and Drainage (ICID) launched the Working Group on Sustainable Development of Tidal Areas (WG-SDTA) during Seoul IEC Meeting in 2001 to address issues related to the sustainable development of tidal areas. The objectives of the WG-SDTA are based on the recommendations of the Task Force on ‘Environmentally Sustainable Options of Tidal Lands and Estuaries’ which was constituted by the Asian Regional Working Group (ASRWG) during the pre-Council meetings at 51st IEC Meeting at Cape Town in October 2000 and are as follows: •

To collect information about the natural environment in tidal areas around the world;

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To identify sustainable development and conservation options in the tidal areas;

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To find a balance between the preservation and development of tidal areas.

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To reach these objectives, the Working Group has the following mandate: •

Identify criteria or decision support system to find sustainable development schemes for the planning and design of dikes and related structures: This implies identification of criteria to find sustainable development schemes. Such criteria or decision support system would help find a balance between the preservation and development of tidal areas.

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Integrate irrigation, drainage and flood management practices in reclaimed area: Guidelines may be developed for integrating irrigation, drainage and flood management practices in reclaimed areas to minimize the impact of land use and development projects.

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Study physical, chemical and biotic characteristics of the tidal areas: Studying physical, chemical and biotic characteristics could result in assessment of tidal areas. The identification of appropriate indicators for assessment of tidal areas may be done. A tidal area policy could be developed as a result of such assessments.

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Examine management and institutional aspects and production system in reclaimed area: Identify relevant institutions involved in management and production in reclaimed area. An operational plan needs to be developed to encourage participation from different institutions.

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Enhance community participation in the sustainable development of tidal areas: There is a need to encourage stakeholders’ involvement in the sustainable development and conservation of tidal areas, in particular, the local community and the private sector. Identify ways and means to provide incentives to stakeholders.

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Study socio-economic impacts and cost/benefit analysis of various development alternatives: The WG carries out socio-economic impact assessments and cost benefits analysis for various alternate developmental approaches. Socio-economic and cultural factors may be considered. Successful developmental approaches (country case studies) can then be disseminated for use all over the world.

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Establish historic aspects of tidal reclamation: The WG considers establishing historical aspects (extent of tidal areas in the world) of tidal areas. Then historic land use patterns on these lands could be established, followed by historic aspects of tidal reclamation.

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Incorporate integrated approaches for sustainable development and conservation options: Guidelines need to be developed for managing tidal areas for sustainable development and conservation options. The WG needs to define the extent of involvement of stakeholder in the integrated approach for sustainable development of tidal areas.

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Chapter 1. Introductiion

Since its establishment, the Working Group has organised six international workshops during regular ICID meeting to present case studies and to discuss its findings, i.e. (Working Group on Sustainable Development of Tidal Areas, 2002 to 2009): •

International Workshop on Sustainable Development of Tidal Areas on July 22, 2002 in Montreal, Canada.

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2nd International Workshop on Sustainable Development of Tidal Areas “Wise Use and Environmental Conservation of the Tidal Areas” on September 17, 2003 in Montpellier, France.

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3rd International Workshop on Sustainable Development of Tidal Areas “Socio-economic Management and Stakeholder Participation for Agriculture in Tidal Areas” on September 6, 2004 in Moscow, Russia.

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4th International Workshop on Sustainable Development of Tidal Areas “Evaluation of Draft ICID Handbook on SDTA” on September 13, 2005 in Beijing, China.

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5th International Workshop on Sustainable Development of Tidal Areas “Evaluation of the 2nd Draft ICID Handbook on SDTA” on September 15, 2006 in Kuala Lumpur, Malaysia.

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International Workshop “Tidal Area Features and Natural Processes” on February 24-26, 2009 in Taipei, Taiwan.

Long debates within the Working Group have clarified new concepts for the development of tidal areas but also have raised the sensitivity of the subject, the diversity of approaches according to different cultures, histories and governmental policies. The aim of this handbook is to present these concepts and sensitivities.

1.2 Historical Context The coastal zone comprises only 3% of the earth’s surface, but contains a disproportionately high amount of its assets (Schultz, 2001; Huntington, 2002). Coastal zones accommodate 60% of the world’s population, a figure set to increase to 80% by 2050. As a result, 2/3 of those cities in the world with a population of more than 1.6 million people are found in coastal areas. It contains ports and harbours for international trade and a major portion of the world’s prime agricultural land, together accounting for 25% of global primary productivity. Coastal areas have a great ecological value, offer recreation and tourism and provide habitat for many endangered species and, at the other hand, are the source of 90% of the world’s fish catch. 3

Tidal areas include all those coastal areas Box 1.1 Definition of tidal areas where the tidal processes are capable The Working Group on Sustainable Development of affecting man’s activity or of being (WG-SDTA) has defined tidal areas as all those influenced by man (Box 1.1).This roughly coastal areas where the tidal processes are capable extends tidal areas between the following of affecting man’s activity or of being influenced by limits: (i) on the seaward side up to the man (Definitions used in this Chapter are presented limit of conventional construction or in the Glossary at the end of the Chapter). dredging activity (typically of the order of 30m water depth) and (ii); on the landward side up to the limit of the action of the sea, including all those areas that might be subject to flooding by seawater and up all estuaries and rivers to the tidal limit. Tidal areas differ greatly depending on their location, geo-physical conditions, climate, tidal range and cultural differences. Throughout the world, tidal areas have been and are being developed (Table 1). Well over thousand years ago, inhabitants of low-lying areas in estuaries in several parts of the World started to reclaim land from the sea. In the following section the historically significant developments in tidal reclamation from the WG member countries area are briefly summarized. For each country the main lessons learned are also presented. These lessons have been derived from case studies and are elaborated in the following chapters. Table 1 Reclamation projects in tidal areas in some major countries Country Total Reclaimed land Lake area Total developed geographical tidal area (Mha) (ha) (ha) (ha) China 959.80 2,600,000 Germany 35.70 India 328.73 55,000 13,224 68,224 Indonesia 190.46 Japan 37.79 24,199 8,248 32,447 Korea, Republic of 10.02 388,700 Malaysia 32.98 The Netherlands 4.15 165,000 200,000 365,000 Taiwan 3.60 24,250 24,250 United Kingdom 24.29

China Chinese coastline extends 16,100 km along mainland from Yalu River mouth at the China–North Korea border to the Beilun River mouth at the China-Vietnam border. At present, along the Liaoning, Hebei, Shangdong, Jiangsu (Box 1.2), Shanghai, Zhejiang, Fujian, Taiwan, Guangdong, there are about 2.6 million ha of tidal land in China. 4

Chapter 1. Introductiion

Box 1.2 Utilization of tidal lowlands in Jiangsu Province, China (Cao and Lee, 2005) The coastline of Jiangsu province is about 954 km long. It stretches from the Xiuzhen River at Shangdong-JIangsu border in the north to the mouth of Yangtze River at Jiangsu-Shanghai border in the south. There are 30 km sand coast, 40 km bedrock coast and 884 km silt sand/ mud coast. Of these silt sand/mud coast there is 666 km depositing and growing coast and 218 km light eroding coast. The total tidal land area of Jiangsu Province is about 0.654 million ha. The land use in these tidal areas is as follows: •

Agriculture. In the period 1949 to 1980, tidal land was reclaimed for cereal and cotton production. At present about 0.52 million people produce annually about 0.18 million tons of grains (wheat and rice), 8,000 ton of cotton and 12,000 ton of vegetable oil.

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Fish and seaweed farms: (i) sea-shrimp farming: about 12,400 ha for: (ii) fresh water fish culture: , about 12,000 ha; (iii) shellfish cultures: about 76,000 ha , and: (iv) for seaweed production: 4,000ha. Currently, the annual production is about 26,000 ton of fish, crab and shrimp, 2,300 ton of (dried) seaweed and 16,000 ton shellfish.

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Husbandry: About 36,000 ha of natural pasture land and 1,600 ha of reclaimed pastureland are used for husbandry. In 1963, large rice grass (spartina anglica) was introduced from UK. This grass is highly salt-tolerant, promotes sedimentation and is good feeding material for sheep and cattle. In 1990, the total area planted with rice grass had increased to 20,000 ha. The government encourages people to raise sheep, cattle and other animals for milk production.

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Forest. About 11,500 ha of the reclaimed tidal land is forest and fruit tree plantations. There are four types of plantations: (i) 30,000 ha of forest for timber production; (ii) about 40,000 ha of forest protected by 670 km of embankments; (iii) about 40,000 ha of agroforest, and; (iv) fruit tree plantation (the major fruits are apple, pear, peach and mulberry). The agro-forest plantations consists of forest belt in the south to north direction with 15 rows of trees planted at 15- 20 m width and separated by 300 – 400 m inter-space used for agriculture and in the east-west direction 5 rows of trees planted at 10 m width separated by 1500 – 2000 m of inter-space

•

Salt production. In about 72,000 ha of tidal land the yearly production of sea salt is about 1.2 to 1.7 million ton.

Lessons learned There is still a lot of potential to reclaim tidal areas using modern technology. Already about 20,000 ha tidal land has been embanked and ripened, but has not yet properly reclaimed. Another 60,000 ha has not yet been reclaimed and in about 1,350 ha the yearly sedimentation rate is such that the land can be reclaimed in the near future. Next, there are 140,000 ha in the intermediate tidal level zone that is not utilized yet. In addition, various areas along the coast that be developed as habour, utilized for mining or tourist development.

Germany In Northern Germany, dike building along the North Sea coast has a long tradition. Since the Middle Ages, dikes were mainly built to reclaim land for agriculture, coastal defence was a secondary effect. With the change in agricultural policies in the fifties of the 20th century it was not longer necessary to reclaim land for farming purposes and the focus shifted to drainage and coastal protection. In the year 1963, one year after the disastrous storm flood of 1962, the federal government implemented 5

a new master plan for coastal defence. This plan described the principles of dike designing and building and contained a list of dike construction measures (Box 1.3). This example shows, that a new dike, which may be seen as an environmental impact at first glance, can be a successful solution by integrating various land use functions and all stakeholders, both institutions and people. This integrated and participatory approach had led to a sustainable solution. India India has a coastline of about 7,500 km (5,400 km on the mainland), with nearly 250 million people living within 50 km of the coast. The coastal area accounts for 130 cities, including Mumbai, Chennai, Kolkata, Goa, Surat, and Thiruvananthapuram (World Bank, 2007). A very significant share of India’s economic infrastructure, including maritime facilities, petroleum industries, and import-based industries is located in the coastal zone, in addition to a large number of poor Box 1.3 Land reclamation in Meldorf Bight, Germany: a new approach in dike building (Probst, 2004). Meldorf Bay is situated at the west coast of the state Schleswig-Holstein near the mouth of the river Elbe. The area has been inhabited since about 5000 years. At first houses were built on dwelling mounds and the first dikes were built around 1100. Since then, a staggered system of dikes in the form of a bay developed after several land losses due to floods and subsequent re-embankments. The extreme storm surges of 1953 and 1962 showed once more that the dikes were not strong enough. In 1964, a new dike was designed based on the following requirements: •

Safety against storm surges

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Shortening the dike line to reduce risk

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Improvement of the poor drainage of the hinterland

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Improvement of the agricultural structures, also in the hinterland

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Creating a military test range

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Nature improvement and conservation

The new dike, with a total length of 14.9 km, was built in two phases: from 1969 to 1972 and from 1974 to 1978. The newly reclaimed area covers about 48 km². The dike has improved cross sections to withstand storm surges with a frequency of 1/100 year. By realignment, cutting through part of the bay, the length of the dike was reduced with 15.6 km, a reduction of more than 50%. New storage basins were created to store the discharge from the low lying hinterland during high tide. At low tide, the water is discharge by gravity. This improvement of the water management system is particularly important because of the rising sea water levels. Part of the reclaimed area is used for agriculture, mainly for farmers whose land was reallocated for other uses (nature, urban development, etc.). Other low-lying parts were developed as salt water nature reserve. The development of the new polder resulted in a far-reaching structural change in the surrounding areas. Lessons learned Building a new dike improves coastal defence, water management, agricultural structures and other fields and has a positive impact on the environment. Involvement and participation of all interested parties in the planning process led to a successful multi-purpose development. 6

Chapter 1. Introductiion

Box 1.4 Kalpasar project in Gujarat, India (Yagnik and Singh, 2003) The Gulf of Khambhat has identified as a promising site for (i) fresh water storage for the irrigation and water supply for the Saurashtra peninsula, and (ii) tidal energy production. Fresh water storage and tidal power generation are two competing uses of the Kalpasar reservoir, since part of the capacity for the storage of fresh water is to be sacrificed for the creation of a tidal power basin. A pre- feasibility study concluded that tidal power generation benefits should be supplemented by creation of a sweet water basin by impounding surplus water of the Narmada, Dhadhar, Mahi, Sabarmati rivers which would provide irrigation, water supply and reclamation benefits (www.kalpasar.gujarat.gov.in/). It was also concluded that the development of Gulf of Khambhat is feasible from the technical and socio-economic points of view. By creating Kalpasar fresh water reservoir, sufficient water will become available for a sustainable agricultural development of the salt affected areas. It has been assessed that an area of 119,000 ha of land for irrigation, industrial development, residential, recreational and social amenities can be reclaimed. The beneficiaries will be mainly the poor communities staying in the peripheral areas of the lake around the Gulf of Khambhat. It is estimated that the Kalpasar Project will provide 900 million m3 water supply for domestic, 500 million m3 for industrial use and 5,461 million m3 of water for the irrigation of about 1,054,500 ha. Tidal power of installed capacity 5880 MW will generate 12130 GWh in the Single Basin (with the Double Basin option the installed capacity would be 1680 MW and 8,078 GWh would be generated). By connecting Saurashtra region with the East coast of Gujarat, transport distances will be reduced by 225 km. The Kalpasar reservoir would also provide an excellent facility of inland navigation, along Narmada river from sea to Hoshangabad (in Madhya Pradesh) through Kalpasar Lake. The proposed carp hatcheries will yield an additional fish production of 9,856 tonnes and generate a total of 55.21 million mandays of employment in fisheries activities. Lessons learned The pre-feasibility report and six specific studies conducted thereafter have shown the technical viability of closure of Gulf of Khambhat on the basis of the known and tried out techniques.

villages that depend on coastal fishing for livelihood. The coastal areas are also subject to recurrent natural disasters, such as cyclones and coastal floods, and the 2005 tsunami devastated large areas especially along the eastern coastal states. India’s coastal zone is endowed with a wide range of mangroves, coral reefs, sea grasses, salt marshes, sand dunes, estuaries, lagoons, and unique marine and terrestrial wildlife. Due to the increasing human population, urbanization and accelerated developmental activities, including industrial and maritime development, the coastal areas have been assuming greater importance in recent years (Box 1.4). The anthropogenic activities have put tremendous pressure on the fragile coastal environment with negative impacts on current and 7

future economic development opportunities. Up to now, the approach to managing India’s coastal zone has been a purely regulatory one, as per the Coastal Regulation Zone Notification of 1991, promulgated under the Environment (Protection) Act of 1986. The 1991 notification restricts and controls development activities within a landward distance of up to 500 meters from the high tide line along the coasts. This approach does not provide room to balance coastal zone conservation and necessary economic growth in the area or seek convergence with other development activities. Indonesia Indonesia contains some 36~39 million hectares of swamplands, of which about 20 million ha are tidal lowlands, mainly located on the islands of Sumatra, Kalimantan and Papua (Government of Indonesia, 2008). Almost 4 million ha of the tidal lowlands have been reclaimed, partly by spontaneous settlers (more than 2.5 million ha) and partly by the central government (about 1.3 million ha). In Sumatra and Kalimantan, the development of the tidal lowlands started centuries ago by indigenous people. These settlers usually developed the land up to some two kilometres inland from the tidal rivers. After established a clearing of the riverbanks for settlement and rice cultivation, they gradually extended the drainage system inland, gradually introducing coconut plantations. Since the early twentieth century, the Government initiated large-scale agricultural development in these tidal lowlands, the peak of which occurred during the transmigration-driven era of the 1970s and 1980s. These Government-sponsored schemes are typically constructed in the swamp interior, further away from the tidal rivers. Transmigrants came from the densely populated islands of Java, Madura and Bali, where farming culture is very different to that required in lowland swamps. On arrival, the farmers were assigned a plot of land, usually 2.25 ha of partly cleared land, and had no choice in site selection. Nether was any consideration given to the farmers’ origins, and hence the social fabric in government schemes was more heterogeneous than in the spontaneous settlements. Drainage is facilitated through a system of primary and navigation canals, allowing for gravity drainage at low tide. Despite the abundance of water in the tidal lands, most governmentsponsored schemes depend on rainfall for water because the tidal range is not enough for irrigation. Over the years, it became clear that this approach was too general. Minimal drainage resulted in stagnant water conditions and crops were affected by acidity and toxicity due to poor leaching and flushing. During the late 1990s, second stage type projects focused more on socio-economic issues, institutions and the provision of services in addition to the improvement of the infrastructure (Box 1.5). Japan Rice cultivation in Japan comes from more than 2000 years ago. Also small scale tidal land reclamation by the farmers was an old practice, although not as old as in China. Unfortunately little is known about technology and other measures that used for the land reclamation. Reclaimed 8

Chapter 1. Introductiion

Box 1.5 Former Mega-Rice Project, Central Kalimantan, Indonesia (Bappeda, 2010) In 2007, the Government of Indonesia launched a five-year program to rehabilitate and revitalize the 1.4 million hectares of degraded peat and lowland that was the location of the former Mega Rice Project. Since this project was halted in 1999, a series of studies have been made that highlighted the need to respond with action on the ground. In March 2007, the President of Indonesia, Dr. H. Susilo Bambang Yudhoyono, issued Presidential Instruction Number 2 of 2007 that targets the conservation and rehabilitation of 1.1 million hectares with the remainder being used for sustainable agriculture. This ambitious goal requires a new approach to peat and lowland management in Indonesia and assistance is being provided by the Government of the Netherlands for the development of a Master Plan for the rehabilitation and revitalization of the Ex-Mega Rice Project (EMRP) area. The planning process to formulate the Master Plan consisted of a series of technical studies and assessments and a series of public consultations with government and people living in the area in all administrative sub-districts (kecamatan). The Master Plan identifies seven key challenges for the rehabilitation and revitalization of the area: (1) wildfires, (2) peatland management and rehabilitation, (3) conservation and environmental management, (4) agriculture, (5) community and socio-economic development, (6) institutional and organisational capacity and (7) climate change. Three future scenarios are analysed based on •

a business as usual scenario,

•

a plantation scenario, and

•

a rehabilitation and revitalization scenario.

Lessons learned The conclusion is that only through a concerted effort to rehabilitate and revitalize the area can balanced development occur that leads to regional economic growth, poverty alleviation as well as positive environmental outcomes. Effective rehabilitation and revitalization of the area can also lead to significant reductions in greenhouse gas emissions.

lowland areas were very favourable for rice fields. Therefore, land reclamation had been one of the significant means for increasing rice production. However, rice cultivation had a direct influence on land reclamation projects in Japan. Land reclamation projects were promoted by the shortage of rice fields. On the other hand during periods of surplus of rice, those projects were discouraged. Rice has been a main foodstuff and a fundamental economic commodity since human habitation in Japan. Because of limited suitable arable lands for rice cultivation, tidal lowlands have been reclaimed to increase rice production. Enormous efforts have been made by local and central governments to achieve self-sufficiency by increasing rice production. The exploitation of low-lying wetlands such as marshes, swamps, whose soils are favourable for rice cultivation, is one of the important measures to expand the rice fields. However, in ancient days reclamation of wetlands was included as excavation of drainages, construction of small dikes and access roads. Drainage using windmills was not possible because of the lack of wind. Only natural gravity drainage was possible. Land reclamation works were limited to the areas where the outside water level fluctuation was large enough to enable excess water inside to drain by gravity such as Ariake-bay, Kojima-bay and Ise-bay areas, since water-lifting devices were not yet developed and 9

introduced. Flap and miter-gates that open automatically to drain the water inside and close when the sea water level is high (tidal drainage) were very important facility. Around the middle of the 20th century, the total reclamation area was 71,000 ha in Ariake-bay, 55,000 ha in Kojima-bay and 14,000 ha in Ise-bay. In these bay-areas, sediments from rivers deposited at the estuaries and near shores and silted up to a comparatively high level. Hence river-flow tended to become clogged and resulted in inundation in the upstream areas. Therefore, reclamation of tidal flats had to extend seaward successively. Technical problems frequently occurred such as excessive rate of subsidence of dikes, failures of canals and gate facilities due to the generally low bearing capacity of soft clay foundation. Therefore polders were exclusively used for agricultural purposes and rarely for other land uses. It is reported that the first drainage pump with a diesel engine was installed in 1929 in Yamaguchi Prefecture. This technological innovation and the technical assistance by experts from the Netherlands drastically changed the planning and operation of land reclamation projects. Almost all tidal flats and shallow lakes in Japan have been investigated for land reclamation projects. Prevention of tidal storm surge disaster and freshwater development by using estuarine reservoirs was generally included in project objectives. Comprehensive plans and designs based on a scientific analysis were first applied in the Hachiro-Gata Land Reclamation in the 1950’s. Various kinds of new engineering approaches related to land reclamation were introduced (Box 1.6). Korea Tidal land reclamation has about 750 years’ history in Korea. In the 20th century, tidal land reclamation became a major source of paddy land development along the western coast of the Korean peninsula. In the Asian monsoon region, sufficient water is available for crops in the growing season. Therefore, arable land was the most important factor to increase crop production in the past years. The need to expand arable land in the agriculture-oriented society became greater in proportion to the increase of population in regional or national basis. Traditionally, the means to expand agricultural land were reclamation of forested area and tidal flats. However, tidal land reclamation in the inter-tidal zone was difficult to be done by individual farmers because it needs mobilization of many workers to fight against the tide. Historically tidal land reclamation was initiated and implemented in river mouth areas and Ganghwado Island. Tidal land reclamation has been developed in Korea because of the following reasons: •

Well-developed tidal flats with big tidal difference along the western and southern coast;

•

Enough rainfall and water resources to leach salts from the soil;

10

Chapter 1. Introductiion

Box 1.6 Impoldering works (“Kantaku”) in Japan (Kazumi Ueda, 2002) In a small nation as Japan, the impacts and benefits of the creation of new land is much more than could be generally estimated. In areas like Ariake-bay, where river sediments deposit in an estuary, impoldering works are indispensable or fated against floods or inundation disaster in newly developed lands and upstream areas. Fresh water reservoirs constructed in estuaries like e.g. Kojima-bay, Hachirogata, Kahokugata and Isahaya-bay Kantaku projects are indispensable infrastructure and resources in each area. In the course of the design and the construction of Isahaya-bay Kantaku Project, almost all of the engineering problems which are peculiar to impoldering projects have been solved. Current impoldering projects are comprehensively evaluated to ensure them to be absolutely safe, agronomically favourable, technically feasible, economically viable and environmentally sound. * Isahaya-bay Kantaku Project The Isahaya Bay in the Nagasaki prefecture is located in the southwest of Japan. The bay is characterized by its enormous tidal range, the maximum difference between low and high tide is around 5.7m. In the 1970’s, the Isahaya Bay Kantaku Project was initiated to reclaim 681 ha of coastal mud lands for agricultural use. The objectives of the project are: •

To reclaim land for agricultural use

•

To promote ecological farming by combining safety food production with enriched waterfront environment

•

To protect hinterland against surge, flood and waterlogging.

The project included (1) the construction of 7 km of sea dike with 8 drainage gates; (2) the creation of a 2500 ha fresh water lake, and (3) the construction of 11 km of inland dike. Lessons learned •

Careful investigations and analysis on the impact on land, water, flora-fauna and ecoenvironment in project and adjacent areas have to be carried out completely.

•

Systematic environmental assessment need to be fully established.

•

Practical analyses and design manuals for sea water level rise and increase storminess etc. caused by global climate change have not yet been systematically carried out.

•

High population density in the country that required more agricultural lands for food production;

•

Abundant rock and soil materials for embankment construction in the coastal areas.

The first period of tidal land reclamation in Korea started during the Mongolian invasion in the 13th century. The second period of tidal land reclamation started with the invasion of Ching, China, in 1636 and continued until the 18th century in Ganghwado Island. The third period 11

started in 1963 and is still going on. During the last four decades, many comprehensive tidal land reclamation and development projects including freshwater reservoirs were implemented. The first law prescribing the development of tidal flats and marshlands was enacted in 1907. During Japanese occupation from 1910 to 1945, many small size tidal lowland areas were developed to increase rice production as to meet the Japanese army food needs. During the last five decades, the tidal land reclamation has greatly progressed primarily to gain arable land for rice cultivation. Until 1970 traditional tidal land reclamation was to develop tidal flats in the bay area and water was generally supplied by gravity flow from higher places, canals or reservoirs. The Asan Reclamation Project constructed during 1970 to 1973 was the first project with an enclosing dam that closed off a river mouth. After that many enclosing dam schemes were implemented. The technology for the construction of enclosing dam has advanced and the size of the projects increased gradually (Box 1.7). Now, the Saemangeum Project with 33 km long sea dike and 40,100 ha land reclamation is under construction. This is the largest tidal land reclamation project in South Korea. The aim of tidal land reclamation has diversified with time. Until 1960s, agricultural development to increase the rice production was the only aim. From the 1970s, water resource development was added and from the 1980s industrial and urban area development. After 2000, nature reserve and tourist attraction areas and environment-friendly facilities are being added. Traffic networks in the coastal area were also greatly improved and contribute to the regional economic development. Malaysia The coastal zone of Malaysia covers 4.43 million hectares or 13% of the total land mass. About 1.18 million hectares are in Peninsular Malaysia, 1.0 million hectares in Sabah and 2.25 million hectares in Sarawak. About 27% is under agriculture, 70% under forest and the balance has been utilized for urbanization. Out of the above forest areas, swamp forest accounts for 2.5 million hectares or 58% of the coastal zone, of which 1.7 million hectares are peat swamps. About 70% of the total population lives in the coastal zone. There are 22 urban settlements and already 12,400 rural settlements/villages in Peninsular Malaysia alone. The population density in the urbanized areas is comparable to the most densely settled parts of the Netherlands. The trend of urban concentration in coastal locations is expected to be further sustained as a direct result of population increase and the ongoing industrial development. The major crops cultivated are rubber, coconut, rice and oil palm. The mangrove wetlands, near shore waters, islands and coral reefs areas support a viable marine fisheries industry. The local aquaculture industry has also been expanding rapidly in response to the increasing demand for fish, prawns and cockles, both for local consumption and export. Despite the fact that the contribution of agriculture to the national GDP is declining, the absolute value of the agricultural sector (including fisheries and forestry) is still increasing. 12

Chapter 1. Introductiion

Box 1.7 Types of tidal land reclamation used in Korea (Park and Kim, 2005; Park et al., 2002) Three types of tidal land reclamation are used, based on the morphology of the river or estuary, as well as land and water demand for long periods: •

River mouth closure dam: Dam or dike at narrow river mouth with the main aim to develop water resources. Where river estuary area is wide, the water basin upstream of the dike is divided into water area and reclaimable land area. In this case, both water resources and land area are developed and divided by the levee or lowering of water level of the water area. Examples are the Asan, Geumgang and Yeongsangang projects.

•

Coastal area closure dike with river inlet: Dikes are exposed to the open sea and the line of the dike is not straight but polygonal and generally long. The reclaimed area is larger compared to the other types. Levees are required between the freshwater reservoir and the reclaimed land to protect the land from floods. Examples are the Daeho and Saemangeum (Photo) projects.

•

Bay or coastal area closure dike without river inlet: This type of, usually small-scale, tideland reclamation was done by the farmers. Most times, there is no river and water comes from water sources located outside the reclamation area. Most of the historical tideland reclamation belongs to this category.

(Photo: Land use plan of Saemangeum project)

Lessons learned The tidal land reclamation technology has been developed gradually in succession for food security, disaster prevention, and environmental conservation depending on the necessity and surrounding circumstance for several centuries in Korea. In Korean situation with high population density and reasonable amount of rainfall, tideland reclamations carried out in the past contributed greatly for the poverty alleviation and food crop production.

The Government of Malaysia has identified the populated coastal zone as a major region for development. Coastal areas are preferred sites for industrial development because of the existence of good support infrastructures such as roads, ports and other amenities and resources which include power, energy, raw material and labour supply. There are 103 ports in Malaysia and as the country is moving towards industrialization, total shipping is estimated to increase at a rate of 7 to 9% per year. Drainage is needed to make these waterlogged coastal areas suitable for agriculture or other land use. As soon as the peat swamps are drained the process of irreversible subsidence commences. This subsidence is a well-known and hard-to-overcome constraint to the development and use of coastal lowlands. Furthermore, the conversion of forest areas in agricultural land and the expansion of urban and industrial areas have increased river runoff during extreme rainfall events. In combination with the never-ending subsidence of the drained areas and the siltation in the

13

mouth of the major rivers these high river flows have increased the risk of flooding. This increased risk of flooding has resulted in appropriate conservation, adaptation and mitigation actions to sustain the development of the coastal zone (Box 1.8). The Netherlands The Netherlands is the delta (with a coastline approximately 350 kilometers long) where major European rivers like the Rhine and the Meuse flow into the North Sea. The total territory, including inland lakes, estuaries and territorial waters, is 42,000 km2. The land area (34,000 km2) mainly consists of alluvial deposits and about 25% of the country lies below mean sea level. In the absence of dunes and dikes more than 65% of the country would be flooded at high sea and high river Box 1.8 Coastal lowland development in Sarawak, Malaysia (Department of Irrigation and Drainage, 2001) The Malaysian Government has identified the coastal zones of Sarawak as a major region for development. About 500,000 hectares of the total 1.2 million hectares of plantation development will be in the coastal lowland areas. It is estimated that the major part of the proposed agricultural development, mainly oil palm, forest plantation, sago, aquaculture, paddy and miscellaneous crops including vegetables, is on peat, located mainly in the Central Region (i.e. Sibu and Sarikei Divisions). Non-agricultural land uses, i.e. agro-industries and urban development, are concentrated around the major cities, i.e. Mukah and Sibu, both located in or around peatlands. Peatlands in Sarawak account for 13% of the state’s total land area and for about 63% of the 2.7 million hectares of peat swamps in Malaysia. The coastal areas are dominated by densely populated peatlands with the challenge of climate change, including sea level rise. Drainage is needed to make these waterlogged peat swamps suitable for agriculture or other land uses. As soon as the peat swamps are drained the process of irreversible subsidence commences. This subsidence is a well-known and hard-to-overcome constraint to the development and use of tropical peatlands, threatening the long-term sustainability. The dilemma is how to strike a balance between two contrasting needs, namely, intensive drainage in order to optimize land use and less intensive drainage to avoid irreversible damage to these fragile eco-systems. Subsidence can be reduced by using alternative water management and construction practices. For agricultural land use control structures can improve water management and at the same time reduce subsidence. High water levels and increasing runoff from built-up areas require additional storage. Innovative solutions, e.g. floating roads, buildings and structures, buildings on piles, etc., are required to reduce and counterbalance the never-ending subsidence. Higher water levels and more space for water will fundamentally change the way our peatlands are being managed. It should be remembered, however, that subsidence cannot be completely arrested; it is the price one has to pay for utilising lowland peat swamps. Spatial planning need to be based on these long-term subsidence processes. Appropriate conservation, adaptation and mitigation actions need to take place in the context of sustainable development. Lessons learned The dilemma for the development of the coastal lowlands in Malaysia, which are largely covered by peat swamps, is how to strike a balance between two contrasting needs, namely, intensive drainage in order to optimize land use and less intensive drainage to avoid irreversible damage to these fragile eco-systems.

14

Chapter 1. Introductiion

levels. The western part has an elevation varying between 0 and 5 m below Mean Sea Level (MSL) and has little relief except for the coastal dunes. The lowest point north of Rotterdam is some 7 m below MSL. In the western parts of the Netherlands, through cultivation of peat areas by drainage subsidence occurred and considerable areas where lost to the sea in the period 800 to 1250. Thus people started to build dikes to protect the peat areas from the sea. As the areas were elevated above the river levels, drainage by gravity was possible. The water levels, which were controlled by sluices, could be maintained at a depth that allowed arable crops to be cultivated. Because of the subsidence of the peat layers, however, the drainage deteriorated and, in the fifteenth century, arable cultivation was gradually replaced by grassland. Nevertheless, the land continued to subside, and new techniques were needed to drain the areas. From the sixteenth century onwards, windmills were widely used to pump out the drainage water, thereby maintaining a good drainage base, but consequently increasing subsidence. Subsequently, the drainage base has been lowered from time to time, and nowadays, instead a few metres above mean sea level, these areas are now several metres below it. In addition, much land was gained by embanking silted up lands along the coast and inland seas. At the end of the 16th century and throughout the 17th century, many inland lakes and tidal forelands were reclaimed. In the 19th century, the use of a steam engine enabled the reclamation of larger lakes, e.g. the Haarlemermeer, the polder in which Schiphol Airport is located. In the 20th Century the largest land reclamation scheme in the history of the Netherlands was implemented, the Zuiderzee Project. The Zuiderzee Project consists of a man-made system of dams, land reclamation and drainage works, and is one of the largest hydraulic engineering projects that were undertaken by the Netherlands during the 20th century. It involved the closing-off of the Zuiderzee and the reclamation of land in the newly created lake by means of polders. The Afsluitdijk is the major enclosing dam which initiated this project and constructed during 1927 to 1932. This enclosing dam runs from Den Oever on Wieringen in the province of North Holland to the village of Zurich in the province of Friesland, over a length of 32 km and a width of 90 m, with a crest level around 7.25 m+MSL. This is the fundamental part which turned the saline estuary of the North Sea into a fresh water lake IJsselmeer. Parts of the newly created lake were to be drained to create four polders with a total surface area of 165,000 ha. The created IJsselmeer became an important freshwater basin which feed fresh water from the river IJssel. The Zuiderzee Project differs from previous schemes not only because of its size but also of its nature. It was a typical multi-purpose scheme, primarily aiming at: increase in safety against floods; gaining of new arable lands; creating room for new cities and industries; halting salt water intrusion; storage of freshwater; improvement of drainage; shortening of national road network system and nature development. It changed the geography of a large part of the country for many centuries to come. Most of the population (nearly 11 million) lives in the coastal area, which is also the fulcrum of the Dutch economy: Schiphol Airport, the Port of Rotterdam, Amsterdam, the capital, and The Hague, seat of government. Roughly 65% of GNP is produced in this region. Currently, The Netherlands is safe, but will it be the same for the future (Box 1.9). 15

Box 1.9 Working with water: coping with climate change, now and in the future (Delta Committee, 2008) In 2008, the Government of the Netherlands requested an independent Committee of State (Delta Committee, 2008) to give its advice on flood protection and flood risk management in the Netherlands for the next century, while keeping the country an attractive place to live, work and invest. Large parts of the Netherlands lie below sea level and are even now experiencing the effects of climate change and sea level rise. The Netherlands delta is safe, but preserving this safety over the long term involves action now.

Photo: Urban development in Lelystad, IJsselmeer polders

The Delta Committee has made twelve recommendations to ‘future proof ’ the Netherlands, even over the very long term, securing the country against flooding, assured of adequate fresh water, while remaining an attractive place to live. The basic issue is security, but the advice interfaces with life and work, agriculture, ecology, recreation and leisure, landscape, infrastructure and energy. Together, the twelve recommendations make up the Delta Programme, which must be financially guaranteed by a Delta Fund. A new Delta Act will provide the legislative anchor for the political-administrative organisation for the improvement of water security and the Delta Fund. Lessons learned Managing tidal areas is a never-ending process: likely changes in the climate, economy, social setting and the natural environment as for adaptive management.

Taiwan Taiwan has a coastline of about 1,150 km. The area of the coastal plains (with an elevation < 100m) covers about 37% of the total land area (about 36,000 km2). These coastal plains are densely populated. High rainfall (average about 2,500 mm/year) mainly occurs during the typhoon season. The coastal plains experience flooding in the summer (typhoon) season because of the short streams with very steep slopes (over 200 mountains exceed 3,000 m). The flood-prone area is about 1,534 km2. On the other hand, water shortage occurs in winter; the overdraft of groundwater results in severe subsidence problems. Subsidence, which can be as high as 8.4 cm/y (in Changhua county), increases the risk of flooding and infrastructural failures. The maximum recorded subsidence is 3.2 m in Pingtung county. Since, 1992, about 11,000 ha have been reclaimed, mainly for urban and industrial development (Box 1.10). Coastal wetland restoration has recently initiated to protect villages against flooding and restore nature values. UK The issues affecting the UK’s socio-economic use of tidal areas include demands for flood defence and coastal protection, ports and harbours, mineral resources, urban regeneration, renewable energy 16

Chapter 1. Introductiion

Box 1.10 Land fill in Mailiao district (Liu et al., 2005) Yulin offshore industrial park is located at the central western coast of Taiwan. Since 1992, 11,000 hectares have been reclaimed for industrial purposes. This reclamation has affected the coastal environment. To mitigate its impacts on the nearby coastal area, the industrial park is buffered by a waterway separating it from the main island. The original design of the separation waterway has a width of 500 m. However, this width has been a controversial issue for the past 10 years. Since the separation waterway receives discharges from two streams in the main island, the Shu-Chu-Liao Stream and Hsin-Hu-Wei Stream, the potential inundation during flood events and water quality conditions during low flow periods are two of the major considerations for the width of the waterway. A numerical model was used to evaluate the potential impact of these mitigation measures and to help the design of the alternation to mitigate its impacts. Model calibration and verification were conducted with current, residual velocity, salinity, and water quality variables measured in the completed portion of the waterway. The overall performance of the model was in qualitative agreement with the available field data. The model simulation indicated that coastal water quality standard may be attained and inundation by the 50-year flood may be avoided by such a separation waterway. To obtain input for the modelling and to monitor the environmental impact of the reclamation works a large scale monitoring programme was initiated. The following investigations are conducted: (i) wave, current and the tidal movement; (ii) the changes in the ecosystem on the land, in the estuaries and in the sea; (iii) coastal and estuarine water quality; (iv) groundwater levels and subsidence; (v) air quality, and; (vi) commercial fishery.

Lessons learned Numerical models are useful to evaluate the potential impact of human alternation of natural water bodies and to help the design of the alternation to mitigate its impacts. To reduce environmental impacts the changes of the natural coast should be minimized and considerable efforts are needed to recover the coastal environment. 17

production, waste disposal and leisure. These have to be set against the demands for environmental conservation of habitats, geological exposure, cultural heritage and landscape. The UK is advancing down the road of sustainable practice and environmental protection, but may need to re-emphasise the potential of sympathetic development of tidal areas for socio-economic gain. Sustainability is about choosing a development path that will not disadvantage the social or economic welfare of present or future generations as well as not adversely affecting the environment. To achieve this, significant technical challenges remain, including finding adaptable, acceptable and sustainable solutions to climate change, appropriate materials resources and being able to predict long-term morphological change with comprehensive and balanced implementation involving all stakeholders. The UK government has a policy aim of reducing the risk to the natural and developed environment from flooding and coastal erosion by adopting technically sound and economically, socially and environmentally sustainable solutions (Box 1.11). Climate change is leading to sea level rise and increased or changing patterns of storminess. This, combined with isostatic land adjustment, is leading to significant “coastal squeeze” resulting in eroding coastlines and the narrowing and steepening of intertidal areas, such as beaches and salt marshes. Despite this, there are still pressures (from industry, housing) to develop land that is already at risk of tidal flooding, and to “reclaim” areas presently within the inter-tidal zone. Box 1.11 Strategic planning in the United Kingdom (United Kingdom Interdepartmental Liaison Group on Risk Assessment, 2002) In determining the way the UK should move forward in its management of the coastal zone, it is faced with significant uncertainty: • • •

There are spatial and temporal variations in natural hazards There is incomplete knowledge of physical processes and such descriptions as are available are based on incomplete data. There are differing and conflicting views on what is a desirable outcome, because different coastal attributes are valued differently by a range of stakeholders. For example, there are some 37 consultees that might have a legitimate interest in a Coastal Habitats Management Plan (CHaMP)

The only way to deal with these issues is by a whole systems approach with tiered or nested analysis and decision making, supporting national strategy and feeding down via regional planning (Shoreline Management Plans and Estuary Management Plans, with nested and more detailed Strategy Plans) to specific schemes. The building blocks of such a system are currently under development and include: • • • • • •

Data with associated metadata, plus a reliability trail Knowledge bases – to guide decision makers through key issues and processes Tiered risk assessment methods Techniques for representing and propagating uncertainty Open modelling support systems GIS interfaces to present risk and other information to decision makers and stakeholders

Lessons learned There is a need to take into account the widest possible set of management actions (including major schemes and structures) that may impact on the coast and in estuaries along with climatic, morphological, demographic and socio-economic changes. 18

Chapter 1. Introductiion

1.3 Towards Sustainable Development of Tidal Areas Tidal lowland development will continue to meet the needs of the expanding population. The world population is projected to grow from 6,500 million people today to more than 9,100 million in 2050 (United Nations Population Information Network, 2004). To be able to feed this growing world population and to banish hunger from the world, food and feed production will need to be doubled in the coming 50 years (Molden, 2007). This will be required to meet the needs of the expanding population and the expectation of this growing population for a higher standard of living. It is estimated that, whilst the major part of increase will need to come from already cultivated land, 10% of the increase will have to come from newly reclaimed lands (Van Hofwegen and Svendsen, 2000). These lands will be required partly to compensate for loss of agricultural land by urbanisation and industrialisation, erosion, desertification and partly to compensate for reduction in yields by waterlogging, salinisation, environmental considerations or degeneration of existing irrigation and drainage systems. The development focus in tidal areas is, however, gradually moving to ports, harbours, transportation routes, industries, aquaculture, housing and recreation facilities. Reclamation of these areas may sterilise their availability for such uses as waste disposal, abstraction of construction aggregates and other materials and as the location of renewable energy generators such as wind turbines. At the same time, these developments threaten their valuable natural resource functions. On this basis, the burden of guaranteeing sustainable development must be shared locally and globally for the wise use and conservation of tidal areas (Box 1.12). Doing nothing is not an option. Development of tidal areas is closely linked to the availability of fresh water, a finite and vulnerable resource, essential to sustain life, development and the environment and development should be based on the Dublin principles (Box 1.13). In tidal areas, fresh water is needed to reclaim saline land for agriculture, to irrigate new agricultural land, to create and maintain fresh water lakes, etc. The quality of fresh water resources is threatened by the various (land) uses, e.g. non-point source pollution by intensive agriculture, point-source pollution by untreated waste water from industries and households and salt water intrusion. Development of tidal areas will also be affected by systemic changes such as population growth and those arising from climate change, e.g. the predicted sea level rise and increases in storminess. To make development sustainable, it should meet the needs of current generations without compromising the ability of future generations to meet their needs and aspirations. Sustainable development is often conceptualised as having three dimensions: environment, economy and society (Global Water Partnership, 2003). These three dimensions can be symbolised as overlapping circles with a triangle in the centre representing sustainable development (triple bottom line concept), based on 19

Box 1.12 Convention of Ramsar The Convention on Wetlands, signed in Ramsar, Iran, in 1971, is an intergovernmental treaty which provides the framework for national action and international cooperation for the conservation and wise use of wetlands and their resources (Convention on Wetlands, 1971). The contracting Parties have agreed on the following principles: •

Recognizing the interdependence of Man and his environment;

•

Considering the fundamental ecological functions of wetlands as regulators of water regimes and as habitats supporting a characteristic flora and fauna, especially waterfowl;

•

Being convinced that wetlands constitute a resource of great economic, cultural, scientific, and recreational value, the loss of which would be irreparable;

•

Desiring to stem the progressive encroachment on and loss of wetlands now and in the future;

•

Recognizing that waterfowl in their seasonal migrations may transcend frontiers and so should be regarded as an international resource;

•

Being confident that the conservation of wetlands and their flora and fauna can be ensured by combining far-sighted national policies with co-ordinated international action.

three overriding criteria: (i) Economic efficiency in water use; (ii) Equity, and; (iii) Environmental and ecological sustainability (Fig. 1). From these three dimensions of sustainable development, it is often most difficult to get grips with the social dimension of sustainability. The triple bottom line concept illustrates the complex interlinkages between all three dimensions, and also illustrates that sustainable development is not working on one of these dimensions separately of the others. It should be realised that sustainable development is not only balancing the three dimensions, but also successfully delivering all of them at the same time. In tidal areas, the principles on Integrated Coastal Zone Management and Integrated Water Resources Management are a prerequisite for sustainable development (Box 1.14). ICZM and IWRM are both processes that promote the co-ordinated development and management of water, land and related resources, in order to maximize the resultant economic and social welfare in an equitable manner without compromising the sustainability of vital ecosystems. Public participation in decision-making and access to information and to justice should be guaranteed (United Nations Economic Commission for Europe, 1998). Capacity building plays an essential role in this. Box 1.13 Dublin principles At the International Conference on Water and the Environment, organised in Dublin in 1987, the following development principles were agreed upon (Bruntland, 1987): •

Fresh water is a finite and vulnerable resource, essential to sustain life, development and the environment;

•

Water development and management should be based on a participatory approach, involving users, planners and policy-makers at all levels;

•

Women play a central part in the provision, management and safeguarding of water;

•

Water has an economic value in all its competing uses and should be recognized as an economic good.

20

Chapter 1. Introductiion

Based on the above considerations, the WGSDTA has developed a vision on the sustainable development of tidal area (Box 1.15) and based on this vision addressed the following research questions: •

Why are tidal areas changing or being developed? What are the sustainable options for future development?

•

Is it possible to balance environmental, social and economic objectives in the development of tidal areas?

•

Who needs to be involved in that balancing process?

•

How would development options have to be selected that optimise the potential for a particular area?

Fig. 1 Sustainable development; the triple bottom line

Box 1.14 Principles on Integrated Coastal Zone Management and Integrated Water Resources Management Principles of Integrated Coastal Zone Management (ICZM) The EU Demonstration Programme on ICZM identified eight principles for successful ICZM (European Commission, 2000): •

A broad ‘holistic’ perspective (thematic and geographic);

•

A long term perspective;

•

Adaptive management during a gradual process;

•

Reflecting local specificity;

•

Working with natural processes;

•

Participatory planning;

•

Support and involvement of all relevant administrative bodies; and

•

Use of a combination of instruments.

Principles of Integrated Water Resources Management (IWRM) Integrated Water Resources Management is defined as a process that promotes the coordinated development and management of water, land and related resources, in order to maximise the resultant economic and social welfare in an equitable manner without compromising the sustainability of vital ecosystems. IWRM is based on the Dublin Principles (Box 1.13) and three groups of tools have to be addressed to reach its objectives (Global Water Partnership, 2003): •

Creating an enabling environment with appropriate policy and legal frameworks;

•

Institutional development, including community participation, and;

•

Human resources development and strengthening of management systems 21

These questions have been studied by the working group members and consistent with ICID’s Strategy, the WG-SDTA has developed a position paper in which the following principles and issues to promote sustainable development of tidal areas have been defined (Park et al., 2009). Principle 1 – Integrated multi-functional approaches Issue 1.1: Integrated land management Which approaches are most strategic taking account of future changes (see also Issue 3.2)? Is it possible to identify and promote multi-functional approaches (e.g. agriculture, aquaculture, recreation facilities, housing, industries, ports, transport, renewable energy, water supply, material resource abstraction, waste disposal) as part of the development scheme being considered? Are integrated catchment (watershed) management and integrated coastal zone management being adopted? Which international conventions, laws and government policies should be taken into account? Have social conventions, economic regeneration and biodiversity been considered? Issue 1.2: Integrated water management How can the adoption of integrated water resource management be promoted, both now and in the future? How can the (sometimes conflicting) quantity and quality requirements of irrigation, drinking and industrial water, of water for nature and aquaculture and of drainage and flood control be managed? Which water management approaches help to implement agreed multi-functional requirements? Principle 2 – Holistic engagement with social, economic and environmental issues Issue 2.1: Engagement with all stakeholders Have all stakeholders involved in or affected by the management and development of tidal areas been considered (see also Issue 4.1)? What kinds of information, communication techniques, technical tools and institutional framework(s) will support stakeholder engagement? Should innovative or previously unused approaches to Box 1.15 Vision of the WG-SDTA on stakeholder consultation be considered? How sustainable development of tidal area may enduring partnerships with stakeholders be Sustainable development of tidal areas built? How may the awareness and responsibility provides appropriate social and economic of local communities and other stakeholders development and productivity of tidal areas, be increased? What kinds of risk management whilst caring for and working with the natural environment, in a way that is fair and measures will reduce the consequences of natural affordable both now and in the future. and man-made hazards for local communities 22

Chapter 1. Introductiion

and other stakeholders (see also Issue 3.1)? Has the scientific and systemic information on natural and man-made hazards been made available in a form that can be understood by all? Issue 2.2: Management of resources and promotion of sustainable production How may the use of non-renewable resources be minimised and the use of renewable resources and reuseable and recycled materials be promoted? To what extent will reclamation developments sterilise the availability of the tidal lands for waste disposal, material resource abstraction and renewable energy generation? How might the amount of waste generated in developing and managing tidal areas be minimised? In what ways could the amount of energy from non-renewable sources used in construction and management of land and water be minimised and those of renewable resources be maximized? How may sustainable agricultural production be promoted? Issue 2.3: Environmental enhancement and stewardship of natural resources To what extent have existing developments ‘modified’ the natural environment of the tidal area? How could developments or uses of tidal areas be promoted that preserve or enhance their natural functions? Are there innovative solutions that would enhance the ecological status of modified tidal areas and/or the creation of new wetland habitats in reclaimed areas, e.g. in paddy fields, irrigation and drainage canals and freshwater lakes? How might future impacts on natural systems, including water quality, biodiversity and landscape be mitigated? To what extent is environmental degradation likely to be a temporary effect and can ecological recovery be achieved with time? Principle 3 – Management of risk and uncertainty and adaptation to change Issue 3.1: Risk management to protect people, property and the environment from natural and manmade hazards What options have been considered either to reduce the probability of natural and man-made hazards such as flooding, or the consequences of such events? How have risks and uncertainties in the management and development of tidal areas been considered? How has the performance of the reclamation and flood protection works been assessed and assured? How may safety, health and environment risks be minimised? Are effective and efficient warning systems in place to predict the occurrence of natural and manmade hazards and to promote appropriate responses from those at risk? Have all interested parties been provided with the best available information as to the locations and degree of natural and manmade hazards? What strategies will be used to prevent inappropriate housing or industrial development in areas at significant risk? How could land and water quality pollution be limited? Has risk management been matched with opportunities to identify economic, social and environmental improvements? 23

Issue 3.2: Adaptive management to take account of climate change, population growth and other longterm changes and uncertainties Have the effects of climate change (e.g. sea level rise, increased storminess) and of population growth been assessed? Has the precautionary principle been adopted? How may resilient and adaptive management be promoted? Have social, economic and environmental uncertainties been taken into account in decision-making? Will developments ensure a fair balance between reducing risks and increasing opportunities both for present and future generations? Will developments reduce energy consumption and greenhouse gas emissions (see also Issue 2.2)? Principle 4 – Enabling methods and means Issue 4.1: Appraisal using methods that are rigorous, coherent and transparent and consider social, environmental and economic costs and benefits Have alternative courses of action been compared by a process that is open and transparent and that adopts a rigorous, logical and accountable framework? Have local communities and stakeholders participated from the beginning (see also Issue 2.1)? Has multi-functionality been optimised? Have all important societal objectives including equity been taken into account? Do the adopted appraisal methods increase understanding of the nature of the choices that must be made and encourage the invention of new and better approaches to the management and development of tidal areas? Have full life-cycle costs been taken into account in making decisions? Issue 4.2: Knowledge, skills and awareness to promote sustainable approaches Has an enabling environment with appropriate policy and legal frameworks been created? Has awareness of key sustainable development issues been raised amongst all those involved in or affected by the management and development of the tidal area(s)? Have decision-makers, planners, engineers and scientists been trained in principles of sustainable development? Is ongoing professional development of planners, engineers and scientists in place to ensure that their practice is up-to-date and appropriate to the engineering, social and environmental challenges? Has best practice and guidance been disseminated to them? Do all practitioners understand the dynamic nature of tidal areas and systems? Has the human resources development strengthened the management systems and is there appropriate institutional development?

24

Chapter 1. Introductiion

1.4 Objectives, Readership and Structure of the Handbook Objectives The Handbook has the following objectives: •

To draw together existing knowledge and experience and the results of recent and current research to produce detailed procedural guidance on sustainable development of tidal areas.

•

To provide an overview of current best practices for use by professionals working in the planning, design, construction and operation and management of flood control and land & water management in tidal areas.

Readership The Handbook will provide guidelines not only for planning, design and management of irrigation and drainage, and flood control system but also for land and water resources development in tidal areas for engineers, decision makers and other stakeholders. Structure The Handbook is based on case studies of historically significantly monumental tidal reclamation projects from member countries, in particular China, Germany, India, Indonesia, Japan, Korea, Malaysia, the Netherlands, Taiwan and UK. All these projects are in a different stage of development. In developing countries, the development is often in an initial stage, mainly aiming to provide agricultural development to feed the growing population. At the other end of the scale, the demands in the industrial world focus on flood defence and coastal protection, ports and harbours, exploitation of seabed resources, barriers and barrages and increased use of water by industry and for power generation, waste disposal and leisure. These different stages of development require different engineering solutions. They all have in common, however, that once started, the development will continue forever facing challenges like falling land levels often in combination with a rise in sea levels due to climate changes (changing rainfall pattern and intensity), population growth and movement. A distinction can be made between natural changes (sea level rise, rainfall pattern, etc) and man-made changes (subsidence, change in land use. etc). The case studies describe the historical development up till its present place in the development cycle, in particular and when

25

appropriate the following aspects are discussed: Physical, chemical and biotic characteristics, including climate, soils, habitat, etc.: •

Water management: irrigation, drainage and flood protection, including water quality, sedimentation, flood mitigation, strategic storage, etc.;

•

Management and institutional aspects, including performance and risk analysis;

•

Socio-economic impacts, including cost/benefit analysis.

Based on the principles and issues towards sustainable development of tidal areas as presented in Chapter 1.3, the case studies have been synthesised and are presented in four chapters, i.e.: •

Planning Framework for Managing Tidal Area Development

•

Tidal Area Features and Natural Processes

•

Engineering for Sustainable Development of Tidal Areas

•

Tidal Reclamations and Their Impacts on Natural Processes

In the last and concluding chapter the experiences presented in the case studies have been used to formulate a set of principles towards an integrated decision support framework for the sustainable development of tidal areas.

26

Chapter 1. Introductiion

References BAPPEDA, 2010. Master Plan for the Rehabilitation and Revitalization of the Ex-Mega Rice Project Area, Central Kalimantan, Indonesia, Palangkaraya, Indonesia, Available at: http:// www.masterplan-emrp.org/en/. Accessed 4 July 2010. Bruntland G (ed.), 1987. Our common future: The World Commission on Environment and Development, Oxford, Oxford University Press. Cao Zhi Hong, Lee Deog-Bae, 2005. Utilization and reclamation of tidal lands in Jiangsu Province of China. In: Evaluation of draft ICID handbook on SDTA. Proceedings 4th Int. Workshop on Sustainable Development of Tidal Areas, Beijing, pp: 286-294. Convention on Wetlands of International Importance especially as Waterfowl Habitat. Ramsar (Iran), 2 February 1971. UN Treaty Series No. 14583. As amended by the Paris Protocol, 3 December 1982, and Regina Amendments, 28 May 1987. Delta Commission, 2008. Working with water: a country that built for its future (in Dutch: Samen werken met water: Een land dat leeft, bouwt aan zijn toekomst.). Available at: www. deltacommissie.com. Accessed 10 July 2010. Department of Irrigation and Drainage, 2001. Water Management Guidelines for Agricultural Development in Lowland Peat Swamps of Sarawak. Department of Irrigation and Drainage Sarawak, Kuching. European Commission, 2000. Proposal for a European Parliament and Council Recommendation concerning the implementation of Integrated Coastal Zone Management in Europe. European Communities Documents no. COM (2000) 545f - 11322/00, Brussels. Global Water Partnership, 2003. Sharing knowledge for equitable, efficient and sustainable water resources. Tool Box Integrated water resources management. Global Water Partnership, Stockholm, Sweden. Government of Indonesia, Directorate Lowlands and Coasts, 2008. Towards formulation of a national lowland development strategy for Indonesia – road map towards preparation of a strategy. Euroconsult Mott MacDonald and Wageningen University. Huntington S, Burgess K, Townend I., 2002. Coastal engineering science to policy and practice. Keynote address. In: Mckee Smith, J. (Ed.). Coastal Engineering. Proceedings of the 28th International Conference on Coastal Engineering, held in Cardiff, Wales, in July 2002. Vol. I: 3-17. 27

Interagency Watershed Coordinating Committee, 2000. Clean Water Action Plan, Glossary of Terms. Available at: http://water.usgs.gov/owq/cleanwater/ufp/glossary.html. Accessed 10 January 2010. International Conference on Water and the Environment (ICWE), 1992. The Dublin Statement on Water and Sustainable Development, Dublin, Ireland, 6 pp. Liu, W.C., Kuo, J.T., Kuo, A.Y., 2005. Modelling hydrodynamics and water quality in the separation waterway of the Yulin offshore industrial park, Taiwan. Environmental Modelling & Software, 20, 3, 309-328 Molden D., 2007. Water for Food, Water for Life: A Comprehensive Assessment of Water Management in Agriculture. London: Earthscan and Colombo: International Water Management Institute. Park, S. H., Simm, J., and Ritzema, H. P., 2009. Development of tidal areas, some principles and issues toward sustainability. Irrigation and Drainage, 58: S52–S59, DOI: 10.1002/ird.474. Park, S.H., Choi, K.W., Chang, J., 2002. History of tideland reclamation and development of reclamation technology in Korea. In: Proceedings International Workshop on Sustainable Development of Tidal Areas on July, 22, 2002 in Montreal, Canada, ICID, pp: 136-147. Park, S.H., Kim Ju Chang, 2005. Paddy Rice Cultivation in Korea, In: Evaluation of draft ICID handbook on SDTA. Proceedings 4th Int. Workshop on Sustainable Development of Tidal Areas, Beijing, Probst, B., 2004. Information and participation in coastal defence in Germany. In: Socioeconomic management and stakeholder participation for agriculture in tidal areas. Proceedings 3rd Int. Workshop on Sustainable Development of Tidal Areas, Moscow, pp: 29-43. Schultz B., 2001. ‘Development of tidal swamps and estuaries.’ Keynote address at 1st Asian Regional Conference at 52nd IEC meeting of International Commission on Irrigation and Drainage (ICID), Seoul, Korea. Simm J, Ritzema H.P., Park Sang Hyun, 2003. Outline for ICID Handbook on Sustainable Development of Tidal Areas: Outline. In: Wise Use and Environmental Conservation of the Tidal Areas. Proceedings 2nd Int. Workshop on Sustainable Development of Tidal Areas, Montpellier, pp: 131-136. Ueda Kazumi, 2002. Impoldering works (Kantaku) in Japan. Proceedings Int. Workshop on Sustainable Development of Tidal Areas, Montreal. International Commission on Irrigation and Drainage, pp: 125-135. United Nations Population Information Network, 2004. World Population Prospects, The 2004 Revision - Highlights. United Nations Department of Economic and Social Affairs, Population Division, New York. 28

Chapter 1. Introductiion

United Nations Economic Commission for Europe, 1998. Convention on access to information, public participation in decision-making and access to justice in environmental matters. Aarhus, Denmark, June, 22 p.p. Van Hofwegen, PJM, Svendsen M., 2002. A Vision for Food and Rural Development. The World Bank and the Netherlands Directorate General for Development Cooperation, The Hague, The Netherlands. Working Group on Sustainable Development of Tidal Areas, 2009. Tidal area features and natural process. Proceedings International Workshop, February 24-26, Tainan Hydraulics Laboratory and National Cheng Kung University, Taipei, Taiwan. Working Group on Sustainable Development of Tidal Areas, 2006. Evaluation of the 2nd Draft ICID Handbook on SDTA. Proceedings 5th International Workshop on Sustainable Development of Tidal Areas, September 15, Kuala Lumpur, Malaysia. Working Group on Sustainable Development of Tidal Areas, 2005. Evaluation of Draft ICID Handbook on SDTA. Proceedings 4th International Workshop on Sustainable Development of Tidal Areas, September 13, Beijing, China. Working Group on Sustainable Development of Tidal Areas, 2004. Socio-economic Management and Stakeholder Participation for Agriculture in Tidal Areas. Proceedings 3rd International Workshop on Sustainable Development of Tidal Areas, September 6, Moscow, Russia. Working Group on Sustainable Development of Tidal Areas, 2003. Wise Use and Environmental Conservation of the Tidal Areas. Proceedings 2nd International Workshop on Sustainable Development of Tidal Areas, September 17, Montpellier, France. Working Group on Sustainable Development of Tidal Areas, 2002. Proceedings International Workshop on Sustainable Development of Tidal Areas on July, 22, 2002 in Montreal, Canada. World Bank, 2007. Integrated Coastal Zone Management Project, India. Report no. AB2702, Washington DC. Yagnik, V.M., Singh, M.M., 2003. Land reclamation under Kalpasar project: a step towards sustainable development. In: Wise Use and Environmental Conservation of the Tidal Areas. Proceedings 2nd International Workshop on Sustainable Development of Tidal Areas, September 17, Montpellier, France, pp: 91-98.

29

Glossary Adaptive management: A type of natural resource management in which decisions are made as part of an ongoing science-based process. Adaptive management involves testing, monitoring, and evaluating applied strategies, and incorporating new knowledge into management approaches that are based on scientific findings and the needs of society. Results are used to modify management policy, strategies, and practices. (Interagency Watershed Coordinating Committee, 2000). Thus adaptive management involves the ability to modify approaches cost-effectively, with optimum reuse of physical resources, without coming up against overriding constraints. Integrated Coastal Zone Management (ICZM): A process of governance for coastal and marine areas in order to optimise benefits form the coastal zone development and coastal resource management, and to minimise negative effects of such activities on the coastal resources and environment (Tiwi, 2004) Integrated Water Resources Management (IWRM): A process which promotes the co-ordinated development and management of water, land and related resources, in order to maximize the resultant economic and social welfare in an equitable manner without compromising the sustainability of vital ecosystems (Global Water Partnership, 2003). Precautionary principle: To ensure that decisions are taken notwithstanding scientific uncertainty about the nature and extent of the risk. It should be invoked when there is good reason that harmful effects may occur and when the best available scientific advice cannot assess the risk with sufficient confidence to inform decision making (United Kingdom Interdepartmental Liaison Group on Risk Assessment , 2002). Resilience: means ‘able to recover quickly and easily’. Resilient management therefore involves minimising the consequences of hazardous events or learning to live with them instead of reducing the hazard (Vis et al., 2003). Sustainable development: Development that meet the needs of current generations without compromising the ability of future generations to meet their needs and aspirations (Bruntland, 1987). Tidal areas: All those coastal areas where the tidal processes are capable of affecting man’s activity or of being influenced by man. This roughly extends tidal areas between the following limits (Simm et al., 2003): •

30

on the seaward side up to the limit of conventional construction or dredging activity (typically of the order of 30m water depth);

Chapter 1. Introductiion

•

on the landward side up to the limit of the action of the sea, including all those areas that might be subject to flooding by seawater and up all estuaries and rivers to the tidal limit (the point where water levels are no longer influenced by tidal propagation).

References Glossary Bruntland G (ed.). 1987. Our common future: The World Commission on Environment and Development, Oxford, Oxford University Press. Global Water Partnership. 2003. Sharing knowledge for equitable, efficient and sustainable water resources. Tool Box Integrated water resources management. Global Water Partnership, Stockholm, Sweden Interagency Watershed Coordinating Committee. 2000. Clean Water Action Plan, Glossary of Terms. Available at: http://water.usgs.gov/owq/cleanwater/ufp/glossary.html. Accessed 10 January 2010. Simm J, Ritzema H.P., Park Sang Hyun. 2003. Outline for ICID Handbook on Sustainable Development of Tidal Areas: Outline. In: Wise Use and Environmental Conservation of the Tidal Areas. Proceedings 2nd Int. Workshop on Sustainable Development of Tidal Areas, Montpellier, pp: 131-136. Tiwi DA. 2004. Improving Environmental Impact Assessment for Better Integrated Coastal Zone Management. PhD, UNESCO-IHE, Delft, 252 pp. United Kingdom Interdepartmental Liaison Group on Risk Assessment (UK-ILGRA). 2002. Third Report prepared by the Interdepartmental Liaison Group on Risk Assessment, 7 pp. Available at: http://www.hse.gov.uk/aboutus/meetings/committees/ilgra/. Accessed: 14 July, 2010. Vis M, Klijn F, Bruijn KM de, Buuren M van. 2003. Resilience strategies for flood risk management in the Netherlands. Intl. J. River Basin Management Vol. 1, No. 1, pp. 33–40

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32

CHAPTER 2

Chapter 2. Tidal Area Features and Natural Processes

TIDAL AREA FEATURES AND NATURAL PROCESSES EDITOR: RUEY-CHY KAO

2.1 Introduction

Author: Chan-Ji Lai

T

he management of environments and ecosystems in ways congruent with green principles and sustainability are important requirements for industries and planners. Human activity impacts the physical, chemical and biological processes of ecosystems. It is particularly important that features and processes typical of tidal areas be recognized. Indeed, the effects of human activity on tidal environments, including subsequent restoration efforts, have been the subject of extensive discussion. The objective of this chapter is to describe the features of tidal environments and the processes that shape them. The chapter includes examples of human-caused effects on tidal areas and the lessons learned from efforts to reverse those effects. This chapter starts with an overview of spatial and time scales of processes commonly identified in tidal areas including, physical, chemical, biological and sediment transport processes. The terminologies regarding these processes are introduced and followed by detailed descriptions in the following sections: Section 2.2 Physical Features, Landforms and Sediment Transport, Section 2.3 Physical processes, Section 2.4 Chemical features and Section 2.5 Biological features. Finally, section 2.6 presents case studies of how the time and spatial scales can be used for understanding a tsunami event and for evaluating sustainability of tidal regions. 33

2.1.1 SPATIAL AND TIME SCALES OF PHYSICAL PROCESSES

Some spatial and time spans of physical processes in ocean and coastal regions are compared with samples of biota generation time (BGT; Molles Jr., 2004) in Fig. 2.1.1. The BGT is the average time interval between newborn biotic organisms and their next offspring. The spatial and time scales are given at the abscissa and the ordinate, respectively. Using meter and hour as measures, four scales namely “Micro (105)” scales, are roughly specified and are indicated in the figure. These terminologies have been used by Pavlopoulos and Poulos (2008) but the intervals provided follow the guidance of Daly and Smith (1993). A line is drawn through the edges of the four scales and shows the correlations between the space/ bio-sample size and time scales for both physical processes, and the BGT plots. The horizontal and vertical double-arrow lines for physical process represent the ranges of the spatial and time scales for that process and they are the axes of ellipses in this diagram, adapted from Tropea et al. (2007). For example, surface waves, shown by the number “1” have wave lengths at the order of 0.1~1km and wave periods of several seconds to hours. The table shown below the figure is adapted from Schwartz (2005), and it gives additional details regarding the physical processes demarked by the four scales. The figure and the adjoining table illustrate that the regular surface waves are generated by the driving force of wind and tide and last from 1 second to 25 hours. The wave lengths span from 0.1m to 106 m extending between micro and mega scales. Furthermore, the figure also indicates that coastal trapped waves, upwelling fronts, and some seasonal cycle currents are mesoscale processes, while the ENSO (El Niño-Southern Oscillation) and decadal oscillations are macroscale or mega-scale phenomena. These terms are described in detail in section 2.3. For comparison, the generation time of several living organisms are also shown in Fig. 2.1.1. E. coli and Sequoia, for example, with physical sizes of approximate 1μm and 100m respectively, are shown as the dots on the far left and the top. Generation time of clams and oysters are around 1~2 years with their body sizes measured in centimeters. 2.1.2 SPATIAL AND TIME SCALES OF MORPHOLOGICAL AND BIOLOGICAL PROCESSES

Geographical features or landforms in tidal and coastal regions are the consequences of physical processes, such as wind and wave actions, combined with transport processes. These physical processes bring variations to the physical and chemical constituents, the non-living environment, of the region. The effect is a gradual modification of the food web flow, biotic composition, the living environment, and the succession of the overall ecosystem. Time and spatial scales can guide communications among participants engaged in coastal projects. Stive et al. (2002) related shoreline evolution response patterns to natural and human-induced causes. The time scale of this evolution can be short term (hours to years), middle term (years 34

Chapter 2. Tidal Area Features and Natural Processes

to decades), long term (decades to centuries), or very long term (centuries to millennia). The terminologies may have different interpretations in other disciplines, e.g., Pavlopoulos and Poulos (2008) related event time scales to be over days to many years: a coastal morphological changes, such as a tidal inlet migration due to engineering works, an engineering time scales, to be a few months to decades; a geologic time scales refer to geomorphological evolution extending from decades to millennia, such as the infilling of an estuary. Fig. 2.1.2 is thus derived to interpret the interactions between physical, environmental, morphological factors and corresponding biological responses on frames of horizontal spatial and temporal axes. On the left of the ordinate, the physical, biological, chemical and environmental processes, as well as the sediment transport and morphological features are marked. Each of them connects to the processes inside the box to the right of the ordinate. There are two “Spatial scales” 1. Surface waves BIOTIC SAMPLES

century

PHYSICAL PROCESS

Turtle

decade

Whale Kelp

Clam& Oyster

year

9 Macroscale

3. Internal tides 4. Surface tides

8

Horsefly

internal solitary waves

10

Megascale

Biota generation time (BGT); Time Scale

2. Intertidal/internal and

Sequoia Human

5. Synoptic storms

month

5b. Estuary outflows

7 Mesoscale

week

6 5;5b



Euglena

4

3

7. Upwelling, fronts, eddies

2

hour

E.Coli

Sediment resuspension

6. Coastal trapped waves

day

and filaments

1

8. Seasonal cycles

minute

Microscale

9. ENSO

second

10

-6

10

-5

-4

10

10

-3

10

-2

10

-1

10

0

10

1

2

10

10

3

10

4

10

5

6

10

10

7

10. Decadal oscillations

Biota body size (m); Spatial scale (m)

Fig. 2.1.1 Spatial and time scales for biota life expectancy and coastal physical processe

Name

Period

Disturbing force

Restoring forces

Capillary waves

0.1 s

wind

Surface tension

Ultragravity waves

0.1~1 s

wind

Gravity

Infragravity waves

0.5~5 min

wind

Gravity

Long period wave

0.1~12 hours

storms/earthquakes

Gravity/Coriolis

Tidal waves

12~25 hours

Gravitation

Gravity/Coriolis

Transtidal waves

>1 day

Land-Air-Sea coupling

Gravity/Coriolis

Note: Micro (105) units in hours and meters (after Molles, MC Jr,. 2004; Tropea et al., 2007; and Schwartz, 2005)

35

shown on the bottom and the top abscissa and the “Time scale” is centered between the biological and chemical process boxes. In the figure, “Micro, Meso, Macro” and “Mega” followed by “–T” or “–S” represent the same order of magnitude for time or space scales as those given in Fig. 2.1.1 and their intervals are marked. The footnote for Fig. 2.1.2 identifies the subsections in this chapter that describe the processes noted in the figure.

1mm

Macro-S(103~105m) Mega-S(>105m)

Meso-S(1~103m)

Micro-S( 100 ppm

Br, C, Sr, B, Si, F : 1 – 100 ppm The chemistry of seawater is very complex because the Trace elements : < 1 ppm properties of water allow many materials to “break down” (dissolve) in water. Seawater is composed mostly of water (H2O). About 3.5% of seawater is “salt”; the other 96.5% is water. Water, due to its polarity is called the universal solvent and the most abundant substances dissolved in seawater are ionic solids (salts such as sodium chloride, Fig. 2.4.1). Major elements in sea water There are 11 main ion chemicals in seawater. Major ions are defined as those elements whose seawater concentration is greater than 1 ppm (parts per million). At a salinity of S = 35.000 0/00 (ppt) seawater has the composition given in Table 2.4.1. These 11 cations and anions, according to Pilson (1998), are (in grams per kilogram of water): Chloride (19.353), Sodium (10.781), Sulfate (2.712), Magnesium (1.294), Calcium (0.4119), Potassium (0.399), Bicarbonate (0.126), Bromide (0.0673), Strontium (0.00794), Boric acid (0.0257), and Fluoride (0.00130).

Fig. 2.4.1 Concentrations of the major constituents in seawater (from Pilson 1998) 57

Seawater is a solution of NaCl in which Na+ and Cl- account for greater than 85.7% of the salt content by mass. The order of the other cations is Mg2+ > Ca2+ > K+ > Sr2+. The anion Cl- is the most abundant ion in seawater and it is approximately equal to the sum of the cations. The order of the other anions is SO42-> HCO3- > Br-> F-, and they are much less significant in the charge balance of seawater. Salinity, Chlorinity and electrical conductivity Salinity is the most frequently used parameter in chemical oceanography. Owing to the difficulty of precisely measuring the salinity, chlorine content is usually accurately obtained and relates to salinity as: S(o/oo)= 1.805 Cl(o/oo) + 0.03, or alternatively it is expressed as a simple relation (Wooster et al., 1969): S(o/oo)= 1.80655 Cl(o/oo) . Table 2.4.1 Concentrations of the Major Ions in seawater (from Pilson, 1998) At Salinity S = 35.000 ppt mg kg-1 S-1

g/kg

mmol/kg

mM

Cations Sodium (Na+)

308.0

10.781

468.96

480.57

Potassium (K+)

11.40

0.399

10.21

10.46

Magnesium (Mg+2)

36.69

1.284

52.83

54.14

Calcium (Ca+2)

11.77

0.4119

10.28

10.53

Strontium (Sr+2)

0.227

0.00794

0.0906

0.0928

Anions Chloride (Cl-)

552.94

19.353

545.88

559.40

Sulphate (SO4-2)

77.49

2.712

28.23

28.93

Bicarbonate (HCO3-)

3.60

0.126

2.06

2.11

Bromide (Br-)

1.923

0.0673

0.844

0.865

Boric acid (B(OH)3)

0.735

0.0257

0.416

0.426

Fluoride (F-)

0.037

0.00130

0.068

0.070

Totals 1004.81

35.169

1119.87

1147.59

58

Chapter 2. Tidal Area Features and Natural Processes

Salinity is dimensionless and the range of salinity for most of the world’s oceans is from 34.60 to 34.80 parts per thousand (g/kg). The lowest surface salinities for the coastal areas are located at about 27°N and 120 °E, which is near the Yangtze River estuary in spring. The Law of Constant Proportions (Marcet’s Principle) A. Constancy of relative ionic composition of seawater The principal compositions of seawater are found in relatively constant proportions throughout the world’s ocean. Marcet’s Principle states that: “Regardless of how the salinity may vary from place to place, the ratios between the amounts of the major ions in the waters of the open ocean are nearly constant.” Marcet suggested that “specimens of seawater contain the same ingredients all over the world, these bearing very nearly the same proportions to each other, so that they differ only as to the total amount of their saline contents” (Measures, 2001). A conservative element has a constant element-to-salinity ratio in different parts of the ocean, as does one conservative element to another. One way to establish a conservative element of unknown reactivity is to plot it versus another conservative element or conservative property like potential temperature or salinity. This is referred to as “The Law of Constant Proportions”. Elements are conservative because they have very low chemical reactivity and their distributions in the ocean interior are determined only by currents and mixing. . B. Conditions under which major elements may not be conservative The concentration ratio of conservative major elements in ocean water may vary, depending upon the interaction among geological, biological, geochemical or biogeochemical activities. These distinctive factors can include: (1) specific dynamics of estuaries and land-locked seas, (2) submarine groundwater discharge, (3) exchange of major ions between sea and atmosphere or sediments, (4) precipitation and dissolution of carbonate minerals, (5) freezing, (6) submarine volcanism, (7) admixture with geological brines, (8) evaporation of seawater in isolated basins, and (9) anoxic basins. The chemical composition of river water is largely related to the nature of the rocks and minerals in which it flows through. So at some places where water sources have different ionic ratios or where extensive chemical reactions modify the composition, the Law of Constant proportions do not hold. For example, at: 59

a. Estuaries: The average composition of river water is compared with seawater in Table 2.4.2 (from Langmuir, 1997), in which the concentrations are given in mg L-1. The principal difference is that HCO3- is the main anion in river water and has a much higher concentration than Cl (which is the lowest of the major anions in river water). Ca is the main cation in river water, followed by Na and Mg, then K. Table 2.4.2 River water versus Seawater (from Langmuir, 1997) Species

Mean

Seawater

Residence time

Concentration in



river water

(mgL-1)

in seawater

seawater relative



(mgL-1)

(my)

to river water

Ca

15

410

1.2

27

times

Mg

4.1

1350

15

330

times

Na

6.3

10500

190

1670

times

K

2.3

390

8

170

times

HCO3-

60

142

▫

2.4

times

Cl

7.8

19000

300

SO4

11

2700

22

SiO2

13.1

6.4

0.016

0.49 times

Fe

0.67

0.003

(0.003?)

0.004 times

Al

0.07

0.001

(0.003?)

0.014 times

TDS

120

34500

▫

2400 times 245

288

times

times

b. Submarine groundwater discharge: Driven by the hydraulic gradient, terrestrial groundwater can be discharged directly into the coastal ocean; it is known as the submarine groundwater discharge (SGD). SGD may be important as a pathway for dissolved constituents and nutrients into the coastal water. Large amounts of SGD may exert substantial influence on chemical, physical, ecological characteristics of the coastal and nearshore water (Gallardo and Marui, 2006). In chemical oceanography, residence time (t) of each element expresses how long it takes to add an amount of the element to the ocean that is equal to the amount of the element in the ocean at steady state: t = Mean Concentration in Ocean × Ocean Volume / Input per year where, the ocean volume is (1.37×1021 L) 60

Chapter 2. Tidal Area Features and Natural Processes

Minor elements Many of the elements in the Periodic Table are present in seawater as minor and trace elements and they are not as conservative as the major ones because of their greater geochemical and biological reactivity involving adsorption and biological uptake which occur at low chemical concentrations. Among them, the micronutrient elements N, P, Si, and Fe are essential for biological production in the ocean so the abundance of minor elements is controlled by horizontal and vertical circulation and by biogeochemical processes of utilization and regeneration. Those processes that may affect their distribution may be: (1) riverine input, (2) atmospheric deposition, (3) volcanism, (4) biological ingest and decomposition, and (5) chemical adsorption and desorption. The sum of all the processes, a kinetic (changing) balance, determines seawater chemistry. Dissolved gases in seawater The gas content in seawater can also be conservative or non-conservative, and it reflects the interaction among physical, chemical, and biological processes in the oceans and coastal environments. Table 2.4.3 shows the gases commonly found in seawater related to the above processes. Table 2.4.3 Gases found in seawater Biologically related gases

O2, CO2

Gases with regular distribution, conservative

Noble Gases: Ne, Ar, Kr, Xe

Gases with unusual distribution

He, Rn

Other non-conservative gases

CO, H2, H2S, CH4, N2O

Atmospheric gases contribute the most to the dissolved gas in seawater. Table 2.4.4 lists the percentage of gases in air and in seawater equilibrated with air based on the total gases dissolved. Solubility of gases varies, with the temperature and salt content of sea water determining these percentages. Excluding water vapor, three gases make up 99.96% of air: nitrogen, oxygen, and argon. Compared to nitrogen, there are significantly greater amounts of oxygen and argon dissolved in equilibrated sea water. The noble gases helium, neon, argon, krypton, and xenon are chemically un-reactive. Thus, their concentrations in sea water result from a number of physical factors. The solubility of a pour gas in a liquid is usually expressed in terms of the Bunsen coefficient (α). This is a volume of the gas at S.T.P. which can be dissolved by unit volume of the liquid, at a given temperature under a gas pressure of 1 atm.

61

Table 2.4.4 Gases in air and dissolved in seawater at equilibrium with atmosphere Gas

Chemical symbol

in Air (%)

in Seawater (%)

Nitrogen

N2

78.08

62.6

Oxygen

O2

20.95

34.3

Argon

Ar

0.934

1.6

Carbon Dioxide

CO2

0.033

1.4

Neon

Ne

0.0018

0.00097

Helium

He

0.00052

0.00023

Methane

CH4

0.0002

0.00038

Krypton

Kr

0.00011

0.00038

Carbon Monoxide

CO

0.000015

0.000017

Nitrous Oxide

N2O

0.00005

0.0015

Xenon

Xe

0.0000087

0.000054

(Data source: http://www.waterencyclopedia.com/Re-St/Sea-Water-Gases-in.html)

Oxygen Marine plants such as phytoplankton, seaweed, and other types of algae produce organic matter from carbon dioxide, release oxygen and nutrients through photosynthesis. The general equation for photosynthesis is: CO2 + 2 H2A + photons → (CH2O)n + H2O + 2A carbon dioxide + electron donor + light energy → carbohydrate + oxygen + oxidized electron donor Since water is used as the electron donor in oxygenic photosynthesis, the equation for this process is: CO2 + 2 H2O + photons → (CH2O)n + H2O + O2 carbon dioxide + water + light energy → carbohydrate + oxygen + water The vertical and horizontal distributions of oxygen in the oceans reflect a balance between: (i) input across the air-sea interface from the atmospheric; (ii) physical transport; (iii) biological processes. The various factors that control the distribution of dissolved oxygen in the sea leads to a number of pronounced features in its vertical profiles. Oxygen plays a very active role in the chemistry and biology of coastal waters, and its concentration is a major indicator of water quality. In many 62

Chapter 2. Tidal Area Features and Natural Processes

areas of the world, large quantities of nutrients enter coastal waters from domestic wastes and agricultural fertilization. These nutrients stimulate the rapid growth of phytoplankton. Once the organic matter produced from these nutrients settles into the bottom waters of bays and estuaries, its decomposition can deplete the waters of oxygen. The result can be fish kills and the formation of hydrogen sulfide gas (H2S), which is poisonous to many types of marine creatures. Nitrogen Nitrogen is an essential nutrient required in biological processes. Only nitrogen in forms of nitrate (NO3−) or ammonia (NH4+) can be useful nutrients for most photosynthetic organisms. While the biological cycling of nitrogen is very important in the ocean, it has only a slight effect on the amount of nitrogen gas in seawater. The nitrogen cycle is the biogeochemical cycle that describes the transformations of nitrogen and nitrogen-containing compounds in nature. It is a cycle which includes gaseous components. Carbon Dioxide Carbon dioxide (CO2) gas has solubility in seawater far greater than one would expect from its molecular weight. CO2 is considered a trace gas in the atmosphere because it is much less abundant than oxygen or nitrogen. However, this trace gas plays a vital role in sustaining life on Earth and in controlling the Earth’s climate by trapping heat in the atmosphere. Because CO2 can move quickly into and out of the oceans, the oceans play an important role in regulating the amount of CO2 in the atmosphere. Once in the oceans, the CO2 no longer traps heat. CO2 also moves quickly between the atmosphere and the land biosphere (material that is or was living on land). However, from a biological standpoint, carbon dioxide is one of the most important gases, and it has the following reactions when it is dissolved in seawater: CO2 (g) + H2O → CO2 (s) + H2O CO2 (s) + H2O → H2CO3 H2CO3 → HCO3- + H+ HCO3- → CO32- + H+ The absorption of carbon dioxide (CO2) into the oceans increases the concentration of hydrogen ions, ([H+]), within ocean water. This is the result of an initial reaction between water (H2O) and CO2 that forms carbonic acid (H2CO3). In fact, the relative concentrations of CO2 (1%), bicarbonate ion HCO3- (91%) and carbonate ion CO32- (8%) control the acidity (pH) of the oceans. pH is a frequently used parameter in chemical oceanography and agriculture especially in describing the carbonate system. Since CO2 is an acid gas, the uptake of anthropogenic CO2 exhausts carbonate ions and lowers the oceanic pH value. 63

If global emissions of CO2 from human activities continue to rise at current levels then the average pH of the oceans could fall by 0.5 units by the year 2100 (Royal Society, 2005). This value is probably lower than has been experienced for hundreds of millennia and, critically, this rate of change is apparently one hundred times greater than at any time over this period. The scale of the changes may vary regionally, which will affect the magnitude of the biological effects. Thus, reducing CO2 emissions to the atmosphere appears to be the only way to minimize the risk of large-scale and long-term changes to the oceans. Oysters can help reduce CO2 emissions. Australian scientists have claimed that oysters could play a significant role in helping reduce carbon emissions. New research carried out by a team at the University of South Australia concluded that, given that oysters make use of carbon from the world’s seas and oceans to grow their shells, investing in the oyster industry could be a feasible way for businesses to offset their carbon emissions. Nutrient elements An organism’s metabolism requires nutrients from the environment to grow. Organic nutrients include carbohydrates, fats, proteins (or their building blocks, amino acids), and vitamins. Inorganic chemical compounds such as minerals, water and oxygen may also be considered nutrients. Nutrients needed in relatively large quantities are called macronutrients and those needed in relatively small quantities are called micronutrients. The chemical elements consumed in the greatest quantities Table 2.4.5 Nitrogen ions, phosphate and silicate concentration in marine and coastal water (in μM) (after Wei, 1988) Element

Nitrogen ions

Phosphate

Marine

Nitrate

Nitrite

Ammonium

environment

(NO3 )

(NO2 )

(NH )

or SiO2

Oceanic

0.05

0.03

0.1

1.0 ~ 5.0

-

-

PO43-

Silicate

+ 4

Maxima from

Si(OH)4

surface

1.0 ~ 3.0

Oceanic deep

15 ~ 45

0.03

0.05

15 ~ 45

125 ~ 170

Coastal

0.1 ~ 15

0.1 ~ 1

0.1 ~ 10

0.3 ~ 10

1 ~ 25



(sometimes 0.05)

Estuarine

0.3 ~ 30

0.1 ~ 200

0.1 ~ 25

0.1 ~ 200

(general)

(rarely to 15)

Natural

1 ~ 150

10 ~ 20

NA

1 ~ 10

1 ~ 3

100 ~ 250

100 ~ 300

NA

50 ~ 1000

100 ~ 250

100 ~ 400

estuaries Urban s estuarie NA: not available 64

Chapter 2. Tidal Area Features and Natural Processes

by plants are carbon, hydrogen, and oxygen. These are present in the environment in the form of water and carbon dioxide; energy is provided by sunlight. Nitrogen, phosphorus, potassium, and sulfur are also needed in relatively large quantities. As with land plants, marine phytoplankton also require certain trace elements for healthy growth. The most important of these nutrients are nitrogen, phosphorus and silicon and their concentration ranges in marine water (Wei, 1988) are summarized in Table.2.4.5. 2.4.2 COASTAL WATER CHEMISTRY

The coast is defined as that part of the land adjoining or near the ocean. Coastal waters are a bridge between estuaries and the open ocean. Coastal water, with abundant nutrients, organics, and metals, is chemically more heterogeneous than oceanic seawater. Chemical concentrations occur on a gradient in coastal waters, varying according to the input of terrestrial materials and the dilution of water offshore. Estuaries may contain many biological niches within a relatively small area, and so are usually associated with high biological diversity. The estuarine environment •

Estuaries are mixing zones, with salinity gradients ranging from coastal seawater (normally 30~35 0/00) to freshwater (0 0/00)

•

Estuaries are corridors for the transit of terrigenous (land-derived) and anthropogenic (humanorigin) chemicals

As noted above, estuaries are bodies of water typically found where rivers meet the sea. Estuaries and their surrounding coastal habitats shelter unique plant and animal communities because their waters are brackish — a mixture of fresh water draining from the land and salty seawater. In general, if river water contains few ionic elements, estuarine water will be diluted by seawater with the same constant ratio of major constituents to chlorinity and salinity. Salinity The mixture of seawater and fresh water in estuaries is called brackish water and its salinity can range from 0.5 to 35 0/00. The salinity of estuarine water varies from estuary to estuary, and can change from one day to the next depending on the tides, weather, or other factors (Levinton, 1995.) In estuaries, salinity levels are generally highest near the mouth of a river where the ocean water enters, and lowest upstream where freshwater flows in. Actual salinities vary throughout the tidal cycle, however. Salinity levels in estuaries typically decline in the spring when rain or snowmelt increases the freshwater flow from streams and groundwater. Salinity levels usually rise during the summer when higher temperatures increase levels of evaporation in the estuary. 65

Nutrients in natural and urban estuaries As shown in Table.2.4.5, natural and urban estuaries without and with major agricultural, municipal or industrial inputs, nutrients in upper estuary (zero salt) have maximum concentrations. The mixing pattern of conservative and non-conservative nutrients in estuarine water constituents is shown in Fig. 2.4.2. As shown, both nitrates and silicates have conservative properties and their concentrations are shown as the linear line, decreasing as the salinity increases. However, other chemicals, like phosphates, in urban estuaries have source concentration characteristics as shown in the figure. Concentrations of these other chemicals increase in the beginning with very low salinity and decrease if the salinity in the estuary is greater than mesohaline scale (around 5~18 0/00 shown between the gray lines). In brief, the estuarine area is an important interface for transporting inland substances to the ocean. Organic matter and nutrients make the estuary a very productive ecosystem. Estuarine water quality can be significantly affected by the tidal cycles due to the discharge of pollutants from waterways to the coastal area during ebb tides (Gyung & Soung, 2000). Additionally, estuaries and tidal flat areas are subject to tidal influences and exhibit great variation in water quality. For this reason, poor water quality has been generally observed in tidal flats due to the discharge from inland origins. For example, the maximum to minimum ratios of ammonia nitrogen, coliform groups, and zinc in one sampling station during a tidal cycle reached up to 114, 944, and 23 times, respectively (Chen et al., 2004). Water quality can be significantly affected by the discharge of pollutants from estuaries to coastal areas during ebb tides. If the tidal conditions are not considered during sampling, there will be great variations in monitoring data for samples taken at different times and locations. Therefore, marine water sampling should be planned carefully to include tidal conditions.

Fig. 2.4.2 Conservative and non-conservative mixing curves of estuarine water (Wei, 1998) 66

Chapter 2. Tidal Area Features and Natural Processes

Marine pollution problems The oceans are becoming increasing polluted as a result of human activities, either incidentally, or as a direct result of deliberate disposal of waste products (Føyn, 1965; Sibthorp, 1969). In fact, harmful levels of pollution are frequently reached in bodies of water which have only limited exchange with the sea, e.g. tidal areas of estuaries and bays. Even in coastal waters with more open circulation, the discharge of effluent or oil may have severe effects. More than that, most of the marine pollution problems lie in the coastal zone, where oil spill accidents, sewage and industrial waste discharges, and commercial developments are changing the composition of the coastal zone. Oil spills and other threats Human dependence on oil, particularly imported oil, results in greater potential contamination of the marine environment. According to U.S. National Research Council (2002) estimates, about 3.2 million tons of oil enters the sea annually from different sources. About 8% of that total comes from natural seepages through the Earth’s crust, four times the amount spilt as a result of oil exploration and production. The biggest single contributor of petroleum incursion into the sea is from urban and industrial inputs while accidents and discharges involving shipping and tankers are the next largest source. Marine ecosystems and water quality are affected by oil generally in the same way as by other marine pollutants. How do oil spills affect the coastal environment? Oil spills can have numerous adverse influences on marine life in coastal environments where estuaries, wetlands, bottom sediments, and recreational activities are concentrated. The severity of damage depends on the type and amount of oil spilled, wind, wave, current and tidal conditions, and other environmental factors. Environmental damage from oil spills could be significant in an estuarine area. Oil contains substances, such as 3, 4-benzpyrene, which have been proven to cause cancer. When marine organisms ingest these hydrocarbons, they may retain and transfer these toxic substances to their predators, which causes danger to commercial fisheries and human consumers. In addition, oil slicks on surface water can decrease light penetration and air-sea oxygen exchange. When a crab, for instance, becomes coated with oil, it asphyxiates. In general, marine communities closer to shore and younger life forms are probably more easily affected. Oil can destroy marine plankton and contaminate marshes and other highly productive estuarine areas. If a spill were to occur in a river, for example, rapid currents and the tidal energy of the estuaries would cause oil to spread rapidly. When oil accumulates on shore, it is not easily removed by natural wave and tidal forces. Low-energy environments (tidal flats, marshes) are most susceptible to longterm damage; wave-pounded rocky coasts are less vulnerable. However, when an oil spill accident occurs, combining remediation and restoration planning to promote timely, effective, and efficient protection and restoration of degraded coastal resources is very important.

67

Nutrient pollution of the coastal ocean The inputs of sewage, with its high content of organic matter and nitrogen and phosphorus compounds, into coastal water produces two effects; one is the depletion of dissolved oxygen, and another is algal bloom. Bacterial oxidation of organic constituents may cause the oxygen content of the water to decrease to almost zero, a level that will not support life. In extreme instances the oxygen may be completely exhausted and the formation of toxic hydrogen sulfides will then occur. The abundance of micronutrient elements, arising from the sewage, is supplemented by phosphorus from any detergents present in domestic waste waters and encourages the explosive proliferation of plankton in the waters (eutrophication). Eutrophication stimulates an explosive growth of algae (algal blooms) that depletes the water of oxygen when the algae die and are decomposed by bacteria. The rapid decay of these organisms at the end of the bloom further decreases the oxygen content of the water and may render it toxic. In this manner, estuarine waters may become hypoxic (oxygen poor) or anoxic (completely depleted of oxygen) from algal blooms. While hypoxia may cause animals in estuaries to become physically stressed, anoxic conditions can kill them all. In the United States, nutrient pollution is the single largest pollution problem affecting coastal waters. Over 60 percent of the coastal rivers and bays in the United States are affected, moderately to severely, by nutrient pollution (Howarth et al., 2000). To sum up, coastal areas, particularly estuaries are some of the most productive ecosystems in the world. Many animal species rely on estuaries for food and as places to nest and breed. Human communities also rely on estuaries for food, recreation and jobs. Unfortunately, human activities have led to a decline in the health of estuaries, making them one of the most threatened ecosystems on Earth. Participants in coastal projects have a responsibility to understand the characteristics and processes of coastal zones so that efforts to maintain and restore healthy ecosystems are successful.

2.5 Biological Features

Authors: Jiang-Ping Wang; Chia-Yang Tsai

This subsection shall give a survey of different types of life forms in the tidal area ranging from microbes to invertebrates to mammals, the interactions between them, and some threats to them (Wang, et al., 2009). The purpose is to provide planners and designers some important biological background so it can be useful when they participate in interdisciplinary or integrated sustainable coastal region projects. 2.5.1 MARINE ECOLOGY

Marine ecology is the branch of ecology dealing with the interdependence of all organisms living in the ocean, in shallow coastal waters and on the seashore. The marine environment for all organisms 68

Chapter 2. Tidal Area Features and Natural Processes

consists of non-living, abiotic factors (geological, physical, and chemical) and living, biotic factors. The biotic factors are the interactions among living organisms. Zonation The pelagic zone Water in the sea that is not close to the bottom or near to the shore is in the pelagic zone. Organisms living in pelagic waters are specifically adapted to the salinity levels, cooler temperatures, and pressures, especially at depth, of the open sea. The neritic zone The neritic zone, also called the coastal ocean and sublittoral zone contains plant plankton, fish larva, invertebrate larva, most of which will be distributed near the coast by wind and currents. The benthic zone The benthic zone refers to the material located at the lowest levels of a body of water, such as an ocean or lake. Organism in the benthic zone is either burrow, crawl, walk (motile) or sessile (anchored to a surface). The sediment substrate can be a source of food. 2.5.2 TIDAL LAND ECOSYSTEM

Zonation The intertidal zone refers to land that is exposed to air at low tide and is underwater at high tide. Tidal zones can include beaches, rocky cliff faces, and mud flats. The water can range from fresh to highly saline and the substrate over which the water flows can range from fine sediment to rocks. Food Web The trophic structure is a complicated web of feeding relationships and competition. Many of the animals are not predators but deposit feeders, filter feeders, or scavengers. Because of a relatively small number of predator/prey relationships, the numbers of mud-dwelling organisms can increase dramatically. The food webs involve the influx of animals from adjacent ecosystems. The birds that use the mudflats feed primarily on amphipods and clam worms. 2.5.3 COMPOSITION OF TIDAL LAND ECOSYSTEM

Tidal land is a highly dynamic and productive ecosystem. The metabolic cycle and the material exchange processes of this zone are rapid (Yáñez-Arancibia, 2004). Fig. 2.5.1 shows the basic 69

elements of the intertidal mudflat ecosystem. Shorebirds, benthic fishes or other predators, and sediment are the three main components. Each component exists co-dependently with the others. The most abundant and common predators are shorebirds and some benthic fishes. However, during

Fig. 2.5.1 Interaction between the three components of intertidal mudflat ecosystem

low tides, benthic fishes are inactive and seldom are seen. Additional parts of this environment are marcobenthos, large organisms such as stony coral and sea grass that live along the bottom of the water. The population sizes and annual variations of benthic fishes are more difficult to monitor than of shorebirds. Therefore, the following sections present the relationship among three components will be focused on the birds and their macrobenthos prey and living environment. 2.5.4 CHARACTERISTIC BIOLOGICAL FEATURES OF THE TIDAL AREA

The organisms that live in tidal area are often unseen because they shelter in the mud. Organisms that can tolerate exposure to sun and air occur at the upper levels of the intertidal zone; those less tolerant of exposure prefer the lower levels of the zone. Mudflats support great numbers of a rather limited variety of invertebrates. 70

Chapter 2. Tidal Area Features and Natural Processes

Animals and plants living in a habitat dominated by mud have developed a range of adaptations to deal with factors such as a high sediment load and extended exposure to sun, wind, and rain. Trophic (feeding) relations Energy transfer is accomplished in a series of steps by groups of organisms known as autotrophs, heterotrophs, and decomposers. Each level on the pyramid represents a trophic level. Autotrophs absorb sunlight energy and transfer inorganic mineral nutrients into organic molecules. The autotrophs of the marine environment include algae and flowering plants and in the deep sea are chemosynthetic bacteria that harness inorganic chemical energy to build organic matter. Food production occurs mainly through photosynthesis. It is measured and called primary production which will occur in the photic zone as phytoplankton manufacture organic matter during photosynthesis. Autotrophic nutrition Autotrophic nutrition supply food molecules to organisms that can’t absorb sunlight. Heterotrophic nutrition Consumers that must rely on producers as a source of energy. Decomposers The final trophic level that connects consumer to producer is that of the decomposers. They live on dead plant and animal material and the waste products excreted by living things. The nutritional activities of these replenish nutrients that are essential ingredients for primary production. Scavengers Feed on dead plants and animals that they have not killed. The dead and partially decayed plant and animal tissue and organic wastes from the food chain are detritus. This contains an enormous amount of energy and nutrients. Many filter feeding animals use detritus as food. Saprophytes decompose detritus completing the cycle. Crabs ripping chunks of flesh from fish on the beach are scavengers. Most scavengers consume detritus rather than flesh. Symbiotic Symbiotic refers to close nutritional relationship between two different species. •

commensalism- one benefits

•

mutualism - both benefit

71

2.5.5 HABITAT CHARACTERISTICS AND SPATIAL DISTRIBUTION OF MACROBENTHOS

Most of the macrobenthos are detritivores or filter-feeding, such as bivalves, fiddler crabs, and polychaetes. They feed on the phyto- and zoo-planktons or organic matters by filtering the sea water or by scratching the sediment into their digestive systems. Due to the physiological adaption and specialization, various benthos species using different part of intertidal mudflats, therefore, spatial distribution of macrobenthos is a gradient along the different sediment types. For example, Hardclam Meretrix lusoria lives near the surface of sandy flats with shallow water (Fig. 2.5.2 a) but Cyclina sinensis (Fig. 2.5.2 b) lives in the deeper and organic-rich mudflats. Some of the fiddler crabs Uca chlorophthalmus crassipes (Fig. 2.5.3 a) and Uca vocans borealis (Fig. 2.5.3 b) prefer living on muddier flats and high vegetation coverage; on the other hand, Uca formosensis (Fig. 2.5.3 c) prefer living on the sandy mudflats at the high tide zone. Thus, the spatial distribution or zonation of macrobenthos can reveal the sediment characteristics of an intertidal mudflat. Polychaetes (sand worms) are another important macrobenthos population in the intertidal mudflats. Polychaetes live down deep in the sediment, and scratch the mud from the surface as their food sources. Some of the polychaetes are red and large (Fig. 2.5.4 a), some of them are green and small (Fig. 2.5.4 b).

(a) Hardclams Meretrix lusoria

(b) Cyclina sinensis

Fig. 2.5.2 Hardclams live near the surface of tidal land, the other clams live deeper within organic-rich tidal flats.

(a) Chlorophthalmus crassipes

(b) Vocans borealis



Fig. 2.5.3 Uca chlorophthalmus crassipes and vocans borealis

72

(c) Male & female formosensis

Chapter 2. Tidal Area Features and Natural Processes

Fig. 2.5.3 Uca chlorophthalmus crassipes and vocans borealis preferred living in the mudier flats; also shown are the male and female Uca formo sensis, which prefer living in sandy mudflats.

(a) Red and large polychaetes

(b) Green and small polychaete

Fig. 2.5.4 Red and green worms

Food chain, food web and trophic level The energy stored in the organic molecules is passed to consumers in a series of steps of eating and being eaten and is known as a food chain. Each step represents a trophic level and the complex food chain within a community interconnects and is known as a food web. Each chain or part of the web serves to link phytoplankton to larger animals through the zooplankton. Plankton Plankton comprises the large and small organisms that drift or float while tides and currents move them through the water. Most plankton do have a limited ability to move and can migrate vertically through the water from day to night. Some drifters can photosynthesize while others are consumers. Plankton is very important as it occupies the first two or three links in the marine food chain. Phytoplankton Phytoplankton is the important primary food producers in the pelagic environment. Phytoplankton is the trees of the sea which float near the surface to make the most of the sunlight for photosynthesis. The nutrients can be considered a limiting factor as well as pH, temperature, light, depth salinity, nesting sites and predation. Silicoflagellates and blue-green algae are abundant in the coastal water. Benthic microalgae are in the sediments of the mudflat. All of these survive in the top layer of mud where oxygen and light will allow them to photosynthesize. Thirty-five attached diatom taxa were identified from the Szu-Tsao mangrove wetlands, in southwestern Taiwan, and mainly were divided into eight dominant or codominant diatom groups. The eight groups in these wetlands were (1) Achnanthes spp. including A. brevipes and A. exilis, (Fig. 2.5.5 a&b) (2) Amphora spp. including A. granulata, A. holsatica, A. normanii, A. exigua and A. strigosa, (3) Cocconeis spp. including C. 73

placentula var. euglypta and C. scutellum, (4) Mastogloia exigua, (5) Haslea sp., (6) Navicula spp. including N. angusta, N. cryptocephala var. veneta, N. cincta and N. margalithii, (7) Pleurosigma normanii and (8) Nitzschia longissima. Mangrove dominant diatoms act as bioindicators of water condition, for example, Amphora spp, Navicula spp. and Pleurosigma normanii were regarded as the most adapted to the pH value from 7.4 to 9.0.

a

b

c

d

(a) Achnanthes brevipes C.Agardh

(c) Amphiprora surirelloides

(b) Achnanthes exilis Kütz;

(d) Euglena sp. (Lai).

Fig. 2.5.5 Examples of wetland diatom and microalgae

a)

b)

c) a) Ulva lactuca b) Enteromorpha intestinalis c) Cladophora albida d) Ulothrix flacca e) Gracilaria tenuistipitatavar. liui – Red alga (Courtesy of Lai)

d) Fig. 2.5.6 Examples of macroalgae species in tidal area 74

e)

Chapter 2. Tidal Area Features and Natural Processes

Wave action and currents are not as prevalent on the mudflat so a number of green macroalgae species can often be found in extensive mats. Most often found are those species that can tolerate lots of fresh water, such as Ulva, Enteromorpha (Order Ulvales), Cladophora (Order Cladophorales), Ulothrix (Order Ulotrichalesn) and Gracilaria (Order Gracilariales), see Fig. 2.5.6 a-e. Zooplankton The zooplankton ranges from the microscale creatures, e.g. Difflugia sp (Fig. 2.5.7 a), Zoothamnium sp. (Fig. 2.5.7 b), Rotifera (Fig. 2.5.7 c) to the mesoscale jellyfish. Almost any animal phylum can be found wandering through the sea but the most common are rotifer and copepods. Many of the animals have planktonic stages in the early part of their life history. Therefore, at specific times the water covering the mudflats will be filled with very young molluscs, crustaceans, and worms.

a) Difflugia sp.



b) Zoothamnium sp. .

Fig. 2.5.7 Examples of microscale zooplankton



c) Brachionus plicatilis (Rotifera)

Nekton Nektons are free swimming organisms equipped to direct their movements through the sea, including cephalopods, fishes, marine mammals, and marine birds. Nektons use fins, jets of water, strong flippers, and flukes to swim through the water. Many are at the top of the trophic levels either as carnivores or herbivores without natural predators except man. Swimming allows escape or movement toward food and methods of locomotion are very diverse. Plants Salt marsh and mangrove Many mudflats are associated with salt marshes and estuarine habitats. A salt marsh (Fig. 2.5.8 a) is a type of marsh that is a transitional intertidal zone between land and salty or brackish water (e.g. estuaries). It is dominated by halophytic (salt tolerant) herbaceous plants. The daily tidal surges bring in nutrients, which tends to settle in roots of the plants (e.g. mangrove, Fig. 2.5.8 b) within the salt marsh. 75

a) Suaeda nudiflora .



b) Mangrove

in Salt marsh

.

c) Phragmits australis (Cav.) Trin ex Steud (Rotifera)

Fig. 2.5.8 Example of Plants in salt marsh and tidal area

Molluscs Molluscs are especially abundant on the mudflats. Stenothyrid species, Fig. 2.5.9, are small to medium-sized operculate gastropods. Members of the family are found throughout East Asia, IndoMalaya and Iran. In Taiwan, the family is found in the inland marshes and lagoons where they typical live in temporary ponds, swamps and sluggish streams.

(a) Stenothyra chilkaensis Preston

(b) Stenothyra edogawensis miyadii Kuroda

(c) Stenothyra edogawensis tanabensis Kuroda (Courtesy of Ueng).

Fig. 2.5.9 Stenothyrid species at mudflats 76

Chapter 2. Tidal Area Features and Natural Processes

Fronsella taiwanica (Ueng and Wang 1999) is a species living in Taiwan. Adults and juveniles inhabit sand, mud, or muddy sand flats near the low-tide levels in channels, mangroves, and estuaries. The juveniles Fronsella taiwanica appear in the winter. The thiarids are parthenogenetic and viviparous, and rely on passive dispersal for colonization of new habitats. Immature snails released from the adult begin their lives in close proximity to their parents and siblings. Thiara (Sermyla) riqueti (Fig. 2.5.10 a) is a dominant species snail belonged to Thiaridae, Mesogastropoda found at the Su-Tsao estuary. This species are distributed throughout the world from the western coast of India, to Southeast Asia, Malaysia, Australia, the Philippines, China, Taiwan and the Ryukyu Islands of Japan. In Taiwan, T. riqueti is euryhaline and the most abundant snail in fresh waters of streams, ponds, irrigation systems and the hard substrate intertidal community. This small shell is a deposit feeder and has been counted in densities of up to 3.00/m2.

(a) Thiara (Sermyla) riqueti (Grateloup)

(a) Ercolania boodleae (Baba)

(a) (c) Eolis gracilis (Courtesy of Ueng)

Fig. 2.5.10 Example of Thiaridae and snail

Crustaceans The most important inhabitant of the mudflat is the small tube-building amphipod. This amphipod is the major source of food for the hundreds of thousands of sandpipers and plovers that use the mudflats as their staging area before migration. It can be found sporadically in mudflat areas as can the isopod. Oithona sp. and Schmackeria dubia (Kiefer) are the most popular species of copepod on the southeast coast. 77

(a) Strandesia sp.

(b) Schmackeria dubia (Kiefer)

(a) Ercolania boodleae (Baba) (c) Uca arcuate

(c) Mictyris brevidactylus

(c) Macrophthalmus banzai

Fig. 2.5.11 Examples of Crustaceans species in tidal area

Worms Worms make up the most diverse group of organisms in muddy intertidal areas. The abundance of these mud burrowers has made these areas internationally important for shorebirds. The most common worms are segmented annelid polychaetes. The polychaetes may be deposit feeders, scavengers, or predatory carnivores. Burrowing polychaete worms, living in mudflat intertidal areas, are extremely abundant. Common on mudflats are Chironomus spp. and sand worms in saltpans. Fish Fish are visitors to mudflats, using them at high tide to search for food. A number of telapia fish feed on the abundant molluscs and amphipods living in the mud. 2.5.6 HABITAT REQUIREMENT OF SHOREBIRDS

The birds that live near the coastal and adjacent area are shorebirds, such as Eurasian Curlew, Kentish Plover (Fig. 2.5.13 a, b), Moorhen (Fig. 2.5.13 c) and Grey Heron (Fig. 2.5.13 d). They prefer feeding on the intertidal mudflats and ponds; sometimes they are called wading birds. Most of the shorebirds are migrants, moving between breeding and wintering grounds every year. They 78

Chapter 2. Tidal Area Features and Natural Processes

(a) Acanthopagrus schlegeli

(b) Oreochromis hybrid

(a) Liza sp. Fig. 2.5.12 Fish- mudflat visitors

breed on grasslands in Arctic area during the spring, and fly down to the southern hemisphere during the winter. Therefore, shorebirds need three kinds of habitat to meet their requirements. 1) Feeding ground There are many types of feeding grounds available for shorebirds, such as intertidal mudflats (Fig. 2.5.14 a), rice fields (Fig. 2.5.14 b), fishery farms (Fig. 2.5.14 c). Energy balance (intake and expenditure) is the most essential for any living bird. Birds must ingest sufficient food to satisfy their energy requirements during a 24-hr cycle (Fig. 2.5.15). Therefore, the habitat quality of feeding grounds is a determining factor that attracts shorebirds. Higher quality of feeding ground area indicating the higher density and higher success rate of feeding benthos, the birds can acquire their energy as soon (higher intake rate and short foraging time) as possible. However, the loss of feeding area is very fast and easy due to human disturbance and industrial development by means of land reclamation (Fig. 2.5.16). The massive feeding ground losses along the migratory staging sites and wintering sites is the key factor that causes the shorebird population decline. Meanwhile, destruction is faster than restoration of feeding grounds. Though the restored processes are slow, and will not be as good as the natural ones. 79

(a) Eurasian Curlew Numenius, arquata, a large Scolopacidae species

(b) Kentish Plover Charadrius alexanderius, a small Charadriidae species

(c) Moorhen

(d) Great Egret and Grey Heron

Fig. 2.5.13 Examples of shorebirds

(a) Intertidal mudflat .

(b) Rice fields

Fig. 2.5.14 types of feeding ground for shorebirds

80

.

c) Fishery farms

Chapter 2. Tidal Area Features and Natural Processes

2) Breeding ground Most shorebirds breed on the ground (Fig. 2.5.17 a, b), except Egrets (Fig. 2.5.17 c) and Storks. They prefer nesting on the short grass, gravels and pebble grounds (Fig. 2.5.17 d). Breeding seasons begin in April and end in August. The hatching period is 20~28 days, depending on the bird species. The hatched chicks (Fig. 2.5.17 e) are well-feathered and their eyes are open, enabling them to walk and quickly feed themselves. The breeding habitat is not always the same as the feeding ground, because the parents will lead the chicks from the nesting site to the feeding site. Rainfall, human disturbance and predators (Fig. 2.5.17 f ) are the most important factors to affecting the breeding success rate.

Fig. 2.5.15 Theoretical energy requirement of a living shorebird based on its basal metabolic rate (Evans, et al., 1992; Kersten and Piersma, 1987)

Fig. 2.5.16 Massive loss of intertidal mudflat due to the reclamation of industrial park development 81

3) Roosting ground During the winter or non-breeding seasons, shorebirds feed in the intertidal zone, fly inland to roost, and reverse the process between tidal periods. Birds must find a roost site where they can stay up to 3 hours after the tide begins to ebb. Hundreds or thousands of shorebirds can flock together to reduce the predation risk. This is referred to as communal roosting behavior. Shorebirds can easily find roosting habitats, such as fishery banks (Fig. 2.5.18 a) and rice fields (Fig. 2.5.18 b). However, disturbance by humans and wild dogs (Fig. 2.5.18 c) are the key factors affecting the quality of roosting habitat.

(a) Nest and eggs of Kentish Plover

(b) Black-winged Stilt hatching on its nest

(c) Little Egret’s nest

(d) Gravels and pebble grounds

(c) Moorhen

(e) Black-winged Stilt chick

(f ) Main threat of breeding birds

Fig. 2.5.17 Examples of breeding grounds of shorebirds 82

Chapter 2. Tidal Area Features and Natural Processes

(b) Rice fields

(a) Intertidal mudflat .

.

c) Fishery farms



Fig. 2.5.18 Shorebirds roosting habitat and disturbance

2.5.7 INTERACTION BETWEEN SHOREBIRDS AND MACROBENTHOS

The quality of feeding habitat is the most important factor for determining whether shorebirds decide to stay or not. The higher the density of available benthic prey, the more likely that the birds will stay. Shorebirds feed on different types of benthos, depending upon morphological features, such as bill types, feeding behaviors, and body size. Bill types Different shapes of bill determine the available prey they consume and different feeding behaviors. There are three main types of bill type: (1) short and straight (Fig. 2.5.19 a), used pecking; (2) down-curved, use for as probing (Fig. 2.5.19 b) and (3) upward (Fig. 2.5.19 c), used as a scythe.

(a) Greater Sand Plover with

(b) Curlew Sandpiper with

(c) Avocet with upwardly-

short and straight bill

long- & down-curved bill

curved bill.

Fig. 2.5.19 Different shapes of bill determine different feeding behaviors

83

2.6 Case Studies 2.6.1 CASE 1: MIGRATION AND RESERVE PROTECTION OF BLACK FACED SPOONBILL

The Black-winged stilt (Himantopus himantopus Linnaeus, 1758) is one of several waders which is distributed in Eurasia and Africa. In Taiwan, black-winged stilt is a migrant and/or a resident bird, primarily found in the saltpans of the southeast coast of Taiwan. During breeding season, birds breed in saltpans during April to September. The female mates with one male and lays eggs which is a typically monoandrous mating system. The chicks remain in the nest area under the parent’s care for 6~7 weeks before fledging. From an ecological viewpoint, saltpans serve as a good representative for studying the foraging ecology. The Black-faced Spoonbill (Platalea minor) is a large migratory waterbird. This breeds on the islands along the coast of the Yellow Sea of the Korean Peninsula and China between April and September. In the winter, black-faced spoonbills migrate to their wintering sites along the coasts of Japan, Taiwan, Vietnam, Macao, Hong Kong, and China. Taiwan is the biggest wintering site for black-faced spoonbill in the world. Now, over 50% of the population in the world regularly winters in the southwest coastal wetlands of Taiwan. In January, 2004, the total world population of black-faced spoonbills was around 1,200, so the species was endangered. Two years earlier, in December, 2002, 90 spoonbills contracted botulinus. Among these, 73 died and the other 17 were rescued, recovered, and were released. In Taiwan, therefore, the management of conservation areas and the foraging sites around the areas are of equal importance. Migration Shorebirds use the mudflats as staging areas, or as feeding areas, to build their energy levels for the long migratory flights. Birds have a very high metabolic rate, meaning that the rate at which they use up energy is very high. Thus, they have to eat great quantities compared to their body weight. Birds use mudflats for staging and resting during migration. The black-faced spoonbill’s main wintering sites are located in eastern Asia, including Japan, Korea, Mainland China, (Hong Kong, Macau, Hainan Island) Taiwan, Vietnam, Philippines, and Thailand. The known breeding sites only lie on the offshore islands along the western coast of the Korean peninsula and the Liau-Tung peninsula of mainland China. During the period of 1998~1999, Taiwan, Hong Kong and Japan cooperatively carried on a satellite-tracking program of the black-faced spoonbill. It was discovered that the northbound migration route of the black-faced 84

Chapter 2. Tidal Area Features and Natural Processes

spoonbill in Taiwan and Hong Kong area was along the eastern-south coast of China to the islands near the intersection of the North and South Korea. Every year, black-faced spoonbills fly to Taiwan in September ~ October, and back to the north in the month of March of the next year. Since 1991 up to now, the population of black-faced spoonbills coming to Taiwan for wintering has been increasing by the year. The main wintering site on Taiwan centers on the Tsengwen River Estuary, bordered by Sicao and to the north, by the salt field of Chiku. Black-faced spoonbills habitats include the mouth of the river to the sea, the abandoned fishpond, the wetland along the seacoast, and fallow farm land. The areas used by the Black-faced Spoonbills as habitats may serve as temporary sites while they migrate north or southbound. The Chiku conservation reserve of Tainan The Chiku area is rich in ecological resources. The government of Tainan County announced in October, 2002 that the main resting habitat and the eastern fishpond were important habitat sites for wildlife, totaling 634 hectares. In the month of November of the same year, it was announced that the Tsengwen River Estuary, the main resting habitat for the main cluster of Black-faced spoonbill was the wildlife refuge, totaling 300 acres (c. 121 hectares). Conservation organizations were established, promoting conservation and education about black-faced spoonbills. During the black-faced spoonbill wintering period, huge numbers of tourists have been attracted to watch the birds. Tourism has been an economic boost for the local economy. The Su-Tsao Wildlife Preserve of Tainan city extends from An Ping on the north and Lu Erh Men on the south, on the near shore of the former Tai Chiang inner sea. In 1823, a severe storm caused flooding that changed the course of Tsen Wen creek and deposited massive amounts of mud and sands from upstream. Over time, new tidal lands were formed. The original vast inner sea at SuTsao shrank; now, only Su Tsai Lake and An Ping Port remain. After a swamp formed at Su-Tsao District, part of the land was developed to create a fishery culture pond and a salt field. This allowed the man-made features and the natural wetland to coexist. This silted wetland along the southwest coast of Taiwan has high ecological value. Located between land and water, crab, fish, shrimp, shells and benthic creatures abound, providing an ideal habitat for many wild birds to stay and seek food. In addition, this area also serves as a key station for migratory birds from Southeast Asia to replenish their energy reserves during their migration. 85

In 1994, the Tainan Scientific & Industrial Park was established in Su-Tsao District. Responding to the urgent need for conservation, the Tainan City administration designated a zone of 515.1 hectares around the Park as a wildlife preserve. The interlacing trenches and waterways around the sanctuary are complemented by flourishing mangrove plants along both banks. The loss or destruction of the habitat The disappearance of habitat is the primary threat facing black-faced spoonbills throughout their range. The historical reasons that could explain the rarity of the species are still unknown. However, their survival is threatened by human-caused habitat destruction. Examples include the conversion of natural land into agricultural fields, fish ponds, shrimp and crab breeding ponds, garbage dumps, and industrial or residential developments. If the migratory route of the black-faced spoonbill passes through a military shooting range or other drill areas, the birds would face serious injury or death and their habitat may suffer additional damage. The destruction of the habitat may be caused directly by transferring habitat to commercial purposes. It can also be destroyed indirectly by pollution or when excessive silt washes into the area from developments built upstream or nearby. Changing the structure of the nearby sea coast and the estuary through activities such as the construction of dikes, dams, and water flow gates at the estuary and upstream, and sediment dredging of the river or nearby seabed, will all result in the severe erosion or silting up of the present habitats. 2.6.2 CASES OF USING TIME AND SPATIAL SCALES AUTHORS: INDRESWARI GURITNO; CHANJI LAI

This section describes how to use the spatial and time scales given in subsection 2.1.1 & 2.1.2 to examine (2) the 2004 Indian Ocean Tsunami impact and what should be considered in its impact studies, (3) the interaction among physical, biological and chemical processes and how to use them for practical evaluation: the San Francisco Bay estuary restoration project. Case 2: Survey of 2004 tsunami and its impact The Indian Ocean Tsunami On December 26, 2004, 00:58:53 UTC an earthquake at 3.94N, 95.94E measuring 9.0 on the Richter scale triggered an “unexpected tsunami”, named by NOAA as the December 26, 2004 Indonesia (Sumatra) Tsunami. It struck the coasts of Indonesia, the Andaman & Nicobar Islands, 86

Chapter 2. Tidal Area Features and Natural Processes

Sri Lanka, Maldives, Bangladesh, Burma, the west coast of Thailand and the east coast of India (Wikipedia 2010, Cocharda R., 2008). This tsunami was the worst single event in recorded history in terms of lives lost. There were over 230,000 fatalities and more than 51,000 injuries as well as devastating destruction and damage to natural resources, buildings and properties. Fig. 2.6.1 shows a simulation of the tsunami wave travelling through the Indian Ocean and it shows that the wave propagated with stronger strength in the east-west direction, because the 1,600 km subduction, strike-slip fault was oriented north-south. Moreover, the wide opening at the Indian Ocean allowed the waves to travel south and west and the first tsunami waves reached Struisbaai, South Africa and the Japanese gauge station (Syowa) in Antarctica, both around 9,000 km away, 12.5 hours after the earthquake (Titov, et al. 2005). The global chart presented by Titov also indicates that there were some energies transmitted via the Southwest Indian Ocean Ridge into the southern Atlantic Ocean or escaped into the Pacific Ocean, producing a 0.5~2m or 0.2~0.4m water level rise along the eastern and western American coasts respectively, after 20~28 hours of travelling time.

The Wave propagation Tsunami Research Group Klp Litbang Kelautan ITB, Kompas 30 12 04

Fig. 2.6.1 Satellite sensing in the coastal area of Sri Lanka, 26 December 2004, when the tsunami struck the coast; AP Photo / Digital Globe

Consideration of tsunami impact The above description shows that the travelling time of the first tsunami wave to the nearby and distant coasts was on the order of minutes to 1 day, and this covers the regions indicated by “2”, 87

“3”, and “4” in Fig. 2.1.1. Therefore, the tsunami which is generally considered as a solitary wave in this order may be pictured as a “Meso-T”, “Macro-S” to “Mega-S” solitary wave or a solitary wave travelling like a tide, since it demonstrated some features of tidal mechanics. Knowing the mechanism of the tsunami, Fig. 2.1.2, shows that within the Meso-T range the processes rendered in the physical process box are internal wave, vertical turbulence, horizontal turbulence, and fronts; in the biological box are physiological, behavioural and community responses; in the environmental box are bacteria and effluent (local); and in the transport & feature box are sediment path, beach/ shoreline change and sediment budget. It may be surmised that the tsunami impact on the area in the corresponding Meso-S at around 1m to 1km will have a mechanical structure similar to that of a front. At this Meso-T, the biological responses, such as the behavioural and population responses of phytoplankton are aroused and that promotes zooplankton behavior response. The biological community response shall act in the Macro-T scale so that an evaluation of the ecological impact should consider several years’ duration as a proper study period. Similarly, the impact studies should also look at some short-term and intensive observations to obtain baseline data of the local effluent, sediment transport, sediment budgeting and beach profile change by the tsunami impact (Kume et al., 2009; Saravanan et al., 2009), and long-term, large district investigations at Macro to Mega scales to evaluate its overall influence. In addition to the impact studies, there are many more urgent considerations such as rescue, hygiene, health and medical issues, and allocations of financial, economic, and social assistance to refugees and districts that need to be done after a disaster in this scale. Many organizations and individuals from different backgrounds have participated in all or parts of the above-mentioned activities (Cochard et al., 2008, Birkmann et al., 2008; Renaud et al., 2010). Illustrations like those presented in Figs. 2.1.1 & 2.1.2 shall help the members of the panel to establish a common frame of reference to set targets for appropriate initiatives. Case 3: A platform for evaluation the success of inter-disciplinary cooperation: San Francisco Bay estuary restoration project Fig. 2.1.2 is used as a platform for sharing knowledge among experts. For example, in a beach protection project or a beach nourishment project in which dredged material is added to an eroding beach, a coastal engineer will normally consider the sediment transport mechanisms within a space of 10 km. The time scale of the project will normally be five years. Within this period, beach profiles and shorelines change and so do the biota within the region. Bed material dredged for beach nourishing alters the surface of both the source and target areas. Vertical and horizontal currents (turbulence) will spread the plume of suspended solids and cause it to settle within a severalkilometer zone. All the phytoplankton and zooplankton within the affected area will progress through stages of physiological, behavioural, population, and community response. At each stage, the trophic relation within the food web of the biological community changes correspondingly 88

Chapter 2. Tidal Area Features and Natural Processes

and impacts the composition of the predator groups. The evolutionary adaption for the ecosystem seems to be just starting when the project is finishing. All natural or human constructed processes require a certain length of time to reach a reasonable balance. Conflicts among experts of different organizations may be minimal if each of them can understand the time required for the process designed by the others. This concept can be seen in the following practical case. San Francisco Bay (Williams and Faber, 2001) is the Pacific Coast’s largest estuary and in 1966 it benefited from the first wetlands protection legislation enacted in the U.S. to prevent further land reclamation in the region. To reverse environmental damage in the Bay, a series of tidal wetland restoration projects using a variety of techniques by different agencies were undertaken between 1972 and 1999 and a total of about 2,000 hectares of former tidal marsh were restored to tidal flows. Plans to restore more than 29,000 ha over the next few decades have also been recommended. Since the projects have been implemented by a variety of agencies with different objectives, methods and projected outcomes for the restoration were altered several times over the 30-year period. The varying effectiveness of the results evolved from misconceptions or divergent views regarding the scale of the ecosystem, how the original ecosystem functioned and the time required to reestablish damaged marshland. Williams and Faber concluded with lessons which emphasize that, (1) restoring physical processes properly and monitoring other processes during the revitalization are the keys to restoration success, and (2) that it is important in restoration projects to have clear statements of measurable, achievable biologic objectives that have been agreed upon by all participating parties. The above study raises questions regarding how measurable objectives should be defined. In particular, planners must agree upon project time horizons and scope. Referring to Fig. 2.1.2, designers may divide these objectives into Meso-scale and Macro-scale themes so that evaluation and monitoring procedures can be developed.

2.7 Summary Tidal areas are important ecological systems that are very often linked to and affected by human activities. If these ecosystems are to be used sustainably, all of their biotic and abiotic components as well as the natural processes connecting them should be understood and treated carefully. These natural phenomena are presented in section 2.1, grouped according to physical, morphological, chemical, and biological processes and linked to spatial and time scales. Micro (105) units in meters and hours for the scales are introduced. Detailed explanations of these processes are given respectively in subsections 2.2, 2.3, 2.4 and 2.5. Three case studies include the 2004 Sumatra Tsunami; black-faced spoonbill migration patterns 89

and the related spoonbill reserve protection, and the San Francisco Bay estuary restoration project, as described in section 2.6. Tidal areas are regions that have both ocean-coastal and inland influences. Planners and designers of tidal zone projects should be aware that these influences can occur not only locally at the Macroscale but can also be affected by Mega-scale phenomena. These factors should be taken into account during planning. At the macro-scale level, participants in coastal projects should understand that to change or add structures to the nearby seacoast and the estuary will alter existing tidal habitats and the ecosystem. A restoration project is always a slow process. Proper monitoring with clear statements of measurable, achievable biologic objectives that have been agreed upon by all participating parties is the key to success. At the Meso-scale range, the strength of tropical cyclones has been shown (section 2.3.2) to intensify as a result of global warming-induced sea level and temperature rise. Consequently, the traditional methodology for determining engineering and design parameters has to be re-investigated and reexamined. Many countries submitted environmental pledges under the 2009 Copenhagen Accord and planners and designers shall be faced with establishing new methodologies to satisfy these commitments. To sum up, tidal and coastal areas are some of the most productive ecosystems in the world and many animal species and human depend on them. Humans have great responsibility for keeping these systems healthy. Understanding the characteristics and processes of coastal zones is the one of the keys to fulfilling this responsibility.

90

Chapter 2. Tidal Area Features and Natural Processes

Acknowledgement: It is acknowledged that this chapter has been revised depending on review and suggestions by Dr. Willem F. Vlotman, the Vice President of ICID (Australia), and the professional editing work by Ms. Mary Metzger. It is also acknowledged that the photographs were kindly provided by the following contributors: Fig. 2.2.1 by the 6th River Management Office, Water Resources Agency, Ministry of Economic Affairs, Taiwan; Figs. 2.5.5 & 2.5.6 by Lai, Sheue-Duan; Figs. 2.5.9 & 2.5.10 by Ueng, Yih-Tsong.

91

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Howarth R, Anderson D, Cloern J, Elfring CH, Hopkinson C, Lapointe B, Malone T, Marcus N, McGlathery K, Sharpley A. et al. 2000. Nutrient pollution of coastal rivers, bays, and seas. Issues in Ecology (7), 2-14. Hwang KS, Lai CJ, Wu YJ, Hwung HH. 2008. Short term morphological changes of Suang-si estuary, Proceeding coastal engineering, pp. 2256-2267. Ippen AT, Goda Y. 1963. Wave Induced Oscillations in Harbors: The Solution for a Rectangular Harbor Connected to the Open-Sea, Hydrodynamic Laboratory Report No. 59, Massachusetts Institute of Technology. Ippen AT. 1966. Estuary and Coastline Hydrodynamics. New York: McGraw-Hill. Kersten M, Piersma T, 1987, High levels of energy expenditure in shorebirds; metabolic adaptations to an energetically expensive way of life, Ardea v75, p 175-187. Kinsman B. 1965. Wind waves, their generation and propagation on the ocean surface. Englewood Cliffs, N.J.: Prentice-Hall. Kjerfve B. 1989. Estuarine geomorphology and physical oceanography. In, Estuarine Ecology, edited by Day J, Hall C, Kemp M, Yanezz-Arancibia A. New York: Wiley, pp 47-78. Kume T, Umetsu C, Palanisami K. 2009. Impact of the December 2004 tsunami on soil, groundwater and vegetation in the Nagapattinam district, India. J. Environ. Management 90 (10): 3147-3154. Langmuir D. 1997. Aqueous Environmental Geochemistry. Englewood Cliffs, NJ: Prentice Hall. Levinton J. 1995. Marine Biology: Function, Biodiversity, Ecology. Oxford: Oxford University Press. 448 p. McCall RT, Van Thiel de Vries JSM, Plant NG, Van Dongeren AR, Roelvink JA, Thompson DM, Reniers AJHM. 2010 Two-dimensional time dependent hurricane overwash and erosion modeling at Santa Rosa Island. Coastal Engineering 57: 668–683 McNinch JE, Luettich R A Jr. 2000. Physical processes around a cuspate foreland: implications to the evolution and long-term maintenance of a cape-associated shoal. Continental Shelf Research 20 (17):2367-2389 DOI:10.1016/S0278-4343(00)00061-3. Measures C. 2001. The origin of sea salt. OCN 201 Chemical Oceanography Class Notes, Fall 2001. Mei CC. 1989. The Applied Dynamics of Ocean Surface Waves, Adv. Series on Ocean Eng., Vol. 1. River Edge, NJ: World Scientific. Molles, MC., Jr. 2004. Ecology: Concepts & Applications NY: McGraw-Hill. Nasetti R, Fagherazzi S, Montanari A. 2008. Application of a barrier island translation model to the millennial-scale evolution of Sand Key, Florida. Continental Shelf Research 28: 1116–1126. DOI:10.1016/j.csr.2008.02.021. 93

Pavlopoulos K Poulos S. 2008. Geomorphological time scales and processes. CoastalWiki. Available at http://www.coastalwiki.org/coastalwiki/Geomorphological_time_scales_and_processes. Pawlowicz R, Beardsley B, Lenz S. (2002), Classical tidal harmonic analysis including error estimates in MATLAB using T-TIDE. Computers and Geosciences 28 (8): 929–937. Phillips O M. 1977. The Dynamics of the Upper Ocean, 2ed. Cambridge, UK: Cambridge University Press. Pilkey OH, Young RS, Riggs SR, Smith AW, Wu H, Pilkey WD. 1993. The concept of shoreface profile of equilibrium. a critical review. J. Coastal Res. 9 (1): 255-278. Pilson, MEQ. 1998. An Introduction to the Chemistry of the Sea. Upper Saddle River, NJ: Prentice Hall, 431 pp. Renaud FG, Birkmann J, Damm M, Gallopin GC. 2010. Understanding multiple thresholds of coupled social–ecological systems exposed to natural hazards as external shocks. Nat Hazards. online. DOI10.1007/s11069-010-9505-x. Rosati JD, Stone GW. 2009. Geomorphologic evolution of barrier islands along the northern U.S. Gulf of Mexico and implications for engineering design in barrier restoration. J. Coastal Res. 25 (1):8-22 DOI: 10.2112/07-0934.1. Saravanan S, Chandrasekar N, Hentry C, Rajamanickam M, Immanuel JL, Subramanian, PS. 2009. Post-tsunami assessment in the coastal region between Kanyakumari and Ovari, Tamil Nadu – a case study. Earth Science Frontiers 16 (6):129-137. DOI:10.1016/S18725791(08)60111-6. Schwartz, M. ed., 2005. Encyclopedia of Coastal Science. NY: Springer. Shepard FP, Wanless HR. 1971. Our Changing Coastlines. NY: McGraw-Hill. Sibthorp, MM. 1969. Oceanic Pollution, a Survey and Some Suggestions for Control. David Davies Memorial Inst. for International Studies. Stive, MJF, Aarninkhof SGJ, Hammb L, Hanson H, Larson M, Wijnberg KM, Nicholls RJ, Capobianco M, 2002 Variability of shore and shoreline evolution. Coastal Engineering 47 (2): 211–235. Stoker JJ. 1957 Water waves. The mathematical theory with applications. NY: Wiley Interscience. Tarbuck EJ, Lutgens FK 2005. Earth Science (11th edition) Prentice Hall. Titov V, Rabinovich AB, Mofjeld, HO, Thomson R-E, Gonzalex, FI. 2005. The global reach of the 26 Dec 2004 Sumatra tsunami. Science 30y, 2045-2047. Trenhaile AS Iavalle PD Iakhan VC. 2000. Canadian Landform Examples - 39 Point Pelee - a large cuspate foreland on Lake Erie. The Canadian Geographer 44 (2) 191 -195 Tropea C, Yrin J, Foss F. (eds.) 2007. Oceanographic measurement, Springer Handbook of 94

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Experimental Fluid Mechanics. Berlin and Heidelberg: Springer-Verlag. U. S. National Research Council, 2002. Oil in the Sea III: Inputs, Fates, and Effects. Ueng YT, Wang JP. 1999. Pseudogaleomma japonica (Galeommatidae), a familial and generic record new to Veneroida fauna of Taiwan. J. Taiwan Museum 52 (1): 7-11. Vila-Concejo A, Ferreira O, Morris BD, Matias A, Dias JMA 2004 Lessons from inlet relocationexamples from Southern Portugal. Coastal Eng, 51:967-990. Vaughan DG, 2008 West Antarctic Ice Sheet collapse - the fall and rise of a paradigm’, Climate Change, v.91, No.1-2, p 65 – 79. Tropea C, Yrin J, Foss F. (eds.) 2007. Oceanographic measurement, Springer Handbook of Experimental Fluid Mechanics. Berlin and Heidelberg: Springer-Verlag. U. S. National Research Council, 2002. Oil in the Sea III: Inputs, Fates, and Effects. Ueng YT, Wang JP. 1999. Pseudogaleomma japonica (Galeommatidae), a familial and generic record new to Veneroida fauna of Taiwan. J. Taiwan Museum 52 (1): 7-11. Vila-Concejo A, Ferreira O, Morris BD, Matias A, Dias JMA 2004 Lessons from inlet relocationexamples from Southern Portugal. Coastal Eng, 51:967-990. Vaughan DG, 2008 West Antarctic Ice Sheet collapse - the fall and rise of a paradigm’, Climate Change, v. 91, No. 1-2, p 65 – 79. Wang JP, Wu S, Chu YT, Ueng CK, Guo CK, Hung WJ, Chen EL, Chen CL, Hang YF, Chen HC. 2009. The environmental change impact on the ecosystem of south-western coast of Taiwan. 2009 The international symposium on coastal wetland and water conservation 2009/12/013. Wei CL. 1988. Marine Chemistry Handbook, Institute of Oceanography. Taipei: National Taiwan University. Williams P, Faber P. 2001. Salt marsh restoration experience in San Francisco Bay. Journal of Coastal Research, Special Issue No. 27, 203-311. Wooster W S, Lee AJ, Dietrich G. 1969. Redefinition of salinity. Deep Sea Res. 16, 321-322. Wright LD, Boon JD, Kim SC, List JH. 1991. Modes of cross-shore sediment transport on the shoreface of the Middle Atlantic Bight. Marine Geology 96, 19–51. Yáñez-Arancibia A, Lara-Dominguez, AL, Sanchez-Gil P, Day JW. 2004. Estuary-Sea ecological interactions: a theoretical framework for the management of coastal environment, in Environmental Analysis of the Gulf of Mexico, Kim Withers and Marion Nipper, Ed., Harte Research Institute for Gulf of Mexico Studies, Special Publication Series No. 1, 271-301.

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Websites By the sea – A Guide to the Coastal Zone of Atlantic Canada: Tidal mudflats 2007, Fisheries and Oceans Canada. http://www.glf.dfo-mpo.gc.ca/os/bysea-enmer/index-e.php Coastal portal; coastalwiki, http://www.coastalwiki.org/coastalwiki/ Estuaries.gov, National Oceanic and Atmospheric Administration (NOAA), http://www.estuaries. gov/estuaries101/Default.aspx Indian Ocean earthquake, http://en.wikipedia.org/wiki/2004_Indian_Ocean_earthquake Intergovernmental Panel on Climate Change. Fourth Assessment Report: Climate Change 2007. http://www.ipcc.ch/publications_and_data/ar4/syr/en/contents.html NOAA BI: http://www.csc.noaa.gov/beachnourishment/html/geo/barrier.htm NOAA website Frequency ask question, What is an extra-tropical cyclone? http://www.aoml.noaa. gov/hrd/tcfaq/A7.html Office of Response and Restoration, National Oceanic and Atmospheric Administration), http:// response.restoration.noaa.gov/orr_search.php?keywords=oil+spill&submit=Go Oceans, Coasts, & Estuaries, U. S. Environmental Protection Agency (EPA), http://www.epa.gov/ owow/oceans/ Royal Society. Ocean acidification due to increasing atmospheric carbon dioxide. http://www.us-ocb.org/publications/Royal_Soc_OA.pdf Science Encyclopedia: Land-Sea Breezes http://science.jrank.org/pages/3800/Land-Sea-Breezes.html US NOAA/NCDC website, NOAA/NCDC Global Warming Frequent Asked Question http:// www.ncdc.noaa.gov/oa/climate/globalwarming.html US NCEP website, Climate Prediction Center, ENSO FAQ. National Centers for Environmental Prediction http://www.cpc.noaa.gov/products/analysis_monitoring/ensostuff/ensofaq.shtml#HOWOFTEN Water Resources of the United States, U.S. Geological Survey (USGS), http://water.usgs.gov/ 96

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Glossary aeolian: produced or carried by the wind aggradation: build up of any land surface by the deposition of sediment bathymetry: measurement of ocean or lake depth and the study of floor topography (CW) beach nourishment: beach nourishment is the supply of sand to the shore to increase the recreational value and/or to secure the beach against shore erosion by feeding sand on the beach bed load: bed load refers to the sediment which is in almost continuous contact with the bed, carried forward by rolling, sliding or hopping (CW) benthos: organisms living on sea or lake bottoms Bergeron process: formation of precipitation in the cold clouds of the mid and upper latitudes by ice crystal growth coastally-trapped wave: an ocean wave that balances the Earth’s Coriolis effect so that it retains its shape in the alongshore direction over a period of time. Also called a Kelvin wave. Copepod: planktonic crustaceans, very abundant in the world’s oceans, and often the first prey of fish larvae (CW) degradation: lowing of any land surface by removing of the surface material Diatom: one of the most common types of phytoplankton, serving as foundation of the marine food web (CW) distributary: A distributary, or a distributary channel, is a stream branches off and flows away from a main stream channel. downdrift: movement of (beach) sediments approximately parallel to the coastline (CW) embayment: a bay or baylike shape eutrophication: a process occurring in a body of water in which increased levels of mineral and organic nutrients has reduced the dissolved oxygen, producing an environment that favors plant over animal life gastropod: a mollusk, such as a snail, cowry, or limpet, having a single, coiled shell ENSO – El Nino-Southern Oscillation: a climate pattern that occurs across the tropical Pacific Ocean, on average very five years, warming (el Nino) or cooling (la Nina) surface waters and triggering widespread meteorological changes. 97

ephemeral: living or lasting for a brief time, often only one day euryhaline: capable of tolerating a wide range of salt water concentrations harmonic analysis: a branch of mathematics that studies wave theory isopycnal: a surface of constant potential density of water. Temperature and salinity act to modify the density of water macrobenthos: large organisms that live at the bottom of a water column nektons: the total population of marine organisms that swim independently of currents, ranging in size from microscopic organisms to whales overwash deposits: sediment deposited inland that does not directly return to the water body (such as ocean, sea, bay or lake) where it originated parthenogenetic: reproduction of organisms without conjunction of gametes of opposite sexes photic zone: upper zone of a body of water into which sunlight penetrates progradation: a process wherein a river delta extends farther out into the sea over time rotifers: minute multicellular marine organisms common in freshwater environments and sometimes in salt water environments saprophyte: a plant that lives on and derives its nourishment from dead or decaying organic matter silicoflagellates: unicellular algae found in marine environments spectral analysis: a method of analyzing the chemical properties of matter from bands in their visible spectrum stochastic method: analysis of a random variable substrate: a surface upon which plants can grow, including marine environments succession: gradual and orderly process of ecosystem development brought about by changes in species populations swash: a narrow channel through which tides flow tidal ellipsis: a tide pattern in which the flood flow and the ebb flow trace an ellipse over a tidal cycle trophic levels: distinguishes organisms as producers, consumers, and decomposers. Producers are usually plants and algae; consumers are usually animals; and decomposers break down dead animal and plant material. turbulence: water demonstrating local velocities and pressures that fluctuate randomly 98

Chapter 2. Tidal Area Features and Natural Processes

upwelling: associated with the divergence of ocean currents that bring deeper, colder, nutrient rich waters to the surface. viviparous: in animals, giving birth to living young that develop in the mother’s body; in plants, germinating or producing seeds that germinate before detaching from the parent plant. zooplankton: floating, often microscopic marine animals

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CHAPTER 3

Chapter 3. Planning Framework for Managing Tidal Area Development

PLANNING FRAMEWORK FOR MANAGING TIDAL AREA DEVELOPMENT EDITOR: PARK SANG HYUN

T

his Chapter provides a planning framework for harmonized development of land and water for economic efficiency and environmental conservation for human being and biodiversity in tidal areas. In addition, the issue on management and institutional context is included for the efficient usage and comprehensive conservation. The coastal zone comprises only 3 % of the earth’s surface, but contains a high amount of its assets. Some 60 percent of the world population lives within 60 km of the coast and three quarters of world population will live within 100 km from the sea by 2025. For a long period, the tidal areas have been developed mainly for the agricultural land and water. In the recent periods, some of it has been diverted as harbor, leisure and trade spaces as long as human activities are concentrated in the area. As the natural resources are limited, tidal areas should be utilized for the benefit of mankind and conserved for future generation in a sustainable way.

3.1 Multifunctional Role of Tidal Reclaimed Areas

Author: Shigetaka Taniyama

In recent years, there are opinions that tidal land development has a negative impact on the environment, leading to the view that tidal flats and wetlands should be preserved as they are. Nevertheless, they are lowlands that have a high economic value, and therefore need to find ways of achieving a balance between environment and economy while integrating them into national land use plans. 101

3.1.1 APPROPRIATENESS OF PROJECTS IN TWO-DIMENSIONAL TERMS

Agricultural and non-agricultural economic effects (production effects) Recently, when judging the appropriateness of projects, methods of evaluation that include effects other than agriculture (non-agricultural effects) have come to be adopted. These non-agricultural benefits include the function of preventing floods on land lying behind reclaimed land by constructing dikes, improved traffic conditions on surrounding roads and waterways through the use of levees and reclaimed land, land substitution effects based on evaluation of new land creation, and so on. While these benefits differ from project to project, they account for a large proportion compared to direct agricultural effects. Proportions of benefits in the Isahaya Bay Development Project In the case of the Isahaya Bay Reclamation Project, for example, calculations using the Replacement Cost Method (RCM) prove that, while the direct benefits of creating farmland accounted for 40.6% of the overall benefits, the three non-agricultural benefits mentioned above accounted for 59.4%, as shown in Fig. 3.1.1.

Fig. 3.1.1 Proportions of benefits in

Fig. 3.1.2 Non-agricultural benefits of

Isahaya Bay Development Project

reclamation projects in Korea

Jong-Wan Lim and Sang-Bong Im(2002) in Korea, meanwhile, have measured the non-agricultural benefits of five large-scale reclamation projects (reclaimed area 17,131ha) completed in South Korea up to 1993, as shown in Fig. 3.1.2, non-agricultural benefits consisted of regional development effects (42.8%), land substitution effects (22.9%), traffic improvement effects (17.8%), flood control effects (10.2%), and health & recreation effects (6.3%).

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Chapter 3. Planning Framework for Managing Tidal Area Development

Classifying costs and benefits Costs and benefits are classified into elements directly related to Production (P) and those not directly related to production {Environment (E)}, as shown in Table 3.1.1. Production benefit (PB) includes not only the agricultural and non-agricultural effects described in above, i.e. the production of agricultural products that individuals can trade directly on markets, fishery production in inland waters, and provision of living space, but also the public sector benefits such as disaster prevention in the hinterland, improvement of traffic on roads, waterways, etc., and land substitution as benefits. The depletion of traditional fisheries is a negative benefit or is therefore a cost (PC). On the other hand, those elements {Environment (E)}, as the environmental effects are the depletion of tidal flats and wetlands as the cost (EC), and, as the benefit (EB), the manifestation of eco-system functions, nitrogen removal functions arising from paddy fields, and the creation of landscapes Criteria for judging projects taking account of the environment The decision to undertake a project is generally taken if the benefits exceed the costs (B>C), as shown in Table 3.1.1. In this case, benefits directly related to Production (PB) are easy to calculate. However, parts that are not related to Production (E,B) in Table 3.1.1), though new methods, such as CVM(Contingent Valuation Mehod) and TCM(Travel Cost Method) to evaluate in monetary terms having been developed, cannot simply be aggregated together with Production (PB), since the evaluation methods and degree of precision are rather different. Table 3.1.1 Main costs and benefits of tidal flats and wetlands development Category

Production (P)

Environment (E)

Cost (C)

n Construction cost

n Loss of tidal flat and wetland



n Operation and management costs



(locks, dykes, etc)



n Loss of traditional fishing grounds

Benefit (B) n Gains in agricultural production

functions (ecosystems, carbon cycle, etc)

n Loss of purification functions n Creation of new eco-system



n Provision of living space

n Improvement of water quality



n Fishing in remaining areas of water



n Fish farming in paddies

n Formation of landscape



n Disaster prevention by dykes

n Creation of rural societies



n Transport improvement by using dykes



n Nitrogen removal functions

(such as nitrogen removal)

Thus, rather than a one-dimensional approach PB/PC whereby everything is converted into monetary terms and appropriateness is evaluated in terms of economic value alone, a twodimensional approach could be taken, as shown in Fig. 3.1.3, with another Environment added as a secondary evaluation axis. 103

Here, the evaluation of Environment is taken as the X axis, while the evaluation of the part that is expressed in monetary terms and is traded on markets (Production) is taken as the Y axis.

Σ

Τ2 Environment

Υ

Production

In this figure, the horizontal axis represents the Environment. Conservation efforts intensify as one moves toward the right, while environmental destruction becomes more serious as one move toward the left.

Τ1

Φ1 Φ2

Fig. 3.1.3 Relationship between production and environment (J. Nakanishi, Iwanami Shoten, 1994)

The vertical axis shows Production, which increases in an upward direction. A negative level means a decrease in production. Thus Quadrant I represents the simultaneous attainment of Production and Environmental Conservation. Quadrant II represents an increase in Production at the cost of the Environment. Quadrant III represents a policy failure: a devastated Environment in combination with falling Production. The situation in Quadrant II2, in which damage to the Environment is disproportionate to any gains in Production, is unacceptable, but that in Quadrant II1 — although there is a negative impact on the Environment, gains in Production efficiency are even greater — is a realistic stepping stone to Quadrant I, Nakanishi contends. Similarly, she divides Quadrant IV into IV1 and IV2; IV1 represents an effort to foster environmental conservation with minimal losses in production. The value of the multi-functionality of agriculture and its positive effect on the environment has come to be recognized internationally. In 1998, an OECD communiqué stated that “Beyond its primary function of supplying feed and fiber, agricultural activity can also shape the landscape, provide environmental benefits such as land conservation, the sustainable management of renewable natural resources and the preservation of bio-diversity, and contribute to the socio-economic viability of many rural areas”. Moreover, these functions of agriculture, and particularly those of paddy fields, are positioned as one of the “nontrade concerns” in discussions on trade problems by WTO. In this way, recognition of the multifunctionality of paddy fields is felt to be spreading throughout the world.

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Chapter 3. Planning Framework for Managing Tidal Area Development

3.1.2 PRODUCTION EFFECTS OF DEVELOPMENT FOR TIDAL AREAS

Agricultural production effects Paddy field rice is suited to reclaimed land because rice is highly resistant to saline concentrations and surface inundation, and high in productivity and sustainable, in that it can be planted every year. Conversely, wheat and barley, maize and other cereal crops grow poorly in farming land, where groundwater levels are high. They have no resistance to inundation, and surface inundation therefore has to be avoided. Under Japanese drainage standards, inundation damage caused by concentrated torrential rains occurs between July and September, during which time rice plants reach a height of 30 centimeters. With 1~2 days’ inundation the yield loss due to inundation damage is only 20% or less, and therefore the tolerable inundation depth is 30 centimeters for 24 hours.

Other non-agricultural effects that can be measured in monetary terms n Flood prevention effects: Flood

prevention effects are the effects whereby damage caused by high tides and overspill from rivers in areas behind those scheduled

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In recent years, however, demand for rice has declined with economic growth in Japan, South Korea and Taiwan, while on the other hand import pressure due to the globalization of agricultural products is making it difficult to create new paddy fields.

ｄｒａｉｎｇａｅ　 ｃａｐａｃｉｔｙ

Kameda Polder in Niigata Prefecture was a wetland covering about 10,000 hectares, where rice cultivation used to be practiced at slightly higher land elevations, but at the frequent cost of flood damage. For this reason, dikes (called a “ring levee”) had implemented with drainage facilities gradually improved. In particular, as drainage pumps had been placed, the average yield per unit area of rice had increased. Fig. 3.1.4 shows that it increased about five-fold in the hundred years of the 20th century. It should be stressed that this increase was not only due to improved drainage alone, but improved drainage system has acted as a motivating factor.

ｙｅａｒ

Fig. 3.1.4 Change in per-unit rice yields (Polished rice kg per 0.1ha) accompanied by drainage intensity (m3/s/km2) 105

for reclaiming can be mitigated by installing sea dikes and drainage sluices. The facilities protected from flood are existing levees, public facilities, housing and business establishments, farmland, agricultural facilities, agricultural products, roads, railways, rivers, and so on. The estimated annual benefits can be calculated by subtracting the amount of damage after project implementation from that before project implementation, and multiplying this by the rate of return. n Access improvement effects: Access improvement effects are achieved when personnel costs

and vehicle expenses are economized by shorter traveling times due to reduced automobile transportation distance and improved traveling speed, when levees constructed in projects are used as roads. The annual value of effects is calculated by subtracting traveling expenses after project implementation from those before project implementation. n Land substitution effects: For land substitution effects, the latent effects whereby opportunities

for land use increase with the creation of new land in a project are evaluated. The annual value of effects is found by calculating the difference between land rent if farmland is used for other purposes and land rent if used as farmland, and multiplying this by the area in which effects arise. 3.1.3 ENVIRONMENTAL EFFECTS

Besides the benefits that can be calculated directly in this way, there are also the so-called environmental effects, the economic benefits of which are difficult to measure. These include both positive and negative benefits. The positive benefits are the creation of new eco-systems on reclaimed land, the formation of landscapes, the creation of rural societies, and the improvement of water quality. These are the benefits manifested by the so-called “multi-functionality of paddy fields” when land is developed as paddy fields. Of course, “the multi-functionality of paddy fields” also includes groundwater recharging effects, soil consolidation effects on sloping land, and other functions besides these, but these are not normally involved in cases of tidal area development and are therefore not taken up here. The negative benefits, on the other hand, include the effects of tidal flat depletion, which has to be regarded as a cost. It goes without saying that, as tidal flats and wetlands nurture a large number of living organisms, constitute part of the marine eco-system, and have the capacity for purifying water quality, among others, these will be lost if the tidal flats and wetlands are reclaimed in projects. This is therefore seen as a negative benefit. Measuring environmental effects As criteria for judging whether or not to carry out public works projects, production effects have only been evaluated in monetary terms. In recent years, methods of evaluating environments 106

Chapter 3. Planning Framework for Managing Tidal Area Development

that are difficult to measure in this way (eco-systems, landscapes, and water quality) in monetary terms have been developed. For example, the Contingent Valuation Method (CVM) is a method of using direct questionnaire surveys to evaluate the monetary amounts that local residents or other evaluators are willing to pay for the maintenance of benefits, by showing them hypothetical situations in which the benefits brought by the functions subject to evaluation are lost. The Travel Cost Method (TVM) estimates a function for traveling costs and frequency of visits to the targeted area, and counts changes in travel costs accompanying changes in the area’s situation as an increase or decrease in benefits. Eco-systems of paddy fields Rice paddies furnish a habitat to numerous organisms, which adapt themselves to the alterations in environment that occur over the course of the agricultural cycle of planting, ponding, drainage, and reaping. Paddies, being shallow, have a higher water temperature than do ponds and lakes. They abound in plankton, are lush with aquatic plants, and teem with organisms like loaches, fresh-water snails, frogs, crayfish, and dragonflies; fish species such as crucian carp and medaka, meanwhile, live in the adjacent water channels and ponds. These creatures in turn attract waterfowl. Furthermore, paddies form part of a secondary natural network. For example, medaka switch habitats between rice paddies, water channels, and irrigation ponds depending on the season. Since their young, being weak swimmers, cannot survive in rivers, medaka spawn and breed in rice paddies, where the current is gentle, the water is warm, and there is a plentiful supply of organic matter. In 2002, Japanese Ministry of Agriculture, Forestry and Fisheries conducted a survey of biodiversity in rice paddies, counting freshwater fish species in 1850 locations and frog species in 697 locations. During this survey 79 of the 300 species of fish and 12 of the 42 species of frog found in Japan were identified. In another survey conducted in the Minuma paddy lands situated 20-30 km from Tokyo, 1915 animal species (204 birds, 13 mammals, 14 reptiles, 8 amphibians, 28 fish and 1648 insects) and 1003 plant species were identified. This area consisted of wetlands until 1629, but in 1728 the Tokugawa shogunate reclaimed it. In 1965 restrictions were placed on converting the Minuma paddy lands to other uses under the Agricultural Land Law, and have been preserved for paddy farming despite their proximity to Tokyo. Comparison of eco-systems before and after reclamation Instead of expressing the environmental effects of the X-axis in Fig.3.1.3 in monetary terms, changes of the number of species can be adopted for evaluating the environmental effects. It might become one of substitutes for evaluation in monetary terms. For example, Fukushima Lagoon consists of small-scale wetlands and lakes near the mouth of the 107

River Agano in 1965, and by 1982, about 250 ha of land had been reclaimed, leaving some 50 ha as a regulating reservoir. Viewing changes in plant species in the regulating reservoir and reclaimed land before and after reclamation, as shown in Table 3.1.2, a reduction in plant species around the time of reclamation can be seen, but 20 years later they had nearly all recovered to their original numbers. Table 3.1.2 Change in plant species in Fukushima Lagoon

Before land reclaimed



1982

1982

1989

2002

31

30

54

92

5

5

8

23

—

—

2

13

Naturalized species Escaped species Cultivated species Endangered species

After land reclaimed

30

19

26

27

Other

289

219

266

298

Total

355

273

356

453

Fukushimagata reclaimed land, including lagoon, deserves special protection as a wetland, for it serves a wintering ground for migratory bird species, most notably Middendorf ’s bean goose (Anser fabalis middendorffi). Native to the Kamchatka Peninsula, this species winters to the south in China, the Korean Peninsula and Japan. There are believed to be 50,000-70,000 individuals worldwide, and according to a 1995-96 survey some 6,000 of them visit lakes and marshes along the sea side. According to Miyabayashi’s 1994 survey, Toyano Lagoon attracts 2,000 of these geese and Fukushima Lagoon another 3,300; these numbers are considerable, indicating the area’s crucial importance as a wintering ground. Clearly, the region offers a tranquil environment for nesting, with the local rice paddies furnishing an abundant supply of plants and animals to serve as feed. Nitrogen removal capacity of tidal flats A tidal flat forms a distinctive ecosystem with an interacting population of microscopic bacteria, benthic algae, and plant plankton invisible to the naked eye; benthic organisms, including sandworms and bivalves such as short-necked clams; seaweed and other marine plants; and larger organisms such as fish and birds. These organisms are exposed to severe changes in environment caused by the tides, and they suffer heavy predation pressure from the ocean, land, and sky. For that reason relatively few species inhabit tidal flats, but on the other hand they maintain a high level of productivity and form a dense food chain. That is because there is an abundant supply of nutrient salt that seeps in from dry land and rivers, and large amounts of organic matter are generated by the plant bodies of benthic algae, plant plankton in the water, and seaweed and other marine vegetation, since the shallow waters allow sunlight to penetrate to the bottom. 108

Chapter 3. Planning Framework for Managing Tidal Area Development

Moreover, in tidal flats material is recycled by consumers and then decomposers, which derive their energy from organic matter produced by benthic algae and supplied by the rivers and ocean. This constitutes one of the most characteristic roles of the tidal flat: its cleansing function. Several types of factors govern material recycling in a tidal flat: physical factors in the form of tides and other forces that carry the material; chemical factors such as oxidation-reduction reactions, nitrification reactions, and conversion between dissolved and inorganic states; and biological factors, chief among them the food chain. The activity of the diverse species that make up the bio-community is a key ingredient of the material recycling process in a tidal flat. Attempts have been made to assess the water cleansing capacity of tidal flats using various methods, including employing the results of laboratory experiments to trace the elementary material recycling process or create a circulatory model of the process. However, because complex environmental factors are involved, a consensus has yet to be reached on what approach is best. But lately a form of analysis has emerged that employs simulations based on ecosystem models. CONCLUSION

In conclusion, Tidal flats and wetlands represent important focal points of economic activity for humans, but are also important in providing habitats for various species of flora and fauna. Therefore, when developing these tidal areas, development must proceed in harmony with eco-systems based on comprehensive judgments before or during the master planning stage, in sustainable way for future generation.

3.2. Land Use Planning

Author: Park Sang Hyun

3.2.1 OPTIMAL ALLOCATION OF TIDAL RECLAMATION AREA

The tidal reclaimed area shall be allocated considering the relationship between production and environmental conservation in sustainable way. As environmental policy strengthened in many countries, the concept of sustainability has penetrated into the land use planning in the tidal area. Fig. 3.2.1 is derived, referred to Fig. 3.1.3, to show the contribution effects of tidal development to increase production in harmonized with the environmental conservation, as result of land allocation for farm, freshwater lake, nature reserves as well as housing, harbor and traffic facilities. In the figure, conservation efforts intensify as one moves toward the right, while environmental destruction becomes more serious as one move toward the left, while production increases in an upward direction of the vertical axis when appropriate water management schemes are applied in the tidal areas. 109

Box 3.2.1 Utilization of reclaimed tidal land in China (Lee Deog Bae) TIDAL LAND IN JIANGSU PROVINCE OF CHINA Chinese coastline extends 16,100 km along mainland from Yalu River mouth at the China–North Korea border to the Beilun River mouth at the China-Vietnam border. At present, along the Liaoning, Hebei, Shangdong, Jiangsu, Shanghai, Zhejiang, Fujian, Taiwan, Guangdong, there are about 2.6million ha of tidal land in China. The coastline of Jiangsu province is about 954km length from the Xiuzhen River at Shangdong-JIangsu border in the north to the mouth of Yangtze River at JiangsuShanghai border in the south. There are 30 km sand coast, 40 km bedrock coast and 884 km silt sand/mud coast. Of these silt sand/mud coast there is 666 km depositing and growing coast and 218 km light eroded coast. The total tidal land area of Jiangsu Province is about 0.654million ha.

Husbandry: About 36,000ha natural coastline pasture and 1,600 ha of artificial pastureland in tidal flat of Jiangsu Province is used for husbandry. Large rice grass (spartina anglica) has been introduced into tidal flat in Jiangsu Province since 1963 from UK. It is highly tolerant to salt and promote the deposition in tidal land. Meanwhile it is also a good feeding material for sheep and cattle. There are 20,000ha of plantation in 1990, and government encouraged people to develop sheep, cattle and other animal and milk production in order to lower investment and increase production and supplication of protein from tidal land reclamation. Forest: There is 11,500ha reclaimed tidal land for forest and fruit tree plantation. It can be classified as 4 type forest plantations. First type, artificial forest, there were 30,000 ha of timber forest in total. Second type, the dyke protection forest belt, it has build up to 670km of dyke protection forest belt occupied about 40,000ha of reclaimed tidal land. Third type, agro-forest net around farmland: the major forest belt is directed from south to north with 15–20m width (planted 15 row of tree) and 300–400m of inter-space, the minor forest belt is directed from west to east with 10 m width (planted 5 row tree) and 1500–2000m of inter-space. There have built up to 40,000ha of Agro-forest net farmland in 1990. Fourth type, fruits and mulberry tree plantation along the tidal land, major fruit trees are apple, pear, peach and mulberry trees.

Coastal line in China

Sea Salt production: It has built about 72,000ha of tidal land for salt production. The yearly output of sea salt is about 1.2–1.7million tones, 51.5 million tones in total from 1950–2000 in Jiangsu province.

UTILIZATION OF RECLAIMED TIDAL LAND IN CHINA

FURTHER RECLAMATION OF TIDAL LAND IN JIANGSU PROVINCE

Agricultural plantation: Chinese government regulated that reclaimed tidal land to be allowed for cereal and cotton production from 1949 to 1980. At present population there are of 0.52 million capita involved in the tidal land reclamation and produce grains (wheat and rice) 0.18 million tons, seedless cotton 8,000tons, oil 12,000 tons annually.

There are still a lot of potentials to extend based on the modern technology.

Raising of Fishery and Seaweed: There are 12,400 ha for sea shrimp raising, other 12,000 ha for fresh water fish culture. It has already used of 80,000ha in the intermediate tidal zone in this province: about 76,000 ha used for shellfish raise and 4,000ha used for seaweed production. Fish, crab and shrimp are produced 26,000 tons, seaweed (dried) 2,300 tons, and shellfish 16,000 tons annually. 110

Firstly, About 20,000 ha tidal land already enclosure and dried, but not properly used. There are about 60,000 ha of first class tidal land not reclaimed yet and each year have 1,350 ha newly growing tidal land can be reclaimed. Meanwhile, there are 140,000 ha of intermediate tidal level zone have not been used yet. Secondly, Use higher technology to process these products then its value will be much increased. In addition, many valuable ports, mineral products along the coastline and tourist scenery resources in this region have not been properly evaluated and plan to use them yet.

- Fertilizer and pesticides in farming area

Production

Chapter 3. Planning Framework for Managing Tidal Area Development

- Housing, harbor, traffic

- Organic farm

- Freshwater lake - Aquaculture

Environmental conservation - Nature Reserves, forest and habitats for birds

- Inappropriate water management: Sewage water from village and urbanized area

Fig. 3.2.1 Production and environmental conservation in the tidal areas

Thus Quadrant I represents the simultaneous attainment of production and environmental conservation from optimal allocation of tidal reclamation area. Quadrant II represents an increase in production at the cost of the environment. Quadrant III represents a devastated environment in combination with falling production. Quadrant IV represents the sacrifice of production to the cause of protecting the environment. On the other hand, Table 3.2.1 shows that most of the reclaimed tidal land has been allocated for agriculture and lake to supply food and water resources in many countries. In the Zuiderzee project in the Netherlands, 80,090 ha of reclaimed area have been used as nature reserves to conserve eco system in the Wadden sea area since reclaimed in 1930th. It is reported by Bernd Probst (2005) that more than one third of Wadden Sea area has been reclaimed over the last 1,000 years. Concerned on the land use plan of the Saemankeum Project, Korean government has revised the land use plan that agricultural land, reduced from 20,450 ha to 8,570 ha and it will be used for industrial, tourism, ecological park and business town in the near future. Table 3.2.1 Reclaimed tidal land allocation in different projects Project area

Isahaya

Kalpasar

Saemangeum

(Unit: ha) Zuiderzee



Japan

India

Total

3,550

326,000

40,100

350,000

230,000

1,477

71,400

20,450

120,760

41,600

15

47,600

590

12,700

Agriculture Housing Nature reserves Waterway etc, Lake

Korea Netherlands

Jiangsu, China





5,473

80,090

15,000

348



1,787

11,450

65,500

1,710

207,000

11,800

125,000

Fishery Forest

11,500

Salt farm

72,000

24,400

111

On the other hand, more land has been for fishery, forest, and salt farm in Jiangsu Province, China. 3.2.2 OPTIMAL ALLOCATION OF CROP AREAS IN TIDAL AREA

Optimization scheme has been widely applied to determine the appropriate allocation of crop area to maximize agricultural benefits for the farmers. As the irrigation and drainage cost in low land area is rather higher and salty soil water characteristics are to be considered to select crop pattern, the technology of optimization schemes are valuable tool for the agriculture in tidal areas. To maximize the efficient use of irrigation water and investment of capital, the technology of Linear Programming (LP) has been adopted to in various crop areas by Park (1995). Crop area shall be allocated to maximize the economic returns and minimize production cost as follows: maximize NB = PB - PC



(2.2.1)

where, NB is net benefit (US $), PB is profit from selling of crops and PC is farming cost. The profit from selling various crops is defined as follows:

J

PB = ∑ pbj × Aj × Yj



j=1

(2.2.2)

where, pbj is the expected selling price for j-th crop in the market, Aj is crop land area for j-th crop, Yj is crop yield of j-th crop, and J is total number of feasible crops to be planted.

J

PC = ∑ C j × A j j=1

C j = CW j + CL j



(2.2.3)

(2.2.4)

where, Cj is the total production cost in j-th crop area and CW is water cost and CL is labor cost, including other operation and maintenance cost. Example of optimal allocation of crop area An experimental study has been carried out for the crops of sesame, red pepper, bean and Chinese cabbage. The Chinese cabbage was planted followed by bean and sesame harvested in autumn.

112

Chapter 3. Planning Framework for Managing Tidal Area Development

Table 3.2.2 Benefit and cost values used in optimal crop area allocation Crops

(Unit: ha)

Red pepper

Bean

Sesame

9,570

3,150

3.3

0.9

2,900

3500

800

122.5

2,826

1,025

1,388

1,398

2,682

905

1,268

1,254

24

20

20

24

* Benefits - Price (won/kg) - Yields (kg/ha) * Cost - Fixed cost - Pump - Labor

C. cabbage

Remarks

2,800

6,125

unit: US $

3.5

0.05

120

100

100

120

6,684

2,085

1,412

4,727



(6,812)

* Net benefit (NB)

(6,139)

( ): C. cabbage included

The object function has been derived as follows; maximize PC= 6,684 × AR + 6,812× AB + 6,139 ×AS



(2.2.5)

where, AR is crop area for red pepper, AB is for bean and Chinese cabbage, AS is for sesame and Chinese cabbage in the area. The constraints of the object function are as follows: • Total crop areas should not exceed 3 ha of available field area 3 > AR + AB + AS



(2.2.6)

• The minimum crop might be more than 0.1 ha for self supply for the farmer. AR > 0.1 ha, AB > 0.1ha, AS> 0.1ha



(2.2.7)

• Total labors can not exceed 30 available labors during each crop stage of 10 days.

30 》AR × 6 + AB × 5 + AS × 5



(2.2.8)

In Eq. (2.2.8), required labors are evaluated to be 6 for red pepper, 5 for bean and 5 for sesame, respectively. Maximized benefit can be derived by applying Linear programming which change the various inequality equations to simultaneous equations. Table 3.2.3 indicates that red pepper is the most benefit crops when there are enough labor, however, in case labors are not enough, bean and Chinese cabbage will be desirable.

113

Table 3.2.3 Optimal crop area allocation Crop allocation Total labors and crop area

Unit

Total: 3 ha

30

20

10

5

No. of labors

- red pepper

2.8

0.1

0.1

0.1

Crop areas in

- bean/C. cabbage

0.1

2.8

1.76

0.76

- sesame/C. cabbage

0.1

0.1

0.1

0.1

20,357

20,357

13,273

6,461

Net benefit

ha US $

CONCLUSIONS

In tidal reclamation areas, the optimal crop patterns shall be decided depending on labor and market price as well as other water management cost. Especially, there are a lot of constraints and limitations to apply the optimal schemes, such as labor, water resources constraints, to be supplied from other neighborhood areas. Crop diversity is important issue to keep the traditional and rare species, even if the species are not economically feasible for the farmers.

3.3 Conservation of Habitat and Biodiversity

Author: Kim Hyung Joong

3.3.1 CREATION OF WETLAND FOR THE HABITATS FOR LIVING THINGS

In the tidal reclaimed area, various wetland has been created to prevent chemicals or bioaccumulation of toxic materials in the water and increase fisheries enhancement as well as to create ecological corridors such as migratory flyways or spawning runs. Wetlands have the potential for developing a diversity of plants, animals, and biogeochemical processes. Deepwater areas, devoid of emergent vegetation, offer habitat for fish, can enhance nitrification as a prelude to later denitrification if nitrogen removal is desired, and can provide low velocity areas where water flow can be redistributed (Steiner and Freeman, 1989). The sediments retain certain chemicals and provide the habitat for micro-and macro-flora and fauna that are involved in several chemical transformations. In many constructed wetlands, wildlife enhancement begins within a few years after construction. At a constructed wetland at Pintail Lake in Arizona, the area’s waterfowl population increased dramatically. By the second year of use, duck nest density had increased 97 percent over the first year (Wilhelm et al., 1989). Individual wetlands cells, placed in series or parallel, often offer an effective design to create different habitats or establish different functions (Steiner and Freeman, 1098). Cells can be parallel so that 114

Chapter 3. Planning Framework for Managing Tidal Area Development

alternate drawdown can be accomplished for mosquito control or redox enhancement, or they can be in a series to enhance biological processes (Mitsch, et al., 1993). A wide variety of aquatic plants have been used in wetland systems designed for wastewater treatment. The emergent aquatic macrophytes are the most commonly found species in the marshtype constructed wetlands used for wastewater treatment. The most frequently used plants are cattails (Typha sp.), reeds (Phragnmites communis), rushes (Juncus sp.), bulrushes (Scirpus sp.), and sedges (Carex sp.). The U. S. Soil Conservation Service estimated that about 50,000 ponds are constructed each year, for a 20-year total of close to 800,000 hectares of marsh created (40,000 ha/yr) from these ponds and the enlargement of existing ones (Office of Technology Assessment, 1984). Many of these ponds are built with large, shallow areas to attract waterfowl, and these shallow zones become typical pothole marshes. Following plants are known to contribute for the habitats of various birds in the wetland. n Cattail: seeds and roots - feed source for water birds; nesting cover for birds. n Bulrush: seeds and rhizomes - feed source for many water birds; nesting area for fish when

inundated. n Reeds: low feed value for most birds and animals, some value as nesting cover for birds and

animals. n Rushes: feed source for many bird species. n Sedges: feed source for numerous birds.

3.3.2 CONSTRUCTED WETLAND

There are two types of constructed wetlands to improve water quality in farm land areas. The first is free-water-surface (FWS) wetland as shown in Fig. 3.3.1 whose water surface is exposed to the atmosphere. The other is subsurface-flow (SF) wetland as shown in Fig. 3.3.2 whose basin is filled with porous media, usually gravel, and the water level is maintained below the top of the gravel. Free-water-surface (FWS) wetland The FWS (free-water-surface) wetland has greater potential for beneficial habitat values because the water surface is exposed and accessible to birds and animals. Further enhancement is possible via incorporation of deep open-water zones, and the use of selected plantings to provide attractive feed sources (i.e., sago pond weed and similar plants). Nesting islands can also be constructed within these deeper-water zones for further enhancement. The bed contains emergent aquatic vegetation, 115

a layer of soil to serve as a rooting media, a liner if necessary to protect the groundwater quality, and appropriate inlet and outlet structures. The depth of FWS wetland is designed depending on the normal tolerance range of the plant species selected. The depth influences on the effective wetland volume and, consequently, the hydraulic residence time (HRT). Water depth, volume, and HRT are interrelated by Eq. 2.3.1 (Reed et al., 1990). HRT = (10,000) (H) (A) φ / Q

Fig. 2.3.1 Free-water-surface wetlands

(2.3.1)

where, HRT is hydraulic residence time (days), H is water depth (m), φ is void fraction, A is wetland area (ha), and Q is flow rate (m3/d). The water depth in this type of wetland can range from a few centimeters to 0.8 m or more, depending on the purpose of the wetland. A normal operating depth of 0.3 m is typical. Aspect ratios (L:W) from less than 1:1 up to about 3:1 or 4:1 are acceptable. Short-circuiting can be minimized by careful construction and maintenance of the wetland bottom, by use of multiple cells, and with intermediate open-water zones for flow redistribution. Constructed wetlands should be compartmentalized with several cells arranged in series or in parallel. The use of multiple cells allows redistribution of flows, maintenance of plant communities, and isolation of different plant populations and any associated diseases or pathogens (Reed et al., 1995). A study carried out in Rural Research Institute of Korea. Size of each plant bed in the constructed wetland system was 3.3 m (width) X 46 m (length) and aquatic macrophytes were Typha angustifolia, Zizania latifolia, and Oenanthe javanica. Bed soil was composed of sandy-loam with 10% of gravel. The results showed that removal efficiencies of the O. javanica beds, Z. latifolia beds, and T. anguistifolia beds increased as the HRT got longer. However, the removal efficiencies were lower than U. S.EPA data, because the concentration of pollutants, such as BOD, TN, and TP of influent was lower than that of background concentration that the free surface water flow wetlands suggested from U. S. EPA have (1999 and 2000). The removal of SS under 1 hr ~ 6 hr of HRT was higher than under 1 day ~ 5days of HRT, and the highest efficiency appeared in 3hr of HRT. Therefore, HRT for the removal of SS by the constructed wetland did not need more than 1day, and it may be effective even under short HRT as 3hr with high hydraulic condition. A large amount of Chl-a in influent from the reservoir was effectively removed in the constructed wetland. In the removal of nutrients for reservoir, this constructed 116

Chapter 3. Planning Framework for Managing Tidal Area Development

wetland system with short HRT and high hydraulic loadings were very effective, and removal activity is relatively higher than those of other similar studies. Therefore, emphasis should be on the daily purification amounts with high hydraulic loadings for the quality improvement of eutrophic reservoir water with relatively low nutrient influents and large quantity to be treated. Subsurface-flow (SF) wetland The SF (subsurface-flow) wetland concept has less potential habitat value as compared to the FWS wetland because the water is below the surface of the SF media and not directly accessible to birds and animals. Enhancement of habitat values or esthetics is possible via selected plantings around the perimeter of the SF bed. The same species of vegetation are used in both types of wetlands. In the SF case the vegetation is planted in the upper part of the gravel media. A liner is also used, if necessary, to protect groundwater quality. There are several advantages to the SF wetland concept. Since the gravel media has more surface area than the FWS wetland, the gravel bed will have higher reaction rates and therefore can be smaller in area. Since the water surface is below the top of the media and not exposed, the SF type does not have mosquito problems, which can be an issue for FWS type wetlands in some locations (Reed et al., 1995). For SF system, cross-sectional area is calculated based on Eq. 2.3.2 (Reed et al., 1990):

Ac = Q / (Ks S)

(2.3.2)

where, Ac is cross-sectional area of bed (W × d, m2), Ks is hydraulic conductivity of the media (m3/m2/d), S is bed slope, W is bed width (m), and d is bed depth (m). The depth of the media is typically 0.3~0.6 m. An ecological wastewater treatment system was developed for the rural sewage by Rural Research Institute in Korea. It consists of Ultra Hydrophilic Media Biofilter as pretreatment unit and Stair-Type Up and Down Subsurface-Flow (SF) Constructed Wetland as treatment unit (Fig. 3.3.2).

Fig. 3.3.2 Stair-type of subsurface flow constructed wetland

117

Box 3.3.1 Habitats of microorganism in the mild sloped seadike in Saemangeum Project (Park Sang Hyun) A mild sloped seadike structure is not only efficient to decrease wave run up height of seadike but also to provide feed and shelters for living creatures. Fig. Box 3.3.1 shows the cross section of mild sloped seadike structure in northern part of Saemangeum seadike.

Upper Site

Middle Site

Lower Site Tidal Zone

A biological study has been carried out to compare the inhabitation circumstances between rock and concrete structures located 3 km away from the sea dike. The results shows in Table Box 3.3.1.

6 m

Fig. Box 3.3.1 Cross section of mild sloped seadike in the northern part of Saemangeum Project

Table Box 3.3.1 Species distribution of adhesive animals and seaweed in the survey Area (Unit: number) Times & areas /Species

September

October



Stone

Concrete

Stone

Concrete



riprap

tetrapod

riprap

tetrapod

Adhesive animals

56

21

44

23

Adhesive animals

13

2

9

2

Fig. Box 3.3.2 Seaweed on the surface of rock & concrete block (July 2003)

In conclusion, the riprap structure provides better shelter for adhesive animal and seaweed than concrete structure. 118

More detailed descriptions are in ICID Workshop Proceedings on SDTA in 2002.

Chapter 3. Planning Framework for Managing Tidal Area Development

The hydraulic loading rate and hydraulic residence time of the process were 0.7~1.1m2/m2 day and 0.9~1.4 days, respectively. The average influent concentration of DO was 5.3 mg/L and effluent was 5.9 mg/L. Average influent concentration of BOD was 122.1 mg/L and effluent was 6.1 mg/L with average removal rate of 94.5%. Average influent concentration of SS was 75.4 mg/L and effluent was 2.3 mg/L with average removal rate of 97.1 %. Average influent concentration of T-N was 46.7 mg/L and effluent was 8.1 mg/L with average removal rate of 82.1 %. Reason for high removal rate of the nitrogen might be mainly nitrification and de-nitrification in wetland and uptake by plants. Average influent concentration of T-P was 4.1 mg/L and effluent was 0.5 mg/L with average removal rate of 85.7 %. Reason for high removal rate of the phosphorus might be mainly strong adsorption characteristic onto media particles. The BOD, COD, SS, TN, TP concentrations of effluent were lower than water quality standard. Compared to existing system, this system is quite competitive because it requires low capital cost, almost no energy and maintenance. 3.3.3 HABITATS ROLE OF THE TIDAL RECLAIMED AREAS FOR MIGRATORY BIRDS AUTHORS: PARK SANG HYUN, LEE DEOG BAE

A lot of migratory birds visit Korea from Siberia during early winter season and visit from South eastern Asia, Japan or Australia to take foods and shelters during their stay in the areas, as shown in Fig. 3.3.3.

Fig. 3.3.3 Migratory route of passing from Oceania to Siberia 119

Many winter birds stay in tidal wetland and reclaimed areas in the south and western parts of Korea as shown in Fig. 3.3.4. Tidal flat forms distinctive ecosystem with an interacting population of microscopic bacteria, benthic algae, and larger organisms such as fish and birds. Moreover, in tidal flats material is recycled by consumers and then decomposers, which derive their energy from organic matter produced by benthic algae and supplied by the rivers and ocean. However, these organisms are exposed to severe changes in environment caused by the tides, and they suffer heavy predation pressure from the ocean, land, and sky. For that reason relatively few species inhabit tidal flats. Recently, many countries have adopted the Convention on Biological Diversity (CBD) with farmers. The budget has been used for farm landowners who provide habitats to the migrants such as spreading rice straw in paddy field, barley cultivation, rice no harvest and paddy field flooding. Migratory birds in tidal areas Fig. 3.3.5 shows the comparison results between averaged number of distinctive and rare migratory birds and watershed areas in freshwater lake and river estuary, surveyed by Ministry of Environment of Korean Government from 1999 to 2005. It shows the numbers of migratory birds are increasing in proportional to watershed areas. And the increasing rate related to the watershed areas is larger in freshwater lake than river estuary. The largest numbers of migratory bird gather in Geum river estuary. More winter migratory birds visit freshwater lake because of less wave and tidal influence in the lake than in the estuary. In addition, rice grain remained in the reclaimed paddy provide sufficient nutrients for the winter migrants. Among the migratory birds in the tidal reclaimed areas, main species are geese and ducks, however, small waders are so rare that more effort is needed to provide shallow water shelters and to improve bio-diversity in the tidal reclaimed areas.

Fig. 3.3.4 Tidal reclamation areas in Korea 120

Table 3.3.1 represents the survey of feed available to the migrants, in Cheorwon

Chapter 3. Planning Framework for Managing Tidal Area Development 10000

No. of Distinctive and Rare species

9000

Lake/ 1010 담수호/ Estuary 하구

Geum Lake

8000 7000

Haenam Lake

6000

Han River estuary

5000 4000 Yeongsan Lake

3000

Nakdong River estuary

2000 1000 0

0

5000

10000

15000

20000

25000

30000

2

Watershed(km )

Fig. 3.3.5 Number of migratory birds and watershed areas

County, in the De-Military Zone at the upstream of Han River, Korea. The area provide habitats for migrants, such as bean goose, black-billed magpie, white-front goose, whooper swan, greenwinged teal and baikal teal, hooded crane and white-naked crane during winter season. Number of rice grain shed in the field is estimated to be 422 per m2, resulting total shed grains of 212 kg/ ha. This is equivalent to 3% of the total rice grain yield. To estimate available feed to the winter migrants in a district, the area of autumn plowing area, about 35% of the harvested area shall be excluded. It is estimated 1,061 Mg of feed available. The shed grains attract winter migrants, owing to shedding grains during mechanical harvest. Daily energy budget to birds Table 3.3.1 Feed available to the migrants in Cheorwon paddy plain Number of

Amount of

Paddy field

Total shed

Feed

grains (m-2)

grains (kg ha-1)

(ha)

grain (Mg)

available1 Mg)

422

212

7,700

1,632

1,061

Note: 1) 212 kg ha-1 × 7,700ha (1-0.35); here 0.35 is average portion of autumn plowing

The daily energy budget is calculated by equation (Koplin, et al., 1980) to estimate feed requirement for the grain-eating birds such as ducks and swans. Daily Energy Budget (DEB) = NFA×EM (Ta) + FA×BM×FC



(2.3.3)

where, BM is basal metabolism (0.5244 W 0.7347), FC is flight coefficient (13.7), EM is 4.235 W 0.5316, W is body weight, DEB is daily energy budget, NFA is proportion of the 24 hours spent 121

in non-flight activity, FA is proportion of the 24 hours spent in flight activity, EM is existence metabolism of non-passerine birds in winter as a function of ambient temperature (Ta). This equation shows that daily energy budget depends upon body weight, temperature and flight hours. Daily flight hours are 1 to 2 hours for geese, 0.5 to 1.5 hours for swans, 2 to 3 hours for mallard and 3 to 4 hours for teals. Table 3.3.2 shows daily energy for various migratory birds such as bean goose, green winged Baikal teal, et al. Requiring grains (RG) for the winter migrants is defined as the following equation: RG = (BP×WP×DEB)/UERG



(2.3.4)

where, BP is bird population, WP is wintering period (days), DEB is daily energy budget, and UERG is unit energy of the rice grain. Table 3.3.2 Daily energy budget for the winter migrants Migrants

Daily energy

Daily grain



Flight hours

budget (kcal D-1)

requirements (g D-1)

Bean goose

1~2

479.3~601.3

136.9~171.8

White-fronted goose

1~2

353.4~435.6

101.0~124.5

Whooper swan

0.5~1.5

632.1~884.0

180.6~252.6

Mallard

2~3

263.0~306.9

75.1~87.7

Green-winged teal

3~4

152.0~170.4

43.4~48.7

Baikal teal

3~4

152.0~170.4

43.4~48.7

Recently, many countries have conducted to identify fluctuation and monitor the main wintering and staying ground for birds and strengthened its relationships with neighboring countries, and signed an agreement on conserving migrants. Species-oriented networks, such as East AsianAustralasian Shorebird Reserved Network, Northeast Asian Crane Site Network and Asia-Pacific Anatidae Reserved Network have been launched for the conservation of migrants in various regions. CONCLUSION

Well managed paddy rice, irrigation canal and freshwater lake have excellent conditions as artificial wetland to provide habitats for migratory birds and other creatures in tidal area. To increase biodiversity in the tidal reclamation area, supporting systems should be so prepared nationally as well as internationally that more effective habitat space could be created. 122

Chapter 3. Planning Framework for Managing Tidal Area Development

3.4 Irrigation and Drainage Planning 3.4.1 SUSTAINABILITY OF IRRIGATION AND DRAINAGE CANAL AUTHOR: PARK SANG HYUN

For the sustainable development of irrigation and drainage canal system in tidal low land area, agricultural production, water quality and biological conservation, as well as flood prevention are main issue for the design, operation and maintenance of the water management system. Water productivity of irrigation water Irrigation water requirement is depend on climate, crops and soil characteristics. Canada does not need irrigation water while Egypt and most of African countries need100 % of irrigation water for crop yields. IWMI (2004) derived Water Productivity function to estimate water use efficiency for crop yields. WP = Y/IRR



(2.4.1)

where, WP is water productivity, Y is crop yield (kg/ha) and IRR is amount of irrigation water (m3/ha), respectively. As shown in Fig. 3.4.1, water productivities in south eastern Asian countries are lower than other countries as actual evapo-transpiration is comparatively high, and Japan and Korea use more than 10,000 m3/ha of irrigation water to get 5,500 kg of paddy rice per ha, however, large quantities of water are reused in lowland areas such as tidal reclaimed area.

Rice

1.4

Water productivities kg/ m

3

1.6

Wheat

1.2 1

0.8 0.6 0.4 0.2 0

China

Egypt

Indonesia

Japan

Korea

EU15

India

Thailand

USA

Countires

Fig. 3.4.1 Water productivity of cereals in each country (1995)

In the Figure, EU 15 countries have highest water productivities based on advanced water management systems and moderate weather characteristics. 123

In tidal low land area, larger quantities of water will be used than upstream areas, as watershed area is larger, however, water quality shall be considered to avoid harmful effects for human being and ecological system. In the long term, soil ripening will be promoted and leaching acidity and toxic elements from soil and water will be considered in tidal reclamation areas (Refer Md. Liakath, F.X.Suryadi, and Bart Schultz, et. al, 2002). In addition, Drainage in the tidal reclaiming area is affected by tidal movement in the near shore, storage volume of the freshwater lake. The drainage canal is located in flat area that the flow is so slow that it increases the capacities of sluice and pumps to release flood water in the area.

Photo 3.4.1 Flap gate in Drainage canal in the tidal lowlands of Sumatra,Indonesia

And it is need operation and maintenance operation cost of drainage pump stations to release water from the upstream. In the Netherlands, hundreds hector of the crop area have been immerged as the operation cost of pump is more than the farmers benefits.

Fig. 3.4.2 shows the planning procedure of drainage system in tidal reclaiming areas. Recently, retardation basins have been expanded to store more flood retarding water before release it by drainage pumps in the freshwater lake. The expanded storing basin is not only contributed to decrease the operation cost of the pump station but also to enhance ecological environment in the lake. Photo 3.4.2 Automatic Electrical Drainage pump

Wet agricultural land, such as paddy field station in a polder, the Netherlands area, is defined by the Ramsar Convention as human made wet land. As a lot of migratory birds stay not only in agricultural land but also in freshwater lake as well as in the irrigation canal drainage canals. To keep ecological and water quality environment, many sustainability indicators will be prepared in the tidal reclaimed area. The sustainability indicates derived by Kazumi Yamaoka (2003) are adoptable to assess the agricultural land in tidal areas. 124

Chapter 3. Planning Framework for Managing Tidal Area Development

-

Biodiversity Integrity Index related to water use = wet land required for breeding of birds / total arable land. (2.4.2)

-

Water circulation Network index = Drainage canal length per agricultural land (m/100ha) (2.4.3)

-

Multiple Positive Index = Length of irrigation and drainage canals that have multiple external functions/ total length of all irrigation and drainage canals (2.4.4)

Traditional earth canal have more positive roles than modernized pipe line system and concrete structure to keep biodiversity of species and water quality in the water way. In addition, the water ways should be wetted not even irrigation periods in case biodiversity is important. In tidal areas, as waterways are so mild that it provides boating and swimming place for visitors. To increase the multiple positive roles, water quality should be maintained in allowable level.

Fig. 3.4.2 Planning of drainage system

-

Flood Reduction Index = Total usable capacity of agricultural water storage facilities × Ratio of vacant capacity in the reservoir × Flood days per year (2.4.5)

Participatory irrigation management is very important not only increase irrigation efficiency but also keep tradition and culture in rural areas. -

Participatory Irrigation Management (PIM) Index = Irrigated area where farmers manage agricultural water in participatory or organized manner/total irrigated area (2.4.6)

125

Averaged annual rainfall in the world is 970mm and per capita rainfall amount is 26,800m3. However, only 2 percent of all the earth’s water is fresh water. Irrigated agriculture has contributed to improve rural welfare in the tidal areas of eastern Asia and Western Europe for long century. In a market situation, however, irrigation in tidal reclaimed area is less economic than upper catchment because there is accost to irrigation in pumping, conveyance and system management. In case, there are less water resources in the lowland, it is inevitable to use waste water from upstream or brackish water for tolerance crops. CONCLUSIONS

Irrigation and Drainage system is quite related to the optimal usage of land and water resources and environmental conservation in the tidal reclaiming area. In case more farm land is needed the maintenance water level of the freshwater lake should be decreased and the flow capacity of the irrigation and drainage facilities should be increased to cope with drought disasters in the benefit areas and flood disaster during storm periods. Especially, in the recent era, when climate change is hot issue, farmland created in lowland areas need more capable irrigation and drainage canals and subsurface drainage systems to increase agricultural products, to conserve ecological environment as ecological corridors and to decrease drought and flood disasters in the tidal reclamation areas. 3.4.2 WATER MANAGEMENT IN CREEK-FIELD SYSTEM AUTHOR: MASAHARU KURODA

In tidal reclaimed area, the creek-field system will be applied for the planning of irrigation and drainage system for effective using of the reuse mechanism of water and for suitable water managements. The actual operation of the creek-field system has been applied to the Kase River Irrigation Project in Japan (Kuroda, M. 2005). The tidal reclaimed lands usually have creek networks originated from tidal water channels spreading over shallow sea bottom. The creek networks were irregularly overspread and connected each other in reclaimed area in past former ages. The land consolidation projects were started covering the creek-field system in the early 1970s. The creek networks are separated in individual blocks by regulating gates from upstream side to downstream side. The networks have three remarkable functions. One is the buffer and regulating function of water storage and another one is the conveyance function and last one is drainage function. These functions are realized by operating sluice gates as illustrated in Fig. 3.4.3. 126

Chapter 3. Planning Framework for Managing Tidal Area Development

Reuse mechanism of water in creek-field system

Fig. 3.4.3 Layout of creek-field system

The reuse mechanism of return flow in the irrigation system is effectively realized using the functions of creek networks above mentioned. Each paddy plot faces to creek, therefore, almost of seepage water and leakage water from paddy plots return into the creek network. There are restricted limitations for getting new sufficient water resources in newly reclaimed areas, because, almost of water resources has already been used for the previously existing paddy areas in upstream side.

Therefore, the reuse mechanism of water resources in the creek-field system is effectively used for paddy irrigation in newly reclaimed area (Kuroda, M., 1987). Conceptual explanation of water balance in creek-field system

Fig. 3.4.4 Water balance in creek-field

The layout of the creek-field system is shown in Fig. 3.4.3, in which the water is supplied from the main canal to each creek and each creek is connected by the water gate for surface drainage. Water circulation in the creek-field system for paddy culture is illustrated in Fig. 3.4.4 (Kuroda, M. and Cho, T. 1982). The water level in creeks is always lower than the surface of paddy plots in the creek-field system. Therefore, water supply to paddy plots from creeks, denoted by Qup is usually carried out by pumping. The equations of water balance are given as follows.

Water balance in paddy plots: Qup = Qetf + Qper – Qinrf + A∫(δh/δt)dt + Qsr

(2.4.7)

Water balance in creeks: Qinc = Qevc + Qup + Qsoc +∫a(δH/δt)dt – Qrc – Qsr – Qinrc (2.4.8) Water balance in seepage: Qper = Qda + Qrc

(2.4.9) 127

where, Qup is water supply to paddy fields from creeks by pumping, Qetf is evapotranspiration of the paddy plots, Qper is water percolation from the paddy plots, Qinrf is effective rainfall to the paddy plots, A∫(δh/δt)dt is variation of surface storage on the paddy plots, Qsr is surface runoff from the paddy plots, Qinc is water supply from main canals to creeks, Qevc is evaporation from creeks, Qsoc is runoff from creeks to out of the system, ∫a(δH/δt)dt is variation in water storage of creeks, Qrc is seepage from the paddy plots to creeks, Qda is vertical downward percolation from the paddy plots, and Qinrc is rainfall to creeks. Actual concrete examples of terms The values of each terms concerning to the conceptual explanations was derived based on the actually measured data (Ikushima, Y and Kuroda, M. 1973). -

The value of the evapotranspiration rate will be, for example, 5 mm/day in fine day of rice planting season. The flooding depth on paddy plots is shallow around 3~10 cm, and the depth is changeable according to growing stages and cultivating process.

-

The water percolation from paddy plots Qper is consisted of the vertical downward percolation from paddy plots Qda and the water seepage through the levees of the plots Qrc. The quantity of Qda is very small around 2~3mm/day as shown in water depth indication. Because, in usual, the soil of tidal reclaimed lands is heavy clay soil and the ground water level is high affected by tidal pressure. Especially, the clay soil is usually consisted of clay mineral “montmorillonite” and it has small permeability around 10-5~10-6 cm/s. The value of Qrc is around 7~8mm/day in actual measurements by water balance survey on fields consisted of many paddy plots. The reasons of such value are considered that levees are very thin and each plots face to creeks. The differences of water table between plots and creeks are 0.6~1.0m in usual. Since the total water percolation from paddy plots Qper is summation of Qda and Qrc, therefore, the value of Qper is around 10mm/day.

-

The seepage water through the levees Qrc returns into creeks, and the returned water is available to be used in the irrigation system.

-

The water requirement of each paddy plot is given as summation of Qetf and Qper. The actual value of water requirement is relatively small in reclaimed paddy plots. For example, the water requirement is around 15 mm/day in the reclaimed paddy plots in Saga, Japan, and this value is almost a half of the value in alluvial paddy areas. The actual amount of pumped water from creek network to each paddy plot is increasing or decreasing due to rain falls and to control flooding depth covering each paddy plot, but the fundamental value of water requirement is able to regard as summation of evapotranspiration Qetf and water percolation Qper.

-

The surface runoff from paddy plot Qsr and the seepage water through the levees Qrc returns into creek network. Thus, the returned water is available to reuse again as irrigation water using buffer function of creek network. Therefore, it is expected that the water requirement of the creek-field system becomes smaller and this phenomenon is relating to saving water resources.

128

Chapter 3. Planning Framework for Managing Tidal Area Development

Actual Operation of Creek-Field Irrigation System The Kase River Irrigation Project was chosen as a model for investigating the operation of the creekfield irrigation system. The project has 11160 ha of irrigation command area in Saga Plain facing Ariake Sea, Japan. The command area is covered with the typical creek-field irrigation system. The dynamic programming method was applied for evaluating the actual operation of the creekfield irrigation system. The objective function is given as Fi=min∑Qinci

(2.4.10)

in which subscript i denotes the number of days counted from the beginning of the irrigation season. Qinci is the daily time series of water supply from water sources through main canals to the creek-field irrigation system. Fi is, therefore, the minimized water resources supply during one irrigation season in the irrigation project. The limiting conditions for simulation are 1) capacity of pumping from creek networks to fields, 2) upper and lower limits of water level in creek networks and 3) the limiting depth of flooding water on paddy fields. Qinci is given as recurrence function derived for the ith day in time series: Qinci (Hi) = Qevci + Qupi + Qsoci + [ Vi (Hi) - V i-1 (H i-1) ] - Qrci - Qsri - Qinrci

(2.4.11)

in which V is storage volume of water, H is water level in creek networks, and the relation between V and H is given by the V-H curve from measured data. In this case, the recurrence function becomes Fi (Hi) = min [Qinci (Hi) + Fi-1 (Hi-1) ]

(2.4.12)

and the initial value is F1 (H1) = min [Qinc1 (H1)]

(2.4.13)

CONCLUSIONS

In the actual operation of water supply, the ratio variations of yearly effective use of irrigated water are large; and the ratios of effective use increased in drought years to levels which are close to the ratios obtained with the simulation, and the ratios of effective use decreased in normal years. These results have led us to recognize that in drought years the water supply was carefully controlled for saving water resources by the irrigation association. On the other hand, in normal years the operation was targeted for avoiding the serious flooding damage due to sudden heavy rainfall events, therefore, the drainage function of creek network is prior to saving water. 129

3.5 Catchment Flood Management Planning 3.5.1 HYDRAULIC STRUCTURES IN RELATION TO FLOOD PROTECTION AUTHOR: F. G.J. DE JAGER, J.D. STOOP AND C.J.J. ZIMMERMAN

In tidal areas, hydraulic structures have been installed to protect against flooding at sea, as a consequence of storm surges, or in one of the rivers, due to increased discharge from the hinterland (F. G.J. de Jager, J.D. Stoop and C.J.J. Zimmerman, 2002). Primary flood defenses along the rivers mainly consist of dikes. Hydraulic structures such as sluices, pumping stations and flood ways, form constructed elements within the primary flood defenses for water management. Precise management of these structures is required optimal water management schemes for sustainable development of agriculture, navigation housing and other nature development functions. Furgo (2001) carried out a flood risk analysis, to be applied for the design of hydraulic structures in the tidal areas. Safety approach for flood protection After the disastrous floods of 1953, when the Southwest part of the Netherlands were flooded and over 1,800 inhabitants drowned, flood protection policy had been prepared for flood defenses based on an economical cost-benefit analysis [Delta Commission 1960]. The construction cost and maintenance of flood protection structures are weighed against damage caused by flooding. From an economic point of view, the optimal flooding frequency for a dike-ring area can be derived from this analysis (see Fig. 3.5.1). This safety concept was not implemented completely at the time. The main reason is that given the technical capabilities at the time were not available to estimate the probability of flood protection structures collapsing and therefore the probability of a dikering area, as shown in Fig. 3.5.2 flooding was unknown. Fig. 3.5.1 Cost-benefit analyses to determine economic optimal frequency of flooding

130

Chapter 3. Planning Framework for Managing Tidal Area Development

The Flood Protection Act (1996) sets safety standards for each dike-ring areas, expressed in a frequency that corresponds to the frequency of a certain Design Water Level (DWL) being exceeded. Frequencies are set at 1/1,250 per year for dike ring areas in the less inhabited east of the country, threatened by high river discharges. A frequency of 1/10,000 per year is set for dike-ring areas in the west of the country, where population and economic activities are concentrated and that are threatened by storm surges at sea. All primary flood protection structures must be dimensioned sufficiently high to safely withstand the locally prescribed DWLs.

Fig. 3.5.2 Flood defences enclosing a dike-ring area, the Netherlands

The flood retarding structure is defined as being overloaded once the volume of water flowing through or over the structure exceeds an admissible volume. This admissible volume corresponds to the onset of damage in the dike-ring area to be protected. Three mechanisms for a structure being overloaded are identified: (1) overflow of a structure in closed condition, (2) overflow through an open structure and (3) structural collapse. The height is the first design parameter. Every structure is to be designed that the locally prescribed DWL can be retained. Usually an extra height is maintained for wind- or wave overtopping and the fact that water levels may rise in the future due to climate changes e.g. sea level rising. 131

To ensure a structure is able to safely withstand the hydraulic loads induced by this DWL, a safety factor of 10 is set for the reliability of closing procedures. Reasons for failure of structures closing include technical or human errors in the operating procedures e.g. closing too late. Warning, mobilisation and backup systems (e.g. for electricity) should provide this extra level of safety. Structural collapse is never accepted. Therefore this Design Guideline for Structures sets safety factors for design of the foundation, closing doors, sheet piles, materials etc.. A safety factor of 100 is applied to ensure the structure is sufficiently strong and stable during high water periods. In accordance with the Flood Protection Act (1996) all primary flood defences are subjected to a safety assessment every five years. This ensures that vital flood defences are not neglected. Local authorities are responsible for the safety evaluation of structures under their control. The Guideline for Safety Assessment of Flood Protection Structures (1999) presents practical formulas and criteria to perform safety assessments for all types of flood protection structures. The assessment provides information about the condition a structure is in and whether design parameters, as mentioned in the Design Guideline for Structures [TAW, 1997], are met. The Guideline is to be updated with new methodologies, models and boundary conditions including DWLs, every five years. Other parameters include wave-height, wind speed, flow-velocities and duration of storm surges and high discharges. The assessment does not however provide information about the actual probability of a structure failing and the probability of flooding due to unsafe structures. The safety of hydraulic structures is thus still unknown and determined by some neglected causes: •

The fact that water levels exceeding the DWLs doe not immediately involve flooding of the entire dike-ring area. Limited wave overtopping or overflow is acceptable in certain occasions. The structure does not necessarily fail or collapse at water levels equal to DWL: the additional design requirements provide structures with some extra safety margin. This margin is not exactly known.

•

Flooding can still occur at water levels below the DWLs. In the Design Guideline for Structures (Ref. TAW ,1997], requirements are prescribed to prevent structures failing at lower water levels, but as frame 1 shows, it is impossible to exclude all possible events.

Flooding risk and probabilities in tidal areas As mentioned in the introduction, the Dutch Ministry of Transport Public Works and Water Management is developing a safety concept for flood protection structures, based on flooding risks. In this concept flooding risk is defined by: 132

Chapter 3. Planning Framework for Managing Tidal Area Development

Flooding Risk = Pflood * D

(2.5.1)

where, Pflood denotes the probability (1/year) of a certain dike-ring area flooding, due to failure or collapse of any individual section in the dike-ring. The term D denotes the effects caused by the flooding event. The effects are usually separated into economical (monetary) damage and victims. Models to predict the number of victims, or the level of economic damage, are in development, for example see Waarts (2001). The unit flooding risk is thus expressed in euro/year or victims/year. It is not only the probability of flooding, but also the relationship with the subsequent consequences that determines the (social) acceptability of flooding. Jorissen (1997) stated that the flood risk concept can be applied for the following goals, such as Monitoring developments which influence the flooding risk and the risk perception, Comparing the flooding risk with other sources of risk, Measuring the effectiveness of various flood protection strategies and Optimising the selected strategy and structural design of flood protection measures. The risk concept requires safer (higher or stronger) structures for areas with a high level of potential damage to provide the same level of risk as for areas with a low level of potential damage, where structures can be constructed ‘lower’ and ‘less stronger’ and thus less expensive. The method for determining the contribution of hydraulic structures in the flooding probabilities is separated into three mechanisms for a potential flooding event that is caused by the failure of each hydraulic structure present in the dike-ring: •

Overflow due to insufficient retaining height

•

Collapse due to insufficient strength and stability

•

Not closing (when necessary) due to failing of operations

a. Insufficient strength and stability

Fig. 3.5.3: Distinguished failure mechanisms from which flooding occurs 133

The actual water retaining height of the structure and the probability of the water level exceeding this height (see Fig. 3.5.3) defines the probability of a structure overflowing: Pflood,height = P(water level > retaining height structure)

( 2.5.2)

Where, Pflood, height is the probability of a dike-ring area flooding due to overflow of the structure. The water retaining height Y of a structure is measured in the field or read from drawings. The probability of a certain water level occurring is derived from river discharge and water level frequency analysis. An example of a frequency line is shown in Fig. 3.5.3. A water level just exceeding the height of the structure does not immediately involve flooding. Limited overflow can be safely stored in most occasions. The amount of water that can be safely stored Vadm, is dependent of the storage capacity of water system behind the structure. In cases where a large lake or channel is situated directly behind the structure, Eq. 2.5.2 changes to: Pflood,height = P(water level > critical water level)

(2.5.3)

The critical water level in the river or at sea is determined from hydrological analysis of the storing capacity in the lake or channel. This analysis of retaining height is not restricted to hydraulic structures, but applies for dikes and dunes as well. For the determination of flooding probabilities of a whole dike-ring area, the section in the chain of flood protection structures surrounding an area with the highest probability, is decisive.

Fig. 3.5.3 Determining flooding probability as a consequence of a structure overflowing

Flooding due to insufficient strength or stability of structures can have several causes. The most common causes include: • 134

Collapse of water retaining elements (i.e. sluice gate) due to (excessive) hydraulic loads

Chapter 3. Planning Framework for Managing Tidal Area Development

•

Accident (ship locking) and bad state of structure elements (maintenance)

•

Piping and Collapse of foundation

Drawings and documentation of design and construction provide information about materials used, dimensions, construction methods, soil parameters etc. From these, the initial strength and stability can be (re)calculated. Some structures are so old and documentation is not available. A field inspection of the structure and an interview with the maintenance service usually provides information about the actual condition the structure is in. The actual strength and stability can then be recalculated and related to the probability of the maximum acceptable water level. This probability of exceeding this level is the flooding probability Pflood, strength & stability. b. Not closing when necessary This probability has three constituent parts: From the operations protocol, the probability of the structure being open, Popen is known, for example based on an average number of ship-lockings per year. A second probability, f(h>okp| sluice open) is the probability of water exceeding a given admissible level which corresponds to the onset of flooding. Finally, Pns denotes the probability of a structure ‘refusing’ to close when demanded and has to be estimated. Eq. 2.5.3 then generates the overall probability of flooding due to the open structure. Pflood, not closed = Popen × f(h>okp| sluice open) × Pns (2.5. 4) c. Uncertainty and required information For numerous structures built over decades ago, information about the initial design parameters is not available. A detailed investigation has to be carried out for those structures. The required information can be drawn from: •

Observations from (periodical) inspections or maintenance and during high water periods

•

Interviews with responsible authorities

•

Design methods and drawings

•

Safety evaluations made in the past in accordance with the Flood Protection Act.

Where characteristics cannot be evaluated, or uncertainties appear, conservative values must be applied. This results in a safe but sometimes unrealistic estimation of the flooding probability. d. Overall probability of flooding The overall probability of flooding due to the structure failing is then combined from the above 135

probabilities and shown in Table 3.5.1. The first column mentions the flooding mechanism. The second column shows for each mechanism the lower boundary of the safety index β, where Pflood, mechanism = Log(-β).The safety index β itself is described by a normal distribution function Φ. The lower boundaries of the safety index β (interpreted as the upper boundaries of the flooding probability) are derived directly from the methods explained in paragraphs a to c. These are defined as lower boundaries, because they appear as a result of the principle that characteristics are unfavorable estimated when uncertainties arise. Table 3.5.1. Flooding probabilities from three distinguished flooding mechanisms (values for β are for example) Flooding mechanism

β (lower safety index)

Uncertainty * β (conditional)

Insufficient

-Φ- (Pflood,height)

-

height

eg β=3.3 → Pflood, height = 1/2000 years

1/2000 years

Insufficient strength

-Φ-1(Pflood, strenght & stability)

-Φ-1(Pflood, strenght

& stability

eg β=2 → Pflood,strenght = 1/100 years

1

•••

-β-1(Pflood,height)

& stability

)



1/500 years

Not closed

-Φ-1(Pflood, not closed)

-Φ-1(Pflood, not closed)



eg β=2,5 → Pflood, height = 1/300 years

1/500 years

Total

-Φ-1(Pflood, height+ Pflood, not closed

-Φ-1(Pflood, height+



+Pflood, strenght & stability)

• •••

Pflood, not closed +



Pflood, strenght &



stability

)

In the third column a qualitative classification shows if and to what extent uncertainties, for example a lack of information, might affect the result. The last column shows the safety index β under the condition that the uncertainty is reduced or eliminated. It represents therefore best-case or least conservative safety index. This column provides initial information for closer assessment of the weakest element in the ring and may be used in following cost-benefit analyses. e. Recommendations for improvement The above method for quantifying the probability of flooding due to failure of hydraulic structures forms a step towards a risk-based safety approach for the design of flood protection structures. However, further developments can be considered to eliminate some shortcomings of the present method, and to advance to a more comprehensive method based on a more realistic model. 136

Chapter 3. Planning Framework for Managing Tidal Area Development

SUMMARY AND CONCLUSIONS

History shows that hydraulic structures for other purposes than flood protection can be unexpected weak spots in the flood defense system. Much uncertainty exists about their behavior during high water, their actual strength and stability, and the reliability of operations. The legally prescribed periodical safety assessment of structures does provide information about the condition of structures. Hydraulic structures are assessed in relation to a minimum strength as prescribed in the Design Guidelines for Structures. The assessments do not however provide information about the actual probability of an area flooding due to several failure or collapse mechanisms. Therefore the actual level of safety is still unknown. The contribution of individual structures to the probabilities of areas flooding is required to perform a integrated risk analysis of flood protection structures. Based on this risk approach, an effective flood protection policy can be pursued in the future. In this paper a method is presented to quantify the contribution of hydraulic structures to the probability flooding from sea or rivers. The method separates the contribution from the dominant mechanism: overflow, not closing and strength and stability are separate mechanisms for hydraulic structures from which a flooding event can occur. 3.5.2 FORESIGHT OF FLOOD AND COASTAL DEFENSE AUTHOR: EDWARD EVANS, JIM HALL AND JONATHAN SIMM

This subsection is the summary of the analysis of foresight of flood and coastal defense, provided in the ICID Workshop Proceedings of 2004 held in Moscow Russia. The flood risk are to be increased unless current flood management policies, practices and investment levels are changed as a lot of population are gathered in tidal areas. Potential responses to flooding are very different in the four future worlds of World Markets, National Enterprise, Local Stewardship and Global Sustainability. In the National Enterprise scenario there is, for example, low regulation of flooding with reactive rather than a

Fig. 3.5.3 Foresight futures (SPRU et al. 1999; OST 2002) 137

strategic approach to flooding problems and limited emphasis on the environment. In contrast, strategic regulation of development, management of run-off and strategic soft engineering of rivers and oceans are important in the Global Sustainability scenario. The paper addresses the responses under the four scenarios in terms of the three pillars of sustainability (social, environmental and economic) and addresses how flood defense will be delivered in terms of governance. The scenarios are not intended to predict the future, but to help clarify present-day choices by exploring the value of different options against alternative futures (OST, 2002).The potential future drivers and impacts of flood risk were evaluated for a simple baseline assumption under which the present day approach to flood management and expenditure is held constant under the four Foresight Futures. This might at first appear to be in conflict with “true” scenario analysis and it provides a baseline to evaluate the effectiveness of different flood management programs. For the assessment of responses a similar scenario framework was used as for the prediction of future flood risks, but in this case the approach to flood management and expenditure was allowed to vary in a way that was consistent with the storylines in each of the four scenarios. Quantified flood risk assessment The input data required by the risk assessment models do not correspond exactly to the information provided in either in climate change or socio-economic scenarios. It was therefore necessary to construct approximate relationships between the variables for which scenarios information was available and the variables required for flood risk analysis. Future flood risk is greatly influenced by flood management policy and practice, perhaps more so than it is by changes outside the control of the flood manager, such as climate change or economic growth. However, in the analysis described here current flood defense alignment and levels of investment in maintenance and renewal were kept the same across all scenarios. Clearly flood defense policy will change in the future and will tend to reflect the nature and public expectations of future society i.e. flood defense is scenario-dependent. However, the aim of the current study was to inform present-day policy makers and in order to do that, the present day flood defense policy was subjected to particular scrutiny, by analyzing its effectiveness in a range of scenarios. In all scenarios other than the relatively low growth Local Stewardship scenario, annual economic flood damage is expected to increase considerably over the next century assuming the current flood defense policies are continued in future. A roughly 20-fold increase by the 2080s is predicted in 138

Chapter 3. Planning Framework for Managing Tidal Area Development

the World Markets scenario, which is attributable to a combination of much increased economic vulnerability (higher floodplain occupancy, increased value of household/industrial contents, increasing infrastructure vulnerability) together with increasing flood frequency. Table 3.5.2 Correspondence between UKCIP02 scenarios and foresight futures SRES

UKCIP02

Foresight



Futures 2020

B1

Global sustainability

Low emissions

Commentary Medium-high growth, but low primary energy consumption. High emphasis on international action for environmental goals (e.g. greenhouse gas emissions control). Innovation of new and renewable energy sources.

B2

Medium-low

Local stewardship



emissions

Low growth. Low consumption. However, less effective international action. Low innovation.

A2

Medium-high

National

Medium-low growth, but with no action



emissions

enterprise

to limit emissions. Increasing and unregulated emissions from newly industrialized countries.

A1F1

High emissions

World markets

Highest national and global growth. No action to limit emissions. Price of fossil fuels may drive development of alternatives in the long term.

Change in the ratio of flood risk to per capita GDP provides an indication of how severe or harmful flooding will be when compared with economic growth over the next century. In the World Markets and National Enterprise scenarios flooding is expected to remove a greater proportion of national wealth than it currently does (and thus merit a greater investment to reduce risk). In the Local Stewardship and Global Sustainability scenarios flooding is predicted to remove a lesser proportion of national wealth since these scenarios will tend to be less vulnerable to flood damage and are expected to be subject to somewhat less climate change. What should our aims be for future flood management? Should we: •

Accept increasing levels of risk of flooding?

•

Seek to maintain risks at current levels?

•

Seek to reduce the risks of flooding? 139

If the first option is chosen, significant flood damages will be increased. This would have undesirable social as well as economic consequences. The third would require considerable additional investments in flood management. However, the analysis suggests that the economic benefits would be significantly greater than the costs. In the higher growth scenarios the increases would be less than the economic growth and so would be most easily affordable. Nevertheless, the challenge would remain to find the most efficient way of using our money and the approach that is best for society and the environment. While the second option – maintaining current risk levels – might seem reasonable, this is set against a trend in society which expects increasing standards of safety and risk reduction. It can not eliminate floods, but society may well expect fewer than at present. How important is managing climate change to the risks from flooding? Climate change will strongly affect the challenge to be faced. The probability of flooding increases significantly in the high-emissions scenarios. The World Markets scenario was analyzed for both High emissions and Low emissions scenarios – it was found that economic damages could be reduced by 25% if achieve the Low emissions scenario. Reducing climate change will not solve our future flood-risk problems by itself, but it could substantially ease them. What factors should inform our long-term approach to flood management? There are three key issues to be considered: where to concentrate future urban and economic development, when to invest in flood-risk reduction and how to manage flood risk in those areas. Where to invest: Influencing where to build houses, factories and other infrastructure is a key tool in managing future flood risks. It is about avoiding building on areas at risk from flooding – or, if building in areas at risk, ensuring that there is space to allow for river and coastal processes. This approach needs to be balanced against other economic, environmental and social needs, such as the demand for new housing. If decisions are taken to build in areas at risk of flooding, the costs must be recognized and planned for. When to invest: Different measures have different lead times, some of which are very long. These need to be recognized in any long-term strategy. Land-use planning is an obvious example. Massive inertia in the built environment means that decisions taken now could take many decades to become fully effective. This will also affect decisions on whether to maintain flood defenses in some areas as well as decisions on areas for new build. If an effective way forward is to use the realignment of defenses, retreat or even abandonment of some areas, then the sooner long-term plans are in place, the easier it would be for those affected to divest assets with minimum negative impact. 140

Chapter 3. Planning Framework for Managing Tidal Area Development

How to manage long-term flood risk: The extreme uncertainty of the future is a major challenge in devising effective long-term flood-management policies. It is important to decide how much flexibility is required to cope with an evolving future, and to choose a portfolio of responses to achieve that. In this respect, reversible and adaptable measures would be the most robust against future uncertainties. Adaptability would include approaches such as setting aside areas in floodplains that may be used for flood storage if required, or building defenses to cover the lower limits of our expectations in changes in flood risk, but with the ability to upgrade if needed. What are the implications for Science and Technology and skills? The Foresight project has shown the benefit in adopting a broad and integrated approach. The project has identified areas that have the greatest bearing on future risks, but which are also the most uncertain. These fall into three broad categories: - Reducing uncertainty in risks and responses: e.g. intra-urban precipitation; land-use planning and management. - Strategic assessment of responses: e.g. strategic risk assessment for intra-urban flooding; evaluation of non-monetary flood damages. - Sustainability and Governance: e.g. whole-system costs and benefits; human and ecological consequences of managed realignment and abandonment of defenses. Finally it is necessary to ensure a sufficient supply of engineers and other scientists for flood management in the future, and ensure that they have a broad understanding of different areas of science. CONCLUSIONS

The analysis focused on current flood management policy, projected unaltered into the future, in order to identify strengths, weaknesses and particular areas of vulnerability. To this end, a risk-based analysis framework has been established within which two separate types of analysis fit coherently: spatially explicit quantified flood risk analysis, and expert appraisal and ranking of the drivers of changing future flood risk. In both cases change in risk was analyzed by (implicit or explicit) consideration of the influence that projected climate and socio-economic change would have on the state variables describing the flooding system and the impact that changes in state variables would have on risk in a Source-Pathway-Receptor framework. Analysis of environmental and socio-economic phenomena over a timescale of 30-100 years in the future involves formidable uncertainties. Model uncertainties in climate projections up to the 2050s exceed the differences between emissions scenarios. There is considerable disagreement about the spatial patterns of climate change down-scaled to the UK. Changes in some climate 141

variables, for example extreme sea levels and short, high intensity rainfall events are particularly difficult to predict. Socio-economic change, which on a global scale leads to changing greenhouse gas emissions trajectories and on the UK scale also determines economic and social vulnerability to flooding, is even more difficult to predict and, it is argued, succumbs only to a scenarios-based approach that can merely illustrate some of the potential range of variation between different futures. The uncertainty is reflected in this analysis, to propose a partial ranking of drivers, rather than a complete ranking. Precise results have been quoted for the quantified risk analysis but they have been interpreted merely as providing an indication of the magnitude, rate and spatial distribution of potential change rather than being firm predictions. Notwithstanding the uncertainties in the analysis, it provides important new insights for policymakers. ‘Business as usual’ in flood risk management over the next century will be accompanied by large increases in flood damage, the magnitude of which will depend on the trajectory broader socio-economic change. The analysis demonstrates how the increase in flood risk will be a function of multiple interacting drivers. Climate change makes a contribution to this process but the severity of its impacts are modulated by socio-economic context, not to mention adaptive capacity, which has not featured in the current analysis. The situation is particularly severe on the coast, where the proportion of flood losses, relative to fluvial flooding, is projected to increase in future. In terms of responses there are two key messages. Firstly, continuing with existing policies is not an option – in virtually every scenario considered, the risks grow to unacceptable levels. Secondly, the risks need to be tackled across a broad front. Reductions in global greenhouse-gas emissions would reduce the risks substantially, however, this is unlikely to be sufficient in itself. Hard decisions need to be taken – either for the investment more in sustainable approaches to flood and coastal management or learn to live with increased flooding.

142

Chapter 3. Planning Framework for Managing Tidal Area Development

3.6 Water Quality Management Planning 3.6.1. CATCHMENT WATER QUALITY MANAGEMENT AUTHORS: JOONG-DAE CHOI

The catchment, basin has important physiographic property to affect the volume of water quality. The catchment divide is the loci of points (the ridge line) that separate two adjacent watersheds, which drain into two different outlets. Tidal land reclamation projects generally are pursued in high-population-density areas where land demand for agricultural, industrial, residential, or commercial use is high. Such projects necessarily accompany the construction of sea dikes and the creation of freshwater reservoirs at the mouth of rivers and streams. As environmental concerns among stakeholders increase, the water quality management of freshwater reservoirs becomes one of key elements in the success of tidal land reclamation projects. The water quality of a freshwater reservoir in tidal areas is affected by many factors such as pollution load from the catchment area through stream flow, the reservoir’s primary production mostly by photosynthesis and natural attenuation processes in streams and reservoirs. Among these factors, the pollution load from the catchment area is critical in the control of freshwater reservoir. This load is largely dependent on the land use of the area. The land use patterns of various catchment areas are quite different depending on population, industrial activity, topography, soil texture, rainfall intensity, agricultural management methods and other factors. Therefore, from the commencement of a tidal land reclamation project planning, the utmost priority must be given to the control of nutrient discharges from the catchment area. Strategies for catchment management Pollution discharge control from a catchment can be divided into two major pollution sources, that is, point source pollution and non-point source (NPS) pollution. Point source pollution is pollution of which the quantity and quality is known or easily measured and analyzed where as NPS pollution is pollution of which the quantity and quality can not be easily measured nor analyzed because NPS pollutants are mostly transported by storm runoff and groundwater flow to streams and lakes. As pollutants in catchment area have been increased, strategies for catchment management must be focused first on the elimination of point source pollution and second on the control of NPS pollution by adopting the best management practices (BMPs).

143

NPS pollution is difficult to control in that it is a sort of “natural life” pollution. Pollutants that are generated in the course of daily life activities, such as household waste, dust, agrochemicals, livestock waste are either applied to crop field or naturally accumulated on the soil surface or in the drain ditches. Such accumulated pollutants are only slowly decomposed, some of soluble nutrients moving into soil with infiltrating water and the rest of them washing away with surface runoff when storms occur. This is why NPS pollution is closely related to runoff events and is also referred to as runoff pollution. Clearly, NPS pollutant loads increased with the increase of daily rainfall.

Fig. 3.6.1 Shallow groundwater and stream water T-N concentration from a mountainous rural watershed in Korea

As shown in Fig. 3.6.1, the T-N concentrations for streams and groundwater are closely related. The results show that the stream water quality in rural areas is affected mainly by storm runoff during rainy days and by groundwater seepage during dry days, if there is no point-source pollution input. NPS pollution loads by either surface storm runoff or groundwater are also affected by topography, soil texture, agricultural management methods and rainfall. For effective water-quality control, point-source in the watershed, pollution must be reduced by adopting cutting-edge wastewater treatment systems. And if point source pollution is eliminated, NPS pollution loads, still, must be tackled effectively and economically. It is necessary to experimentally understand the generation and transport process mechanisms of NPS pollution before developing detailed NPS control methods, because NPS pollution is extremely site-specific. This means that one method can be successful for a particular site, but it cannot be applied to other sites. And if point source pollution is eliminated, NPS pollution loads, still, must be tackled effectively and economically, as it is extremely site-specific.

144

Chapter 3. Planning Framework for Managing Tidal Area Development

Effect of land use on water quality a) Pollution loads from forests Stream water quality from intact natural forests is considered to be the “background” or “natural” water quality. The pollutant concentrations in forest streams might be relatively lower than in any other streams and lakes in tropical and temperate regions. However, pollution loads from forests in terms of total maximum daily load (TMDL) might yet be large, owing to the large-area coverage of forests, and thus has a certain impact on water quality management. The author investigated the water quality of a stream in a well conserved mountain forest for 20 months (August, 2004- April, 2006), and reported that the NPS pollution loads were high. b) Pollution loads from upland areas Recently, farmers use more chemical and organic fertilizers and pesticides on a small land parcel for higher agricultural yields. NPS pollution loads in alpine agricultural area are generally high. Because NPS pollutants generally are discharged with sediment, the more the sediment load, the larger the NPS pollution loads. It is inevitable to minimize NPS pollution from upland areas to keep the water quality of a freshwater reservoir in tidal land reclamation project in the failure. c) Pollution loads from lowland (paddy) areas Drainage flow through paddy outlets is quite controllable except during days of heavy rain. It is common that drain water quality is worse than irrigation water quality. However, in some paddies by urbanized or densely populated areas, drain water is better than irrigated water, which means that the paddy acts as a constructed wetland. The ranges of NPS pollutants from paddies in Korea are shown in Table 3.6.1. Again, the loads are closely related to the drainage control at the outlet, assuming that the nutrient input for rice culture is well established. More than 40% of pollutants are believed to discharge during the short transplanting season when the paddy soil is disturbed and fertilizers are applied. Table 3.6.1 NPS loads (kg/ha) in paddy rice during irrigation seasons Measured Index

1999

2000



Inflow load

Outflow load

Inflow load

Outflow load

T-N

104.4

102.6

94.4

113.5

T-P

3.59

3.53

2.82

3.03

COD

462.4

458.1

500.8

476.9

*Data from Oh et al., 2002. . J. of the KSAE 44(2), pp.136-147. (in Korean) 145

d) Pollution loads from rural watersheds The pollutants at the source are subject to attenuation while they are transported through intervening lands to the receiving water body. Intervening land is the land located between a pollution source and a receiving water body. Ridges between fields, levee slopes, dry channels, small ditches, vegetated filter strips, constructed wetlands, sediment basins, and riparian forests are examples of intervening land. Specifically, pollutants are filtered, deposited, decomposed, nitrified, denitrified, incorporated into soil, taken up by plants and assimilated into the body of microbes and small animals in the intervening lands. NPS loads from a catchment area are affected not only by the pollution loads at the edge-of- fields but also by the natural treatment processes in the intervening lands and streams. e) Pollution loads from urban watersheds Urbanized areas produce the highest pollution loads and adversely affect receiving water quality much more than any other land uses. Point source pollution discharged from urban areas and industrial complexes must be completely eliminated by mechanical treatment systems. And nonpoint-source pollution must be minimized for successful water-quality conservation. Because of the severe adverse impact of urban storm runoff on receiving water quality, the US EPA has designated urban runoff from cities with a population greater than 100,000 as point-source pollution, and has asked municipal governments to build sediment basins or other treatment systems to reduce urban NPS pollutants in storm runoff. Urban storm runoff contains not only suspended solids, organics, nutrients and microbes but also toxic heavy metals and chemical carcinogens. Therefore, the utmost priority in the control of water quality should be given to reducing the urban pollution load. It is also recommended not to plan a tidal land reclamation project at the mouth of a river basin where large cities are located because of the huge pollution loads from urbanized and industrialized areas. The pollution loads from urbanized areas are much greater than those from other land uses. T-P is the limiting factor for eutrophication in rivers and lakes, and a T-P concentration of 0.03 mg/L is considered to be the threshold concentration for eutrophication. Dust and soil deposits in ditches of large cities contain high concentrations of metals. Deposits are subject to being washed away with storm runoff unless they are removed before rainfalls, and affect not only water quality but also aquatic ecosystems over the long term. Basic principles of Best Management Practices (BMPs) NPS pollutants are generated and transported by runoff. The power of runoff is expressed in terms of transport capacity and tractive force. Accordingly, it is important to reduce the velocity 146

Chapter 3. Planning Framework for Managing Tidal Area Development

of runoffs in order to reduce NPS pollution loads. Many BMPs are focused on the reduction of flow velocity. For example, reduction of runoff volume by increasing infiltration, increasing the drag force of residues, grasses, riparian forests or any obstacles in water courses, preparing diversion ditches to cut off inflow from other areas, constructing sediment basins to temporarily store runoff, and constructing grade structures to smoothen the slope of fields and channels, are all intended to reduce the velocity and volume of NPS pollution discharges. Filtrated or deposited pollutants can be removed manually or treated by natural treatment processes. Physical, chemical and biological treatment mechanisms work well to decompose and transform pollutants into less toxic and ionized materials, or to assimilate them into the bodies of microbes and small animals such as earth worms. Therefore, it is important to create good conditions for natural treatment processes. A sufficient supply of oxygen, good substrates (or soil) for microbial growth, sufficient moisture, temperature, and nutrient balance (C:N ratio) are the major factors affecting the natural treatment processes. Such conditions are met well in riparian corridors and vegetative filter strips, and thus these are the typical BMPs to reduce NPS pollution loads. The only exception is the denitrification process, which requires a completely anaerobic environment. A sediment basin is the effective alternatives for NPS pollution reduction from cities. However, because a sediment basin requires a large area from which available land is quite limited, various devices can trap pollutants in storm runoff. These devices are usually deployed in manholes or at the outlet of a sewer drain, the trapped pollutants in the devices having to be removed manually and regularly. One other means of reducing NPS pollution loads in cities is the use of parks. City parks can function as excellent sediment basins in removing NPS pollution without jeopardizing their primary function, if they are carefully designed and managed. Many cities these days are remodeling parks to act as a sediment basin during runoff events. Besides the above-mentioned technical approaches to controlling pollution loads in water-quality management, education, public relations and legal enforcement can help. Because most pollution is caused by people, education and legal enforcement can be the most effective method. Point source pollution should be strictly enforced by laws in order to completely eliminate it. It is known that legal enforcement on NPS pollution control is ineffective in general. However, legal standards to observe by farmers and citizens can help adopt BMPs effectively and follow guidelines to reduce pollution loads. Adoption and management of BMPs require farmers and citizens more labor, cost and technical information than conventional practices. Therefore, it is necessary to formulate policies amenable to farmers and citizens by means of incentives, educational opportunities, information services, visitation of experimental sites and farms, and yet other ways.

147

Role of Paddy field as artificial wetland Paddy field contribute to purify nutrients flowed in the paddy by settle down and resolve during irrigation periods, as follows;. -

The flows in the paddy field are so slow to settle down and lag the suspended materials in the bottom. The loading rate in the paddy is 7~8mm/day that is lower than the standard of artificial wetland (20mm/day). The depth of the paddy field is only 15 cm that is quite lower than definition of Ramsar (6 m) and provide good shelters for the small birds, such as waders. Freshwater lake provides comfortable shelters for the migratory birds to avoid high wave attacks and rapid tidal flows in the tidal areas. Irrigation canal create excellent ecological corridor from coastal areas and freshwater lake to paddy field and watershed area of the drainage canal.

- - - -

There have been competitive studies on productivities and conservation role of tidal areas. Fig. 3.6.2 shows the comparison result of paddy rice yields and average number of insect collected in each plot that includes raising ducks and snails as well as fallow and supplying conventional insecticides in four times and only once insecticide in early stage. The results shows crop yields in conventional paddy is highest followed by duck paddy. On the other hand, early supply of insecticide provided rather low paddy yield however, largest number of insects were found as it provided best habitat for various insects

Fig. 3.6.2 Rice yields and number of insects in each insecticide treatment Plot, Tested by Han Min-Soo, 2006 RDA Korea 148

Chapter 3. Planning Framework for Managing Tidal Area Development

It is more than the number of insects found in fallow paddy field. As the early insecticide paddy has reasonable crop yields and number of insects, it would be most sustainable among four management schemes to be applied for optimal supply of insecticide and herbicide in the paddy field. Conclusions and suggestions The major factors affecting water quality are two pollution loads, from catchment areas and from primary production within the reservoir. In the Catchment area, point-source pollution should be eliminated mechanically, and non-point-source pollution shall be reduced by adopting BMPs. A significant portion of NPS pollution is discharged during rainfall periods. Pollutants are largely produced and transported by runoff, and thus the importance of runoff to the control of pollution loads was emphasized. Once pollutants are separated from a water body, they should be quickly decomposed and transformed manually or naturally by BMPs. Natural treatment systems for treatment of wastewater and organic waste need to be applied together with BMPs. Besides the technological approaches to reducing pollution loads, the effect of education, public relations and legal enforcement was identified as one of the best pollution reduction methods. 3.6.2 WATER-ENVIRONMENTALLY CONSERVATION IN RECLAIMED LAND EISAKU SHIRATANI

Mechanism of nitrogen removal in surface water Transformation of nutrients in surface water could be conceptualized as an aquatic ecosystem model (Fig. 3.7.2), which consists of growth, decay and sedimentation of algae, sedimentation of particulate matter (PM) and decomposition of dissolved matter (DM). Considering the decrease of nutrient concentration to be the water purification, the sedimentation of algae and PM and decomposition of DM play as water purification based on this model while, the release of DM from sediment plays as the water pollution. Paddy fields and wetlands can show a nutrient removal function only when the water purification rate outweighs the water pollution rate.

149

CO2

N2

AC: algae COD AN: algae nitrogen

AC

DC

PC

AN

DN

PN

AP

DP

PP

AP: algae phosphorus DC: dissolved COD DN: dissolved nitrogen DP: dissolved phosphorus

Fig. 3.6.3 Conceptual model for aqua-ecosystem

It can be certain that most reactions in paddy fields and wetlands occur on sediment where bacteria inhabit and that nutrient release from sediment is driven by the disparity of nutrient concentration between the surface water and the pore water in sediment, the change in water quality concentration in the surface water is simply expressed in Eq. 2.6.1.

dC 1  L = − aC + b(Cs − C ) +  dt h  A

(2.6.1)

where, C is water quality concentration (mg/L), CS is water quality concentration of pore water in sediment (mg/L), h is surface water depth (m), A is area of surface water (m2), L is load from outside (g/d) e.g. fertilizer, a is rate constant of water purification (m/d) and b is rate constant of nutrient release (m/d). The water quality concentration decrease under the following condition (Shiratani et al., 2002a);

bC s +

L < (a + b )C A

(2.6.2)

Put another way, paddy fields and wetlands show the nutrient removal function under this condition. If PM concentration or algae concentration in the surface water is high, Eq. (2.6.2) is often satisfied. From this, nutrient can be removed effectively under solar radiation where algae grow. Comprehending factors of nutrient reaction, nutrient removal rate in surface water could be generally expressed by a first order kinetic. Thus, the nutrient concentration in the surface water decreases as an exponential form written in Eq. (2.6.3).

 k  C = C 0 exp − t   h  150

(2.6.3)

Chapter 3. Planning Framework for Managing Tidal Area Development

where, C0 is initial nutrient concentration (mg/L) and k is rate constant of nutrient removal (m/d). From this, nutrient removal per unit area and unit time is as follows:

D=



h   k  C 0 1 − exp − t  t  h  

(2.6.4)

≈ kC 0 where, D is nutrient removal rate (g m-2 d-1), and C0 in the second line of Eq. 2.6.4 may be assumed to be nutrient concentration of inflow water (Shiratani et al.). N removal rate using the rate constant k is convenient for the mutual compare of N removal rates which were found in various N concentrations of surface water listed in Table 3.6.2. Table 3.6.2 Rate constants of nitrogen removal in paddy fields and wetlands (m/d) Rate constant of N removal

Notes

Paddy field soils

0.012

Investigated by

Dark condition,

Tabuchi et al.



at 25oC

(1993)

Paddy field soils

0.007~0.014

Dark condition

Tabuchi (2001)

Fallow paddy fields

0.02~0.03

Yamaguchi & Hata (1993)

Wetland

0.021

Hosomi & Sudo (1991)

Wetland with reeds

0.024

Hosoi et al.(1995)

Constructed wetland

0.025

Hosomi (1994)

Clay canal

0.010

Dark condition, at 30 oC



Shiratani et al.(2002c)

Nitrogen removal in paddy fields In paddy fields, N is supplied through fertilizers, rainfall and irrigation water. Fertilized N is generally in the forms of ammonia N, which is immediately nitrified to NOx-N and used by algae in surface water. Based on laboratory tests under constant temperature and dark conditions, Tabuchi et al. (1993) proposed the following equation that estimates the rate constant of nitrate removal (denitrification) involving temperature change. k = 0.000011T 2 + 0.005 ( 10 oC < T < 40 oC ) (2.6.5) where, T is water temperature (oC). At T = 25 oC, k = 0.012 m/d. 151

Tabuchi (2001) also estimated nitrate removal rate for several types of soil sampled from experimental paddy fields, and got k = 0.007~0.014 m/d of the rate constants. It appears that the primary factor in these conditions is denitrification as these investigations were carried out under dark conditions in a laboratory. Yamaguchi and Hata (1993) clarified the relationship between N concentration of irrigation water and N removal rate in fallow paddy fields. Estimating rate constants from their data by Eq. 2.6.1, a varied from 0.02 to 0.03 m/d depending on water temperature and N concentration of irrigation water. These findings give an interesting interpretation. It states that N is removed effectively under light conditions where algae and vegetation grow. Judging from the above, it seems reasonable to suppose that the rate constant of N removal in paddy fields is approximately 0.025 m/d under solar radiation. Apart from this, Tabuchi (2001) summarized the relation of N removal rate to the N concentration of irrigation water from many investigations carried out on general rice cultivation in the past, and he revealed that the N removal rate which is defined as the balance of input N to output N during an irrigation period increases proportionally to the N concentration of irrigation water. The proportional constant is 0.01 m/d. It is considered that fertilizer might affect negatively on the N removal. Nitrogen removal in wetlands The N removal rate in wetlands seems to be the same as that in paddy fields. Brix (1994) reviewed the results of a series of previously reported efforts aimed at understanding the natural purification of wetlands in many countries, and found the mean rate constant of N removal in natural wetlands with free water surface was 0.025 m/d. In Japan, few investigations on N removal in wetlands have been carried out, and the central interest of these investigations was to determine the N removal capacity of wetlands inflowing waste water. Hosomi and Sudo (1991) investigated a wetland with free water surface inflowing gray water to estimate the capacity of natural purification, and reported 0.13 g m-2 d-1 as the net N removal rate. Considering the N concentration of the inflowing gray water in Eq. 2.6.4, the rate constant of N removal was 0.021 m/d. Also, Hosoi et al. (1995) reported that the rate constant of N removal in a wetland with reeds was 0.025 m/d from their laboratory test. It is assumed that the rate constant of N removal in wetlands is approximately equal to that of paddy fields. Regarding clayey canals, Shiratani et al. (2002c) estimated nutrient fluxes across/on the sediment surface of a clayey canal without reeds on the basis of hydraulic model experiments under dark conditions, and 0.01 m/d of the rate constant of N removal was suggested.

152

Chapter 3. Planning Framework for Managing Tidal Area Development

Nitrogen effluent from upland fields 350

Effused N (kg ha-1 year-1

300 250 200 150 100 50 0 0

200

400

600

800

1,000

Applied N (kg ha-1 year-1 Fig. 3.6.4 Relationship between N fertilizer and effluent N load (Shiratani, et al., 2008)

As upland fields are cultivated under dry field condition, little NOx-N nitrified from fertilizer is deoxidized to N2, and NOx-N effluent occurs with field drainage in rainy days. The relation between annual N effluent load and fertilized N seems to be a direct proportion as shown in Fig. 3.6.4. The proportional constant (= 0.29) means that about 30 % of fertilized N could be effused out of upland fields. As upland fields in a polder generally equip underdrain systems at about 50~60 cm depth, most of the field drainage are

N concentration 　(10 2mg/L)

0.7

100 90 80 70 60 50 40 30 20 10 0

0.6 0.5 0.4 0.3 0.2 0.1 0 Dec

Jan

Feb Mar Apr May Jun 1985

Fig. 3.6.5 Under-drainage and N concentration of drainage during a barley cultivation period (Shiratani et al., 2005)

Drainage 　(mm)

through the underdrain systems. Fig. 3.6.5 shows the change in N concentration of the under-drainage from a barley field where a fertilizer was applied once at the beginning of the cropping. The N concentration changes from 1 mg/L to 40 mg/L in the first half of the cropping period, and it appears that the change in N concentration corresponds to that of NOX-N in the field due to the multiple transformations of N.

Shiratani et al. (2005) developed a mathematical model which can simulate the N concentration of the under-drainage involving fertilization, N transformation in soils and plant uptake. In upland fields cultivated with vegetables, 100~2,500 kg/ha of N fertilizer are applied a year. When vegetable are cropped on upland fields in a polder, it is supposed that high N concentration water would be drained through underdrain and that the N concentration changes widely. 153

Land use for reduction of N effluent in a polder Typical land reclamation in tidal area is composed with cultivated fields where an irrigationdrainage system is constructed and a regulating reservoir. Agricultural drainages are gathered into drainage canals and pump to the regulating reservoir (Fig. 3.6.6). In the reservoir, there should be an aqua-ecosystem, and it could play like a wetland where N is removed. Culvated fields Upland fields

P

Paddy fields

Drainage canals

P

Sea

Regulang Drainage canals N removal zone

Fig. 3.6.6 Water-environmentally conservational use in a polder

The N effluent from cultivated fields is reduced in the reservoir exponentially based on Eq. 2.6.3. Taking the hydraulic retention time of the reservoir, Eq. 2.6.3 can be rewritten as following equation.

 kA L = exp − r L0  q

  

(2.6.6)

where, L is N load (g), L0 is N effluent load pumped to the reservoir (g), Ar is area of the reservoir (m2) and q is drainage pumped to the reservoir (m3/d). q/Ar is the hydraulic overflow rate (m/d) with which engineers involved in water and waste water treatment have historically correlated sedimentation in treatment reactors (Chapra, 1997). Fig. 3.6.7 shows the relation of L/L0 to hydraulic overflow rate at k = 0.025 (m/d). A regulating reservoir which can accept the field drainage below 36 mm/d of hydraulic overflow rate is required to reduce the N effluent load from cultivated fields to half. As mentioned above section, paddy fields have the N removal function of which the rate constant is assumed to be approximately equal to that of wetlands. Thus, paddy fields are regarded in N removal sites by using a part of the reclaimed land for paddy fields and arranging land use. Then, the drainage canals at the end of upland fields should have enough capacity to store the drainage and regulate the lag to the irrigation.

154

L /L 0

Chapter 3. Planning Framework for Managing Tidal Area Development

1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 0

0.02

0.04

0.06

0.08

0.1

0.12

Hydraulic load q /A r (m/d)

Fig. 3.6.7 Relation of L/L0 to the hydraulic load at k = 0.025

CONCLUSION

In conclusion, paddy fields and wetlands remove N according to the first order kinetic, in which the rate constant of N removal was approximately 0.025 m/d under solar radiation and that upland fields could effuse out about 30 % of fertilized N. Based on these findings, it is proposed a water-environmentally conservational land use in a polder. A part of the reclaimed land should be used for paddy fields and the drainage from upland fields should be irrigated on the paddy fields, then the regulating reservoir and paddy fields could play N removal sites. To take shape the water-environmentally conservational land use, it is desirable to analyze the N flow in detail by employing the unsteady N effluent model.

155

3.7 Economic Issues on Tideland Reclamation AUTHOR: KIM, HONG SANG

Issues related to the economic feasibility of tideland reclamation projects Most public works projects need cost-benefit analysis process. Economists are under an obligation to give the government and public sector agents the answer on whether they drive forward the projects or not. There are several methods such as B/C (Benefit-Cost) Ratio, NPV (Net Present Value) and EIRR (Economic Internal Rate of Return) to judge the economic feasibility of public works projects. Among them, B/C Ratio analysis is the most universal method. It can be taken a decision to undertake a project if the benefits exceed the costs, i.e. B/C ratio > 1. In subchapter 3.1, Table 3.1.1 shows the relationship between the costs and benefits for the development of paddy fields in tidal flat areas, considering the elements directly related to Production and Environment not directly related to production. In the Table, the elements of costs should include the costs for preventing environmental pollution, operation and management of farming, and improvement water quality as well as the costs for construction of dykes and lakes and making paddy fields. In general, only operation and management costs for maintaining locks and dykes are considered, however, it is desirable the cost for water quality and ecological conservation should be considered appropriately and be included for the sustainable management of the tidal areas during and after the construction of the tidal projects. The elements of benefits should also include benefits not related to production as well as benefits directly related to production. In measuring the benefits directly related to production, the prices of agricultural products applied to the calculation of benefits have also engendered a lot of controversy. The appropriateness of the cost-benefit analysis is very important issue in the process of the economic feasibility of Tideland Reclamation Project as follows: - - - - 156

Avoid double counting of benefits (e.g. expansion of land, gains in agricultural production) The pecuniary benefit in total benefit (e.g. the increase of asset value by increase of land price in island area that is connected to the mainland by dykes) Valuation of multi-functional roles of paddy field Prices of commodities applied to the costs-benefits analysis

Chapter 3. Planning Framework for Managing Tidal Area Development

-

Value environment (e.g. the loss of tidal flat functions, such as tidal flat ecosystems, carbon cycle).

Issues related to the optimal allocation of tidal reclamation area The optimal or reasonable allocation of reclaimed land and water resources is considered with two different points; (1) within agricultural sector, (2) between agricultural sector and non-agricultural sector. The latter is more controversial issue than the former. Even though tidal flats are developed primarily for use as paddy land (for rice production), more than planned of the reclaimed tideland are demanded for non-agricultural uses by the non-agricultural sector stakeholders. They made considerable points of economic efficiency and profitability. For the optimal allocation of land and water resources, institutional regulation and stakeholder participation are essential as described in subsection 3.1 of this Chapter. When establishing the plan to optimize the developed land and water resources use, the values not traded in the market should be considered together with the values traded in the market. When only the values tradable in the market are considered, most of farmland and fresh water will be transferred into non-agricultural uses. It is needed to consider not only the values tradable in the market but also the values not tradable in the market and to estimate the diverse demand of land. Even though there is a controversy over the value of food security as one of the most important multifunctional roles of rice paddy farming, it is obvious that food security still provides positive externalities such as social stability and national security that are applicable to every country. As Maastricht (1999) mentioned, owing to the nature of public goods attached to rice paddy farming, consumers enjoy environmental gains without paying for them. There do not exist readily observable market prices for environmental goods or resources, because there is usually no traditional economic market for them. Nevertheless, their economic values cannot be ignored. It is important, therefore, to make available and reliable background information and data relating to monetary values of environmental conservation functions embedded in rice paddy farming and to set up enabling policy measures. If the markets do not properly and efficiently function, market failure occurs and then results in resources misallocation. In this case, government intervention in the markets can correct the market failure and enable more efficient allocation of resources. And there are many methods to 157

internalize the positive externalities generated by rice paddy farming on the basis of their economic values. And the comparative study between the roles of rice paddy and tidal flat as well as between rice paddy and urban land and between rice paddy and dry field for agriculture is required to understand the multi-functional roles of the paddy field objectively and appropriately. But, for the optimal or reasonable allocation of reclaimed land and water resources, the comparative study is needed between the roles of rice paddy and urban land and between rice paddy and dry field for agriculture more than that between the roles of rice paddy and tidal flat. Objectiveness and appropriateness of measuring the values not traded in the markets To measure the values of the multi-functional roles of paddy field and loss of tidal flat functions not traded in the market, it should be clarified the problem of objectiveness and appropriateness on measuring the values. Commonly, Tideland Reclamation Projects have used CVM (Contingent Valuation Method) to calculate the values of the multi-functional roles of paddy field and loss of tidal flat functions (tidal flat ecosystems and carbon cycle). On the other hand, many economists have expressed their doubts about the valuation of the multi-functional roles of paddy field and loss of tidal flat functions by the methodology of estimation of WTP (willingness to pay). WTP can be changed with the change of main stream of opinions. The appropriateness and objectiveness of CVM and WTP calculation Methodology will be controversial issues relating to the economic feasibility of tideland reclamation. Until several years ago, the results of measuring the values not traded in the market (environmental effects) by using the methods such as CVM (Contingent Valuation Method), TVM (Travel Cost Method), etc. had not been recognized as the criteria for judging whether or not to carry out public work projects. The values tradable in the markets have only been evaluated in monetary terms. Recently, many economists have inclined to measure the values not traded in the market, especially the values of tidal flat functions. Many people begin to recognize the values of and importance of loss of tidal flat functions. And there is a tendency that they reveal more WTP for the tidal flat functions than that for development of tideland reclamation in developed countries. However, there are so many areas to be developed in sustainable way for present and future generation in developing countries. The methods of measuring environmental effects such as CVM (Contingent Valuation Method), TVM (Travel Cost Method), etc. have been acquired appropriateness and objectiveness through the environment group and economists’ efforts. The data made by diverse surveys of WTP have been important criteria for judging whether or not to carry out public work projects. But, there is a 158

Chapter 3. Planning Framework for Managing Tidal Area Development

tendency that the WTP for the tidal flat functions increases or sometimes is overestimated and that for food security decreases or is underestimated. Now, what is the main stream of opinions about environment is considered to be more important than whether or not the methods of measuring the values are appropriate in the decision of the valuation of the multi-functional roles of paddy field and tidal flat functions. It is needed to secure the objectiveness during the survey of WTP for the multi-functional roles of reclaimed land and loss of tidal flat functions and measuring the values. That becomes an important economic issue of tideland reclamation as well as an issue of economics. Besides, there are several other issues relating to the objectiveness of measuring the indirect effects of tideland reclamation. And the dykes can prevent coastal disasters, such as inundation during flood time, tidal wave, Tsunami, and salty water intrusion. In addition, the lakes and dykes will create a complex ecological zone for environment-friendly tourism with sightseeing. In some Tideland Reclamation Project, the effects of transport improvement by using dykes are reported to be more than flood control by dykes, the effects of preventing tidal wave are much more than those of transport improvement by using dykes, and the effects of creating a complex ecological zone are more than those of transport improvement by using dykes. Most environmental economists recognize the fact that those indirect effects will be revealed, while they are worried about overestimation of the effects.

159

3.8 Management and Institutional Context AUTHOR: PARK SANG HYUN 3.8.1 INSTITUTIONAL APPROACH TOWARD SUSTAINABLE MANAGEMENT

Tidal areas have been developed to supply land and water for human being for thousand years. As shown in Fig.3.8.1, there are a lot of tidal reclamation projects that have been developed by many countries such as China, India, Indonesia, Japan, Korea, Malaysia, the Netherlands, and UK to increase food production, however, there are still many population suffering from undernourishment, as shown in the Fig. 3.8.1.

Fig. 3.8.1 Undernourished population and tidal reclamation projects in the world

According to IWMI (2004), total cereal production is 2 billion tons in the world. Among them, 1,087 million tons are from the developed countries and 909 millions from the developing countries, as shown in Fig. 3.8.2. The Figure shows that total wheat and rice productions are not less than total consumption, however, part of the production need to be transferred to the developing countries for balanced consumption. Consequently, tidal area development for crop production shall be continued in the developing countries to solve food and water problems, while more attention is given on the wise use of tidal area to prevent disaster and conserve biodiversity in the developed countries, especially, the regions near highly populated areas that are vulnerable to disasters. 160

Chapter 3. Planning Framework for Managing Tidal Area Development

Fig. 3.8.1 Undernourished population and tidal reclamation projects in the world

3.8.2 INTERNATIONAL INSTITUTIONAL MANAGEMENT

Recently, increasing world trade of agricultural products has contributed to supply cheaper products for consumer. However, it threatens rural areas to accelerate aging society and degrade crop diversity. There are many different sources of legal and institutional measures to be adopted for sustainable management in a given area, as shown in Fig.3.8.3. It would be classified in international, national, regional and local levels(Refer Ramsar Secretariat,2004). Agri-environmental indicators suggested by OECD (2001) are important measures to reform agricultural policies and strengthen environmental policies both domestically and multilaterally among OECD countries. Implementation of the Ramsar Convention The Convention on Wetlands (Ramsar, Iran, 1971) is an intergovernmental treaty whose mission is the conservation and wise use of all the wetlands through local, national actions and international cooperation, as a contribution towards achieving sustainable development throughout the world.

161

Optimal use of land and resources - Agriculture (paddy rice, livestock) - Industrial complex - Energy plant, Commercial port - Fishing harbor, Freshwater lake - Aquaculture, Agro-tourism

water

Disaster prevention - Inundation by flood - Typhoon, Tsunami - Sea water rise - Tidal land degradation - Beach erosion

International Level - OECD Agri-environmental Indicators - Direct Payment - The Convention on Wetlands (Ramsar) - Convention on Biological Diversity - ICZM National and Local Level - Convention on Biological Diversity - Agriculture Disaster Control Act - Wetland Conservation Law - Migratory Birds Regulation (Canada, et al.)

Preservation of biodiversity and mitigating measures - Habitats for birds and fishes (Artificial wetland) - Responsible governmental agency and stakeholder participation

Fig. 3.8.3 Institutional approach toward sustainable management in tidal areas

Table 3.8.1 Current set of OECD farm management practices and resources use efficiency Issues

Agri-environmental Indicators

Protecting the stock

1. Land use changes between agriculture and other land use.

of natural resources

2. Soil erosion, soil organic carbon and soil diversity.

impacted by

3. Agricultural water use and groundwater recharge.

agriculture

4. Biodiversity levels, including habitats on agricultural land).

Reducing

* Water emissions

environmental

5. Nutrient balances: nitrogen and phosphorus balances.

emission from

6. Pesticide use: aquatic, territorial and human health risks.

agriculture

7. Water quality: risk and state indicators of agricultural impact. * Air emissions 8. Ammonia emissions: atmospheric emissions- climate change. 9. Agricultural energy balance and greenhouse emissions

Improving agri-

10. Resources use efficiency

environmental farm

11. Farm management (nutrient, pest, soil, water, biodiversity and

management

162

whole farm management)

Chapter 3. Planning Framework for Managing Tidal Area Development

Table 3.8.2 Guiding principles of ICZM Sections

Principles

A. Recognizing the role

1. The Ramsar Convention is intergovernmental treaty that

and significance of the

specifically addresses the conservation and wise use of

Ramsar Convention and wetlands in the coastal zone B. Ensuring full awareness of the values and functions of wetlands in the coastal zone C. Using mechanisms for securing the conservation and sustainable use of wetlands in the coastal zone

coastal zone ecosystems. 2. Coastal wetlands have important values and functions and provide multiple goods and services of high economic value. 3. Mechanisms to resolve jurisdictional overlap in the coastal zone must fully include the legal and institutional frameworks for wetlands. 4. Stakeholders using coastal wetlands must participate fully in their management. 5. The designation and management of wetlands of international importance in coastal zone provide a global mechanism for the identification and recognition of important parts of costal zone ecosystems. 6. Coastal wetlands are highly vulnerable to degradation

D. Conservation and

and loss, but their restoration is costly and sometimes

sustainable use of

impossible.

wetlands in integrated ecosystem management

7. ICZM should be linked with river basin/catchment management so as to secure the conservation and sustainable use of coastal wetlands.

As the results of the Ramsar Convention’s Work Plan 2000-2002, the Principles and Guidelines have been prepared for incorporating wetland issues into Integrated Costal Zone Management (ICZM). It is intended to increase understanding and recognition of the importance and vital role played by wetlands in the coastal zone. The guiding principles are divided into four sections as described in Table 3.8.2. 3.8.3 NATIONAL AND LOCAL INSTITUTIONAL MANAGEMENT

To conserve biological diversity, most of the countries have given great efforts in tidal areas since Rio Conference of UNCED in 1992. A number of governments prepared institutional frameworks for low intensity agriculture, landscape maintenance in tidal areas. It includes stern institutional regulation to mitigate water pollution stemmed from inappropriate practices in the use of chemical fertilizer and pesticides and other wastes from livestock feedlots and upper catchment. The use of agricultural chemical should be restricted to protect water quality. Livestock concentrations and disposal of effluent should be regulated in tidal area to keep freshwater lake. Excessive use of 163

pesticides leads to greater pollution and numerous risks to land, water and inhabitants who apply it and consume the products. Direct payment and incentive for farmers To keep stable income for farmers and to restrain pesticide and fertilizer in farm land, direct payment has been widely applied to support farmers in several countries. In addition, society is increasingly willing to compensate the farmer for protecting the environment and preserving the landscape. Since 1992, EU converted price support policy to the Direct Payment System for farmers and annual budget for Direct Payment became 70 percent of total budget of agriculture. USA increased 7.3 billion Dollars in 1995 to 32.2 billion Dollars in 2000. Accordingly, this kind of support has stimulated farmers to change their management practices and rate of input use such as irrigation water, fertilizer and pesticide. To improve biological diversity in rural area, there is another incentive for the service of farmers who remain their crops, straw for wild animal after harvest. In many countries, the covenants between farmers and local governments have contributed to the increase of winter birds in tidal reclaimed land areas and freshwater lakes to be described in subchapter 3.3. Stakeholder participation for the management of tidal areas According to Bernd Probst (2005), society has become so open and information technology is so developed that there have been increasing demands for more participation to development and management of tidal areas. To meet the demands, policy of government and willingness of farmers and other stakeholders should be integrated for the optimal usage of land and water resources in sustainable way. In addition, qualified information on land and water issues is needed for the participation of people who are willing to join in decision making procedures. For the well-informed stakeholders, many government provided legal and institutional measures with management information system such as Geographical Information System (GIS) and advanced numerical models to assess optimal use of land and water, effect from tide and wave phenomena, disasters from flood and drought, effect on biodiversity and water quality, sediment and erosion and economic benefits for the sustainable development of tidal areas.

164

Chapter 3. Planning Framework for Managing Tidal Area Development

Agriculture, Environmental Aquaculture conservation

Stakeholders Coastal Industries, defense Habitation

Traffics

Tourism

- GIS and mathematic models: Land and water use, Tide and wave, Runoff, Flood and drought control, Biodiversity, Water quality, Sediment and erosion, Economics

- Central government policy - Regulation of local government - Technology and experience of agencies or public sectors

Fig. 3.8.4 Stakeholder participation for the management of tidal areas

Box 3.8.1 Geographic Information System in the Hwaong Freshwater Lake (KIM, SEONG JOON) GIS/RS-based study of geo-morphological change in tidal reclamation areas Landsat TM multi-temporal imageries can be used to detect the changes of tideland reclamation mudflat area during and after sea dike construction. Three stages [4 images before and early stage of project (Feb. 8, May 31, Oct. 22 of 1991, Sept. 22 of 1992), 3 images in the middle of project (Feb. 22, April 10 of 1996, June 16 of 1997), and 3 images at the end of project (Jan. 16, May 7 of 2000, June 22 of 1999)] were designed, and analyzed using the observed tidal levels at the time of acquiring Landsat images. Table Box 3.8.1 shows the relationship between tidal level and mudflat area for 3 selected periods. Based on 5 m of tidal level, mudflat areas inside and outside dike increased 332.4 ha and 89.3 ha during 10 years. Table Box 3.8.1 Estimation of mudflat area changes by sea dike construction using Landsat TM Multi-temporal Imageries under 5 m tidal level. Year

Mudflat



area (ha)



Increased Mudflat Area (ha)

Total

Yearly mean



Inside dike

Outside dike

Inside dike

Outside dike

1991

3,692.3

-

-

-

-

1996

3,837.9

145.6

46.5

29.1

9.3

2000

4,170.3

186.8

42.8

49.7

10.7



Total (Mean)

332.4

89.3

(36.9)

(9.9) 165

Grid-based watershed storm runoff and sediment transport in the Freshwater Lake For the estimation of watershed storm runoff into the freshwater lake, GIS system is a useful tool to be supported by mathematical model. A grid-based KIneMatic wave STOrm Runoff Model (KIMSTORM) was developed that uses regular gridded ASCII-formatted data from GRASS to predict the temporal variation and spatial distribution of saturation overland flow areas. The model adopts the single overland flow path algorithm and simulates surface and/or subsurface flow depth at each cell by using water balance of hydrologic components. For the study of soil erosion process, a physically-based soil erosion model is widely used to simulate soil-water erosion and deposition. The model simulates sediment concentration at each grid element for a given time increment. The model was tested to a 162.3 km2 watershed of Hwaong tideland reclaimed area located in the upper west of South Korea (Fig. Box 3.8.1).

Fig. Box 3.8.1 DEM, generated stream network, soil type and land cover of Hwaong watershed

3.8.4 CONCLUSION

There are many international, national and local institutional frameworks for the optimal use of natural resources and conservation of biodiversity in tidal areas. The institutional mechanisms should be composed with integrated management system based on scientific data and technology such as GIS and advanced numerical models to assess optimal allocation of land and water resources for various stakeholders and sustainability for future generation.

166

Chapter 3. Planning Framework for Managing Tidal Area Development

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Ministry of Transport, Public Works and Water Management, 1996, Flood Protection Act, the Netherlands. Mitsh, W. J., and James G. G., 1993, Wetlands, Van Nostrand Reinhold, New York. Office of Technology Assessment, 1984, Wetlands: Their use and regulation, OTA, U. S. Congress, OTA-O-206, Washington D. C., pp. 08. OECD, 2001, Environmental Indicators for Agriculture Volume 3: Method and Results. Publications Service, Paris, France. The executive summery is available from the OECD agrienvironmental indicators web site at: http://www.oecd.org/agr/env/indicators.htm OECD, 2005, Agriculture, Trade and the Environment, The Arable Crop Sector, OECD. Office of Science and Technology, 2002. Foresight Futures 2020: Revised Scenarios and Guidance. Department of Trade and Industry, London. Park Sang Hyun, 1995, Optimal Allocation of Crop Area and Capital Investment, ICID PROCEEDINGS/ACTES of Special Technical Session, Volume 1, ICID European Conference, Rome P.H. Waarts (ed.), 2001; Wat als we nat gaan? (What if flooding occurs?) Delft Cluster Symposium Proceedings (in Dutch), October 17, 2001, Delft, The Netherlands. Penning-Rowsell, E.C., Johnson, C., Tunstall, S.M., Tapsell, S.M., Morris, J., Chatterton, J.B., Coker, A. and Green, C., 2003. The Benefits of Flood and Coastal Defence: Techniques and Data for 2003. Middlesex University Flood Hazard Research Centre. R.E. Jorissen, 1997, Safety, Risk and Flood Protection Policy - key note lecture Workshop on River Basin Modelling (RIBAMOD), February 1997, Delft, The Netherlands. Ramsar Secretariat, 2004, Law and institutions- the 2nd edition of Ramsar Handbook 3, the Ramsar Secretariat. Rapport, D. and Friend, A., 1979. Towards a comprehensive framework for environmental statistics: a stress-response approach. Statistics Canada, Ottawa. Reed, S. C. et al., 1990, Natural systems for wastewater treatment, manual of practice FD-16, Water Pollution Control Federation. Reed, S. C. et al., 1995, Natural systems for waste management and treatment, McGraw-Hill, Inc., New York. Reynard N.S., Prudhomme C., Crooks S.M., 2001. The flood characteristics of large UK rivers: potential effects of changing climate and land use. Climatic Change, 48, 343-359. Sayers, P.B., Hall, J.W., Dawson, R.J., Rosu, C., Chatterton, J.B. and Deakin, R., 2003. Risk assessment for flood and coastal defense systems for strategic planning (RASP) - a national scale application and a look forward to more detailed methods. Proceedings of the 38th DEFRA Flood and Coastal Management Conference, Keele, pp5.2.1-5.2.13. 170

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Shigetaka Taniyama, 2003 Sustainable Development for Tidal Areas: The Case of Japan, Proceedings of 2nd International Workshop on Sustainable Development of Tidal Areas, ICID Conference in Montpellier, Sept. 17, 2003. Shiratani, E., 2002, Water-Environmentally Conservational Agriculture in Reclaimed Land, Proceedings of 1st International Workshop on Sustainable Development of Tidal Areas, pp.18, ICID Congress in Montreal, July 22, 2002. Shiratani, E., H. Hasebe and I. Yoshinaga, 2002a. Economical valuation on water purification of paddy fields and wetlands by replacement cost method, Proc. of 2nd Conf. of Water Purification by Natural Wetlands, Japan-Korea Joint Research, 1-7 (in Japanese with English abstract) Shiratani E., T. Shiofuku, T. Kubota, I. Yoshinaga and H. Hasebe 2002b. Estimation of nutrient elution and removal on sediment surface of clayey canal by hydraulic model experiment. Japan. Agricultural Research Quarterly 36(4), 195-200. Shiratani, E., I. Yoshinaga I., Y.W. Feng and H. Hasebe 2004. Scenario analysis for reduction of effluent load from an agricultural area by recycling the run-off water. Water Science and Technology 49(3), 55-62. Shiratani, E., I. Yoshinaga and R.K. Singh 2005. Model analysis for nitrogen effluent from upland field constructed with under-drain. Water Science and Technology 51(3-4), 91-98. Shiratani, E., H. Kiri and H. Tanji 2008. Economic valuation of the agricultural impact on nitrogen in the water environment by a newly proposed replacement cost method. Japan Agricultural Research Quarterly 42(4), 285-289. SPRU, CSERGE, CRU, PSI, 1999. Socio-economic futures for climate impacts assessment, Final Report. Science and Technology Research, University of Sussex. Steiner, G. R., and R. J. Freemen, Jr., 1989, Configuration and substrate design considerations for constructed wetlands for wastewater treatment, in Constructed wetlands for wastewater treatment, D. A. Hammer, ed., Lewis Publisher, Inc., Chelsea, Mich., pp. 63-378. T. Tabuchi, 1985,Nitrogen and Phosphorous Discharge from Catchment Areas, Tokyo University Publication, 1985. Tabuchi T., Shinoda Y. and Kuroda H., 1993. Experiment on nitrogen removal in the flooded paddy field. Jour. JSIDRE., 61(12), 1123-1128 (in Japanese) Tabuchi T., 2001. Nitrate removal in the flooded paddy field. Proc. of the Int. Workshop on efficiency of purification processes in riparian buffer zones, The Organizing Committee for International Workshop of Riparian Buffer Zones (ed.), 81-90. Tapsell, S.M., Penning-Rowsell, E.C., Tunstall, S.M. and Wilson, T.L., 2002. Vulnerability to flooding: health and social dimensions, Philosophical Transactions of the Royal Society London – Series A, Mathematical, Physical and Engineering Sciences 360(1796), 1511-1525. 171

TAW Technical Advisory Committee on Water retaining Structures, June 1997; Design Guideline for Structures, the Hague, The Netherlands. TAW Technical Advisory Committee on Water Retaining Structures, August 1999; Guideline for Safety Assessment of Flood Protection Structures, the Hague, The Netherlands. Tomas. C. R et al., 1996. Identifying Marine Diatoms and Dinoflagellates. Academic Press, Inc. pp. 598 Turner, R.K., Lorenzoni, I., Beaumont, N., Bateman, I.J., Langford, I.H. and McDonald, A.L., 1998. Coastal management for sustainable development: Analysing environmental and socioeconomic changes on the UK coast. Geographical Journal 164(3), 269-281. UK Climate Impacts Programme, 2000. Socio-economic scenarios for climate change assessment: a guide to their use in the UK Climate Impacts Programme. UKCIP, Oxford. Weller, M. W., 1981, Freshwater marshes. University of Minnesota Press, Minneapolis, Minn., pp. 146. Wilhelm, M., S. R. Lawry, and D. D. Hardy, 1989, Creation and management of wetlands using municipal wastewater in northern Arizona : a status report, in Constructed wetlands for wastewater treatment, D. A. hammer, ed., Lewis Publishers, Inc., Chelsea, Mitch., pp. 179185. Yamaguchi Y. and Hata K., 1993. Change of water quality on nitrogen and phosphorus in surface of fallow paddy fields, 61(10), 915-920 (in Japanese)

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CHAPTER 4

Chapter 4. Engineering for Sustainable Development of Tidal Areas

ENGINEERING FOR SUSTAINABLE DEVELOPMENT OF TIDAL AREAS EDITOR: DR. KAZUAKI HIRAMATSU

4.1 Dike and Final Closure

Author: Kiichiro Tanaka

4.1.1 ALIGNMENT OF DIKE

In tidal areas, sediments from rivers deposit at estuaries and near shores and silt up the ground level of the areas to comparatively high. These areas have been enclosed by dike and developed for mainly agriculture, installing drainage canal, drainage sluice gate and so on. Then the dike-line is planned to locate seaward as far as to enable excess water inside enclosed areas to drain by natural gravity. That means the dike-line base is almost the same as the contour line of sea-level of average low-tide at neap tide. Still now, we can find many dike-lines constructed parallel with sea-coast age to age. When mechanical drainage by using machinery pump and water-lifting device can be introduced, any lands which are always under-water can be technically feasible for reclamation. Many shallow lakes, swamps, lagoons and estuary-bays are developed by the method so-called double–dike system. Double-dike system comprises of so-called front-dike (enclosing lake and bay from outside water), inside-dike, drainage pump and canal, retarding basin and so on. The water in the retarding basin is used as fresh water resources. The front dike is so effective to prevent surge storm disaster. The dike-line (front and inside) is designed taking geo-hydrological condition, multi-purpose benefits and economic viability into consideration. Environmental and ecological aspects are also carefully examined in the course of the planning of dike-Line. 173

Recently, in most advanced countries, development of tidal areas, are discouraged because of new policies related agriculture and environment. In these countries, the construction of new dike is very rare, and now related works are strengthening of existing dikes. Dikes are threatened by extreme storm surges (see Fig. 4.1.1). The worst case is a dike failure as shown Fig. 4.1.2. Strengthening a dike means to heighten the crest and to flatten the slopes considering sea level rise, climate changes or changes in safety standards of the country.

Fig. 4.1.1 Damaged dike by storm

4.1.2 TYPES OF DIKES

In order to utilize the tidal area as dry land through impoldering, the structure of dikes that prevent offshore tide is important. For dikes, the wave, soil quality of the foundation ground, dike materials, method of construction and the cost of construction are comprehensively examined in order to adopt the most appropriate type. The Fig. 4.1.2 Dike failure happened in 1976 types of dikes are classified by outer slope gradient, structure, and dike materials, as shown in Table 4.1.1 (Agricultural Land Bureau, Japanese Ministry of Agriculture, Forestry and Fisheries, 1966; Japanese Society of Irrigation, Drainage and Reclamation Engineering, 1979; Japanese Society of Irrigation, Drainage and Reclamation Engineering, 2000). The types of dike can also be classified into foreland dikes and waterfront dikes depending on the existence of seaward extended forelands (salt marshes). 1) Sloping dike Sloping dikes are adopted in many projects in order to enable the construction of large scale and mechanize construction of impoldering projects in recent years. The main characteristics of sloping dikes are as follows. (1) Since a large amount of earth and sand is applied to the dike body, the pit for such earth and sand should be in close proximity to the construction site thus allowing obtain these materials easily.

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Table 4.1.1 Types of dikes Outer slope

Upright type (sharp slope)

Sloping type (moderate slope)

Structure

Front works + banking

Covering works + banking

Materials

Front works

Banking

Banking

Outer slope covering works

Sand Mountain soil Tidal clay

Sand

Concrete Concrete block Stone pitching Asphalt

Concrete buttress Semi-gravitational types type Concrete Steel reinforced concrete

Concrete Masonry

Composite type

The upright type and sloping type are combined depending on the site conditions.

(2) Safety against sliding failure and piping of the dikes shall be ensured. (3) A large part of the energy of waves may be dissipated by the slope so that the structure of the covering can be relatively simple. The reflection of waves is also reduced. (4) Sloping dikes are suitable for a mechanized construction system, (5) They enable large-scale reclamation in the deep sea. 2) Upright dike Upright dikes have long been adopted in small scale foreland reclamation and the main characteristics are as follows. (1) Since the width of the dike body is small, banking may be accomplished with a relatively volume of earth and sand. However, since concentrated load on the foundation ground is large, foundation improvement or large amount of counterweight by rubble will be required for construction in soft ground. (2) Since the front surface of the dike is an upright surface, the waves become combined waves, thus reducing the wave force and the changes in the water pressure become slow. For this reason, the height of the wave runup does not differ significantly from the slope gradient of 1:2 to 1:5 that is generally used for sloping dikes. It is however necessary to make the internal and outer covering solid. (3) Construction may be implemented using relatively simple equipment.

175

3) Composite dike A composite dike employs a cross section with the advantages of both a sloping dike and an upright dike in view of the conditions and objectives of the construction. It is often constructed in the form of placement of an upright structure such as caisson or block on the inclined structure built by rubble foundation or banking. The main characteristics of the composite dike are as follows. (1) Construction is possible at places where the water is deep or the foundation is relatively weak. (2) By using materials such as obtainable soil and earth, stones, and concrete from comprehensive judgment, a composite dike is composed of inclined and upright structures in proper proportion, enabling to determine an economical cross section. (3) A composite dike is constructed only by means of a mechanized construction method, thus making the construction equipment complex and construction cost high. Fig. 4.1.3 shows a general cross section of dikes (Agricultural Land Bureau, Japanese Ministry of Agriculture, Forestry and Fisheries, 1966; Japanese Society of Irrigation, Drainage and Reclamation Engineering, 1979; Japanese Society of Irrigation, Drainage and Reclamation Engineering, 2000). 4) Foreland dike and waterfront dike Foreland dikes have seaward extended forelands (salt marshes) grown up out of sedimentations of the sea. Usually forelands have a height of some decimetres above mean high water. Such a foreland is the best protection of the dike against the influences of normal tides and slight storm tides, which are not very strong but frequent. Hence there is no need for special safeguarding of the dike foot. The slopes of the dike arise smoothly out of the foreland. An example of such a dike is shown on Fig. 4.1.4.

(a) Sloping block pitching type

(b) Sloping concrete pitching type

(d) Upright stone piling type

(c) Upright wall type

(e) Mixed gravitational type

Fig. 4.1.3 cross secon dikes by type Fig. 4.1.3 General crossGeneral section of dikes byoftype

176

If there is no foreland in front of a dike, every mean high water is flooding the dike foot and attacks the dike even on normal tides. Such so called waterfront dikes have a solid revetment consisting out of stones, concrete blocks or asphalt.

Chapter 4. Engineering for Sustainable Development of Tidal Areas

Fig. 4.1.4 Cross section of dike

4.1.3 BASIC CROSS SECTION OF DIKES

Fig. 4.1.5 shows an example of cross section of the enclosing dam in the Delta Project, Netherlands. A boulder clay dam created the basis of the enclosing dam. It then got its shape by spouting sand, covering the dike body with clay and by making a slope of natural stone and bricks. 1) Outer slope The outer slope has to withstand against waves and currents during storm surges. The amount of the possible attacks is depending on the local site Fig. 4.1.5 A cross section of enclosing dam in the Zuiderzee Project, the Netherland and the exposure to main wind directions. There is an interrelation between geometries of the slope on one hand and the construction material on the other. Steep embankments need solid, hard material. Erosive material can only be chosen with flat slopes to get a stable construction. That’s why even in comparable stress situations there may be different combinations of material and geometry. Table 4.1.2 Outer slope gradient Structural type

Outer slope gradient

Clay and asphalt covering

>3.0

Rubble foundation

>2.0

Stone pitching type, concrete block pitching

>1.0

Concrete cover Masonry Semi-gravitational type, concrete buttress Artificial concrete block

>1.0 0.3~1.0 0~0.5 >1.5

The outer slope is determined by taking into consideration the type of covering works and the materials of dike body, foundation soil quality, depth of front water, and method of construction. The main principles that are taken into consideration in Japan are shown in Table 4.1.2 (Agricultural 177

Land Bureau, Japanese Ministry of Agriculture, Forestry and Fisheries, 1966; Japanese Society of Irrigation, Drainage and Reclamation Engineering, 1979; Japanese Society of Irrigation, Drainage and Reclamation Engineering, 2000). An outer slope has recently adopted a moderate average gradient for large-scale dikes. Moreover, outer slopes adopt the design method as follows: installation of a wide berm on the outer slope in order to dissipate the energy of waves; or change of outer slope depending on wave force. The regular profile which is used in most cases in Germany has inclinations of 1:10, 1:8 and 1:6 from the berm to the crest depending on the elevation of the section. The material of the covering layer is clay with a thickness of 1.1 to 1.5 m over a core of sand. In special situations, for example, if the possible dike line is narrow, the slopes must be steeper. In these cases the material of the covering layer has to be more resistant against wave attack, such as asphalt or concrete coverings. Merely at the lower parts of the slope, being exposed to attacks from waves or currents, the covering layers are constructed as bank revetment in stone or concrete. In former times, dikes had smaller cross sections and were built homogeneously out of clay. Economical reasons and the lack of suitable cohesive material lead to the design of today. Furthermore, a core of sand allows a shorter construction time because of geostatic reasons. In dike slopes, strong changes in the gradient, in surfacing material and installations like piles, fences and so on can affect additional turbulences in the up-running waves. Hence they should be avoided wherever possible. Sharp kinks between the angles of the slope should be rounded. Generally there should be chosen flat slopes with natural construction materials. 2) Outside berm A berm is a horizontal or gently inclined part of the slope. Hence there are changes of the slope angle on both sides of the berm which needs additional constructions of the points of contact to avoid damages. Therefore berms should be used sparingly. In Germany, foreland dikes berms are applied as lines to construct a way for maintaining purposes. These ways allow traffic of vehicles and equipment on the dike being not dependent on bad weather and road conditions. They are constructed in a height of 1.0 to 2.0 m above mean high water. Their width is generally 3.0 m. (Fig. 4.1.4). The construction has to cover the load of the used vehicles. At Fig. 4.1.6 Berm at waterfront dike 178

Chapter 4. Engineering for Sustainable Development of Tidal Areas

waterfront dikes, there is attached a berm of 3.0 to 5.0 m width at the upper edge of the revetment. This berm is, besides its function as maintenance way, used as protection element against waves overtopping the revetment (Fig. 4.1.6 and Fig. 4.1.7). It diminishes the splash of the breaking waves and acts as transition to the flatter slopes of the dike. 3) Dike foot The dike foot is the lower part of the seaside slope. It has to withstand frequent loads by normal tides or currents. Dikes with a foreland (foreland dike) have different toes from dikes being directly exposed to normal tides (waterfront dike). Waterfront dikes have a solid revetment consisting out of stones, concrete blocks or asphalt. Revetments are comparably rigid constructions, whereas the surface of the adjacent sea area is flexible. If this surface is lowered by erosion beneath the bottom of the revetment, it can hollow out and cause a breakdown of the revetment. To avoid such damages, it is necessary to construct the points of contact very carefully. A possible construction method is a horizontal layer of stone on a geotextile Fig. 4.1.7 Berm mat being strong against tension. Another method is to position the foot of the revetment in a certain height under the expected horizon of erosion. Additionally this point should be safeguarded by a row of wooden piles. The upper border of a revetment should be placed in a height, so that slight but frequent storm surges can’t threaten the slope. As experience value a position at about 1.5 to 2.5 m above mean high water is proven. The example on Fig. 4.1.8 shows a revetment consisting of boulder with a weight of 850 kg/m2. Fig. 4.1.9 shows the construction of a revetment with sand core, filter fleece, boulders and stone rubble. The grouting of a revetment consisting of stone rubble is shown in Fig. 4.1.10. After grouting, there will remain some open fugues by which the revetment is not dense and dangerous ground water pressure cannot occur.

Fig. 4.1.8 Cross section of revetment and berm 179

Fig. 4.1.9 Building site of a revetment

Fig. 4.1.10 Grouting of a stone rubble revetment

4) Crest elevation The crest elevation, or the crest level where the crest is provided with a parapet, is determined by adding the numeric value given below to the design high water level: (1) 1.0 or 1.3 times the wave height in the case where waves surge; and (2) 1.0 or 2.5 times the wave height and freeboard in the case where waves run up. The amount of settlement is further added at the places where the settlement of the foundation ground or dike body continues for a long period of time. The banking elevation of a dike with which the crest is provided with a parapet takes a numeric value of which half of wave is added to at least the design high water level. As in the case of double-dike-system reclamation, the crest elevation of a dike inside the regulating reservoir made by enclosing part of the open sea and its crest elevation is decided in consideration of water surface area and shape of the reservoir, and dike location. When it is necessary to take the storm surge and seiche into consideration, the dike adopts the same design criteria as for sea coast reclamation dikes. On the other hand, in the case where dike design covers just flood, it employs the same design criteria as for the river dikes. i) Design high water level: The design high water level shall have the highest recorded high water level or an additional value of the high water level plus recorded sea level departure from normal. If past actual measurements cannot be obtained, it is estimated based on the calculation method using storm surge such as drifting, barometric drop, variations from movement of low atmospheric pressure. ii) Wave surge height and run-up height: Since the wave surge height and the run-up height change in a complex manner depending on the front shape of the dike, it is desirable to 180

Chapter 4. Engineering for Sustainable Development of Tidal Areas

determine the heights by means of model tests in important dikes. In the case of estimation, the following method shall be employed. First, the wave surge height and run-up height are determined using the results of past experiments. In the event the wave surge height and runup height so determined are less than 1.0 times the design wave height, 1.0 times all values shall be adopted. Moreover, if the wave surge height and run-up height are 1.3 times or 2.5 times or more of the design wave height, a change is given the design section of the dike by means of installing a berm on the covering of the front slope for suppression of the wave surge height and run-up height, and reinforcement of the structure in the crest and covering. iii) Wave height: An expected wave height is obtained for calculating wave surge height and runup height in consideration of the influence such as refraction, diffraction, changes in water depth, breaking wave, offshore breakwater based on the dimensions of deep water wave used in the design. iv) Freeboard: The calculated crest elevation cannot be said to be absolutely reliable. For this reason, freeboard is added to the calculated crest elevation. Freeboard is determined as appropriate from the status of the backland and scope of the impoldered land. In the event a high safety level is required, about 1.0 m is adopted. v) Aging settlement: In the case where settlement of the ground or dike body is expected to take place for a long period of time, the dike height shall be decided in principle by adding the amount of settlement. However, since settlement continues for a long period of time, the amount of settlement is added to the dike elevation by each year for a period of about 3 years after the completion of dike. The settlement problem is solved by raising the dike according to settlement degree. 5) Crest width In order to counterwork erosion induced by waver overtopping, it is effective to increase the crest width but from an economic standpoint, the crest width is decided based on the following criteria. (1) In the case of a moderate slope type: The crest width with no parapet shall be 3 meters or more. Fig. 4.1.10 Grouting of a stone rubble revetment 181

(2) In the case of an upright type: From past examples of disasters, since it is necessary to place the point of fall of the wave overtopping of the hydraulic jump within the crest to the extent possible, the concrete part (front construction) shall be 0.5 meters or more, and the crest width of the banking part shall be 5 meters or more. In addition to the above, the crest width shall be decided in consideration of the phreatic line, final form of the dike and future plans for use. In the cases of the dikes that have relatively gentle and long slopes as recently constructed in Germany, the load of a dike crest by attacks from the sea is less than the load of the outside slopes. It takes place only during extreme storm surges accompanied by wave overtopping. More often the dike crest is stressed by traffic of pedestrians, cyclists and in certain cases vehicles, which can cause damages of the patch of grass. Especially in tourist areas where the crests are crowded the dike safety can be threatened. Therefore the clay covering on the crest should have the same thickness as on the outside slope (Fig. 4.1.11). Additionally the crest should be rounded up. This allows a better draining off of rainfall. Fig. 4.1.12 shows a photograph of a well rounded dike crest and our best maintenance workers – the sheep, Fig. 4.1.13 Crest with pavement who mow the grass and consolidate the soil surface. Fig. 4.1.12 Dike crest

In Germany, the crest has a width of 2.5 to 3.0 m, so that vehicles can drive on the crest for maintaining purposes. In the cases of very strong loads (tourism regions) the crest will be surfaced with an asphalt or concrete pave. The points of contact to the neighbouring turf have to be secured against the splash of overtopping waves. An example construction is shown in Fig. 4.1.13 and Fig. 4.1.14. 6) Inner slope The inner slope of dikes needs to be protected in order that the allowed wave overtopping cannot cause any damages by erosion or infiltration. For this reason, the inner slope shall be decided 182

Chapter 4. Engineering for Sustainable Development of Tidal Areas

in consideration of the foundation ground, dike body material, type of covering works, and phreatic line. As the dike height becomes higher, the stable slope ensures moderate average gradient by installing a berm. Besides that, in the cases of the dikes with relatively gentle and long slopes and with green surface, it should be taken into consideration that within the scope of maintenance the slope can be driven by mowers. These high demands can be met by a sloping Fig. 4.1.14 Crest with paved footpath inclination of 1:3, a thickness of the clay layer between 0.6 and 1.0 m as experience has shown. If in special circumstances the slope must be steeper or a higher amount of overtopping waves has to be allowed, the inside slope can be solidified with a cover, for example, a concrete pavement. 7) Inside berm and dike ways The inside berm is a foundation for the inner dike foot and it extends the flowing distance in cases of high groundwater levels in the dike. On the berm, the obligatory dike defence road (dike control track) is constructed. This way is necessary not only for maintenance purposes but even more for allowing working and traffic in disaster situations during and after extreme storm surges.

Fig. 4.1.15 Inside berm with track

In Germany, the height should be 1 m over mean high water so that even after a dike breach with a flooded hinterland the dike can be reached by transportation vehicles and equipment. The width of the berm is normally 10.0 m whereas the way has a width of 3.0 to 4.0 m. This guaranties sufficient room to move and storage place along the dike for emergency material. The road should have a load capacity even for heavy vehicles. A reliable construction is shown in Fig. 4.1.15 and Fig. 4.1.16. 183

8) Special situations Exceptions from the principle of simple construction and green surface are necessary in special situations. The available space may be very narrow, if there are houses or other buildings near the dike. The stress by touristic or industrial activities may be high. The available building material may not be sufficient referring to quality or even quantity. The subsoil at the construction site may not have enough soil bearing capacity. All these and other situations need responses in the design of the dike. An example for a special design is shown on Fig. 4.1.17 - a dike at the Baltic Sea coast in Germany. The photograph on Fig. 4.1.18 shows the local situation. The right side is the seaward side. Because of the hotel and other buildings the regular cross section could not be implemented. Hence the dike has a revetment on the whole seaward slope and additionally a wall on the crest reversing the waves. A design like this is reducing the width of the whole construction and in this Fig. 4.1.16 An example of inside berm with dike way the needed space. control track

Fig. 4.1.17 Dike with wave return wall 184

Chapter 4. Engineering for Sustainable Development of Tidal Areas

4.1.4 DIKE STRUCTURE

1) Dike body banking The dike banking is an essential constituent of dike works, preventing infiltration of outer water in combination of covering works and foundation works as well providing resistance against failure settlement and sliding of the dike. For this reason, banking materials must be carefully examined for physical properties. The baking materials of dikes usually used have the main characteristics as follow.

Fig. 4.1.18 Houses or buildings near the dike

i) Sand: (a) Since eradication of excess water in the sand bed is easy, construction using such equipment as a pump dredger is possible: (b) From the physical properties, banking is stable but the amount of water seepage is large, and empty cavities may be generated as a result of drawout of waves; (c) When sand bed is left without processing for a long period of time, loss due to wind erosion is large; and (d) Depending on the grain size or compaction, the quicksand phenomenon may take place. ii) Mountain soil: (a) Mounting soil is often used in the case where baking material is procured on land for the reason that sand cannot be obtained. It is ordinarily transported on land, making rather expensive; and (b) Compared to sand, the stability of the banking is low, and the material may become clayey in water making banking difficult. iii) Tidal clay: (a) Tidal clay is used in the vicinity of construction site, resulting in reduction in cost; (b) Compared to mountain soil, the physical properties are inferior and in the banking works, earth retaining to prevent flow to the side and sliding is required; and (c) Tidal clay remains moist for long periods and is not adequate for quick construction, making construction period longer. 2) Dike body covering works a) Outer slope covering The outer slope covering needs to have a structure that is adequately safe in terms of wave force caused by waves, uplift pressure and earth pressure. For this reason, it is necessary to decide the 185

covering materials, strength and size taking into consideration the wave that acts on the slope, the shape of the slope and the method of construction. Even if the strength of the covering is strong upon construction, failure and attrition caused by the external force of the waves, uplift pressure and drawout makes continuous repair and strengthening necessary. For this reason, the outer slope covering must have a Fig. 4.1.19 View of a modern dike strong attrition and a certain flexibility. It is preferable to adopt the structure which enables easy and partial repairing. From the above, judgment based on experience becomes an important element to decide kinds of materials adopted for the outer slope covering, and the strength and size of the covering. Besides the goal of flood defence, dikes should recently aim at the preservation of landscape in coastal areas as well as at simplicity of maintenance works. Therefore dikes are sometimes built mainly with a green surface. Fig. 4.1.19 shows an example in Germany. At the North Sea coast and her tidal rivers and estuaries in Germany, dikes are constructed almost exclusively with a core of sand or other voluminous building material. This core is covered by a layer of clay with a patch of grass to achieve a great resistance against erosion. The outer slope covering method may be categorized roughly into the following types based on the shape of the dike. i) Moderate slope type: rubble foundation, stone pitching, concrete block cover, concrete cover and asphalt cover ii) Upright type: masonry, concrete semi-gravity type and concrete buttress type b) Crest and inner slope covering works The structure of the crest and inner slope covering works will differ significantly depending on whether adequate height of the dike is to be ensured or a certain level of wave overtopping is to be accepted. i) In the case of significantly high dikes: Dikes such as moderate slope dike are structured to break water by means of the outer slope over which water is run up, so that their inner slope 186

Chapter 4. Engineering for Sustainable Development of Tidal Areas

shall be covered up to the crest or berm road. ii) In the case of dikes that permit wave overtopping: These dikes are generally covered on the three surfaces: outer slope, crest, and inner slope for protection against disasters during typhoon. The covering works employ a method that can respond to the contraction or settlement of the banking dike body. The crest shall be well drained by installing a traverse slope. If this traverse slope is to act also as maintenance road, the structure shall be sufficient to endure such use. The inner slope covering method shall comply with the outer slope covering method of the preceding section. 3) Foundation works The foundation not only supports the upper structure of the dike body safely but also shall be of a structure to endure the wave force and scour as a result of waves. Moreover, in the event the pervious nature of the foundation ground is large and dike safety is not ensured, cut off works are carried out in combination of foundation works. a) In the case of good foundation ground If as a result of investigation, the foundation ground is found to be composed of rock mass, gravel, hard clay and other durable materials, and it is determined that the foundation ground of the dike body has good bearing capacity, spread foundation as described below shall be employed. i) Wood foundation: This is adopted as foundation for masonry and stone pitching and concrete product is the prerequisite in principle of the body. If timber is to be used, the timber should be laid deeply and immersed in ordinary water and the material shall be limited to materials that cause little shipworm damage. ii) Pile foundation: In principle, concrete or steel piles shall be used. In the case where the pile foundation is also used for prevention of draw-out of banking, short pile structures are often used. iii) Concrete block and cellular concrete block foundation: This is used in the case where the water depth is relatively large and the use of cast-in-place concrete foundation is difficult and blocks are combined into a unit to form the foundation. iv) Rubble foundation, concrete block foundation: In the case where the water depth is large, the foundation mound is produced by the deposition of stone or of concrete block material and the dike body is constructed above this foundation. 187

v) Deep foundation: In places where the water depth and wave force are large, well-foundation or caisson foundation may be used but the construction cost is high in both cases. b) Soft ground foundation In the case of soft clayey ground or loose sand ground, the bearing capacity of the sand is small, and there is the risk of sudden or excessive settlement of the dike body. In such ground, the following processes may be taken. i) Sand foundation: Sand foundation that is capable of distributing the load of the dike body so that the load is below the bearing capacity of the ground should be constructed. As a result, the sand foundation is so constructed that the foundation floats. If the surface layer of the foundation ground is extremely poor, from the perspective of management of the construction of the sand foundation, the surface of the original foundation with thickness of about 2 meters is replaced by sand. ii) Fascine foundation: Fascine is constructed in order to integrate the upper structure that is comprised of loose materials such as soil and rubble foundation to distribute the load uniformly and to float such load on soft ground. This is a traditional method of construction that has long been used in the creation of foreland reclamation. iii) Rubble foundation: Rubble foundation often settles down to the ground, and so increases the amount of rubble foundation, thus requiring longer construction period. This method is appropriate when the rubble foundation part of a dike body is large. c) Improvement of soft ground Banking on soft ground, with the development of geotechnical engineering and the progress in mechanized construction in recent years, may be subjected not only to current methods of construction explained above but is also applied widely as a method of construction that attempts active soil stabilization and rational foundation treatment. Table 4.1.3 shows these methods of construction (Agricultural Land Bureau, Japanese Ministry of Agriculture, Forestry and Fisheries, 1966; Japanese Society of Irrigation, Drainage and Reclamation Engineering, 1979; Japanese Society of Irrigation, Drainage and Reclamation Engineering, 2000). i) Replacement method: This is a method of construction whereby soft stratum of the ground is replaced by dredging in water using such equipment as a pump dredger and replaced with good soil (mainly sand), and the banking is constructed above this. As shown in Fig. 4.1.20, this method is effective in increasing stability in terms of the sliding failure of banking dike 188

Chapter 4. Engineering for Sustainable Development of Tidal Areas

Table 4.1.3 Foundation treatment method for dikes on soft ground Excavation replacement

In the case of shallow soft ground, complete replacement is carried out, and in the case of deep soft ground, partial replacement is performed, both of which are a safe foundation treatment method.

Push out replacement

Planned sliding failure allows the ground to be replaced with high quality soil.

Sand drain method

Placement of sand piles causes consolidation to be promoted, increasing bearing capacity.

Paper drain method

The objective is the same as a sand drain method but card board is used.

Sand compaction pile method

In addition to the formation of a compacted sand pile, the foundation in the vicinity is also compacted, increasing bearing capacity.

Replacement method

Improvement method

Counterweight banking method

A dike is baked at the tip (toe of slope), suppressing sliding failure.

body. Construction width that adequately covers the critical circle (sliding surface) in the stability analysis is required. The depth of excavation replacement is determined so that the stability analysis satisfies the required safety factor and at the same time, satisfies economic aspects. ii) Drain and compaction method: This is a method of construction whereby consolidation is promoted by applying compulsory drain force to the pore water in the ground and the ground is given the required bearing shear resistance. The sand drain method using sand piles is commonly adopted as the Critical circle drain method. There is also the paper drain method whereby drain paper is Banking applied in place of sand pile. There is a sand compaction method as method Replacement sand Soft ground applied for the same purpose. This is a method used for pressing sand while making a vibration or impact The part where the shearing resistance of the sliding surface has been in the vertical direction and forming improved sand piles in the ground, and at the Fig. 4.1.20 Partial excavation replacement method same time for compacting the ground around the piles, which is frequently adopted in recent years. iii) Counterweight fill method: This is applied when the result of review of the stability of the planned banking does not satisfy the determined safety factor in the critical circle. In this

Fig. 4.1.21 Counterweight fill method 189

measure, counterweight fill is implemented to the edge of the critical circle as shown in Fig. 4.1.21 in order to obtain stability of the banking.

4.1.5 STABILITY OF THE DIKE 1) Seepage The body of the dike is affected not only by water level and wave attack but even by rainfall and ground water corresponding with the sea water level. Rainfall is flowing along the slopes to the outer and inner foot. At the outer side, the water is flowing into the sea area or the drainage system of the foreland. At the inner side, the water is taken by a ditch running parallel to the inner berm of the dike. High ground water levels inside the dike arise from infiltrating rainfall and –time shifted- from high tidal water levels. The revetment at the seaward side has to withstand possible water pressures from the body of the dike. It is recommended to construct drain alongside the foot of the inner slope to catch seeping water. The weep drain (infiltration ditch) on Fig. 4.1.15 with a drain pipe, gravel filling and geo-textile filter fabric is proved successfully. As for the seepage from the dike body, the shape of the phreatic line and volume of seepage and stability in terms of piping need to be examined to prevent the generation of seepage failure. a) Seepage In the case of dikes in tidal areas, since the outer water level fluctuates with the tide, the seepage flow on the interior of the dike body becomes unsteady flow and accurate estimation of this flow is difficult. For this reason, in the examination of stability with respect to seepage flow, the mean high water level of the spring tide is considered the outer water level and in the study of seepage flow, computation is implemented considering the outer water level to be the mean water level. The status of seepage in the dike body is shown in terms of the phreatic line and flow net and in order to obtain these values there are many methods including (1) diagram analysis; (2) mathematical analysis; or (3) model test. As for the method with respect to (1) analysis, the Casagrande’s method is used. The important consideration with respect to stability of a dike body in terms of seepage is that the phreatic line does not appear on the inner slope thus inducing slope erosion. For this reason, in the event the phreatic line appears on the inner slope, such measures as (1) increase the width of the crest; (2) install a perm in order to moderate the average incline of the inner slops; and (3) install an appropriate drain at the end of the inner slope in order to lower the phreatic line need to be taken. 190

Chapter 4. Engineering for Sustainable Development of Tidal Areas

b) Piping Safety design made for protection of dikes against piping action adopts creep ratio proposed by Bligh as a guide. The creep ratio is a fraction of minimum creep length inside the dike to maximum head between outside and inside water levels. This method adopts the creep ratio of the banking material of a dike to examine a section of a dike. 2) Seepage problems due to seawater intrusion through embedded rock layer of sea dyke Lee, Haeng-Woo and Chang, Pyoung-Wuck (2005) carried out model study and seepage analysis for the study on seawater intrusion through embedded rock layer of seadike. a) Model test and Seepage Analysis Model (SAMTLE) Earth fill facilities and sea dike in the marine area are often constructed by soil fill over the gravel and rock layers which have completely different seepage characteristics from soil layer. In general, soil layers are known to be Darcy’s flow, while gravel and rock layers are known to be Non-Darcy’s flow. However, some recent reports show that the water flow through gravel and rock layers under soil fill is more like Darcy’s flow.

Fig. 4.1.22 Changes in piezometric head in dredged soil with/without embedded gravel layer with different hydraulic gradient (Le=0.5m) 191

A seepage analysis model for two-layer embankment (SAMTLE) was developed under the assumption that water flows through the two-layer structure obeyed the Darcy‘s flow. A series of laboratory model tests were run with the sea dike embedded gravel layer under the soil fill in order to check the application of the model. Two-layers embankment model consisted of gravel and earth fill layers. Gravel layers were built under the earth fill for a half and one-third width of earth fill of the model. Permeability of earth fill was ranged between 5.0x10-5 ~ 3.0x10-4 m/s. The tests were performed with hydraulic gradients 0.10 ~ 0.55. From the test results, hydraulic head of earth fill with gravel layer was 1.6 times higher than that of earth fill without gravel layer as shown in Fig. 4.1.22. Fig. 4.1.23 indicated that seepage rate was increased up to 4 ~ 22 times and safety factor for piping was decreased to 13 ~ 43 % comparing the earth fill with gravel layer to that without gravel layer. The gravel layer under the earth fill could, in general, give some serious seepage problems to sea dike embankment. The calculated heads by SAMTLE and observed ones from model test are significant under 90% of confidence interval. It can therefore be said that the water flow through gravel layer within embankment is Darcy’s flow. b) Seepage Characteristics of Embedded Gravel and Rock Layers of Sea dike At the beginning of the construction of the sea dike, gravels and rocks were dumped to soft marine ground in order to improve trafficability and construction conditions. With gravel and rock layers

Fig. 4.1.23 Seepage rate of the model with 3 different soils and 3 three different heads (dH=0.55, 0.35, 0.15m) with embedded gravel layer 192

Chapter 4. Engineering for Sustainable Development of Tidal Areas

Fig. 4.1.24 Relationship between velocity and gradient in embedded gravel layer (left: dredged sand, right: mixing with dredged and river sand)

under earth fill, some serious seepage problems occurred after construction. However, seepage behaviors of those embankment structures were not properly investigated. Seepage characteristics of gravel and rock layers were known to Non-Darcy’s flow. However, recent papers said that the embedded one under earth fill is not clearly known whether its flow was Darcy’s or Non-Darcy’s. Numerical analysis, laboratory model test and field investigations were performed for analyzing those seepage characteristics. After operating the hydraulic gradient of 0.10~0.55 upon laboratory model, these seepage characteristics of the embedded gravel layer showed that Reynolds Numbers are less than 10 and relationship between seepage velocities of gravel layer and hydraulic gradients was linearly proportional with over 0.79 of coefficient of correlation (R2) as depicted in Fig. 4.1.24. As these results, seepage characteristics of embedded gravel or rock layers under earth fill were inferred to be laminar and Darcy’s flow. c) Simulation by SAMTLE Numerical analyses were carried out for studying on seepage characteristics of sea dike that was consisted of rock and soil layers with SAMTLE model. Relative permeability between embedded rock and soil layers up to 100 times had a significant effect on the seepage characteristics of sea dike. However, the relative permeability of greater than 100 times had less effect on them. In the actual construction site, many seepage problems were induced by the higher seepage force in sea dike and high seepage force was causes of piping in embankment. Construction operations against the seepage problems were ended up to lengthening and thickening the embedded rock layer when the dike was constructed. 193

Correlation of the calculated heads and seepage rates by SAMTLE and observed ones in the laboratory test was significant with 90% of confidence interval. It was said from the test results that seepage of embedded gravel layers in soil fill can indirectly be characterized by Darcy’s flow. Therefore, the SMATLE model can be a useful tool for analyzing, operating and maintaining the seepage problems of earth fill facilities and sea dike in the marine area. 3) Sliding failure of foundation ground The simplified segmentation method (Fig. 4.1.25) generally assuming a rotational sliding surface is used to ensure the stability of dikes on soft ground. In addition, the total stress method is employed to calculate shear strength, whereby foundation failure is examined (Agricultural Land Bureau, Japanese Ministry of Agriculture, Forestry and Fisheries, 1966; Japanese Society of Irrigation, Drainage and Reclamation Engineering, 1979; Japanese Society of Irrigation, Drainage and Reclamation Engineering, 2000). In this case, the safety factor against sliding failure may be obtained from the formula given below

Fs =

r ⋅ ∑ [C u l + (W cos α − u 0 l )] tan φ u

∑ (W ⋅ x + k

h

⋅ W ⋅ y)

(4.1.1)

Here Fs is the safety factor against sliding failure; r is the radius of the slip circle; Cu is the cohesion of the indication of total stress; øu is the internal friction angle that indicates the total stress of the soil; l is the length of the base of the fraction; W is the total weight of the fraction (wet weight of that segment that is above the phreatic line and saturated weight of the segment that is below the phreatic line); u0 is the neutral pore water pressure that acts on the base of the fraction; α is the angle that the base of the fraction makes with the horizontal; x is the distance of the center of gravity of the fraction to the slip circle; and kh is the horizontal seismic coefficient and y is length of the arm of the earthquake load in the horizontal direction (= kh W) in terms of the slip circle. In ordinary cases, the safety factor shall be 1.2 or higher. Moreover, stability analysis adding the earthquake load shall be 1.0 or above.

Fig. 4.1.25 Circular sliding surface (simplified segmentation method; during an earthquake) 194

The section of the dike is decided through these stability analyses in principle according to the procedures that follow: (1) decision of crest structure in the light of dike height and crest width; (2) decision of minimum counterweight fill required for elimination of crest sliding through the above stability analysis; and (3) decision of crest and counterweight fill added to the initial counterweight fill through successive same steps. Fig. 4.1.26 shows an example of these procedures.

Chapter 4. Engineering for Sustainable Development of Tidal Areas

4) Settlement of the foundation The settlement of dikes is caused by: (1) compaction of the rubble foundation, dike body and banking; (2) rubble foundation settling down to ground; (3) side flow of the ground; and (4) consolidation of the ground soil. Dikes must so designed as to eliminate these causes wherever possible. In the case of unavoidable settlement, examination shall be made of whether or not such settlement will directly impact the dike or whether there will be negative impact on the targeted structure. In other words, since consolidation settlement is unavoidable, the foundation is required to execute planned construction of raising for prevention of long-term settlement. Settlement due to other causes may be suppressed to certain extent by means of the design and construction methods (Agricultural Land Bureau, Japanese Ministry of Agriculture, Forestry and Fisheries, 1966; Japanese Society of Irrigation, Drainage and Reclamation Engineering, 1979; Japanese Society of Irrigation, Drainage and Reclamation Engineering, 2000). Estimated values of the amount of settlement and consolidation time arising from consolidation settlement of ground are usually calculated by the method presented by Terzaghi. a) Calculation of the amount of consolidation settlement

(a) First stage counterweight fill

(b) Second stage counterweight fill

(c) Third stage counterweight fill (determination of the cross section of the dike)

In order to obtain the amount Fig. 4.1.26 Method of calculating stability in order to determine of settlement and consolidation the dike cross section time, it is necessary to determine: (1) the coefficient of consolidation of the ground obtained from the results of the consolidation test; (2) stress distribution analysis of the ground based on the load; (3) initial analysis of neutral stress; (4) drainage conditions of the consolidation layer; and (5) thickness of the consolidation layer. The amount of final settlement through consolidation is calculated using the following formula S = ∑ mvi ຒ pi h i

(4.1.2)

Here S is the amount of final settlement; hi is the thickness of the various layers of the properly divided consolidated layers; ∆pi is the increment of vertical mass; and mvi is the coefficient of volume compressibility of the load on the various layers. 195

b) Calculation of temporal changes of amount of consolidation settlement The temporal changes of the consolidation settlement found by section i) above are obtained according to the steps that follow. The amount of settlement for a given degree of consolidation U% is calculated using Formula 4.1.3 while the consolidation time that corresponds to the degree of consolidation is calculated using Formula 4.1.4.

s = SU 100 T H2 tu = u cv

(4.1.3) (4.1.4)

Here, s is the amount of settlement corresponding to the degree of consolidation; S is the amount of final settlement; U is the degree of consolidation; tu is the time required for the degree of consolidation U; Tu is the time dependent coefficient required for the degree of consolidation U that is calculated from Fig. 4.1.27; H is one half the consolidation layer thickness in the case of double drainage and consolidation layer thickness in the case of single drainage; and cv is the coefficient of consolidation. In Fig. 4.1.27, I is the case in which the consolidation stress is distributed uniformly in the double drainage, II is the case in which the layer thickness is large in relation to the loading width in single drainage (only the upper surface) and the stress is zero at the lower surface; and III is the case in which the water surface coincides with the upper surface of the layer and drainage occurs only at this upper surface and the stress is zero at the upper surface increasing in the direction of the lower surface. 4.1.6 FINAL CLOSURE WORKS

When constructing a front dike that prevents offshore tide in order to make part of the tidal area dry land, enclosing part of the open sea is executed and the front dike works are carried out at the final stage of dike works, which collectively mean final closure works (Agricultural Land Bureau, Japanese Ministry of Agriculture, Forestry and Fisheries, 1966; Japanese Society of Irrigation, Drainage and Reclamation Engineering, 1979; Japanese Society of Irrigation, Drainage and Reclamation Engineering, 2000). As the open width decreases with progress in the construction of the front dike, thus reducing the length of the final gap, scouring due to tidal flow becomes severe. For this reason, the construction of dikes by means of the normal baking method becomes difficult. As a result, dike works are executed by installing a final gap with covering at the bottom of the sea at the initial stage followed by closing off the dike opening at the final stage, leading to the completion of the dike works. 196

Chapter 4. Engineering for Sustainable Development of Tidal Areas

Since the final gap during the construction of the dike is the passageway for the tidal flow due to the rise and fall of the water level, solid protective works are required. The solid protective works contain consolidation works that protect dikes against erosion at the final gap; and final gap works that protect dikes against erosion at the ends of the final gap, each of which is executed. 1) Timing for final closure A season with infrequent strong rain or wind should be selected as the timing for implementing final closure works and should be the season of neap tide during which the tidal range is small. The final closure works shall be implemented by forming a construction plan whereby the final closure dike is completed by the day of minimum tidal range. Moreover, in the study of the timing for the final closure, total consideration in all procedures for final closure works should be examined as follows. (1) For the front dike section, the structure should be safe with respect to waves and the head between the outer and inner water level after final closure. (2) The total dike line should be completed prior to the next storm surge. (3) In order that there are no impediments during the final closure work or in drainage after the final closure, the drainage gate shall have enough capacity to drain.

The timing of final closure differs by the method and scale of the final closures such as (1) closure of the outer water in a short period through rapid method of final closure such as using stoplogs and gates; (2) closure of the outer water over 1 to 2 days due to the relatively small scale of the method of final closure; and (3) closure of the outer water over a period of about 1 week due to the large scale of the method of final closure involving rough closure using rubble foundation. For this reason, upon construction schedule control and decision of construction planning it is necessary to examine the date of commencement and completion of the final closure and the tidal condition carefully.

2) Method of final closure The methods of final closure may be categorized as follows. i) Gradual contraction method: This is a method that makes sequential contraction of the closure gap by means of land work from an artificial land constructed at the ends or in the middle of the final gap, increasing the velocity near the gap as the banking progresses. 197

ii) Gradual elevation method: This is a method that raises the final gap uniformly from the lower part by means of offshore work. The velocity near the gap increases up to the elevation at which the flow becomes complete overflow but when exceeding the complete overflow, the velocity decreases with reduction in overflow water depth. iii) Combined use: This is a method that is in combination of the above two methods and controls the hydraulic condition which occurs at the site of the gap to an adequate range. The final closure method must be examined comprehensively for a final closure works process in consideration of: (1) final closure scale; (2) bottom elevation from the floor of the final gap; (3) length of time (period) required for final closure works; (4) final closure dike; and (5) capacity of construction machinery, and then the most appropriate method will be selected. 3) Final gap a) Site and cross-sectional area of flow i) The selection of the site for the final gap: The final gap shall be installed at a site where the sea water passes in the most natural manner and the construction of the final closure is easiest. In selecting the site of the final gap, the following items will need to be taken into consideration. - Almost former water routes are soft ground, thus frequently making the construction of the final closure works difficult. - The final closure works need to be executed at a construction-easy site in order to procure materials such as stones, soil and sand, and to ensure transportation route. ii) The cross section of flow of the final gap: Once the site of the final closure has been selected the bottom elevation of the final gap is determined by the elevation of the foundation ground and the cross-sectional area of flow that ought to be achieved at the final gap is adjusted using the width of the final gap. In this case, first the maximum velocity at the final gap is examined targeting the spring tide. The width of the final gap is adjusted so that the velocity obtained in this manner is equal to or less than the allowable velocity shown in Table 4.1.4. In determining this cross section of flow, it is also necessary to take drainage in the backland into consideration. In other words, the inner water level is examined for the neap tide and cross-sectional area of flow that does not pose a significant impact on the drainage of the backland is achieved. b) Structure of the final gap i) Consolidation works: The foundation of the sea bed of the final gap is scoured by tidal current that flows over a long period of time. In the sea area where the tidal range is large and the 198

Chapter 4. Engineering for Sustainable Development of Tidal Areas

outer tide level declines significantly, the outside of the dike is scoured to some distance at a moderate slope and the inner side of the dike shows deep scouring close to the bottom of the final gap. For this reason, the bottom of the final gap will need to have a strong floor consolidation works throughout the width required for safety in terms of sliding failure of the dike. The structure of consolidation works may be categorized into covering works, foundation works and cut off works. In the design of such consolidation works, the fact that scouring force, uplift pressure, loading, hydrostatic pressure, wave pressure, piping and other complex external forces act will need to be given sufficient consideration. The covering works shall protect the foundation ground with combination of materials with high level of abrasion durability and ensure a safe structure resistant to scour and uplift pressure. The general method for covering includes stone pitching, concrete block pitching, concrete pitching as well as traditional fascine mattress. In recent years, such a method is frequently employed as to lay down asphalt mat or geo-textile-based everlasting sailing cloth on the ground, and to fix it by means of rubble foundation. These methods may be adopted singly or in combination giving consideration to the conditions of the site. Table 4.1.4 Allowable flow velocity of the final closure works Type of covering works Rubble foundation Stone or block pitching Concrete pitching

Allowable flow velocity m/ sec 2~3 2.5~3.5 3~4

Remarks In the case where the flow velocity is increased for a short period of time at the time of final closure, the allowable velocity shall be increased by 20%.

ii) Final gap works: Final gap works are installed in order to prevent erosion of the final gap of the dike. The final gap works provide adequate safety with respect to such external forces as scour, waves and piping. The structure shall be in compliance with the outer slope covering of the dike body and in particular by means of integrating a water proof wall, it is necessary to prevent seepage. For this reason, the final gap works are provided with a protective wall by means of a masonry method, concrete block retaining method, concrete wall method, steel sheet-pile method as well as cell structure at sea level with large wave force. Moreover, in general, the inlet to the final gap is often subjected to significant contraction flow and, vortex is generated on the inside of the contraction flow, thus the final gap work foundation area is damaged by scouring. Moreover, high velocity flow is produced by flow contraction on the downstream side, and thus the area near the edge of the floor is damaged by scouring. In order to avoid the effects of such sudden changes in the flow, a training levee or groin may be installed. 4) Final closure dike The final closure dike is a dike for temporary final closure in the process of constructing the final closing work and after the completion of the entire dike; either becomes part of the dike body or is removed. 199

Box 4.1 Optimal dimension of dumping materials in tidal closure (Park, 2000) Gabion and rock has been used for the final closing of sea dike construction during the last decade. As the flow characteristics and stability of dumping materials in the tidal closure is too complicate to be shown in empirical function, physical model study has been recommended for the design of large scaled projects. To derive optimal size of dumping materials in the tidal closure of Saemangeum Tidal Reclamation Project of Korea, Park (2000) had carried out a physical model study out in 60 m long and 3m wide flume. Stability of the closing materials has been shown as a function of shear stress in the sea dike closure, as following equation.

F* =

τ S ' gDm

where, F* is dimensionless shear stress of filling materials, S’ is relative density of filling materials in the water. The shear stress is evaluated by the following equation.

τ = ρ wV* 2 =

ρ wV 2  11d  5.75 log 2.5 Dm 

  

2

where, ρ w is density of water and V* is relative shear velocity as function of flow depth d and diameter Dm of filling materials. For the rock dumping in the closure, critical shear stress is recommended to be 0.04 considering the safety of construction. Fig. Box 4.1.1 shows the optimal weight of rock in each of water depth and current velocity condition. For the gabion dumping in the closure, critical shear stress is recommended to be 0.10. Fig. Box 4.1.2 shows the optimal weight of gabion in each of water depth and current velocity condition in case dimensionless shear stress is 0.13. For the stability of gabion, to decide the diameter of rock inside of the gabion to prevent deterioration of the gabion, an average filling rock diameter can be simplified as follows.

Dm = 0.11d (0.81Fr )

2.5

where, Fr is Froude number. At the head of spur dike where most severe shear stress is occurred in the flow, the critical shear stress Fc is more than 0.042. In case mixing ratio of rock and gabion is 80% and 20 %, Fc is 0.044 for rock and 0.10 for gabion, respectively. In case mixing ratio of 5 tons of rock and 3 tons gabion is 50% and 50 %, Fc is 0.05 is for rock and 0.106 for gabion, respectively. The mixed materials could resistible for the current of 7.8 m/s in the closure. For the rock, the critical velocity is 6.3 m/s for the rock of 1.2 tons and 7.5 m/s for the rock of 5 tons. On the other hand, in case all the closure materials are gabion, the critical velocity is 8.7 m/s for the unit weight of 2 tons and Fc is 0.147, respectively. On this basis, It could be concluded that shear stress of gabion is 3 times larger than rock in the tidal closure gap. 



G



G



G



 &XUUHQWYHORFLW\LQP V



Fig. Box 4.1.1 Optimal weight of rock for the closure gap (Fc=0.04) 200

:HLJKWLQWRQV

:HLJKWLQWRQV



G





GP



GP



G



G G

 

G 

 &XUUHQWYHORFLW\LQP V



Fig. Box 4.1.2 Optimal weight of gabion for the closure gap (F*=0.13)

Chapter 4. Engineering for Sustainable Development of Tidal Areas

The elevation of the final closure dike is in principle determined by adding the freeboard to the mean high water level during the spring tide. Since final closure works avoid the storm season, the sea level departure from normal and wave height is relatively small. In the case a small scale final gap is closed during neap tide, the crest elevation is adequate to allow for some freeboard in the high water level in that season. On the other hand, in large scale final closure works, it is necessary to forecast the sea level departure from the normal and the wave during the construction period. The final closure dike is a structure that is constructed in order to close the outer water within a limited period of time. For this reason, since old days, various methods and structures of the dike body have been applied depending on the scale of the final gap and materials that are locally available. In other words, the final closure dike is constructed by means of the sand bag pitching method, masonry method, rubble foundation method, stoplog method and concrete block method. In recent years, the Caisson method with a feature of fast construction is frequently adopted. i) Sand bag pitching method: This method has long been applied when the scale of the final gap is small and the bottom elevation of the consolidation works is about the elevation of the original foundation and the work can be completely within a relative short time. Sand bags with weight of between 30 and 60 kg are stacked preventing water from seeping into the joints and this is used as final closure dike in this method. ii) Stoplog method: This method is often used for closing medium to small scale final gaps where the bottom elevation of the consolidation works is about the same as the elevation of the original foundation and the work needs to be completed within a short period of time. In the consolidation works, piles (timber piles, concrete piles, H type steel piles) are raised at intervals of 2 to 3 meters and stoplog materials (12 to 15 centimeters square) made from cedar and pine are placed between these piles in order to close the entire width of the final gap simultaneously at low tide. This is often used in combination with such methods as the sand bag pitching method. Today, a method of using steel gates in the place of stoplogs is adopted and is applied to the final closing works of relatively deep water as a rapid method of final closure. iii) Block retaining method: This method is often employed for closing medium to large scale final gaps where the bottom elevation of the consolidation works is lower than the elevation of the original foundation and the work is to progress from the medium to long term. After placement of concrete blocks and steel frames during low tide or stand of tide to effect rough closure, banking is immediately performed using a sand pump dredger to close the outer water. It is desirable that the blocks be large capacity and in recent years, with the enlargement of construction machinery, there is a tendency to use larger blocks.

201

iv) Caisson works: In the Delta Project in Netherlands, caissons and pontoons were used for filling closing gap by sinking them into the gap and by filling them up quickly with earth and rocks. With torpedo nets, underflow and side underflow could be combated. Fig. 4.1.28 shows tow Phoenix caissons by which the Braakman closure gap was Fig. 4.1.28 Braakman closed off with two Phoenix caissons in closed off. Because the tidal the Delta Project, Netherlands differences were much greater and up to 3 to 5 m (neap tide and spring tide) resulting in a very strong current and a closure gap with a width of 110 m was required in this case(G. P. van de Ven, 1993; G. P. van de Ven, 2004).

202

Chapter 4. Engineering for Sustainable Development of Tidal Areas

4.2 Water Facility and Water Management System AUTHOR: SHIOMI SHIKASHO 4.2.1 Water Source Facility

In the development of a tidal area, obtaining irrigation water is an important requirement. The following facilities may be considered as an irrigation water source in the tidal area. 1) Estuary barrier, fresh water intake (Japanese term “Ao-shusui” and tidal irrigation) The method of water intake from a tidal river contains estuary barrier and fresh water intake. Estuary barrier: An estuary barrier is a facility that blocks salt water by installing a low weir at the river of the tidal area as well as store fresh water on the upstream side used as an irrigation water source. An estuary barrier exerts a significant impact on the transition area between the fresh water and salt water. For this reason, utmost care is required with respect to the ecological system. The design of the estuary barrier shall be in compliance with the design standards of the head works. Fresh water intake (tide irrigation): Fresh water intake refers to the intake of fresh water in the upper layer that rises at high tide in the tidal reach. This water intake method takes water depending on tide, and therefore intake time varies daily. Normally, the weir can take water only for several hours at high tide (particularly in spring tide). If dry weather continues, the salt concentration increases, and so the weir cannot take fresh water. This method of water intake is seen in estuary delta areas in Japan and Southeast Asia. Fresh water intake method is a method of taking fresh water above a certain water level in a canal or reservoir through an intake gate, or a method with a water lifting pump. 2) Groundwater There are places with ample fresh water in the groundwater of tidal areas. From this view, sustainable water utilization is made possible if pumping a proper quality of water. However, the intake water facilities may have problems with salt water intrusion or settlement of ground from pumping, and for this reason, it is desirable that adequate investigation take place during the planning stage. In the case where the groundwater is used for water source, pumping from a well will be required. Wells are divided into two types: shallow well that takes shallow groundwater; and deep well that takes deep groundwater.

203

Shallow well: This is a facility that takes water primarily from shallow unconfined aquifer. The radius of the well is within 2 meters and the depth of the well is about 10 meters and the sidewall of the well is constructed from piled stone or porous concrete and the groundwater that flows in from the wall is taken in. Shallow wells are often constructed as domestic water sources. Deep well: This is a facility that takes water primarily from deep confined aquifer. A hole with radius of 150 to 500 mm is drilled vertically from the surface and the well is completed by inserting a casing pipe into this hole. The gap between the borehole wall and casing pipe is generally filled with sand. A slit is opened or a screen is inserted on or in the casing pipe into a stratum taking groundwater. 3) Fresh water reservoir The term “fresh water reservoir” here refers to a reservoir in which the water with high salt concentration inappropriate for irrigation water has been replaced by fresh water available for irrigation water. A fresh water reservoir is a facility that is enclosed by part of sea surface or a water area with fresh and salt water, replaces salt water by fresh water, ensures a water source for polder, and has an effect on disaster prevention such as flood control, sea coast conservation, salt injury. The fresh water reservoir utilizes the infective discharge at the end of the river, and since no particular problems are encountered in arrangement with existing water rights, the fresh water reservoir is characterized by the fact that relatively free planning may be implemented. The fresh water reservoir needs an adequate quantity of inflow of fresh water and amounts of precipitation as well as yields a water area with high salt concentration at the bottom and mixes water in the water area with fresh water in the upper layer due to wind disturbance, thus increasing the significance in salt control. 4) Desalting siphon The method of replacing salt water in the fresh water reservoir by fresh water is divided broadly into three categories: (1) discharge gate method that replaces salt water by fresh water by enclosing part of sea surface and brackish lake by a dike and using a gate for controlling water level, as in impoldering (example: Kojima Bay, Hachirogata); (2) desalting siphon method that replaces salt water by fresh water with desalting siphons while controlling water level by means of a gate or overflow dam during flooding (example: Miike impoldering reservoir); and (3) curtain wall method that encloses part of the sea surface or brackish lake by a curtain wall with an open part to develop a reservoir, making the reservoir a fresh water reservoir by replacing the inside sea water by fresh water. Of these, the desalting siphon method builds up thickness of the fresh water layer (usable water 204

Chapter 4. Engineering for Sustainable Development of Tidal Areas

depth) of fresh water reservoir and is superior in maintaining critical salt concentration of fresh water that can be used as agricultural water. The factor of controlling replacement of salt water by fresh water includes inflow of fresh water, volume of the reservoir, and mixed action of fresh and salt waters in the reservoir. In particular, the mixed action of fresh and salt waters in the reservoir is important, which are dependent on change in water level, status of inflow of fresh water, influence of wind (wind wave and wind-induced current), and status of operation of the gate. In order to replace salt water by fresh water efficiently using the desalting siphon method, it is important to make proper decision of diameter of desalting siphon, its inlet shape and installation height, and sill height of the outlet of the siphon on sea side (retarding pond side). The condition of these factors enables effective selective drainage of high concentration salt water in the layer below the salinocline and can promote to lower the salinocline, resulting in increasing usable water depth of upper layer fresh water. They enable to avoid influence by wind disturbance induced by strong wind such as typhoon and seasonal wind, thus making it possible to maintain stable salinocline. 4.2.2 Water Facility

This section explains the various standard methods of design as relates to water facilities for the management of water (Hiroyuki Ogata, 1972; Japanese Institute of Irrigation and Drainage, 2004; Japanese Society of Irrigation, Drainage and Reclamation Engineering, 2000). 1) Irrigation canal and drainage canal The method of transport of water includes gravitational transport (open channel) or pressure transport (pipe). In designing a canal for irrigation water or drainage water, a pipe may be adopted because of being convenient for water management in the case of a little quantity of flow through an irrigation canal, while an open channel is chosen in the case of a large quantity of flow through a drainage canal. Handbook of Irrigation, Drainage and Reclamation Engineering, Revised 6th Version (in References) shall be used for the design of an irrigation canal or pipe and here, water facility design for the drainage canal will be explained. A drainage canal, normally planned as an unlined canal, is so designed as to allow design discharge to be carried through the canal within the allowable velocity and to provide its section with depth adequate for storm drainage and ordinary drainage, and stable gradient of the canal side wall. The procedures for designing the cross section and gradient of the drainage canal are as follows (refer to Fig. 4.2.1). 205

i) The design discharge is obtained as the product of the specific discharge and the drainage area; ii) The design water level is set so that this does not exceed the ground elevation along the canal; in general, the drainage canal is designed as uniform flow canal and the drainage canal gradient coincides with the water surface gradient that is determined from the design water level; iii) After the cross section is determined, the depth and flow velocity are obtained using the Manning’s mean velocity formula; iv) It is required that the mean velocity is within the range of the allowable shape and if this allowable velocity is not satisfied, the width of the canal bed or gradient will need to be adjusted and the water depth and velocity are obtained; v) Once the water depth is determined, the water flow that is determined by the design water level, freeboard and ordinary drainage are taken into consideration and the width of the canal bed and cross section of the canal are determined. Planned inner water level within the design criteria (Allowable inundation depth, inundation time)

Planned outer water level curve Inflow curve Water level inundation area curve Structure of the drainage gate

Inner water level curve Cross section of the drainage gate

Cross section of the drainage gate

Fig. 4.2.1 Design procedures for cross section of drainage

2) Regulating gate and sluice The water facility is provided with a regulating gate or sluice for avoidance of excessive concentration of discharge water in the downstream facilities depending on the topography. The regulating gate controls flow as well as forms a control section therein which acts as an internal boundary point to analyze the flow in an open channel, being an important structure in water management. The regulating gate and sluiceways are so designed as to provide a cross section that allows the downstream flow of the designed flood discharge at the planned water level. 3) Draining gate The draining gate is a facility that is installed at the downstream end of the drainage network in order to discharge water in the area to the outside in a natural manner. The location, sill height, cross section and structure of the drainage gate are important elements in a gravitational drainage plan. The following three values are basic to the cross section of a drainage gate. 206

Chapter 4. Engineering for Sustainable Development of Tidal Areas

(1) A cross section that is capable of draining the design maximum flood discharge at the design outer water level; (2) A cross section that is capable of draining the design maximum flood discharge at the ordinary outer water level; and (3) A cross section that meets the requirement of the design inner water level and allowable inundation duration giving consideration to the water level in the inner area or the storage of the regulation reservoir. In the case of 1) and 2), determination of the cross section does not pose any special problems but in the case of 3), a cross section that satisfies the requirement of the design inner water level will need to be provisionally estimated using the procedures shown in Fig. 4.2.2. Specific discharge Drainage area Freeboard Ground height

Designed discharge Roughness coefficient

Design water level

Gradient

Minimum allowable velocity Maximum allowable velocity Freeboard Depth

Flow velocity

Cross section

Depth Designed ordinary water level at all times

Elevation of channel bottom route Cross section

Designed ordinary discharge

Fig. 4.2.2 Design procedures for drainage gate cross section

4) Pump a) Irrigation pump The irrigation pump is generally used throughout the year at small pumping discharge and high pump head and for this reason, a volute pump or high pump head mixed flow pump is adopted. For pumps used in deep wells for pumping groundwater, a submersible motor pump is used as shown in Fig. 4.2.3. b) Drainage pump It is important to perform drainage by means of natural drainage wherever possible. There are a number of situations in which drainage has no choice but depends on pumping drainage due to the relationship between the ground elevation and the outer water level. In this section, the design of pumping drainage in Japan will be explained. 207

Sluice valve Automatic air valve

Operating water level Natural water level

Manometer Pipe hanger Switch Well lid

Depth of the well

The model of drainage pump is decided after comparing investigation of type, bore, number of pump units which are in compliance with the design dimensions such total pump head, discharge determined based the process as shown in Fig. 4.2.4 in consideration of the functionality, economy, and operation and maintenance, etc. In particular, drainage pumps entail a lot of cost for operation and maintenance, and it is desirable to examine facility design in consideration of management plan. The main parts of the procedures are explained in Fig. 4.2.4. Pumping drainage: Determination of the rough value for the pumping drainage is undertaken using the following procedures under the drainage plan standards in Japan. i) The cumulative inflow curve of the hydrograph that flows into the inundation area is obtained (production of the cumulative inflow curve; S-shaped curve shown in Fig. 4.2.5)

Switch

h

Underwater cable Radius of the well

Socket

Pumping pipe Radius of the pumping pipe

Water level alarm Cable clip

Chucking valve Main unit of the pump Strainer Submersible motor

h: Ground pump head Fig. 4.2.3 Submersible motor pump

ii) Cumulative discharge line with several points that are tangent to the lower part of the cumulative inflow curve (production of the cumulative discharge line for the pump; the straight line of Fig. 4.2.5) Velocity head Screen loss Planned inner water level Initial and minimum water absorption level Planned outer water level Sluiceway loss Planned drainage discharge

Absorption water level Discharge water level Pump discharge

Pump application line diagram Characteristics of the pump Type

Actual pump head Standard bore Discharge

Total pump head Loss head

Number of units of pumps Fig. 4.2.4 Procedures for selecting type of drainage pump 208

Bore Model

Chapter 4. Engineering for Sustainable Development of Tidal Areas

iii) Obtain the maximum inundation amount curve from the distance between the straight line that is parallel to the above cumulative discharge line of the pump with the peak of the cumulative inflow curve as tangent (determination of the maximum inundation amount; see Fig. 4.2.5) iv) Depict the relationship between the maximum inundation amount and pump discharge amount of the group of values obtained in iii) as a graph (production of the maximum inundation amount curve; see Fig. 4.2.6) v) Depict the relationship between the inundation water level and inundation amount as a graph (see Fig. 4.2.6) vi) Using the procedures indicated by the arrows in Fig. 4.2.6, determine the pumping drainage Number of pump units and standard bore: The number of pump units is determined by the frequency of pumping, risk dispersion in the event of a breakdown of the pump, space for the pump units and management. Ordinary and storm discharge shall be assumed to be drained using several pumps and the number of units and standard bore of the pump shall be determined in view of economy and safety. The relationship between the standard bore and the amount of discharge is as shown in Table 4.2.1. Table 4.2.1 Standard radius of low water head pumps and discharge Standard bore (mm)

Pump discharge (m3/min)

Standard bore (mm)

Pump discharge (m3/min)

Standard bore (mm)

Pump discharge (m3/min)

400

12~23

1,000

115~150

2,000

480~600

500

23~36

1,200

150~200

2,200

600~740

600

36~50

1,350

200~255

2,400

740~850

700

50~70

1,500

255~325

2,600

850~1,000

800

70~90

1,650

325~400

2,800

1,000~1,150

900

90~115

1,800

400~480

Actual pump head: Actual pump head refers to the difference between the intake water level and discharge water level and the pump head of drainage pumps for storms changes with the fluctuation of the inner and outer water level and the drainage amount of the pump differs significantly depending on the changes in the pump head. Actual pump head (designed pump head), when applied in design of pump, must ensure the maximum efficiency of the pump at the pump head with highest frequency of pump usage. So the designed pump head of the pump should be frequently about 80% of the maximum designed actual pump head (that is, difference between maximum designed flood discharge level and initial designed inflow water level), as shown in Fig. 4.2.7. 209

Pump type: The characteristics of the pump differ by the pump type and specific speed. Specific speed (Ns) is shown by the following formula and is a value that is derived from the hydraulic similarity rule of the pump and is the required number of rotations (min-1) for a pump head of 1 meter being discharged at 1 m3 per minute. The specific speed is rule of thumb for the categorization of a pump. Ns = N

Q

H 3/ 4

(4.2.1)

Here N is the rotation of the pump (min-1), Q is the discharge (m3 per minute) and H is the total pump head (meters). Next, the characteristics of a pump by the type and axial form are shown in Table 4.2.2 and Table 4.2.3. The model of pump is decided from a comprehensive standpoint of these factors. After having decided rough design dimensions of pump, the designers perform drainage and inundation analysis in view of the pump head curve of pump, examine the whole function of the drainage facility, and check whether or not the facility capacity satisfies the initial objectives. Drainage and inundation provides important material for such drainage control plan as operating plan of the pump. 5) Regulation reservoir a) Regulation reservoir in an irrigation network This regulation reservoir is a facility installed in the canal system for the purpose of controlling water facility function in a flexible manner with respect to temporal change in flow or water level due to variation of supply and demand in irrigation planning. The capacity of the regulation reservoir is

Pump discharge volume (P1) Pump discharge volume (P2)

Pump discharge volume (P2)

Cumulave inflow 3 volume (Q) m

Cumulative inflow volume curve

Maximum amount of inundation assuming pump P2 Maximum amount of inundation assuming pump P1 Pump discharge volume (P1) Time

Fig. 4.2.5 Relationship among the inflow volume, drainage discharge volume and inundation volume 210

Chapter 4. Engineering for Sustainable Development of Tidal Areas

Discharge volume curve for the maximum inundation volume Elevation (m) of the inundation level (H)

Planned inner water level

V-H curve

Required pump capacity (m3 per second) Pump discharge volume (m3 per second) Initial water intake level

Volume of inundation (V) (m3)

Fig. 4.2.6 Rough determination of the pump discharge volume

(1) the regulating capacity by time delay of the difference in supply and demand; (2) capacity for regulating the imbalance between the demand and the supply; (3) capacity for regulating the delay in response of the canal and these are taken into consideration to determine the scale of the facility. The design of a regulation reservoir may be the large scale dam type or small scale farm pond type. b) Regulation reservoir in a drainage network In the tidal area, since the outer water level to which water is drained changes by the tide, it is not possible to obtain the appropriate level of discharge volume just from the drainage gate and drainage pump and this may cause impairment in water management. The regulation reservoir is installed in order to respond to the fluctuation in the amount of flow in a flexible manner. Needless to say, in double dike system reclamation also in single dike system reclamation, the regulation reservoir plays an important function from the perspective of water management. Table 4.2.2 Comparative table of pump characteristics Item

Mixed flow pump

Axial flow pump

Movable wing axial flow pump

Pump discharge and pump head

The change of discharge against the fluctuation of the water head is larger than in the case of the axial flow pump.

The change in discharge relative to the change in the head of water is smaller than in the case of the mixed flow pump.

It is possible to adjust discharge at will in response to the increase or decrease of the wing angle.

Axial force

About uniform regardless of change in the discharge.

The closed axial power gradually decreases from the maximum efficiency at 200 to 250% and continues to decline even after the point of maximum efficiency is exceeded.

By operating the wing to correspond to the fluctuation of the water head, it is possible to increase or decrease discharge and operate at a given specific axial power.

Efficiency

The planned point efficiency is about 2% better than in the case of the axial flow pump.

The planned point efficiency is about 2% poorer than in the case of the mixed flow pump.

By operating the wing with a specific axial force, discharge to efficiency curve becomes the same curve as for the mixed flow pump.

Care in selection

While closure operation is possible, long term operation should be avoided.

Closure operation is possible. Cavitation is prone to occur and the usable rang of the water head is limited.

Appropriate for the adjustment of discharge for large bore pumps with low water head or discharge pumps with a broad change in the water head and closure operation is possible.

211

Pump efficiency

Pump operaon

Pump actual head of water discharge cure

Designed pump head

Planned maximum actual pump head (H)

Efficiency: actual pump head

The volume of the regulation reservoir that is installed for smooth operation of the pump is generally designed with 2 to 3 minutecapacity as the rule of thumb per unit of pump. Moreover, in the case of regulation examined that is installed in order to mitigate flooding, the scale and cost of the pump or drainage gate should be examined and an optimum volume of water in a regulation reservoir should be determined. The regulation reservoir that is installed in double dike impoldering system reclamation is in a trade off relationship with the area of poldering and the impact on use in the area and on crest elevation of inner dikes is large so that adequate consideration is required in determining the area of the regulation reservoir.

Pump discharge

Fig. 4.2.7 Planned actual pump and designed pump head Fig. 4.2.7 Planned actual pump and designed pump head

6) Fishway and lock A fishway is a structure on or around artificial obstructions such as weirs, dams, culverts and waterfalls to facilitate fishes’ natural migration. Most fishways enable fish to pass around the obstructions by swimming and leaping up a series of relatively low steps into the waters on the other side. A lock is a particular type of device for raising or lowering boats between stretches of water at different levels on navigable rivers and canals. The distinguishing feature of a lock is a fixed chamber whose water level can be varied. Table 4.2.3 Comparison of the axial types Item

Comparison of horizontal axis and vertical axis

Pumping area

The area may be smaller for the vertical axis type

Filling

This is required for the horizontal axis type but not necessary for the vertical axis type

Suction characteristics

The vertical axis type is somewhat more advantageous

Start up characteristics The vertical axis type is somewhat easier Internal inspection

While for the horizontal axis type, inspection is possible by removing the upper casing, for the vertical axial type, the pump as a whole needs to be removed and disassembled for inspection

Durability to erosion

The horizontal axial type is more advantageous

Crane capacity

The crane required for the horizontal axial type is smaller

Height of the structure

The height of the structure is lower for the horizontal axial type

Equipment cost

The equipment cost is lower for the horizontal axial type

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Chapter 4. Engineering for Sustainable Development of Tidal Areas

The Nagaragawa Estuary Barrage, which is located 5.4 km upstream of the mouth of the Nagaragawa River in Japan and was completed in 2004, has three types of fishways of an attraction-flow-type fishway, a lock-type fishway and a naturally shaped fishway, and a lock. The attraction-flowtype fishway shown in Fig. 4.2.8 is made of attraction flow channels in the center portion and stair fishways (fish ladder portions) on both sides. Fish are tempted by the flowing water in the attraction flow channels, and travel upstream via the fish ladders on both sides. The lock-type fishway help fish to move through the double leaf wheel gates installed on the upstream and downstream sides.

Fig. 4.2.8 Attraction-flow-type fishway

The naturally shaped fishway shown in Fig. 4.2.9 is about 320m long and 15m wide Fig. 4.2.9 Naturally shaped fishway including a water surface of 3m in width provided on the overflow levee on the right bank of the estuary barrage. A stream resembling a natural brook was created to allow a wide range of fish to travel upstream. The channel is given a gentle slope, and cobblestones and other natural stones are placed in it. Rapids and pools are arranged alternately to diversify the depth and the velocity. The channel was made to meander, and resting places and shelters for fish were formed. Fig. 4.2.10 shows the lock built on the right bank. The lock is operated from the operating room in the lock gate hoist room.

4.2.3 Water Management System

It is important for the sustainable development plan of a tidal area to make a comprehensive control of water storage, intake, conveyance, distribution, drainage, water quality conservation with respect to irrigation water and drainage water. A proper water management needs measurement and control technologies of hydraulic quantity, and prediction technique of water level and water quality in canals and lakes. 213

1) Water management system Water intake, water flow and water distribution management system contacts are provided in water facilities and regardless of the method of operation, it is important to grasp and manage the information from these important contacts in an appropriate manner. Water management is to be performed by incorporating information processing and communications control Fig. 4.2.10 Lock built on the right bank technologies in water use technology. It is therefore indispensable to introduce advanced technology in information communications engineering in the area of water management. Table 4.2.4 and Fig. 4.2.11 show an example of the configuration of a water management system. Measurement method and instruments: The method of measuring such data as the water level, discharge, precipitation, pressure and level of opening shall be examined in consideration of the range of measurement of the various data, precision of measurement and type of output signal required for water management and the appropriate equipment shall be selected based on this required precision. Control method and equipment: The control plan for the facility shall be examined for storms and ordinary conditions and an appropriate method shall be adopted. As equipment for ensuring that the water level and opening level take the specified values, the feedback automatic control system shown in Fig. 4.2.12 is used and based on the characteristics of the control that is targeted, on-off operation, proportional operation, integral operation and differential operation are used independently or in combination (Shiomi Shikasho, 1987). Table 4.2.4 Item and equipment of water management facilities Measurement

Water level meter, flow meter, precipitation meter, manometer, opening meter, etc.

Control

Panel on the equipment, setting control equipment, etc.

Information transmission

Telemeter telecontrol equipment, input output relay equipment, etc.

Information processing

Central processing unit, supplementary storage unit, input output unit, etc.

Man machine interface

CRT equipment, graphic panel, operation console display, etc. Printer, hard copy, etc. Operating console

214

Display Recording Operation

Chapter 4. Engineering for Sustainable Development of Tidal Areas

2) Hydraulic analysis of flood management In order to manage the drainage facility in an appropriate manner during a flood, it is essential for water management facilities to take hold of highly accurate information such as rainfall, water level, discharge, and to perform precise analysis (also called drainage and inundation analysis) mainly of stream regime in the drainage facility system. The continuous equation for the one-dimensional gradually varied flow and the equation of motion are expressed as follows. The x axis shall be the direction of the flow shall be along the bed of the canal and t shall indicate time. Transmission circuit

Pressure meter Opening meter

Public circuit line Wireless

Information transmission system

Information processing system Data processing facility

Precipitation meter

Self managed line

Input and output control facility

Flow meter

Transmission line unit

Telemeter/tele-control device for master station

Information transmission system

Transmission line unit

Measurement system Water level meter

Master station

Telemeter/tele-control device for master station

Substation

Supplementary memory facility

Printer CRT Hard copy

Machine side panel

Gate valve

Man machine interface system Operation console

Mini-graphic panel

Setting value control facility

Fig. 4.2.11 Example of the configuration of a water management control facility

Disturbance

Setting control facility

Amount of control

e Target of control

Operating part

Adjustment part

+ ᧩

Setting part

Target value

Measuring facility Fig. 4.2.12 Configuration of the control facility 215

Continuity equation:

∂A ∂Q + = ± q (+: inflow, -: outflow) ∂t ∂x

(4.2.2)

Equation of motion:

n 2V V 1 ∂V ∂  V 2  ∂h  + +  = i − 4/3 g ∂t ∂x  2 g  ∂x R

(4.2.3)

Here Q is the discharge, q is the side inflow, A is the cross-sectional area, V is the mean velocity, h is the water depth, i is the channel gradient, R is the hydraulic mean depth, n is Manning’s coefficient of roughness and g is gravitational acceleration. These fundamental equations cannot be solved analytically and must be solved numerically and care is required with respect to the following. Calculation of side inflow: Appropriate calculation of the discharge into (or from) a canal during flooding using hydraulic calculation and hydrological analysis impacts the estimation of the water depth significantly. Inner boundary condition: Since the gradient of a canal in the tidal area forms a moderate slope, the flow is subcritical flow but if there are weirs and other facilities, the flow undergoes transition and a control section is generated. This is called inner boundary and in order to process such inner boundary, complex calculation procedures are required. Method of numerical calculation: There are various methods for numerical calculations but since the fundamental equation is a hyperbolic type partial differential equation, it is desirable that a method appropriate for the numerical solution of such hyperbolic partial differential equations be used. In the method of solving fundamental equations using a numerical method, there are also complex problems such as the processing of branching and confluence, and in flat low-lying areas the simpler method of drainage analysis that is the continuous reservoir model is often used. The concept of the continuous reservoir model assumes a virtual reservoir by blocks where the difference in water level occurs in the basin during flooding and creates a model of basin by interlinking the virtual reservoirs into a network of blocks. The concept is to consider the reservoir as being the node that is connected by the various reservoirs that form the branch (drainage facility) and obtaining the water level of the reservoir using the following formula. m dH i AQ = ∑ ij j Fi dt j =1

Q j = f (H i , H j ) 216

(i = 1, 2,L, n )

(4.2.4) (4.2.5)

Chapter 4. Engineering for Sustainable Development of Tidal Areas

Here Hi is the water level of the node, Fi is the water surface area of the node i, Qj is discharge of the branch j, m is the total number of branches, n is the number of nodes of unknown water level and Aij is the node branch connection matrix when inflowing, j is 1 and when outflowing, j is -1 and when there is no connection, j is zero. In this case, the continuity equation becomes a set of simultaneous differential equations in which the water level of the reservoir is unknown and the equation of motion is the calculation equation for the discharge of flow between reservoirs so that even the novice will be able to easily solve the equations. 3) Management and analysis of water quality It is common for water quality management to determine water quality factors to be managed, create a model of water quality analysis for that purpose, and carry out forecast management of water quality. The fundamental equation controlling behavior of substances subjected to water quality management needs continuity equation with respect to water flow, equation of motion plus continuity equation with respect to substances (mass balance equation). When conceiving of the inside of a certain box as shown in Fig. 4.2.13, the continuity equation concerning the substance is shown by Formula (4.2.6). V

dC = ∑ Qin Cin − ∑ Qout C ± K r VC ± K p As C ± K s As C * − C + ∑ K d Ab (C b − C ) dt

(

)

(4.2.6)

Here C is the concentration of the substance, Cin is the concentration of the inflow water, C* is the saturation concentration, Cb is the concentration of the proximate block, Qin is the volume of inflow, Qout is the volume of discharge, V is the volume of reservoir, As is the water area or the bed area, Ab is the boundary cross sectional area, Kr is the reaction rate coefficient, Kp is the settling and pickup rate, Ks is dissolution and volatilization rate coefficient, Kd is the mass transfer rate coefficient as a result of mixture or diffusion at the boundary of the water, and t is the time. A variety of models will be created by subdividing the target area for water quality analysis into several segments in horizontal and vertical directions. It is usual for the models currently used to assume one segment for rivers or canals and several segments for lakes or ponds. Moreover, as a practical matter, even if one water quality factor subjected to management is assumed, it is usual for the factor to be water quality factors or biological factors fluctuating based on such a substance. When considering a simplified ecosystem model as shown in Fig. 4.2.14, equations regarding nutrients, phytoplankton and detritus are formulated as follows and even with respect to nutrients targeted for management, both phytoplankton and detritus need to be concurrently 217

analyzed (Eisaku Shiratani, 1994; Japanese Society of Irrigation, Drainage and Reclamation Engineering, 1988). Outflow

Inflow Dissolving and volatilization Settling and pick-up Reaction

Mixing and diffusion

Fig. 4.2.13 Material balance in the water area

Uptake Photoplankton

Nutrient

Death Settling

Mineralization

Change to inorganic

Release

Settling (Bottom mud) Fig. 4.2.14 Schematic diagram of ecosystem model

dI dt

= - [uptake due to phytoplankton] + [decomposition and mineralization of (4.2.7) detritus] + [release from the bottom mud] + [inflow] - [outflow]

dA dt

= [growth] - [death] - [settling] + [inflow] - [outflow]

dD dt

= [death of phytoplankton] - [decomposition and mineralization] - [settling] (4.2.9) + [inflow] - [outflow]

(4.2.8)

Here, I is the level of nutrient salt, A is the concentration of the phytoplankton, D is the concentration of detritus, and t is time. 218

Chapter 4. Engineering for Sustainable Development of Tidal Areas

4.3 Diversion Channel and Estuary Management AUTHOR: KIICHIRO TANAKA 4.3.1 Diversion Channel

A tidal area is protected against outer tide by a dike, in which drainage water disposal should be conducted inside the area in a planned manner for the sake of substantial land use. Water inside the catchment is to be drained from drainage canals through the river channels and regulation reservoir to the open sea. For this reason, the river channel that leads to the open sea must be so planned and designed as to act as a diversion channel to treat drainage water inside. To this end, counter-measures are required with respect to estuary closures that occur at estuaries (Bureau of Agricultural Land, Japanese Ministry of Agriculture, Forestry and Fisheries, 1967; Japanese Society of Irrigation, Drainage and Reclamation Engineering, 1979). 1) Estuary improvement and drainage plan Rivers discharge drainage water to sand beach or seashore, at the estuary of which littoral drift and wind drift are deposited, reducing the cross-sectional area or closing it completely and so-called estuary closing takes place. When estuary closing occurs, the outflow of water in the drainage in the catchment area is impaired and in flat low-lying areas, flooding or inundation will occur leading to the generation of various types of damages. Estuary improvement is improvement that is undertaken to ensure enough capacity in the drainage channel and various estuary management facilities installed for that purpose are subjected to estuary improvement. For this reason, a diversion channel in a tidal area is planned together with a training levee and other such estuary management facilities in order to ensure a cross-sectional area for the planned drainage discharge. The diversion channels need to take measures for proper improvement including forecast of reduction in drainage volume with age at the estuary of the diversion in consequence of outside tide, sediment, and bed load, calculation of inundation at the backland, comprehensive validation of influence on the backland due to reduction of drainage volume, and determination of the optimal value of crosssectional area at the estuary. 2) Mechanism of estuary closing As beach sand moves severely, it trends to form an uniform seashore. In the case where a river flows into this kind of seashore, the water flow flushes the beach sand deposited at the estuary by littoral drift or wind drift. The estuary section of the time is determined depending on the relationship in the movement of beach sand and amount of flush of the water flow. The strength of the littoral drift of the coast due to waves fluctuates in an unsteady manner so that the cross section of the estuary 219

repeats a pattern of increase and decrease. In other words, the principal cause for the generation of estuary closing is littoral drift of the sand beach and the estuary is maintained by flushing by the river flow. 4.3.2 Estuary Management

The engineering principles of estuary improvement are prevention of littoral drift that intrudes the estuary through stabilization of the estuary and flushing the sediment using the tractive force of the flow of the river in order to maintain the drainage function of the estuary at its maximum. For this reason, estuary management (1) attempts to increase the tractive force; and (2) attempts to prevent sedimentation in the estuary as the basic perspective in its planning and construction. 1) Investigation The mechanism of sedimentation in the vicinity of an estuary is extremely complex and has characteristics that are specific to each river. For this reason, in the proposal of a plan for estuary improvement and in the decision of the method of construction of estuary management, it is important to collect related documents and make thorough investigation at the site. The following shows the overview of such activities. i) Investigation of the estuary: Status of estuary closing (scale, period, frequency, etc.), status of damage in affected areas, etc. ii) Investigation of the weather: Wind velocity, observation of the direction of the wind, long term records, in particular records on storms, etc. iii) Investigation of the form of the river: Discharge, amount of transporting soil and sand, gradient of the river bed, bed material, status of intrusion of sea water, etc. iv) Investigation of oceanographic conditions: Wind waves including during storms, height of the tide, coastal current, estuary flow, etc. v) Investigation of the littoral drift and wind drift: Changes in the shore line, depth of the beach, source of supply of the sand, gradation of the sand, etc. 2) Types of estuary management The policy for estuary improvement and the types of estuary management may be determined to a high level of rationality through a detailed examination based on the results of the investigation 220

Chapter 4. Engineering for Sustainable Development of Tidal Areas

(Bureau of Agricultural Land, Japanese Ministry of Agriculture, Forestry and Fisheries, 1967; Japanese Society of Irrigation, Drainage and Reclamation Engineering, 1979). The following explains the characteristics of the main methods of estuary improvement. These methods may be used singly at times but it is more general to use the methods in combination with each other. a) Culvert works In the case where wave with small steepness laps seashore with a large volume of supply of littoral drift and littoral drift in large particle, the shore gradient becomes large, making significant movement of littoral drift near the shore line. In order to maintain the estuary of small rivers and drainage outlets that flow into such seashore, the culvert works have an advantage over revetment works or other works in the light of economy and structure stability. The design of the construction method for the culvert works involves the important design dimensions of (1) sill height and length of the inlet and outlet of the culvert; (2) cross section; and (3) direction of installation. These design dimensions must be determined through careful examination in consideration of the status and changes in the foreshore terrain for the shore line or seashore, and of tractive force of the sand for cross section. b) Open conduit works The open conduit works are a method of installing a lined diversion channel on the three sides for the purpose of maintaining the outlet of a small drainage channel with weak tractive force that flows out to seashore with a mild shore gradient and little movement of littoral drift at the backland. Since the river bed is lined and anchored, sand flushing is easier than in the case of natural river beds and unexpected scour may also be prevented. Moreover, the open conduit works have features of simple hydrological calculation because of specified cross section and of easier execution of construction work by human power. To improve the inundation problem resulted from the sedimentation of drainage gate, V-typed culvert developed by Jo Jin Hoon (2001) in Korea is a useful tool in the tidal area. The V-typed culvert is installed at the bottom of the main sluice and declined to the outlet side. It is longest at both side and shortest at the middle of canal as shown in Fig. 4.3.1. c) Estuary revetment works Gradually shoring beaches provide relatively small movement of the shore line but beach sand in small particle causes lateral movement of littoral drift due to coastal current or wave current. The 221

estuary of small rivers that flow into such seashore always moves from left to right and the reduction of tractive force often results in estuary closing. If a certain level of tractive force can be expected in such a river, by making the river channel direct and installing a strong training revetment, it is possible to anchor the estuary to the shore line in order to maintain the tractive force to the end of the river. The estuary revetment works are a method that is used in numerous rivers that open to a seashore with moderate gradient.

Fig. 4.2.13 Material balance in the water area

d) Training levee works In such a case that a river flows to seashore on which high waves laps, it is difficult to maintain the estuary, independently of the elevation of the ordinary water level, thus making it impossible to prevent sediment and blockage at the estuary even using the estuary revetment works. Such an estuary can maintain tractive force by installing a training groin on offshore away from the shore line and by guiding river water flow into the sea by means of breakwater effectiveness and can prevent sediment near the shore line. In designing the training levee, the important design dimensions are (1) the length of the training levee; (2) elevation of the levee crown; (3) direction; and (4) interval between training levees. The topology of the seashore, characteristics of the waves and direction at that point and other seashore conditions need to be adequately investigated and through hydraulic experiment, it is necessary to determine the optimum design dimensions.

222

Chapter 4. Engineering for Sustainable Development of Tidal Areas

4.4 Filling-up Reclamation of the Tidal Area and Artificial Shores AUTHOR: MANABU SHIMAYA 4.4.1 Filling-up Reclamation

The objective of filling-up reclamation is not only to secure agricultural land but also to secure residential and industrial land and to develop an aquatic transportation network and filling-up reclamation technology has enlarged scale through progress in the means of mechanization of construction. In recent years, filling-up reclamation is utilized not only for such social infrastructure facilities as ports and airports, electric power generation plants and oil saving base but also to obtain land for the disposal of waste (Japan Dredging and Reclamation Engineering Association, 2000; Japan Mariner Beach Association, 1992; Japanese Society of Irrigation, Drainage and Reclamation, 1981). 1) Planning and design Plans for filling-up reclamation are proposed for a variety of purposes as explained above and regardless of the objective of use, the aspect of creating sustainable filling-up reclamation is common and design is undertaken under the various design conditions. The conditions that are taken into consideration upon design include the topographic and geological conditions of the planned site, the sea level and incoming waves, earthquakes, allowable wave overtopping, gradation of the soil for filling-up reclamation, the site of the filling-up reclamation and conditions for use of revetment and depending on the objective of use, and convenience of access also needs to be considered as a condition. Filling-up reclamation generally involves constructing a revetment on the banking and filling-up on the side of this banking. The materials used in filling-up reclamation are dredged soil, mountain soil construction spoil material and other such materials and waste products as incinerator ash may also be used. The form of the revetment is, as shown in Fig. 4.4.1 the caisson type, steel sheet pile type, cell type, rubble foundation and other methods and the type of structure that is selected is determined in consideration of the climatic and hydrological conditions and foundation conditions at the planned site of the filling-up reclamation, the objective of use, the period of construction, economy and other such factors. Moreover, filling-up reclamation significantly impacts the coastal ecosystem. However, in recent years, environmental conservation and protection of marine resources are given consideration such as causing the wave canceling blocks or rubble foundation of the revetment to create useful seaweed and efforts are being made to move the tidal flat that

223

Tie rod

Caisson

(Reclamation)

Filling sand

Caisson method

Steel sheet pile

(Reclamation)

Stay support

Steel sheet pile method

(Reclamation) Filling sand

Discharge prevention mat (Reclamation)

Steel sheet pile

Cell method

Stone pitching method

Fig. 4.4.1 Standard cross sectional diagram of outer circumference of the dike

is eliminated through the filling-up reclamation to a different location in the vicinity in order to mitigate the impact on the vicinity of the site. 2) Method of construction Sand and gravel are intruded while performing revetment of the banking in filling-up reclamation band in the cause the current ground of the site is expected to undergo consolidation settlement, soil stabilization through such methods and dredging of the soft stratum, sand drain method, sand compaction pile method or deep mixing method will be required. Moreover, as shown in Fig. 4.4.2, the intrusion of sand and gravel may be through blow up of dredged soil using a pump dredger, barge with bottom door, direct intrusion of mountain soil or construction spoil material using a reclaimer barge or through filling-up reclamation. In tidal areas, it is possible to undertake spreading from the land at low tide. Moreover, in the construction various environment measures need to be taken. Pollution control sheet or settling basin is installed when intruding sand and gravel in order to prevent diffusion to the sea area in the vicinity. Furthermore, in the event large machinery is used for soil stabilization, measures having to do noise need to be taken. In parallel with such environment measures during the construction work, through periodic investigation regarding the water quality, atmosphere and noise, efforts are made to grasp the impact on the environment in the vicinity as required. Moreover, in recent years, various construction work management methods are put to practice. A settlement amount management system whereby settlement at numerous points is measured, location determination system that uses DGPS (Differential Global Positioning System), civil 224

Chapter 4. Engineering for Sustainable Development of Tidal Areas

engineering management system that utilizes aerial photographs and concerted management system on the finished form and process using a computer have been developed that respond to large scale filling-up reclamation projects allowing rapid construction work. 3) Points to be noted in filling-up reclamation in tidal areas Filling-up reclamation or impoldering has developed technically thus overcoming the technical problems of the past and today, the methods respond to deep or large projects and have enabled rapid construction. Filling-up reclamation sites have a high freedom for proposing plans and enable the formation of social investment efficiently and for this reason, filling-up reclamation can be expected to be implemented through the world into the future. However, whether the use of the land is agricultural or residential, since important sea surface is reclaimed, the debate on the need for filling-up reclamation may be expected to become more important in the future than in the past. In particular, shallow seas such as tidal areas are areas that are important to the coastal ecosystem and in many cases constitute leisure facilities for the citizens. For this reason, filling-up reclamation of tidal areas should be planned actively taking into account the opinion of citizens and NPO in addition to administrative government, specialists and people in the fisheries industries who are direct beneficiaries of such projects. Consideration given to the natural environment is indispensable for sustainable development of tidal areas. Prior to filling-up reclamation, the impact on the sea area in the vicinity should be studied and needless to say, with Pump vessel

Sand eradication equipment Sea level Sea bed conduit Floater conduit conduit

Land conduit

Number zero

Rudder Cutter

Spud

Protection of the dike

Swing wire Anchor

Pump vessel Bucket Bucket wheel

Reclaimer vessel

Pusher purge

Reclaimer vessel Fig. 4.4.2 Example of dredging and reclamation methods 225

the forecast and assessment of such impact through environment assessment as prerequisite, it is necessary that active measures be taken for environment conservation and creation. For example, in the event shallow waters such as tidal flats or sea grass bed such as eel grass is to be last to fillingup reclamation, conservation will require the relocation to sea area in the vicinity. Moreover, it has become possible to forecast the changes in the status of flow or the deformation of the shore due to filling-up reclamation with adequate precision. The deformation of the shore due to changes in the status of flow may be adequately used to create a naturally generated shallow sea after the filling-up reclamation in order to use the impact of such reclamation effectively is also important. 4.4.2 Artificial Shore

The objectives for creating a shore artificially may be roughly categorized into two. First is the revetment of the sea coast and this involves returning the shore that has been eroded to a stable state through the construction of structures and through beach nourishment. On the other hand, with the objective of environmental conservation and amenity with water use as objective, a shore may be artificially created as replacement for the shore that is lost due to filling-up reclamation or coastal development. Fig. 4.4.3 shows an example of an artificial shore. Here, the development of an artificial shore as part of mitigation in response to coastal development is explained (Japan Dredging and Reclamation Engineering Association, 2000; Japan Mariner Beach Association, 1992; Japanese Society of Irrigation, Drainage and Reclamation, 1981). 1) Functions and roles Artificial shores have various functions that are not found in upright revetment formed through filling-up revetment. 1) The function of recharge of living aquatic resources; 2) The function of purification of polluted water to improve the water quality; 3) The function of recreation; 4) The function of preservation of the coastal ecosystem In addition to being the habitat for bivalve shells such as clams that constitute marine resource, a shore attracts phytoplankton and 226

Fig. 4.4.3 Artificial shore at Kasai in Tokyo

Chapter 4. Engineering for Sustainable Development of Tidal Areas

zooplankton to the vicinity of wave breaks and these are nutrients for fish and fry fish and the shore plays an important function in the maintenance of the marine resource of the coast. Moreover, through collection of suspended substances in the sea water, a shore has the function of purifying the water quality through aeration by the ocean waves in the vicinity of the shore line. Artificial shores in the vicinity of urban centers play a role as a leisure facility for citizens for swimming and digging clam and such artificial shores, as in the case of natural shores, play an extremely important function in natural and human activity. The tidal area is often comprised of the natural shore and natural tidal flat and originally has these functions. For this reason, in the case there is the risk of these beneficial functions being lost as a result of filling-up reclamation, artificial shore and tidal flats need to be actively formed and it is important to minimize the impact on the coast through such initiatives. 2) Planning and designing As explained above, artificial shores are formed for the purpose of sea coast revetment, environmental conservation and amenity with water use and the measures required to maintain stable shores are the same for all of these objectives. Fig. 4.4.4 shows the general design flow for creating a stable artificial shore. Normally, near shore current (littoral current) and rip current are generated at a shore and as a result of the action of these currents, the sand moves to the coast or the offshore direction and in addition to this through the action of external force such as ocean wave and wind, if these become significant, the shore is eroded and for this reason, a cross section and plane form that can maintain stable topography in response to such external force need to be selected. In sea areas where the direction of the ocean wave Understanding the Ut ility c ha racter istics of the coa st changes, in order to stabilize the movement of the sand while responding to the change it is necessary Assumptions on the cr oss sectional form to install such artificial structures as headland and offshore breakwater or curve the plane form like a Location of f ac ilit ies Setting the c ases to be pocket beach. studied As the flow of rip current may be dangerous for users of a beach, when making the twodimensional plan, care must be taken to ensure that sea accidents do not occur. Moreover, when making the two-dimensional plan, in addition to consideration of these factors, the required area of the shore must be calculated in accordance to the assumed number of users. The general standard value or target value is said to be 13 m2 per person

Numer ic al simulation Hydr aulic model test

Review of reproduc ibility

Selec tion of the mater ial f or c onstr uc tion Judgement

NO

Saf ety and ec onomy of flow materials OK Deter mination

Fig. 4.4.4 Design flow 227

Table 4.4.1 Characteristics that is required with respect to viscosity properties of low grade construction materials Requirements Stability of the shore Underwater gradient Cleaning function of the sea shore Feel for users

Viscosity properties of low grade materials In general, coarser material is preferred The gradient becomes more acute as the material becomes coarser Fine grain is better to the extent that the material does not become muddy Fine grain is better to the extent that the material does not become muddy

in the United States and 7 m2 per person in Japan. If the area of the shore per person is small, satisfaction among the users will decline significantly and at the very least, the target value in Japan needs to be ensured. At the same time, with respect to amenity with water use, the water quality of sea areas with artificial shores also impacts user satisfaction to a great extent. The material for forming a shore shall be selected with consideration given to the stability of the shore, comfort of users, impact on the environment in the vicinity and the amount that can be provided. The material quality must meet the indispensable conditions of which the materials do not contain substances of low specific gravity and do not involve hazardous substances. In addition to this, the coloring of the material is a factor that impacts the image of a shore and provided that other conditions are met, selection from this perspective is also required. The texture of the materials is decided after comprehensive judgment in consideration of the characteristics shown in Table 4.4.1. However, when using such materials as dredged soil, since land settlement will be generated, the ground elevation should be set to a level that assumes the amount of settlement. Moreover, even when such a planning design is implemented, it does not mean that a stable topography will be maintained over several decades. So it is important to make a plan such as supply of materials required for seashore maintenance. 3) Method of construction When soil and sand from the sea bed are used in the formation of a shore, there is the method of collecting the soil and sand from the sea bed using a dredger vessel that employs either the pump style or grab style dredger or the method of collecting the littoral drift from a pump station that may be fixed or movable. On the other hand, the soil and sand on land are sampled by a land excavation method and transported to the site by a truck or belt conveyor, or transferred to a barge for conveyance. In the case where dry soil and sand are transported in a ship to the construction site, they are conveyed to the beach from the offshore by means of a barge conveyor. The method of depositing the transported soil and sand includes spraying and banking. The soil and sand sprayed and deposited on land are spread and graded by heavy-duty equipment such as bulldozer, while the soil and sand in water are often spread and graded in the course of nature by wave action. Moreover, upon injection, in order to prevent diffusion of turbidity to the vicinity, it is necessary to install pollution control sheets. 228

Chapter 4. Engineering for Sustainable Development of Tidal Areas

References Agricultural Land Bureau, Japanese Ministry of Agriculture, Forestry and Fisheries: Design Criteria for Land Improvement Plans, Part 3 Design Section 6 Sea Surface Impoldering, 1966. Bureau of Agricultural Land, Japanese Ministry of Agriculture, Forestry and Fisheries: Land Improvement Project Plan Design Standards Part 2; Plan, Group 2; Drainage, Chapter 4: Drainage Facilities, Section 4: Estuary Improvement, 1967 Eisaku Shiratani: Analysis of the Water Environment (Part 4) - Analysis from the Ecosystem-, Journal of Japanese Society of Irrigation, Drainage and Reclamation Engineering, 62 (1), pp.48- 49, 1994 G. P. van de Ven: Man-made Lowlands, First edition, 1993 G. P. van de Ven: Man-made Lowlands, Fourth revised edition, 2004 Hiroyuki Ogata: Drainage Plan (Part 2) Introduction to Drainage Plan (continued), pp.123- 124, 1972. Japan Mariner Beach Association: 1992, Beach Planning and Design Manual, 1992 Japan Dredging and Reclamation Engineering Association: 2002, The Sea, People and Filling-up Reclamation, 2000 Japanese Institute of Irrigation and Drainage: 2003 Report on Drainage Plan Standards, 2004. Japanese Society of Irrigation, 1979, Drainage and Reclamation Engineering: Handbook of Irrigation, Drainage and Reclamation Engineering, Revised 4th Version, 1979. Japanese Society of Irrigation, 1979, Drainage and Reclamation Engineering: Revised Version 4 Agricultural Civil Engineering Handbook, 1979 Japanese Society of Irrigation, 1988, Drainage and Reclamation Engineering: Water Quality Environment Science, Earth Environment Science Series 4: Science for Clean Water; Water Quality Environment Science, 1988 Japanese Society of Irrigation, 2000, Drainage and Reclamation Engineering: Handbook of Irrigation, Drainage and Reclamation Engineering, Revised 6th Version, 2000 Japanese Society of Irrigation, 1981, Drainage and Reclamation (ed.): New Systematic Civil Engineering 78- 2, Land Improvement (Part 2) Filling-up Reclamation, 1981 Jo Jin Hoon and Park, Sang Hyun: Study Report on Management of Hydraulic Facility in Tidal Reclaimed Areas (Korean), Rural Research Institute, KRC, 2001. 229

Lee, Haeng-Woo and Chang, Pyoung-Wuck: Seepage problems due to seawater intrusion through embedded rock layer of sea dike, Proceedings 4th International Workshop on SDTA, Evaluation of Draft ICID Handbook on SDTA , Sept. 13, Beijing, China, ICID Congress in Beijing, 2005. Park, Sang Hyun: Stability of Gabion and Rock mixture in the Tidal Closure, Proceedings of International Conference on Hydro science and engineering (ICH2000 in Seoul), IAHR, 2000 Shiomi Shikasho: Guide to Practical Training in Agricultural Water Facility, 3.12 Drainage Facility, Japanese Society of Irrigation, Drainage and Reclamation Engineering, p.135, 1987

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CHAPTER 5

Chapter 5. Tidal Reclamations and Their Impacts on Natural Processes

TIDAL RECLAMATIONS AND THEIR IMPACTS ON NATURAL PROCESSES EDITOR: BERND PROBST (GERMANY), JIN-HOON JO (KOREA)

5.1 Introduction In a natural, unspoilt tidal area a lot of natural processes are running: Due to tidal movement of water levels and currents and wave action, sand and clay is eroded at some places and deposited at other ones. At mudflats on the seaside of the dikes mostly sedimentation takes place. When the silting up continues it turns into salt marsh with a specific vegetation that can be used as a summer meadow. Salt marshes only are flooded at extended high tide levels. To force this process, people stimulated the deposition of sand and clay artificially by constructing dams of twigs and brushwood and excavating ditches. In older times or for just agricultural use, people built small dikes (summer dikes) to prevent the area from frequent flooding. This is the oldest and softest kind of reclamation, which has the lowest impacts on natural processes. Within the dynamical development of morphology and topology in a tidal area a specific natural environment of flora and fauna was generated. A lot of species are adapted to the tidal movement with its changing influences of water, air, temperatures and salt contents. These species are not able to live in other ecosystems (endemic species). The water discharge from the hinterland is running in a natural gradient of current either by mouth or natural estuary or in the case of old dikes by simple sluice gates into the sea. This chapter provides knowledge about impacts on natural processes. It may serve as a planning framework, to foresee and evaluate these impacts during the design process. This gives the chance to plan avoidance measures for negative consequences of embankments as far as possible. It is always 231

easier to avoid or minimize these impacts in the planning phase, than to compensate them after occurrence of the impacts. This allows implementing the principles of sustainable development in all planning and designing procedures.

5.2 Impacts on the Morphology As tidal reclamations are accompanied with embankments installation in the sea shore area, the above mechanisms for sediment transport will inevitably be changed. So the morphology will be changed, because the hydro-morphological equilibrium in the seaward side is disturbed by the embankment. The change of sediment transport is closely related to the changes of the influence of waves and currents, and also their influences to the hydrodynamics and sediment parameters. The size of sediment particle is also quite important factor to the hydro-morphological equilibrium state. Because the very fine sediment is too cohesive to move independently, it acts rather as a member of flocculation. Therefore when consider the change of hydro-morphological equilibrium state, it is reasonable to separate the sediment in two groups; non-cohesive sediment and cohesive sediment. 5.2.1 TRANSPORT OF NON-COHESIVE SEDIMENT (CITED FROM COASTAL, ESTUARIAL AND HARBOUR ENGINEERS’ REFERENCE BOOK”, H.J. DE VRIEND, E&FN SPON, 1993)

The principal mechanisms for coastal non-cohesive sediment transport are: -

Current-borne transport: Wave motion enhances the mobilization of sediment, by increasing the effective bottom shear stress, the sediment entrainment from the bottom and the vertical exchange of suspended sediment, but it is the current that carries the sediment downstream.

-

Wave-asymmetry transport: Sediment in motion is transported by the wave orbital motion, which is asymmetric in time. Due to the non-linear response of the transport to this motion, this can give rise a residual transport. The effect depends heavily on the transport mode. The same asymmetry can cause an up-wave transport in the grab-and-dump regime, and a downwave transport in the sheet flow regime.

-

Transport due to wave induced boundary-layer streaming: Boundary layer effects in the wave orbital motion give rise to a net mass flux of fluid and sediment, which is usually down-wave. Note that in a turbulent environment (e.g. in the presence of a tidal current), this boundary layer is not necessarily thin.

-

Wave-wave interaction transport, due to phase coupling effects between sea waves and low frequency (LF) waves. Depending on the phase relationship, and so on the type of LF waves

232

Chapter 5. Tidal Reclamations and Their Impacts on Natural Processes

(independent of the short waves, or possibly group bound), the residual transport direction can be up-wave or down-wave. -

Down-slope gravitational transport: Sediment moving on a slope tends to deviate downslope, due to gravitation. Although often a minor effect compared with the other transport components, this turns out to be very important for the morpho-dynamic behaviour of the coast.

In terms of time scale, transport of sediment could be considered separately in short-term process and in long-term process. However hydro-morphological equilibrium is mainly influenced by the long-term process. Therefore the residual transport mechanism could be the key factor for the hydro-morphological equilibrium. Two kinds of residual transport mechanisms are to be considered: wave-residual transport and tide-residual transport. 1) Wave-residual transport The theoretical bases of current-borne transport formulae are usually restricted to regular waves. Through calibration and heuristic arguments, they are extended to random waves. The wave-borne transport models have advanced somewhat further in this respect, because they are easier to handle with random waves. In principle, integration of the instantaneous transport formulae over the waves leads to a number of near-bed velocity moments, which can also be evaluated for random. 2) Tide-residual transport The morphological time scale in most practical applications exceeds the tidal period by far. Still, the tidal motion is an important agent in large-scale transports and morpho-dynamics. This means, that it is necessary to know the tide-residual transport accurately if ever to model large-scale coastal or estuarial behaviour. Tide-residual transports can have various causes. Firstly, the ‘primary’ tidal current, defined here as the current described by the shallow-water equations. Possible agents are residual currents and the asymmetry of the tidal oscillation (like wave asymmetry). Secondly, the presence of ‘secondary’ flows and rectification effects, caused by accelerations (inertia, Coriolis, curvature) or depth-varying external forces deviation of the near-bottom velocity and the sediment transport from the ‘primary’ flow direction, but often in the same direction throughout the tide; consequently, this deviation, though weak as compared with the maximum tidal transport, can be significant as compared with the ‘primary’ residual. And finally, the effect of the tidal water level variation on wave-induced sediment stirring, which is a function of the water depth may lead ebb or flood dominance in the transport. 233

3) Yearly residual transport Within the yearly cycle, there are: Firstly, the astronomic tidal modulation (neap/spring cycle). For the Dutch coast, for instance, the transport during spring tide is so much higher than during neap tide and mean tide that the large-scale morphology seems to be moulded by spring tides alone. Secondly, storm surges, which can drastically modify the tide during a period of one or two days. Since storms also generate high waves, these periods can contribute significantly to the yearly residual transport, although the effect may be mitigated by the low frequency of occurrence of extreme events. Thirdly, the variability of the wave climate (storms, calms), and finally the seasonal variation of conditions, including the water temperature. The sequence of events may also be of influence, obviously on short-term evolutions (it makes a difference whether a series of storms comes in succession or interrupted by calm periods), but possibly also in the longer run (like the groupiness of waves). If this is true, it will have important consequences for the schematization principle in model applications, since linear superposition is no longer adequate. The relative importance of these effects varies in space. Dune erosion is dominated by the combination of storm waves and high tides, including their joint probability, whereas further offshore it is rather the spring tide and storm surges that count. Besides, the transport and the morphological evolution in an area are not only determined by the local climate conditions, but also by remote one, e.g. through swell fields. Apart from this, no year is identical to another, so there is no such thing as an invariant yearly cycle. Every year is a realization of a stochastic process, the parameters of which are gradually changing, in addition to which the climate undergoes longterm changes, and so do extrinsic parameters like the mean sea-level and the tidal amplitude.

5.2.2 HYDRAULIC BEHAVIOUR OF FINE SEDIMENT (CITED FROM COASTAL, ESTUARIAL AND HARBOUR ENGINEERS’ REFERENCE BOOK”, A.J. MEHTA, E&FN SPON, 1993)

Mass fluxes that characterize the dynamic response of the concentration profile to forcing by currents and waves are those that ultimately determine the nature and behavior of sediment layering in the water column. In engineering practice it is found to be convenient to treat both deposition- and erosion-related processes as being controlled by the hydrodynamic bed shear stress acting at the level of the cohesive bed. 1) Settling velocity As in the case of cohesionless sediment, the settling velocity of the floc is a fundamental property 234

Chapter 5. Tidal Reclamations and Their Impacts on Natural Processes

characterizing cohesive sediment transport. As a result of floc aggregation due to inter-particle collision and mutual particle interference, however, the settling velocity of the flocs varies strongly with the volume fraction of the suspension concentration. Consequently the settling flux, i.e. the product of the settling velocity and the concentration, also varies non-linearly with concentration. Aggregation of fine, clayey particles occurs by virtue of net attractive forces between particles brought close enough by Brownian motion, differential settling or flow shearing. Although the relative importance of the collision frequency due to each of these mechanisms depends on the floc diameter, shearing under turbulent flows seems to be the most important factor contributing to the formation of strong flocs, with the exception of slack water times when differential settling becomes dominant. Flocs differ from the constituent individual, or primary, particles in four main aspects: -

Their size is orders of magnitude larger than that of the primary particles; for example, macroflocs can attain a size on the order of millimeters;

-

Their density is considerably less than that of the primary particles due to the large volume fraction of interstitial water;

-

Their shape is much more spherical than the plate like shape of the primary particles, which in turn leads to reduced drag;

-

They are extremely weak, tending to break up easily.

Among the above factor, the increase in fall diameter and, to an extent, drag reduction relative to a decrease in density, with the result that, in general, the settling velocities of flocs are substantially higher than those of individual particles. The magnitude of the floc diameter and settling velocity are, moreover, only weakly dependent on the primary particle diameter. 2) Deposition under turbulent flow The time-rate of decrease of sediment mass per unit bed area, m, under steady or quasi-steady (as in the case of tide), turbulent flow is given by

dm = − pws C dt where p[0,1] is defined as the probability of deposition, ws is the settling velocity, and C in this case is the depth-averaged suspended sediment concentration. The product, is the apparent settling velocity, and is the flux of depositing sediment. Whenever p less than one, the rate deposition is less than the rate of settling, since not all settling flocs are successful in withstanding the high stresses 235

that prevail near the bed; strong ones deposit while weak ones tend to break up and re-entrain. Since ws and p depend on the inter-particle collision frequency, and therefore on concentration, it is useful to examine deposition in various ranges of concentration in order to provide simplified descriptions for the time-rate of decrease of concentration in the water column as represented by the depth-average concentration. 3) Erosion The terms “erosion and re-suspension” are typically considered to be synonymous when dealing with erosion of mud. Resistance to erosion is contingent upon a number of factors including sediment composition, pore and eroding fluid composition, and the degree of consolidation of the deposit. The deposit itself may be in the form of a stationary, high concentration suspension, or a cohesive bed. The bed may be soft, partially consolidated, with a high water content (>100%), or it may be more dense, settled bed of lower water content. The mode of erosion varies both with the magnitude of the bed shear stress and the stress history of the deposit. Three modes have been identified: -

Floc-by-floc, or surface erosion, of a bed;

-

Mass erosion of a bed;

-

Entrainment of high concentration fluid mud suspension.

The hydrodynamic regime can be conveniently divided into two: one (that) determined by steady or quasi-steady (e.g., tidal) current and the other (that) due to waves. These two regimes will be discussed separately. Normally the natural processes create sedimentations near the new coastline. They heighten the flats and diminish the cross sections of the tidal creeks. However in some regions scouring process is developed so that the coast line is retreated backward. In these areas, some of countermeasures for seashore protection should be considered. Some examples of impacts of reclamation on the morphology are shown in Section 5.2.3. 5.2.3 EXAMPLES OF IMPACTS ON THE MORPHOLOGY

River regulation problem caused by reclamation on the estuary (Li-Hua Feng and Yi-Xin Bao, 2005) Since the 1950s, the large-scale reclamation of tidal flats has been carried out on both banks of the estuary of the Qiantang River of China, which has changed the course of the river. The estuary of 236

Chapter 5. Tidal Reclamations and Their Impacts on Natural Processes

the Qiantang River is of a typical tidal estuary system with strong currents and large tidal range. Its main channel has frequent swinging, which has caused serious damage to the sea dikes on both banks. Between 1969 and 1971, 2,700 ha of tidal flat area north of Yuyao was lost. Recently, the deep channel has approached the toe of the sea dike. The bottom elevation of the channel has been deepened to around -5 m, even exceeding -12 m in some areas, and the sea dike faces the danger of being damaged. When a tidal current from the sea enters Hangzhou Bay, it is often divided into three tidal streams (tidal bores) to the estuary of the Qiantang River that form into three deep channels in the south, middle and north of the riverbed. These are named South Channel, Middle Channel and North Channel (Fig. 5.2.1). Following high-water and low-water changes, the main channel swings in a south–north direction. In addition to the impact of high-water and lowwater changes, an important impact factor on the swinging of the main channel of the Qiantang River is the large-scale reclamation of tidal flats. Up to now, the reclaimed tidal flat area above Ganpu on the estuary of the Qiantang River is about 75,000 ha. Currently, there are 11 sea dikes that have been completed here, which has moved the coastline 18 km to the north (Fig. 5.2.2). The reclamation of tidal flats has narrowed the river channel, and the width of the river channel near Haining is narrowed from the original several dozens of kilometers to about 2.5 km at present. Because of its trumpet-shaped estuary on the Qiantang River, the current velocity of the main stream can reach 6~8 m/s, together with acute changes in tidal level. The lowest tidal level of -2.5 m was measured at the Xisan Gate on August 22, 1951 and the highest tidal level of 8.2 m was measured on August 19, 1997. The tidal current has caused serious damage to the sea dikes along the bank. In August 1974, the 1973 Tidal Flat in Shangyu was completely destroyed under the effect of typhoon and high tidal level. From July 1979 to December 1980, three T dikes and four

Fig. 5.2.1 Plane graph of the Qiantang River estuary

Fig. 5.2.2 Change graph of coastline in Cixi City 237

gates to sea, 2,200 m of sea dike, including 800 ha of high beach in Cixi City were breached and damaged, and the fastest collapse speed reached 20 m/day. In October 1985, Tidal Flat in Shangyu abruptly increased to 3,500 m, and more than 2,000 m of sea dike was breached and destroyed. The principle suggested for river regulation is ‘‘to regulate the river and reclaim tidal flats by taking the advantage of local topography’’. ‘‘Taking advantage of local topography’’ requires that the direction of channel must comply with the scientific rules of current and silt movements. ‘‘To regulate the river and reclaim tidal flats’’ requires a combination of river regulation with the reclamation of tidal flats along the riverbank. The reclamation of tidal flats must follow river regulation. Morphodynamic evolution of ebb-tidal delta induced by shortening the coastline (Edwin P.L. Elias, 2006) Texel Inlet is the largest tidal inlet of the Dutch Wadden Sea, and is located in the northwestern part of The Netherlands between Den Helder and the barrier island of Texel (Fig. 5.2.3). Texel Inlet is believed to have evolved from a small local drainage channel that connected to the inland Zuiderzee around the 12th century A.D. after a series of severe storm events (Fig. 5.2.4). The

Fig. 5.2.3 Location map of the Texel Inlet (dashed lines indicate approximate locations of the tidal divides separating the different basins) 238

Chapter 5. Tidal Reclamations and Their Impacts on Natural Processes

size of the inlet increased with time as a result of subsidence of the surface level due to excavation and drainage of low-lying peat areas bordering the inlet’s initial basin for agricultural use. With increasing basin volume the tidal prism through the inlet increased considerably causing the inlet channels to scour and increase in depth and width. The basin dimensions remained more or less equal until closure of the Zuiderzee between 1925 A.D. and 1932 A.D. Preceding the closure the Texel and Vlie tidal basins covered the southwestern part of the Wadden Sea and the former Zuiderzee (Fig. 5.2.4, lower left panel). In total the basin covered a surface area over 4,000 km2 with a basin length of 130 km. In total, the basin covered a surface area over 4,000 km2 with a basin length of 130 km. The closure dam reduced the basin length (a) Paleografic map for the situation in 850 A.D., before development of the inlet. from about 130 km to 30 km, and reduced the (b) Paleografic map for the situation in 1350 A.D. (based on maps presented by Lenselink and Koopstra, 1994). drainage area to roughly 712 km2 (Fig. 5.2.4, (c) Texel Inlet before closure of the Zuiderzee and lower right panel). The tidal characteristics in (d) after closure. the remaining active part of the basin changed from a propagating to a standing tidal wave, Fig. 5.2.4 Development of Texel basin through time and the large decrease in basin length caused greater tidal wave reflection at the closure dam resulting in a drastic increase in tidal range from approximately 1.1 to 1.4 m in Marsdiep. Tidal prism through Marsdiep increased with approximately 26% after 1932. These large changes in hydrodynamics and particularly in geometry, caused pronounced changes in the morphodynamic evolution of the remaining basin, such as a large sedimentation by filling in of the cut-off channels near the closure dam. With the exception of an approximate 40 year period after closure of the Zuiderzee the ebb-tidal delta remained in a stable state, only the main channels relocated to a distinct southward orientation (Fig. 5.2.5, upper panels). The gross changes took about 40 years to complete and a maximum channel length was reached in approximately 60 years. During the same period the ebb-tidal delta showed a southward and northward growth. In the south sediment supplied by the main tidal 239

Fig. 5.2.5 Ebb-tidal delta development. Texel Inlet from 1925 A.D. to 2000 A.D. based on the maps presented by Rijzewijk (1986) and De Kruif (2001)

channels develops a new ebb-delta front, while wave-driven transports contribute to landward and northward directed redistribution of sand from the abandoned ebb-delta front (western margin of Noorderhaaks). This northward transport contributes to the elongate outbuilding of the ebb-delta along the Texel coastline. Prediction of morphological reactions in a tidal basin caused by an offshore diking project (Reinhard Dieckmann) A large Wadden area with a width of 10 to 30 km exists along the coast of the German Bight. This area is subdivided into numerous tidal flats. Since the catastrophic storm surge of 1634, the north western part of this region (Nordfriesland) is in a state of non-equilibrium, with instability increasing over the last few decades. For example, the main tidal channel of this area (Norderhever) has deepened from 2.30 m in 1633 to 23.30 m at present (Fig. 5.2.6). 240

Chapter 5. Tidal Reclamations and Their Impacts on Natural Processes

Since about 1918 a knee-deep marsh channel has evolved into the tidal inlet Strandley, which is 200 m wide and approximately 12 m deep, and which connects the Norderhever and Süderau catchment basins. A flow from the Norderhever and Süderau through the Strandley and into the Süderau, amounting Fig. 5.2.6 Evolution of the southern part of the North to approximately 50 * 10 6 m³, takes place Frisian shallows since 1633 as a result of the differences in the tidal ranges and the phases of the outgoing tides between the two tidal basins. This flow acts as a scouring current and causes constant erosion of the Süderau. At low tide an additional tide volume of 10 * 10 6 m³ flows to the west from the Norderhever into the neighbouring Rummelloch-West (Fig. 5.2.7). By means of a new type of stability criteria developed for more than 25 tidal flats along the Dutch, German and Danish coasts, it is possible to predict future sedimentation or erosion processes in tidal basins, as well as the consequences of planned or executed construction measures. For the area under investigation, an erosion rate of about 48 * 10 6 m³ has to be expected until a state of equilibrium will be reached. These forecasts led to the decision of the state government of Schleswig-Holstein to reduce the main tidal volume of the flats in this region by means of an offshore dike, therefore causing sedimentation, to attain a morphological stabilisation of the constantly eroding shallows. This offshore diking project was completed in 1987.

Fig. 5.2.7 Tidal flow distribution in the Norderhever – Strandley - Süderau – Rummelloch – West tidal-flat system

In order to arrive at an optimal solution for the overall area, 14 variants comprising different offshore dikes and locations of the safety barrage were investigated on the basis of the mentioned volumetric capacity comparisons, this time, however, using the altered sizes of the tidal-flat basins resulting from the construction of the structures (Fig. 5.2.8). The results of these investigations show that the Nordstrander Bucht can best be stabilized by the use of offshore diking with a connection to the Hamburger Hallig, 241

and by the construction of a safety dam to the Island of Pellworm along Line VI (Variation 6). Through these measures, the desired morphological response to the stabilization of the entire study area will be achieved (Table 5.2.1). The federal government has chosen to implement Variation 12 (small offshore diking and safety dam along line IV), although Variation 6 is optimal from a morphological and coastal protection viewpoint. The option chosen can only be viewed as a minimal solution, as it will not prevent further erosion Fig. 5.2.8 Location of various planned offshore dikes and safety dams in Butterloch tidal-flat basin. The choice made was seen as a possible compromise by ecologists and environmental management personnel because, while it alone is inadequate, additional compensatory measures are foreseen.

Table 5.2.1 Results of the investigations into the effects of the planned construction measures in the Nordstrander Bucht

Note: Variation 6 : Offshore diking to Hamburger Hallig and a safety dam to the island of Pellworm along Line VI Variation 12 : Small offshore diking and safety dam along Line IV

242

Chapter 5. Tidal Reclamations and Their Impacts on Natural Processes

5.3 Impacts on the Tidal Dynamics Land reclamations in estuaries or bights may change the tidal dynamics by reflecting or partly reflecting the tide, which causes a deformation of the tidal wave. At the open coast a new dike situated in the upper tidal zone (eulitoral) will not significantly influence the tidal dynamics. But recently the scale of reclamation becomes larger than before and the projects have multi purposes instead of single purpose. These large-scale reclamations lead to changes of tide and current characteristics in near shore area. The design engineers should therefore find out the way to minimize the negative effects of the projects by predicting the future situation. 5.3.1 CHANGES OF TIDAL CHARACTERISTICS (CITED FROM “GUIDELINES FOR THE ASSESSMENT AND PLANNING OF ESTUARINE BARRAGES”, NEVILLE BURT AND A. REES, THOMAS TELFORD, 2001)

The changes of tidal characteristics resulted from the modification of coast line are to be considered in terms of the factors in the follows. 1) External tide The external tide forces the body of water contained in an estuary to co-oscillate with the frequency of the local tidal regime in the adjacent sea or ocean. An analysis of the external forcing tide is a prerequisite to a study of tidal propagation within an estuary. The ocean boundaries of an estuary are most usefully defined, for engineering purposes, at sections where the local tide (level and current) is independent of the motions within the estuary. Such a section is usually located near where small estuary outfalls into a much larger body of water like a sea or an ocean. Sometimes it may not be possible to define a section with a completely independent tide as in the case of a large estuary connected to a relatively small coastal embayment. In this case the tidal motions in the estuary may have a significant effect on the tidal regime in the coastal area, which has to be considered. The tide generating forces, which vary periodically in a predictable manner, give rise to over a hundred different tidal constituents. 2) Tidal constituents The periods of these harmonics are inter-related and have been derived theoretically. They fall into five main species: annual, fortnightly, diurnal, semi-diurnal and quarter-diurnal (Table 5.3.1). The fortnightly and quarter-diurnal constituents are generated by shallow water effects that normally reach a peak within an estuary.

243

3) Tidal propagation The tide propagates through an estuary in the form of an infinitely repeating series of long, shallow water waves. The effective wave length, L, of a tidal constituent in a channel is a function of its period, T, and the depth of the channel d.

L = TC0 = T gd where, g is the gravitational constant, and C0 is the speed of propagation (m/s). Table 5.3.1 Principal tidal constituents Species

Symbol

Frequency (deg/h)

Period (h)

Relative magnitude of equilibrium tide in the ocean (%)

Sa

0.041067

8766.16

-

MSf Mf

1.015896 1.098033

354.37 327.86

-

Diurnal

K1 O1 P1

15.04107 13.94304 14.95893

23.93 25.82 24.07

58.4 41.5 19.4

Semidiurnal

M2 S2 N2 K2

28.98410 30.00000 28.43973 30.08214

12.42 12.00 12.66 11.97

100.0 46.6 19.2 12.7

Quarterdiurnal

M4 MS4

57.96821 58.98410

6.21 6.10

-

Annual Fortnightly

Many estuaries are approximately uniform in depth in their seaward part with a width that decreases exponentially in the landward direction. In such cases, the tidal range and the peak tidal velocities tend to increase in the landward direction in a narrowing channel. Conversely, frictional resistance in the channel tends to reduce the tidal range and peak tidal velocities in the landward direction and reduce the speed of propagation of the tide. The relative magnitude of these opposing effects varies with tidal range, because the frictional term is proportional to the square of the tidal velocities, and the depth and rate of narrowing of channel. Generally there will be a tendency for the tidal amplitude to be maintained or increased in deep, rapidly narrowing channels which are often found in the seaward reaches of estuaries. If the tidal range is appreciable compared to the mean depth, the speed of propagation of high water will be significantly faster than that of low water, and the shape of the tidal wave will become progressively more distorted as it moves in the landward direction. The shallow water distortion takes the form of a more gradually falling ebb tide. This distortion is quantified in terms of the amplitudes of the M4 and MS4 and higher frequency constituents. A tidal bore is an extreme example of a shallow water tide. The tidal velocities on the flood tide become much stronger than that on the ebb tide and hence often give rise to an inland transport of sediment during periods of 244

Chapter 5. Tidal Reclamations and Their Impacts on Natural Processes

low fluvial flows. In the landward shallower tidal channels of and estuary the situation often occurs when the tidal range is again reduced to a small proportion of the depth. The fortnightly MSf constituent is also generated by shallow water effects caused by the interaction of the M2 and S2 constituent is usually very small or insignificant in the open sea but in long shallow tidal systems it gradually build up in the landward direction until it is sometimes significant compared to even the M2 constituent (e.g. in the estuary of the Kent Stour). It Fig. 5.3.1 Effect of bed roughness and rising bed levels appears as a periodic change in mean tide on resinant semi-diurnal tide in the shallow water level which repeats approximately every 15 tide in the Thames Estuary days. It peaks at spring tides, which raises the mean level in the inner estuary as much as large waves raise the mean level of the water on a shallow beach. The behaviour of an estuary can be studied by plotting the longitudinal variations in the amplitude of the harmonic components of the tide (Fig. 5.3.1) 4) Resonance effect Resonance will occur, and the tidal range will be amplified, when the frequency of one or more of the forcing tidal constituents is close to the frequency of free oscillations in an estuary channel system. A non-resonant condition occurs when the forcing oscillations are not close to the frequency of the free oscillations of the system. There may be one or two resonant or non-resonant conditions depending on what fraction of the wave length of the tidal constituent ( i.e. M2 or M4) is contained within the length of the tidal compartment. Frictional dissipation will tend to damp a resonating tide, whereas the natural funnel shape of many channels will tend to magnify a resonating tide. The first non-resonant mode is common in many deep, short deepened estuaries. In this case the tide is not amplified and the water level rise and fall almost simultaneously throughout the length of the tidal compartment. There are also many tidal channels with a mean depth of about 10m and a length of about 100km, which have a tide that is in the first resonant mode. In this case the tidal range tends to be amplified continuously in the landward direction in the absence of frictional effects (Fig. 5.3.2). The pattern of oscillations of a given tidal constituent depends on the actual length of the estuary compared with the effective wave length of the tidal constituent, which depends on its period 245

and the average depth of the estuary. There are usually several tidal constituents cooscillating in result of frictional effects. A non-resonant mode does not mean that the tidal range is minimized at all points along an estuary compared to a resonant mode (Fig. 5.3.3). 5) Tidal velocities

Fig. 5.3.2 Effect of bed roughness on the amplitude of resonant and non-resonant tidal constituents in the Brisbane Estuary

In rough, shallow estuaries the tidal currents are strongly dependent on the instantaneous water surface slope and hence the rate of rise or fall of the tide. The variation in the amplitude of tidal currents in natural channels is strangly dependent on the cross-sectional area of the channel and generally varies much more rapidly with distance than the amplitude of the vertical tide. 6) Frictional resistance Frictional resistance caused by channel roughness usually has an important influence on tidal flow in shallow channels. It controls the peak velocities and generally slow, distorts and dampens the propagation of the tide. The importance of the flow in a particular tidal system can be gauged by the value of the non-dimensional dissipation factor, Ds. Ds =

f T × × U max 64 R

where, T = tidal period (s), Umax = maximum tidal velocity (m/s), f = Darcy Weisbach friction factor, and R = hydraulic radius (m).

Fig. 5.3.3 Resonant and non-resonant modes of motion in a uniform channel 246

The dissipation factor is proportional to the ratio between the rate at which energy is dissipated by frictional resistance and the total energy in the tidal motion. A value of Ds greater than about 5 indicates that frictional effects have an important influence on the propagation of the tide. Ds often has a value of more than 100 in the fluvial reaches of estuaries.

Chapter 5. Tidal Reclamations and Their Impacts on Natural Processes

5.3.2 EXAMPLES OF IMPACTS ON THE TIDAL DYNAMICS

Tidal changes of Gyeonggi-Bay after large reclamations in Incheon-Bay area (Jin-Hoon JO, 1998) In the west coast of Korea large tidal flat areas are developed, which is due to the shallow topography, sediment supplying condition from many rivers, and large tidal differences. Following the progress of the development of society, the land demand for industries, habitations, airports and harbors is increased, and with these reasons reclamations are carried out in many tidal flat areas. In Incheon area two large-scale projects - Incheon International Airport and Sihwa Reclamation Project - are executed. Incheon International Airport is constructed in new land created by two dikes installed between Yeongjong-do and Yongyu-do. Their lengths of dikes connecting northern and southern ends of two islands are 7.3 and 6.0 km respectively. The final closing of them is finished in October 1994. They prevent the tidal current from passing through the area between the two islands (Fig. 5.3.4). Sihwa sea-dike whose length is 12.7 km connects Siheung-si and Hwaseong-si so that the Siheung-bay is closed. The construction is started in June 1987 and finally closed in January 1994. The purpose of this project is creating new land whose area is 17,300 ha for industry and agriculture. 1) Water level change For the quantitative analysis the calculation is executed for one month period so that the tidal constituents are obtained. Table 5.3.2 shows the compared results of M2 and S2 tidal constituents and semi tidal range (Z0) for the before and after the projects, and Table 5.3.3 shows the compared results of phase lag. The semi tidal range (Z0) at Incheon, Yeongjongdo and Palmi-do stations located in main water way are decreased in 8 cm after the projects. However it is decreased only 2~4 cm at Jangbongdo and Sammok-do stations located in shallow area. The phase lags after the projects are decreased so that the time of high water level becomes faster. At Incheon and Yeongjong-do stations the phase lags of M2 and S2 tidal constituents are decreased in 3.5~4.0° so that the high water level takes place about 8 minutes faster than before the projects.

Fig. 5.3.4 Geographical change after construction of two projects 247

2) Current velocity change Fig. 5.3.6 is the comparisons of current velocities and directions in spring time before and after the projects at Incheon and Palmi-do stations. After the projects the maximum velocity at Incheon is increased from 1.20 m/s to 1.40 m/s (17%), but the direction of current is almost not changed. On the other hand at Palmi-do the maximum velocity is decreased from 1.55 m/s to 1.10 m/s (30%). When the tide changes from flood tide to ebb tide, the direction of current at this position changes more strictly than before. This is because the dispersible area for current is limited in the main water way. Fig. 5.3.5 Locations of water level stations

Table 5.3.2 Tidal amplitudes before and after the projects Station

M2 (m)

S2 (m)

Z0 (m)

Before

After

Before

After

Before

After

Jangbong-do

2.78

2.76

0.97

0.97

4.44

4.42

Incheon

3.00

2.94

1.06

1.04

4.76

4.68

Yeongjong-do

3.00

2.94

1.06

1.04

4.76

4.68

Sammok-do

2.90

2.87

1.02

1.01

4.61

4.57

Palmi-do

2.89

2.83

1.02

1.00

4.60

4.52

Deokjeok-do

2.47

2.46

0.86

0.86

4.01

4.00

Table 5.3.3 Tidal phases before and after the projects Station

M2 (°)

S2 (°)

Before

After

Before

After

Jangbong-do

135.1

133.7

188.5

186.6

Incheon

136.4

133.0

190.9

186.5

Yeongjong-do

138.4

135.9

193.5

190.2

Sammok-do

136.4

135.0

190.6

188.7

Palmi-do

133.7

130.6

187.4

183.3

Deokjeok-do

124.7

124.0

175.2

174.2

248

Chapter 5. Tidal Reclamations and Their Impacts on Natural Processes

Fig. 5.3.6 Time dependent variation of current velocity and direction at Incheon (a) and Palmi-do (b)

5.4 Impacts on the Environment and Ecosystems After land reclamation the environment and ecosystems are strongly changed. At the seaward side habitats will change corresponding to the variation of morphology. If the new dike is situated in the lower intertidal or sub-tidal zone, the endemic species of the area will be reduced or disappeared. In the new reclaimed area flora and fauna will change – perhaps with the exception of some birds and other animals, which can live as well in saltwater- as in fresh water surroundings 5.4.1 ECOLOGICAL OBJECTS TO BE CONSIDERED (CITED FROM “GUIDELINES FOR THE ASSESSMENT AND PLANNING OF ESTUARINE BARRAGES”, NEVILLE BURT AND A. REES, THOMAS TELFORD, 2001)

1) Fish The potential effects on migratory fish species tend to elicit by far the greatest concern. There are also consequences for marine fish. The particular species or group of species of interest may very according to the location and specific nature of each scheme. 249

Natural behaviour of migratory fish Gough (1996) describes the natural behaviour of migratory fish in estuaries. Within a natural estuary, diadromous fish enjoy unimpeded free passage in both directions, almost certainly making use of the tides to assist their migration. Selective tidal transport in which a fish moves with the tide, demonstrating oscillatory movements, and then subsequently adopts an appropriate behavioural mechanism to stem the counter-flow, enables the fish to make net progress towards freshwater while minimising energy requirements. Time spent within the estuary may represent an important opportunity for gradual acclimatisation from sea to freshwater and vice versa. The behavioural mechanisms involved and the way in which environmental variables, such as freshwater flow, temperature and season, influence them remains largely unknown. Recent investigations are, however, now beginning to clarify the migratory behaviour of Atlantic salmon adults and smolts. A barrage will change the natural environment of an estuary and this will affect the fish that are obliged to traverse the estuary to complete their life-cycle. For fish to succeed in this they would have to modify their behaviour and it is not yet known whether all species can do this effectively so as to guarantee the maintenance of stock levels. Impact of a barrage on migratory fish Every species of diadromous fish present in UK estuaries, many of which are cited in European conservation legislation, would be affected to some extent by the presence of a barrage. Factors that would potentially disturb patterns of behaviour and interfere with fish migration include the following : (a) The disruption of the natural use of the tidal cycle as the fish traverses the estuary. Similarly, imposition of a new tidal regime that would require fish to behave in a different manner to that for which they have evolved or become adapted. (b) The delayed migration of fish, both at the barrage and within the impoundment. Problems in passing a barrage and within the impoundment. Problems in passing a barrage would delay fish, resulting in a reduced probability of entry to the river. Time spent in the vicinity of a barrage attempting passage could further adversely affect the prospects for subsequent survival and spawning. Important effects include: 1) suppression of migratory instinct 2) physical damage 3) energy costs 4) detention within the impoundment. 250

Chapter 5. Tidal Reclamations and Their Impacts on Natural Processes

(c) Difficulty in identifying, orientating, entering and ascending a fish pass. (d) Physical damage to fish attempting to ascend or descend the barrage. (e) Predation by populations of seals, birds and fish which are known to become established in such locations. Each of these areas of concern also apply to juvenile fish (smolts) migrating downstream. For example, recent observations in Wales indicated significant problems of disorientation of salmon smolts within a barrage impoundment. Marine fish Mass seasonal migration of fish fry occurs in estuaries. Knowledge of this behaviour in estuaries is generally poor but there is a detailed understanding of such migrations in the Thames and Severn Estuaries. Mass seasonal migration in the Thames, utilizing active tidal transport of flounder post larvae, smelt, sand-smelt, common goby, bass and thin lipped grey mullet fry range across the entire length of the estuary with dace, sole, sprat and sand goby making partial migrations. On the basis of this knowledge and understanding, the Thames Estuary is now recognised as the most important nursery ground for a range of species in the southern North Sea. The Severn Estuary boasts one of the most diverse lists of fish fauna. 110 species have been recorded in the estuarine and river systems. It is particularly notable for populations of migratory fish, including the rare twaite shad, Alosa fallax, river lamprey, Lampetra fluviatilis, and sea lamprey, Peteromyson madnus, as well as salmon, Salmon salar. There is a significant population of European eel, Anguilla anguilla, which supports commercial elver fishery. The significance of other estuaries in this regard needs to be established and fry migration considerations ought to be built into the decision-making process on estuarine development from both the economic and conservation perspectives. 2) Invertebrates Typically, most of the primary productivity in estuaries is not utilized directly by consumers but enters the detrital food network. Thus, the estuarine invertebrate fauna is composed primarily of detritivores that are able to live in fine sediments (e.g. worms, mollusks and crustacean). Because of the highly dynamic nature of most UK estuaries, these species must be able to withstand major fluctuations in physico-chemical conditions. As a consequence, the macroinvertebrate diversity in estuaries is generally low but because the relatively few species that are able to thrive under such 251

rapidly changing conditions are, to a large extent, freed from competition with others they flourish and the abundance of individuals may be extremely high. If substrate types change as a result of increased accretion on erosion, an accompanying change in the invertebrate infauna inhabiting these substrates may be expected. For benthic invertebrates living within the sediments of estuaries, their sensitivity to substrate changes is perhaps of greatest significance in governing the way they respond to barrage constructions. Thus, in areas where erosion is increased as a result of barrage schemes, reduced diversity and decreased longevity may be expected. The reverse impact is likely in area subject to increased accretion. Information on the optimum conditions and limits of tolerance of key infaunal species, in terms of factors such as sediment particle size composition, organic content and bed shear-stress, are required to evaluate fully the significance of these phenomena. In the case of tide excluding barrages, all freshwater intolerant species will die out upstream of the barrage once impoundment takes place although they will be replaced, to some extent, by freshwater tolerant species. The overwhelming majority of the invertebrate species in most UK estuaries are freshwater intolerant so, overall, there may be reduction in species diversity. The creation of permanently freshwater conditions will result in new water, e.g. chironomids, etc. If the conditions are suitable there could be significant nuisance problems arising from the mass hatching out of midge or mosquito larvae. 3) Birds A variety of bird species utilizes the salt marsh, intertidal flats and inshore water areas that may be affected by estuarine barrage construction. Principal among these are waders and wildfowl. How they are affected will depend on what precise use they make of the estuary in question. Predicting the effects on species using estuarine habitats as nesting and/or roosting sites will involve consideration of the relative increase/decrease in area of any given habitat as a result of barrage construction. Predicting the effects on birds using estuarine habitats as feeding areas will involve prediction of the abundance and distribution of invertebrate prey organisms following barrage construction. In addition, prediction of how such changes in their food supply will affect the number of birds utilising the food source will also be required. Consideration of how birds compete with one another and other predators will be a major issue in this regard. Changes to tidal range will alter the ratio of sublittoral, intertidal and supralittoral habitats. Consequently, the relative distribution and abundance of communities representative of these 252

Chapter 5. Tidal Reclamations and Their Impacts on Natural Processes

habitats typed will change to reflect the extent of this phenomenon. In addition, the amount of time for which intertidal areas are exposed or are at a suitable depth for normal feeding behaviour may be altered. This is of particular importance to shore birds dependent on intertidal areas for feeding. Indeed, the combined effect of less intertidal area exposed for shorter periods of time could have a significant impact on the opportunities available for feeding and a significant numbers of birds may be displaced as a result. The effects of changes in food supply, related to changes in tidal exposure, on bird populations will depend on how well individual birds are able to adapt to these changes and satisfy their food requirements. Prediction in this regard requires more precise information on specific food requirements of key species and how individuals and different species relate to one another in terms of competition for food resources. 4) Estuarine habitats Biologically, estuaries rank among the most productive of natural systems. However, the biological diversity frequently tends to be low because of the harshness of the rapidly fluctuating physicochemical conditions. Primary producers include phytoplankton, free-floating in the water column, microalgae attached to the surface of sediment and larger plants and macrophytic vegetations, such as salt marsh and eelgrass. Macroalgae, i.e. the typical seaweeds of rocky, coastal shores, are usually distributed sparsely in estuaries owing to the lack of availability of suitable hard substrates for attachment. The principal areas of interest in terms of general nature conservation value of estuaries in the UK lies in the existence of extensive saltmarsh and intertidal mudflat habitats that support abundant populations of invertebrates, fish and birds. In addition, they provide an invaluable natural form of sea defence by dissipating much of the energy of incident waves before they reach the shore. Saltmarshes also have great significance for breeding and roosting birds. Other more rare estuarine/ coastal habitats, such as coastal lagoons and reed beds, may occur at certain locations. The rarity of these habitats makes them especially significant from the conservation viewpoint. 5) Saltmarsh habitat Barrages cause major changes to saltmarshes within the basin, generally causing a decline in the extent of saltmarsh, changes in its species composition and/or replacement by a variety of habitats, including freshwater marsh, grassland and scrub. During the environmental assessment for barrage, opportunities should be sought to find sites to create a new saltmarsh or to improve the management of existing saltmarshes outside the basin. 253

Wetlands of ecological interest can develop behind barrages, particularly if the water margins have a shallow slope and are subject to regular and seasonally appropriate fluctuations in water level. In many cases, the aim could be a succession from open water to swamps/fens, grassland, scrub and woodland. The site will require management to maintain this zonation and mixture of habitats. Where space is not available to allow new wetlands to develop, and there will be steeply sloping shorelines, this will reinforce the division between land and water. Land above the new water level may require seeding and planting as the soil surface may be eroded by the wind. Depending on local factor, such as prevailing wind direction and fetch, aquatic and marginal vegetation may need to be protected from wave action if it is to thrive. With total exclusion barrages, desalination of the basin can take many years and landscape design and planting schemes need to take this into account and include salt-tolerant species. Seepage of saline water may continue post-impoundment, creating areas of brackish marsh. If this is acceptable in terms of the water quality management, such areas should be retained as they can contain interesting vegetation types and rare species. Upper zones of the saltmarsh and transitions to other habitats are the areas of high ecological interest. Where possible, water levels in the basin of partial exclusion or tidal energy should be managed to maintain the submergence times in this zone or allow it to develop at another poison on the shore. The development of new wetlands and changes in existing saltmarshes should be monitored before and after closure. This will provide information to feed into the management plan and also give an early warning of the spread of invasive plants which may need to be controlled. Raised water levels due to a barrage provide the opportunity to control the water level in non-tidal areas adjacent to estuaries. Remedial measures to restore groundwater levels and drainage efficiency should be deigned with the ecological interest of adjacent wetlands in mind. 5.4.2 EXAMPLES OF IMPACTS ON THE ENVIRONMENT AND ECOSYSTEMS

Ecological succession in new diked marshland areas (Polder) (Thomas Tischler) One of the three main areas of salt marshes (Schleswig-Holstein, Germany), which was intensively investigated in the period of 1972~1977 by the author (Tischler, 1985) was destroyed by dike construction in 1978. Two new established research areas of 13 and 0.5 hectares in the diked salt marshes and the former mud-flats were investigated during the period from 1982 to 1989 and from 1992 to 1996. 254

Chapter 5. Tidal Reclamations and Their Impacts on Natural Processes

If life and surviving conditions of flora and fauna are changed by nature itself and/or human related influences a landscape changes its biotical environment. In some cases this means that a previously established “community” of plants and animals is quickly ruined and be replaced by another “community” with different plants and animals. Most of the time this change happens in a chronological order and with strict regularity based on the initial and changing environmental conditions. Sometimes this change means a change forever! How do flora and fauna change within the climatic area of the North Sea coast – especially within the salt marshes – if their former condition is radically altered by building dikes? And what happens with the “biotic communities” if the various influences of the North Sea are not available anymore? In order to protect “their” coastal territory, their homes and properties, human beings have been using extended measures to “conquer” the sea and storms for over 1,000 years. Nowadays, without the help of new technology to build dikes in order to manage and retrain flooding caused by storms, colonization of the shallow land, which sometimes lies below the sea-level, would not be possible. Technology and modern machines made diking so much easier and it has been strongly enforced. However, in this way many salt marshes which used to be situated outside the former embankments (forelands) have changed their biotical environment. Some have been destroyed forever! In the future the destruction of this unique territory should be limited or should be totally stopped because within the environment of the salt marshes extraordinary plants and animals developed and/or settled which do not exist anywhere else around the world. Especially during the seventies big parts of the salt marshes were destroyed by diking and endorsed agricultural utilisation. Only a small part was declared for science and research. Now here are two examples from the seventies and eighties in the partly diked Meldorf Bay (Fig. 5.4.1 to 5.4.4). Now partial test results are available which can help to understand the effects of the influence to the former natural environment. Table 5.4.1 (salt marsh-plants, halophytes) and Table 5.4.2 (sweet grassland-plants) indicate a succession of vegetation within the research reservation which is situated approximately 3 km (beeline) behind the new embankment. After diking and the following desalination by rainfall, the former plants of the salt marshes decreased and were mostly dominated by immigrating sweet grassland plants. Although vegetation never ceased to appear, salt marsh vegetation disappeared and was replaced by sweet grassland vegetation. While some halophyte plants reacted very sensitively towards the changing environment and suddenly disappeared, other species “managed” to remain under the new and competitive situation for some years.

255

Fig. 5.4.1 Aerial photograph 1977; Saltmarshes in front of Christianskoog Meldorf Bay, SchleswigHolstein

Fig. 5.4.2 Aerial photograph 1995; in 1978 diked “Speicherkoog Dithmarschen”; Dithmarschen”; research area in the midst of intensive agricultural utilization

Fig. 5.4.3 Intensive grassed saltmarshes with an enclosed research area; in front of Christianskoog Meldorf Bay, 1974

Fig. 5.4.4 Natural succession of a formerly saltmarsh in front of hristianskoog, Meldorf Bay (now called “Speicherkoog Dithmarschen”), 1995

Sweet grassland vegetation – glycophyte species – in return shows the same “behaviour”. “Pioneerspecies” like thistles (Cirsium), stinging nettle (Urtica), coltsfoot (Tussilago), dandelion (Taraxacum) etc. settle first; later they are followed by more saline-sensitive species. An inventory of the vegetation in 1994/95 revealed 152 different kinds of plants (not including algae, moss, lichen and fungus). A second research area has been established approximately 150 meters behind the new dike where there was shallow sea without vegetation. Since the ground of the new polder – directly situated near the new dike – still consisted of saline water from the shallow sea (brackish groundwater) a different succession occurred. The former ground which showed no vegetation before has been invaded by salt marsh-plants and only a few species of sweet grassland plants which are highly tolerant of saline water. Table 5.4.3 shows all kind of plants, which appeared since the beginning of the research in 1982. However, even when sweet grassland plants settled temporarily by seed dispersal they could not survive or stay for a longer period of time.

256

Chapter 5. Tidal Reclamations and Their Impacts on Natural Processes

Table 5.4.1 Halophyte-Species (Salt marshPlants) in “Speicherkoog Dithmarschen” before and after diking 1978. Plant-Species Recorded in the Year 1976 1985 1994 Agropyron repens littorale X X Armeria maritima X Aster tripolium X X Atriplex hastata X X X Cochlearia anglica X Festuca rubra littoralis X X Glaux maritima X X X Halimone portulacoides X Juncus gerardii X X X Limonium vulgare X Plantago coronopus X Plantago maritima X X X Puccinellia maritima X X Salicornia europaea agg. X Spartina anglica X X Spergularia salina X X Suaeda maritima X Triglochin maritimum X X X Total Number 18 11 5 Table 5.4.2 Glycophyte-Species (Sweet-Meadow-Plants) in Research-Area “Speicherkoog Dithmarschen” before and after diking 1978 Plant-Species Recorded in the Year 1976 1984 1994 Achillea millefolium X X Agrostis stolonifera X X Cerastium holosteoides X Cirsium arvense X X Cirsium vulgare X X Epilobium angustifolium X X Epilobium hirsutum X X Plantago major X X Potentilla anserina X X X Ranunculus repens X X Rumex crispus X X Salix caprea X X Salix cinerea X Sambucus nigra X X Sonchus arvensis X X Taraxacum officinale X X Tussilago farfara X X Urtica dioica X X Total Number 1 16 152 257

Table 5.4.3 Succession in 0,5 Hectare Research-Area in “Speicherkoog Dithmarschen” before diking (1978) still vegetationless (Mud-Flat) 1982

1985

1987

1995

Salicornia europaea agg.

Plant-Species Recorded in the Year

1978

X

X

X

X

Spergularia salina

X

X

X

X

Suaeda maritima

X

X

X

Puccinellia distans

X

X

X

Aster tripolium

X

X

X

Juncus bufonius

X

X

X

Plantago coronopus

X

X

Triglochin maritimum

X

X

Juncus gerardii

X

X

Sagina nodosa

X

X

Centaurium pulchellum

X

X

Glaux maritima

X

Sagina maritima

X

Spergularia salina

X

Festuca rubra ssp. litoralis

X

Parapholis strigosa

X

Atriplex spec.

X

Leontodon autumnalis

X

Trifolium repens

X

Trifolium dubium

X

Agrostis stolonifera

X

Carex spec.

X

Festuca arundinacea Total Number

X 0

2

6

11

23

Parallel to this research of succession, the appearance of phytophagous (plant-eating) beetles and weevils (Chrysomelidae and Curculionidae, Coleoptera) have been investigated before and after diking. Table 5.4.4 shows the summary of results tested within the last 25 years (with short breaks in between). It revealed that before diking, “only” eleven species of beetles were recorded, whereas after diking almost one hundred species of beetles were determined as living in this area. This means that the former species of the salt marsh beetles are nearly extinct and have been “replaced” by wide-spread beetles (ubiquitous species) coming from the inland areas. The number of beetle-species and their host plants selection is shown in Table 5.4.5. Coastal environmental impacts caused by reclamation for urban expansion (Hesp, Patrick A., 1995) 258

Chapter 5. Tidal Reclamations and Their Impacts on Natural Processes

Table 5.4.4 Comparison between the former Salt Meadow Area (Christianskoog/ Foreland) and the same area 25 years later after diking. Host Plants and as their Guests: Phytophagous Beetles (Leaf Beetles/ Chrysomelidae; Weevils/ Curculionidae) Photo Elector-Sampling (each 1 m²) Salt Meadow (Christianskoog) Research Area (Speicherkoog Dithmarschen)

Quantity of recorded m²

Quantity of Quantity of phytophagous phytophagous beetles beetle-species

Quantity of plant-species

1972-1977

125

2,142

11

18

a) 1982-1989

132

757

28

74

b) 1992-1996

790

25,144

93

1521)

922

25,901

Total a) + b)

Sporophytes: 2 Species; Seed Plants: 150 Species; Monocots: 54 Species; Dicotyledons: 96 Species.

1)

Table 5.4.5 Food Selection of Phytophagous Beetle-Species (Chrysomelidae and Curculionidae) in comparison with Salt Meadow and Sweet Meadow Monophagous Species

Oligophagous Species

Polyphagous Species

Salt Meadow Area Christianskoog/Foreland

6 (= 55%)

2 (= 18%)

3 (= 27%)

11

Research Area Speicherkoog Dithmarschen

16 (= 16%)

75 (= 76%)

8 (= 8%)

992)

2)

Total

In addition 6 species have been recorded with other methods of sampling.

The coastal environment along much of the south coast of Singapore consisted of mangrove swamps and estuaries fronted by fringing coral reef, and the east coast by sandy beaches. Today, almost the entire south and east coasts consist of reclaimed land and this process is continuing. Reclaimed land constitutes 6 % of the land area of Singapore and much of this area has been formed at the expense of various types of coastal ecosystems (Fig. 5.4.5). The land area of Singapore in 1960 was 581.5 km2 and by 1986 was 620.5 km2. 45 km2 of land was added to Singapore in the period 1955 to 1989. All reclamation work is covered under the Foreshore Act, with reclamation areas up to 4 ha being authorized by the Minister of Law, and areas larger than this requiring Parliamentary approval. To the author’s knowledge

Fig. 5.4.5 A map of Singapore illustrating the major areas of foreshore reclamation

259

(official information is exceedingly difficult to obtain), only one or two EIAs were conducted on the past or present reclamation projects. Several major impacts have occurred and continue to occur as a result of coastal reclamation and associated construction activities. On the main Island these include the near complete loss of the fringing reef ecosystem, substantial loss of mangrove habitat (originally approx. 13 % of the total land area now down to < 3 %) and fauna (e.g. crocodiles were once common, now totally absent), substantial loss of adjacent estuarine and freshwater habitats and fauna, virtually near complete replacement of sandy beaches and flora, significant marine sedimentation, and high levels of suspended sediment and a resulting reduction in visibility (down from 8 m to 2 m) and impacts on coral growth and survival (Fig. 5.4.6). In the 1990s the major impacts are predominantly sedimentation, particularly in coral reef and mangrove environments, high suspended sediment concentrations, and destruction of marine habitats. On the offshore islands only 1 % of the original mangrove habitat remained by 1980. Secondary impacts include noise and air pollution. These impacts are in addition to marine pollution primarily from shipping. Singapore is the world’s busiest port in terms of the shipping tonnage of ship arrivals (92 655 ship arrivals in 1993). In 1988, 3.23 million barrels of mainly crude oil entered the region daily via the Strait of Malacca. It is also the third largest refining centre in the world. Shipping accidents, spills, and operational shipping and refining activities (including deliberate dumping of ballast) have resulted in 4,705,000 tons of oily waste discharged into the South China Sea per year. Although Tan (1993) states that “the water quality [of the coastal waters around Singapore] meets the recreational water standards”, many Singaporeans and visitors consider the waters unswimmable because of the visual impact of high suspended sediment loads, and physical impacts of the presence of oil slop and sludge, tar balls, floating garbage, and occasional sewage and solid waste from southern Malaysia (especially Johor Bahru). Depression of Manila clam resources in the tidal flats induced by costal structures (Junya Higano, 2003)

Fig. 5.4.6 Extent of mangroves in 1951 (a) and 1994 (b) 260

In Japan, coastal line has been artificially changed for many years. Especially in sheltered bays, reclaimed lands and artificial structures

Chapter 5. Tidal Reclamations and Their Impacts on Natural Processes

such as dikes, breakwaters and jetties have replaced natural coastal line. Ariake Sound has been gradually reclaimed for a long time since the sixth century in accordance with natural land forming. After Meiji era (from 1868), huge undertaking of reclamation was started and the shoreline moved forward up to 5 km. Tokyo bay was reclaimed at the very rapid rate after 1945 and natural coastal line remains only 9.7% whereas 19.6% in Ariake Sound in 1984. It presumably brought about negative ecological impact for filter feeding bivalves through hydrodynamic changes of water and sediment movement. Higher intertidal zone and supralittoral zone are intercepted by artificial structures such as dike and break water. Fig. 5.4.7 Conceptional illustrations of land Consequently decreasing area of tidal flat caused formation on upper level of tidal flat, and the the habitat decrease and increasing suspended impact of land reclamation and construction mud by prevention of their depositing at the of artificial structure around high water level higher intertidal zone (Fig. 5.4.7). Dams and barrages often store sand at the water reservoirs. It sometimes causes not only the decrease of reservoir capacity but also coastal erosion. Very fine sediment particles like silt and clay do not easily settle even in calm water as far as they are still in fresh water. In downstream region of dams and barrages, thus, fine sediments allow to discharge higher ratio in comparison with sand particles. How does coastal changes affect filter feeding bivalves? As described above, coastal changes bring about the loss of habitat, depression of tidal current and accumulation of fine sediments. Fig. 5.4.8 indicates that these factors eventually affect the bivalves on both oxygen deficiency and high suspended load. Hypoxia and anoxia often occur in subtidal zone of eutrophied sheltered coast under the stratified layer in summer. Most of the bivalves can switch to anaerobicbiosis to maintain their lives and survive several days in anoxic condition. However, elongation of anaerobicbiosis requires consumption of reserve substances like aspartic acid and glycogen. The accumulation of metabolites will indicate the limit to tolerate anoxi. Hydrogen sulfide is generated in anoxic layer of sediment and affects bivalves to inhibit aerobic respiration. 261

Bivalves can also survive in relatively high concentration of hydrogen sulfide, but bivalves have to respond as same as under anoxia. Combined effects of hypoxia and hydrogen sulfide may act as anoxia, thus oxygen deficiency is extremely dangerous and should be noticed its effect on bivalve physiology. High concentration of suspended particle suppresses the water clearance of the bivalves and increases pseudofeces ejection. The increase of several tens mg/L of suspended mud mixed with food algae brings down the clearance rate and ingestion rate of food algae. Increase of suspended particles may cause the excess energy expenditure for pseudofeces ejection and owe deficit on energy budget. The bivalves under the high turbidity should show low growth rate. Highly concentrated muddy water may clog the gill of bivalves and force to close the valves. The bivalves have to wait until the overlaying water replaced sufficiently clear for resuming respiration. So, high concentration of turbid water presumably affects the bivalves in almost same manner as anoxia.

Fig. 5.4.8 Conceptual flow of coastal changes affecting to the depression of Manila clam resources 262

Chapter 5. Tidal Reclamations and Their Impacts on Natural Processes

5.5 IMPACTS ON THE SOILS IN EMBANKED AREAS The soils in embanked areas will change their properties because of the change of water quality (e.g. salt- to freshwater) and water levels. Normally the ground water level will sink, especially if an artificial drainage by pumping stations becomes necessary. This can cause further changes of the soil. If peat soils are drained, they will shrink. Changes of the soil characteristics such as hydraulic conductivities, soil moisture characteristic curves and electrical conductivities with the passage of time and the process of desalinization should be known in an early stage of land reclamation projects. Following study about these topics has been carried out by Atsushi Marui et al., Japan chapter 5.5.1: (Soil characteristic improvement and salinity control at the newly reclaimed land in Japan). An efficient advance of land drying is one of the most important processes in the course of land reclamation projects. The drying process determines the time for completion of the whole project and economical benefit of the project as well. As described in chapter 5.5.2 (Land Drying Practice and its Effects on Soil Properties in Reclaimed Lands) by Prof. Dr. Akae, Japan the effects of upside down ploughing on land drying and soil development were examined through field soil survey. The upside down ploughing was verified to promote remarkably soil drying and desalinization of the ploughed layers. The composition and concentration of salt in the soil solution influences the growth of plants by osmotic and specific ion toxicity effects and by changing the physical properties of soils. The accumulation of dispersive cation, such as Na, on the exchange phase affects the physical properties of the soil. This, in turn, affects the production of crops. A successful irrigated agriculture requires permanent control of salinity and sodicity. The relevant interrelations and how to deal with them are pointed out by Lee, Deog-Bae, Korea in chapter 5.5.3 (Desalination of the Reclaimed Tideland). 5.5.1 SOIL CHARACTERISTIC IMPROVEMENT AND SALINITY CONTROL AT THE NEWLY RECLAMED LAND IN JAPAN (ATSUSHI MARUI, YOSHISUKE NAKANO, TAMOTSU FUNAKOSHI, TOMOKAZU HARAGUCHI AND KOJI INOSAKO)

Abstract This study includes the change of soil characteristic such as hydraulic conductivities, soil moisture characteristic curves and electrical conductivities with the passage of time, and the discussion of salinity problems at the newly reclaimed land in Japan. It is important for the sustainable development to know how change the soil characteristic and the process of desalinization at the beginning of reclamation. In this study, some trials to control the salt damages in crop production are introduced. First, the soil’s physical improvement processes from the first stage of reclamation 263

to the present stage are introduced. Second, desalinization effects by the plants at initial stage of reclamation were researched. Third, observational studies using some tensiometers on the soil water movement in the cropped fields are stated. Finally, the optimal irrigation scheduling by the numerical studies to suppress the upward flow of saltish water during the dry season is discussed. Introduction The Isahaya Bay in Nagasaki prefecture located in the southwest of Japan is famous for being atremendous tidal area. The maximum difference between the high and low tides is about 5.7 m. A substantial big reclamation project for agricultural production is currently taking place at there. The Isahaya Bay reclamation project, which began in 1997 (final closure), is aiming to reclaim about 700 ha of agriculture lands. Furthermore, about 2,500 ha of new lake inside the main dike is expected to control floods during the rainy season, because the agricultural area around the bay was severely damaged by many rainstorms in the past. To improve the soil physical properties, about 20 tons/ha of gypsums were added to the original heavy clay soil. Also, leaching was conducted for several months using a sprinkler. The saturated hydraulic conductivities were improved from 10-6 cm/s to 10-3 cm/s at the surface layer during four years. Following these soil improvements, crops were planted. But saltish clay soils near the drainage pipes 70 cm below the soil surface are still probable to damage the crop growth (Nagahori and Sato, 1975, Amaya et al., 1983, Marui et al., 2002). In order to observe the upward flow of soil water from the deep zone, six tensiometers were equipped 10 cm, 20 cm, 30 cm, 40 cm, 50 cm and 60 cm in depth, respectively. To express the soil moisture movement, total potentials were calculated by taking the soil surface as the reference level. In high summer, water potential at the surface layer exceeded –800 cmH2O that is the limitation of the tensiometer measurement. The maximum amount of soil water flow at the deepest layer was estimated to be about 0.6 mm/d at this period. Finally, the water movement and salt transport action in the newly reclaimed soils was calculated using the compartment model. A drought year of the actual meteorological date was used in this simulation, and discussion about salt transport of these two conditions is stated. Though the results of the study are applicable for warm and humid climatic conditions with reclaimed land soils, the objective methodology developed has universal applicability. Changes of soil properties The improvement of the original heavy clay soil at the surface layer has been accelerated by the artificial treatments such as drainage, cultivation, adding gypsum and leaching with a sprinkler. The components of the original soil are 0.3% sand, 29.6% silt and 70.1% clay on average. The bulk density was 0.40 and specific gravity was 2.547. The clay soils with high sodium concentration 264

Chapter 5. Tidal Reclamations and Their Impacts on Natural Processes

showed a dispersed condition when Na+ was leached. When the soil in this condition dried, it formed a dense and hard mass or crust. In order to improve this undesired condition, adding gypsum to the field was effective as the clay soil attracted Ca2+ in replace of Na+. Calculations of the gypsum requirement were made considering the cation exchangeable complex of the clays, exchange efficiency, and the initial and final ESP using the gypsum requirement (GR) equation described by Mitsuno et al. (1991) GR=20 (ESPi - ESPf) x CEC x Ds/100 x rd x 172/40

(5.5.1)

where, GR is the gypsum requirement (ton/ha), Ds is the depth of the soil to be reclaimed (cm), rd is the soil bulk density (g/cm3), CEC is the cation-exchange capacity (meq/100g), and ESPi and ESPf are the initial and final exchangeable Na percentage (%). Table 5.5.1 shows summary of soil test, pH, EC1:5, soluble cations, exchangeable cations, CEC and ESP. The calculated GR using equation 1) were 18.5 tons/ha and 26.6 tons/ha, when Ds, rd and ESPf were assumed 50 cm, 0.6 g/cm3 and 10 (%). About 20 tons/ha of gypsums were added to the experimental field. After three years, the soil matrix extremely changed especially at the surface layers. Fig. 5.5.1 shows the soil moisture characteristic curves of fourth year, 10 cm, 20 cm, 30 cm, and 40 cm depth, respectively. The condition of the available water holding capacity at the surface layer was obviously improved, although the deep layer did not show signs of improvement. The available moistures and bulk densities are listed in Table 5.5.2. The total available moisture in the root zone is 27.4 mm. The soil permeability also improved from 10-6 cm/s to 10-3 cm/s at the surface layer during these four years. Crop desalinization effect To improve salinity problems at initial stage of reclamation, desalinization by the Native halophyte plants were researched. To clarify the actual effects of Na+ absorption by those plants, Na+ and K+ absorption potentials were investigated. Table 5.5.1 Soil test summary (1996) PH EC1:5* Soluble cations (H2O) (mS/cm) (meq/100g) □ □

7.43 7.6

20.5 17.3

Exchangeable cations (meq/100g)

Na+

Ca2+ Mg2+

K+

Na+

Ca2+ Mg2+

84.4 77.2

7.3 4.7

0.4 1.74

12.1 14.0

17.0 22.2

20.6 10.0

13.7 21.3

CEC ESP (meq/100g) (%)

K+ 4.8 3.39

48 36.9

25 37.9

* dry matter : water = 1:5 Table 5.5.2 Available soil moisture and bulk density (Oct. 2001) Soil layer (cm)

0~10

10~20

20~30

30~40

Available moisture (mm) Bulk density (g/cm3)

6.8 0.74

5.6 0.77

5.6 0.90

9.4 0.85 265

FP

FP

FP

FP

  ᨬ)

Halophytes are generally defined as the plants that are able to complete their life cycle under a saline environment (Flowers et al., 1977). Usually halophyte plants can tolerate high salinity concentration more than 100mM NaCl.

 

 The native halophyte plants Shichimensou,          Hamamatsuna, Shiokugu and Yoshi living 9ROXPHWULFZDWHUFRQWHQW᧤᧡᧥ around the reclaimed land in the Isahaya Fig. 5.5.1 Soil moisture characteristic curves bay were picked in October 2002 that was blooming season. Figure 5.5.1 show the colonies of native halophyte Hamamatsuna at reclaimed land. These plants were investigated on Na+ and K+ absorption potentials.

There are two types that halophyte can tolerate to Na+. A monocotyledonous plant such as Yoshi and Shiokugu has ability to suppress Na+ absorption. On the other hand, a dicotyledon such as Shichimensou and Hamamatsuna has Na+ absorption ability. In this study, Na+ and K+ concentration difference of both halophyte a monocotyledonous plant and dicotyledon living around the reclaimed land were investigated. And relationship of Na+ and K+ concentrations were discussed.

266

1D .

1DFRQFHQW UDW LRQV

Figure 5.5.2 shows Na+ concentrations and Na/K ratio of each halophyte. Shichimensou and Hamamatsuna indicated the high concentrations of Na+ and also high value of Na/K. On the other hand, Shiokugu and Yoshi showed the low concentration of that. These results showed the difference between dicotyledonous and monocotyledonous plant mechanism. So monocotyledonous halophyte is not suitable for removing of Na+. Halophyte plants living around reclaimed land were investigated on Na+ and K+ absorption potentials. Those results showed the difference between dicotyledonous and monocotyledonous DERYHJURXQG URRW plant mechanism of Na+ tolerance. The DERYHJURXQG᧤1D .᧥ URRW ᧤1D .᧥ monocotyledonous halophyte is not   suitable for removing of Na+ because   of suppressing Na+ absorption. If   Shichimensou was gathered at 1000   m2 of newly reclaimed land, about 10   kg of Na+ could be absorbed at a simple   calculation. And if Na+ was converted 6KLFKLPHQVRX 6KLRNXJX into NaCl, it shows that desalinization Fig. 5.5.2 Na+ concentrations and Na/K ratio of each quantity was about 25 kg/10a. native halophyte (on dry matter basis %)

Chapter 5. Tidal Reclamations and Their Impacts on Natural Processes

Observation study To monitor the soil capillary upward flow of the crops growing field, six tensiometers were equipped, 10 cm, 20 cm, 30 cm, 40 cm, 50 cm and 60 cm in depth, respectively. The data were scanned every one hour and recorded in the data logger for about ten months in the fourth year of drying. From May to July, corns were planted and from October to April, onions were planted in the row conditions. To express the soil moisture movement, total potentials were calculated by taking the soil surface as the reference level. Figure 5.5.3 shows the daily changes of the total potential and rainfall during the summer season. Irrigation was conducted only at the transplanting period. Attentions are given to the directions of the water movement especially at the deepest layer, where high salt dissolved water is present. When the difference of the total potential between 50 cm and 60 cm becomes positive, it means that the soil moisture movement is directed upward. According to Fig. 5.5.3, upward fluxes were observed within five days after a certain amount of rainfall. Severe draught was observed in late July. Water potential at the surface layer exceeded –800 cmH2O which is the limitation of the tensiometer measurement. The maximum amount of soil water flow at the deepest layer was estimated to be about 0.6 mm/d at this period. To prevent the upward flow of saltish water, it is required to apply an adequate amount of irrigation water. Simulation (1) Fundamental Equation Water movement and salt transport action in the newly reclaimed soils were simulated using the compartment model. One-dimensional vertical water movement is expressed as ∂θ ∂t

∂  ∂z 

∂θ ∂z

 

=− + K (θ )  − S w  − D (θ )

(5.5.2)

where, θ is the soil water content, t is time, z is direction, D(θ ) is the soil water diffusivity, K (θ ) is the hydraulic conductivity and Sw is the absorption from the root of a crop. Salt transpiration in soils is expressed as ∂ (cθ ) ∂  ∂ (cθ )  ∂ =− (V cθ ) + S s −  − Dc ∂t

∂z 

∂z



∂z

(5.5.3)

where, c is the salt concentration, Dc is the hydrodynamic dispersion coefficient, V is the average interstitial flow velocity and Ss is any solute loss or gain due to salt uptake, sorption, dissolution. However, Ss is not considered in this case. 267

7RWDO3RWHQWLDOFP+2

 

Evapotranspiration was calculated by using the Penman equation and the crop coefficient (Kc). The crop coefficient changes with the soil, weather, and crop conditions. Here, the crop coefficient is expressed as the sum of the two parameters depending on the crop transpiration (Kcrop) and the soil surface evaporation (Ksoil). Both values were expressed as the function of the ground cover ratio (GC). These coefficients follow Nakano et al. (1993) as Kcrop = (0.92GC)1/2

(5.5.4)

Ksoil = 0.3exp(-1.1GC)

(5.5.5)

Kc = Kcrop + Ksoil

(5.5.6)

5DLQIDOO FP

FP FP

FP FP

FP



  

   



5DLQIDOOPP

(2) Crop Coefficient

      

 

   

 

 



'DWH

Fig. 5.5.3 Daily changes of total potentials at each depth (2001)

It is supposed that the potatoes, one of the semi-annual crops, are grown two times in a year. (3) Conditions The conditions of the simulation are listed in Table 5.5.3. The diffusivity and unsaturated hydraulic conductivity measured by the one-step method (Doering, E. J., 1965, Gardner, W. R., 1962). Irrigation was started when the soil moistures were consumed up to TRAM (Total Readily Available Moisture) which is 15mm. In periods of fallow, irrigations in the field were stopped. (4) Results Figure 5.5.4 shows that the calculated results of Irrigation, Rainfall, electrical conductivity of 10 cm, 30 cm and 50 cm from the surface. Though a part of calculated values are not moderate, these Table 5.5.3 Conditions of simulation Root zone

31 cm

Groundwater level

70 cm (drainage pipe depth)

Meteorological date

1994 (drought year)

Unsaturated hydraulic conductivity

10-4 (saturation) ~ 10-9 (volumetric water content: 49%)

268

Chapter 5. Tidal Reclamations and Their Impacts on Natural Processes

5DLQIDOO,UULJDWLRQ PP G

(&P6 FP

results show well the relation between rain, 5DLQIDOO ,UULJDW LRQ FP FP FP irrigation and changes of EC. There are   small quantities of rain in summer and   autumn in 1994 instead of much rain    at standard year in Japan. The electrical   conductivities at 10 cm increased up to 5   mS/cm after summer. This value of EC will               cause severe damage to the crops (Ayers, 'DWH R.S. et al., 1984). In this condition, crops Fig. 5.5.4 Daily changes of electrical conductivity were able to extend their roots only to the of 10 cm, 30 cm and 50 cm from the surface with thin surface layer. Irrigation water in this irrigation and rainfall drought year will consume much water than standard year. For determining the appropriate amount of irrigation water, a soil moisture monitoring system is necessary. Conclusion

To improve the soil physical properties, about 20 tons/ha of gypsums were added to the original heavy clay soil. Also, leaching was conducted for several months using a sprinkler. The saturated hydraulic conductivities were improved from 10-6 cm/s to 10-3 cm/s, bulk density was improved from 0.40 g/cm3 to 0.74 g/cm3 at the surface layer during four years. Halophyte plants living around reclaimed land were investigated on Na+ and K+ absorption potentials. Those results showed the difference between dicotyledonous and monocotyledonous plant mechanism of Na+ tolerance. The monocotyledonous halophyte is not suitable for removing of Na+ because of suppressing Na+ absorption. If Shichimensou was gathered at 1,000 m2 of newly reclaimed land, about 10 kg of Na+ could be absorbed at a simple calculation. Six tensiometers were equipped to monitor the soil capillary upward flow of the crops growing field for 10 months. Upward fluxes were observed within five days after a certain amount of rainfall in the summer. The maximum amount of soil water flow at the deepest layer was estimated to be about 0.6 mm/d at severe draught period. To prevent the upward flow of saltish water, it is required to apply an adequate amount of irrigation water. In the simulation, there are small quantities of rain in summer and autumn at drought year although much rain at standard year in Japan. The electrical conductivities at 10 cm increased up to 5mS/ cm after summer. To grow the crops safety, irrigation water in this drought year will consume much water than standard year. For determining the appropriate amount of irrigation water, a soil moisture monitoring system is necessary. 269

Though the results of the study are applicable for warm and humid climatic conditions with reclaimed land soils, the objective methodology developed has universal applicability. Abstract In early stage of land reclamation projects, efficient land drying process is important because it determines the time for completion of the whole project and economical benefit of the project as well. Among land drying methods used in the past land reclamation projects in Japan, the project in Hachirogata and Kasaoka were reviewed. Those effects of upside down plowing on land drying and soil development were examined through field soil survey in the Isahaya project. The upside down plowing was verified to promote remarkably soil drying and desalinization of the plowed layers. The physico-chemical properties of the soils were not changed by drying, but change in particle arrangement and structures of the soils were considered to cause the changes in consistency and water retention properties of the soils. 1. Introduction An efficient advance of land drying is one of important processes in early stages of land reclamation projects. The drying process governs the soil formation process followed by land draining, then, determines the time period of the whole reclamation project and economical benefit of the project. There are two important factors in drying and soil formation process, they are soil characteristics and hydrological conditions of the reclaimed land area. In order to dry the land quickly, it is important to apply the most appropriate drying method considering the two factors of the area. In the latest three reclamation projects at Hachirogata, Kasaoka Bay and Isahaya Bay in Japan, were discuss most on appropriate land drying methods. Full upside down plowing has been questioned and not been practiced in the project Hachirogata and Kasaoka because of poor drainage below the plowed layer. In the Isahaya Project, however, the full upside down plowing method was practiced. The objectives of this paper are to examine the effect of the full upside down plowing on soil drying and ripening in the Isahaya bay polder. In addition, effects of drying on soil physico-chemical properties were examined on the Isahaya soil. 2. Land drying methods in Hachirogata project The Hachirogata project began in 1957 and completed in 1969. The Hachirogata polder soil is marine clay that originated from ‘green tuff’, and contains 50 to 70% clay fraction. The main clay mineral is montmorillonite. The average annual precipitation is 1,746 mm, which considerably exceeds annual potential evaporation 975 mm (Penman, year), particularly in winter season (Fig. 5.5.5). 270

Chapter 5. Tidal Reclamations and Their Impacts on Natural Processes  3UHFLSLWDWLRQ(3PP PRQWK

        -D Q )H E 0 DU  $S U 0 D\  -X Q -X O $X J 6H SW  2 FW  1R Y 'H F

Therefore, surface drainage is the most important in drying the land. For the surface drainage, small drainage ditches were installed, after that, plowing was performed. It was found that the full surface plowing was better in drying the top soil, while, a half (1/2) plowing was better in drying the middle and the lower layer (Esaki, and Takenaka, 1976). The effect of the vegetation on field drying was also investigated. A predominant plant species, reed (Phragmites communis Trinius) and mixed pasture grasses were tested on their land drying ability (Kamio, 1997). The mixed pasture grasses showed excellent drying and oxidation effect on the upper layer, while the reed showed greater drying on the deeper layer.

$NLWDUDLQ $NLWD(3

2ND\D\DPDUDLQ 2ND\DPD(3

1DJDVDNLUDLQ 1DJDVDNL(3

Fig. 5.5.5 Monthly rainfall and potential evaporation (EP) of the three reclamation project sites

3. Land drying methods in Kasaoka bay project The construction work of the Kasaoka bay project started in 1966 and land drainage started in 1975. The work was completed in 1990. The clay content of the Kasaoka soil is 41.5% and the soil texture is Light Clay. The soil contains the 2:1 type clay minerals such as a montmorillonite and a vermiculite, as well as 1:1 type such as kaolinite. Annual precipitation of the Kasaoka polder is 1,160 mm, which is the smallest among the three polders, on the other hand, solar radiation is the greatest among them. The potential evaporation is estimated as 1,102 mm and is almost same as the annual precipitation. Accordingly, Kasaoka polder is in the most favorable condition for field drying. Drain ditch system and 1/2 plowing were recommended as a drying method and performed (Takahashi et al., 1981). The field was initially planned to use as paddy fields, but it was changed into upland field use by the ‘rice crop conversion policy’ in 1969 due to over production of rice. The relatively dry climate was expected to cause salinization problem on the upland field use. In order to promote desalinization that had stagnated in five years after land draining, gypsum was applied and mixed to upper 40 cm layer. The initial Na-soil was changed into Ca-soil, and the soil physical properties such as hydraulic conductivity and soil structure were improved. Furthermore, leaching water was applied to the field (Mitsuno et al., 1991). The leaching water requirement was determined on the basis of that diffusive movement of the salt from the lower zone to the upper zone should be balanced with 271

convective downward salt transport due to percolating water flux to the lower zone. Irrigation of 3 mm/day leaching water was considered to maintain the salt concentration of the upper 40 cm layer soil below 2 dS/m (by EC1:2). 4. Field research on land drying method in Isahaya bay project Land drying in Isahaya bay project started April in 1997 when the sea dike was constructed (Fig. 5.5.6). The Isahaya bay polder soil was developed from to sedimentation of Ariake marine clay originated from the volcanic ash deposition of Mt. Aso and the Kuju mountains. It contains low swelling smectite as to principal clay mineral and clay content is about 45%. The potential evaporation of 1,133 mm is almost the same as that of Kasaoka Bay polder, but annual precipitation of 1945 mm/year is much greater than that of the Kasaoka polder. Therefore, much attention should be paid to surface drainage in Isahaya bay polder. The small drainage ditch system was installed first. Along with decrease in water content of the soil due to surface drainage and drying, decrease of salt concentration, oxidization of soil and development of soil structure proceeded gradually, however, the depth of the soil properties change did not exceed more than 20 cm deep. Then, full surface upside down plowing was performed until 40 cm depth in 2001. After the said plowing, oxidization, drying, desalinization and structural development of the soil advanced remarkably to the deeper zones. Methods 1) Yearly change of the reclaimed soil In the central polder of Isahaya bay project, sampling sites were selected along the center line (B-line) at B1, B2 and B3 (Fig. 5.5.6). Land drying works have been practiced at each point as shown in Table 5.5.4. Soil surveying was made at B1, B2 and B3 sites every year from 1998 to 2002. Soil profiles were observed and undisturbed samples were taken from 10 cm to 60 or 70 cm by to interval of 10 cm. Soil moisture characteristic curves, three phase distribution, bulk density and water content Table 5.5.4 Land drying works practiced in the Isahaya Project. Land drying works Drain ditch

Month of work

Notes

June - September 2000

Width: 50 cm, depth: 80 cm, interval: 5 m

Central branch drain canal

July-December 2000

For temporary use

Full upside down plowing at B1

December 2001

Plowed once

Full upside down plowing at B2

December 2001

Plowed three times

March 2002. July 2002 272

Chapter 5. Tidal Reclamations and Their Impacts on Natural Processes

were analyzed by the undisturbed samples. Disturbed samples were also taken from the same depths as undisturbed samples. Electric conductivity of 1:5 (soil: water) extracts and pH were measured on the disturbed samples. In case soil solution came out from the cracks or pores of the soil profile, the solution was collected and analyzed on EC and cation concentration together with water in drain canal close to the sampling point.

཰ ི

%

B2

ཱ

B3 ཰+DFKLURJDW D ཱ.DVDRND ི,VDKD\D

Fig. 5.5.6 Location of reclamation projects and sampling sites

Soil surveying was made at B1, B2 and B3 sites every year from 1998 to 2002. Soil profiles were observed and undisturbed samples were taken from 10 cm to 60 or 70 cm by to interval of 10 cm. Soil moisture characteristic curves, three phase distribution, bulk density and water content were analyzed by the undisturbed samples. Disturbed samples were also taken from the same depths as undisturbed samples. Electric conductivity of 1:5 (soil: water) extracts and pH were measured on the disturbed samples. In case soil solution came out from the cracks or pores of the soil profile, the solution was collected and analyzed on EC and cation concentration together with water in drain canal close to the sampling point. 2) Soil properties at upside down plowed point and unplowed point The upside down plowing was practiced at B1 in 2001. Soil samples were taken and bearing capacity was measured at the full upside down plowed field and the adjacent field without plowing. Same properties were analyzed as the routine soil surveying. 3) Effect of drying on physical and chemical properties of soils The lower layer soil taken from 60 cm depth of B1 point was treated at different drying stage from natural water content to oven-dry, the change in soil properties by drying was analyzed. The examined soil properties were as follows, (1) Consistency limits (liquid limit and plastic limit):

Fresh soil was dried in 30□ incubator to 110, 90, 40, 25, 10% water content by weight, then Atterberg limits test was made. 273

(2) Water retention characteristics at higher pF levels:

Fresh soil was dried in incubator (25□, 65% humidity) to water content of 65%. The other fresh soil was once oven dried and water was added to liquid limit. The water adsorption characteristics of the samples were measured by psychrometer between pF 4 to pF 5.6.

(3) Cation composition of water extract and acetic acid ammonium (AAA) extract:

Fresh soil, 70% water content soil and oven-dried soil were prepared. Distilled water was added to the soil at 1:5 (soil : water) and mixed, the soil suspension was vibrated for 6 hours and settled for 48 hours, then centrifuged for 1 hour and the supernatent was taken and analyzed for Na+, K+, Ca2+ and Mg2+ by atomic adsorption method as for Cl-, SO42- and NO3by ion chromatography, respectively. Extracted solution from air-dried soil by 1Mol (pH 7) acetic acid ammonium (AAA) was analyzed for the same ion species.

(4) Point of zero salt effect (PZSE):

Measurement of PZSE was conducted following the method described by Sakurai et al. (1988). One batch of fresh soil and another batch of oven-dried soil for 24 hours were prepared. Distilled water was added and mixed with the soil and centrifuged. The centrifuged supernatent was discarded. The desalinization procedure was repeated once and twice and the desalinized samples were adjusted their total salt concentration at 0.005 Mol/L and 0.01 Mol/L, respectively. Two grams of samples were suspended in 100g of water and the pH of the suspension was adjusted to pH range covering zero point of charge (ZPC) by addition of HCl or NaOH solution. After adjusting pH, NaCl was added as to the total salt concentration equals to 0.005 Mol/L and 0.01 Mol/L. Relations of pH and adsorbed H+ at different salt concentrations were obtained and analyzed.

Results and Discussion 1) Fundamental properties of soil Fundamental properties of the soil are listed in Table 5.5.5. The specific surface was measured by N2 adsorption method (ref.) and the CEC was measured by Shollenberger method (year). As shown in Table 5.5.5, the soil has relatively higher liquid limit, plasticity, specific surface and CEC. In addition, salt concentration is also high. The main clay minerals were smectite (38.2%), illite (23.4%), kaolinite (18.3%), chlorite (18.0%) and halloysite (2.1% data not shown).

274

Chapter 5. Tidal Reclamations and Their Impacts on Natural Processes

2) Yearly change of reclaimed soil and effect of upside down plowing Fig. 5.5.5 Fundamental properties of the Isahaya soil (B1, 60 cm) Particle density (Mg/m3)

Bulk density (Mg/m3)

Specific surface (m2/g)

Natural W.C. (weight %)

Soil texture

2.57

0.521

42.4

1.44

LiC

CEC (cmolc/kg)

EC1:5 (dS/m)

pH

Liquid limit (weight %)

Plastic limit (weight %)

38.3

9.5

7.3

149.2

57.1

a. Water content profile:

Yearly change of water content profiles in five years from 1998 to 2002 is shown in Fig. 5.5.7. During three years from 1998 to 2000, water content showed linear increase from top layer to 60 cm depth at all the points B1, B2 and B3. This type of linear profiles gradually shifted to lower content as time elapsed. At B3 where only the drain ditch was constructed and upside down plowing has not been practiced, the linear water content profile with 1.2% /cm gradient continued until 2002 and gradually decreased with time. However, after the upside down plowing was practiced the water content profiles showed a drastic change. At B1 point, the water content of deeper layer from 20 cm to 50 cm remarkably decreased in 2002 (broken line) after the plowing in 2001. The similar decreases in water content of 30 cm and the deeper layer was seen at B2. As mentioned above, upside down plowing decreased water content of 30 cm to 60 cm layer and was found to be effective for drying of the deeper layer.

b. Change in bearing capacity:

Bearing capacities of B2 and B3 showed almost the same value from the top layer to 60 cm until 2000, but that of top 15 cm increased in 2001 and the deeper layer was the same as before. The bearing capacities of B1 and B2 after upside down plowing in 2002 were found to be decreased from the top layer to 30 cm or 40 cm layer and increased in the deeper layer. The decrement in the top layer is considered due to breakdown of soil block by the plowing.

c. Yearly change of salt concentration:

Figure 5.5.8 shows yearly change of salt concentration. At B1 point, salt concentration gradually decreased year by year from1998 to 2000. After upside down plowing was practiced in 2001, salt concentration decrement dramatically in particular in deeper layers from 30 cm to 60 cm where desalinization had been retarded. At B2, salt concentration decreased smoothly until 2001, and the decrease in salt concentration was accelerated at 50 cm after the upside 275

down plowing in 2002. Salt concentration decreased continuously from 1998 to 2002 at B3, and the curves were almost parallel to each other, therefore no specific decrements in the lower layer were observed. Yearly change of relation between salt concentration and water content The salt concentration is plotted against water content for all the depths of B1, B2 and B3 points in Fig. 5.5.9. The plots show general tendency that at the first stage, salt concentration (EC1:5) and water content of the plot were decreased linearly as soil drying proceeds. The straight line suddenly bends at water content of around 100%, then the gradient decrease and desalinization proceed slowly as soil dry. This is the case without upside down plowing. If desalinization from the soil proceeded by push out of the soil solution, the plots should lie on a single straight line between the initial state and the origin point. The larger gradient at first stage means that the desalinization from the initial state to 100% water content took place not only by push out of soil solution but also by diffusion of solutes in the soil. The lower gradient in the second stage of desalinization below 100% means that removal of salt was retarded by some mechanisms that hindered salt extrusion. After the upside down plowing in 2002, the plotted points concentrated in a small area of low EC1:5 (>2mS/ cm) and water content around 70~135%. The decrease in EC1:5 and water content were shown to have proceeded to deeper layer in short time after the plowing. On the other hand, EC1:5 vs. water content plots at B3 where the plowing had not been practiced show similar distribution as that of all the data from 1998 to 2002. 3) Difference in soil properties at upside down plowed and unplowed points a. Water content and bulk dry density: Water content in soil profile measured at adjacent upside down plowed and unplowed points is shown in Fig. 5.5.10 Water content by weight (%) 0

50

100

150

0

200

0

0

10

10

Depth (cm)

30 40 50

1998 1999 2000

60

2001

70

2002

80

Fig. 5.5.7 Changes of water contents in the soil profile (Broken line shows profiles after upside down plowing) 276

Depth (cm)

20

20

30 40

5

EC1:5 (dS/m) 10

15

1998 1999 2000 2001 2002

50 60 70 80

Fig. 5.5.8 Change of electric conductivity (EC1:5) in the soil profile (Broken line shows profiles after upside down plowing)

20

Chapter 5. Tidal Reclamations and Their Impacts on Natural Processes Water content (%)

18 0

14

1998

1999

12

2001

2002

20

8

30

6 4 2 0

50

100

150

200

10

10

0

50

0

2000

Depth (cm)

EC 1 :5 (dS/m)

16

100

150

Fig. 5.5.9 Relation of water content and EC1:5 before and after upside down plowing

200

40 50 60

plowed

70

unplowed

80

Fig. 5.5.10 Water content profiles of the upside down plowed and unplowed points

In the unplowed point, water content increase from top layer to the deeper layer and exceeds liquid limit at 40 cm and onward deeper layers. While, in the upside down plowed point, water content was low around 100% from top layer to 50 cm, soil drying proceeded in the whole profile. In the unplowed point, the bulk density of the top layer increased above 0.8g/cm 3, decreased to 0.5 g/cm 3 at 50 cm and deeper layers. While in the upside down plowing point, bulk density was 0.7g/cm3 throughout the top layer to the 50 cm depth. b. Salt concentration Salt concentration in the soil profiles of the plowed and the unplowed points are compared in Fig. 5.5.11. The salt concentration of the unplowed point increase linearly as with the depth. function 1dS/m in surface as increase to 11.5 dS/m at 70 cm. While that of the plowed point show a quite different fend. The salt concentration was below 1dS/m from the top layer to 30 cm and they gradually increase to 2 dS/m at 50 cm and the deeper layers. The salt concentration decreased with the deeper layers. c. Soil moisture characteristic curve: The soil moisture characteristic curve of the unplowed point show low pF (