settlement patterns and construction technologies. ...... able at http://bibliodyssey.blogspot.nl/2008/10/ .... ards: Cuddalore coast in Tamil Nadu, IndiaâA.
Urbanized deltas in transition HAN MEYER STEFFEN NIJHUIS [EDS.]
LEGEND
ENVIRONMENTAL CONDITIONS AND HUMAN ACTIVITIES TRANSPORTATION NETWORK
URBANIZATION urban area
highway
network
major road
land lower than 10 meter MSL
local road
5 meter MSL contour line
ferry
inland water body
railway airport harbour (symbol size indicates harbour size) intensity of commercial shipping 5 meter MSL contour line urban area inland water body
SUBSTRATUM
AGRICULTURAL LAND USE
coastal floodplain: < 10 meter MSL
post-flooding or irrigated croplands
lowland: 10 - 100 meter MSL
croplands
plain: 100 - 500 meter MSL
mosaic cropland
upland: 500 - 1000 meter MSL
mosaic pasture
mountains: 1000 - 3000 meter MSL
meadow
high mountains: > 3000 meter MSL
5 meter MSL contour line
inland water body
urban areas inland water body
CLIMATE Average wind speed and direction 0-5
NNW
5 - 10
N
600
NNE
NW
10 - 15 15 - 20
Precipitation (mm/year)
800
NE
1000 WNW
ENE
1200
20 - 25 25 - 30
W
3.0% 6.0%
35 >
1400
E 9.0%
1600
12.0%
1800
ESE
WSW SW
2000
SE SSW
S
SSE
- bar direction from center indicates the direction the wind blows from - length of the bar shows percentage of time the wind is blowing from the selected direction - rings support reading percentages - colour indicates wind speed (knots) Tropical cyclone tracks, wind speed (knots) 0 - 50 50 - 100 100 - 155
Average temperature (ºC)
-2 21
of coldest month of warmest month
Urbanized deltas in transition HAN MEYER STEFFEN NIJHUIS [EDS.]
Preface
The further we move into the twenty first century, the clearer it becomes that the world’s coastal cities and deltaic regions are faced with an extraordinary range of problems. The press of global population growth and accelerating urbanization is squeezing commerce, industry, people, and fragile ecosystems together in unprecedented ways. Cities and industry are rapidly moving into previously unoccupied and frequently unprotected low-lying wilderness and agricultural areas. Adding to the challenges created by these pressures, flooding due to urban rainwater runoff, growing demands on limited fresh water supplies, rising sea levels, and increasing instability of weather are all exposing the limitations of traditional settlement patterns and construction technologies. While the world’s many deltas each represent unique local geographies the pressures that they face are global in nature. Climate change, sea level rise, and industrialization are not local problems. That is why it is essential for coastal, environmental, and design researchers from around the world to work together in the search for adaptation strategies and solutions to these extraordinary problems. This project represents a significant step in that direction. Comparatively examining some of the world’s most important urbanized deltas creates an important opportunity for the development of a shared language of coastal and urban planning and a higher level of understanding of the linkages of climate and water issues with urban, landscape and regional design. The deepest challenge that we face is not just to make our coastlines and urban centers safer but also to make these places better, more beautiful and more sustainable. That requires us to make problems into opportunities, to turn negatives into positives for the benefit of future generations. This can only be achieved by bringing leading designers and researchers together to better plan for the future. Efforts such as this are vital to the future of our urbanizing deltas. Patricia Belton Oliver, FAIA Dean, Gerald D. Hines College of Architecture, University of Houston
Content
6 URBANIZED DELTAS IN TRANSITION Han Meyer 10 MAPPING URBANIZED DELTAS Steffen Nijhuis, Michiel Pouderoijen MUDFLAT 23 MISSISSIPPI RIVER DELTA, USA Richard Campanella 33 PARANÁ DELTA, ARGENTINA Veronica Zagare, Wolbert van Dijk PLAIN 41 RHINE-MEUSE-SCHELDT DELTA, NETHERLANDS Han Meyer, Steffen Nijhuis, Robert Broesi 51 MEKONG DELTA, VIETNAM Marcel Marchand, Pham Quang Dieu, Trang Le ESTUARY 59 ELBE ESTUARY, GERMANY Dirk Neumann 67 TAGUS ESTUARY, PORTUGAL João Pedro Costa, João Figueira de Sousa LAGOON 75 GALVESTON BAY, USA Thomas Colbert 85 VENETIAN LAGOON, ITALY Paola Viganò 96 References 103 About the authors 104 Colophon
Urbanized deltas of the world (map by S. Nijhuis, TU Delft)
6
Urbanized deltas in transition HAN MEYER
INTRODUCTION Urbanized delta regions represent a combination, and often confrontation, of dynamic natural environments with dynamic economic and urban developments. The largest and fastest growing metropolitan regions of the world are taking advantage of their position in deltas 1, benefiting from the strategic position for navigation and the fertility of the landscape, at the same time trying to deal with their vulnerability to flooding, salinization and silting. During the last decade, the issue of vulnerability of urbanized areas in delta regions to the powers of nature has become a central issue. The recent series of serious floods in urbanized delta and coastal areas (New Orleans 2005, Japan 2011, Bangkok 2011, New York 2012, etc.) addresses the need to fundamentally reconsider the relation between urban development and the natural environment. A dominant idea is that the increased vulnerability and frequency of floods in urban deltas is the result of rising sea levels, caused by climate change.2 However, the climate is continuously changing and the seas have been rising since the end of the last Ice Age, ten thousand years ago. Delta regions are not undermined but rather built by the natural dynamics of river and sea currents and sediment transport, as will be shown in several chapters in this book. It is true that urbanized areas in delta environments are becoming increasingly vulnerable; the culprit, however, is not the changing climate so much as the urbanization process itself and the flood defence and water management policies associated with that process. The process of increasing urban land use (including the construction of ports, dredging navigation routes, managing water for agricultural purposes) has caused a serious decay of the process of delta formation, resulting in land subsidence, loss of wetlands, coastal erosion, and salinization. If
urban societies are to survive in delta areas, the way of urbanization and accessory flood defence strategies needs to change fundamentally. This awareness is increasing in many delta regions, resulting in new ideas, proposals, and plans for new types of urbanization. We can thus say that many urbanized deltas find themselves in a process of transition, towards a new type of relation between urbanization and the natural deltaic environment. In order to support this process, aiming to find best solutions, the Delft University of Technology started the research program ‘Delta Urbanism’. In this book, we want to present and discuss some of these changing approaches. DELTAS – WHAT’S IN A NAME? There is a legend that the Greek historian Herodotus coined the name delta, referring to the similarity of the form of the Nile-delta with the Greek letter A. Whether the legend is true or not, what matters is the meaning: the word delta refers to the final part of a river, with a number of distributaries, and alluvial land created by the sedimentation of rivers and seas. Not all rivers form deltas in this strict sense. In general, this book focuses on territories characterized by the terminus of one or more river basins, providing sediment loads into an ocean, gulf, lagoon, estuary, or lake. Throughout the world, these deltaic landscapes, where rivers and seas meet, provide fertile ground for urban developments, on account of their rich variety of food resources such as fish, wildlife and fertile soils, as well as their strategic position for trade or geopolitics. This book compares and contrasts eight deltaic landscapes, exploring how each of them copes with their particular deltaic circumstances in relation to processes of urbanization. In addition to a series of regions with a delta in the strict sense (the Rhine-Meuse-Scheldt Delta, the Mekong Delta, the Mississippi River Del-
ta, and the Paraná Delta), we consider other types of river mouths and coastal zones, like estuaries (single river mouths with tidal influences) and lagoons (bays into which several rivers flow that are protected by a series of barrier islands). This delta typology will be elaborated in Chapter 2. The common factor in all these cases is that they have deltaic lowlands, which are very attractive for human settlement and exploitation, but are also very vulnerable for any human intervention and exploitation. As soon as humans started to urbanize and exploit these regions, and especially when urbanization, navigation, industrialization and agricultural exploitation intensified during the nineteenth and twentieth centuries, the territorial conditions of these lowlands changed fundamentally. In most delta areas, urbanization has been accompanied by the construction of infrastructures for drainage, navigation and flood defence, which has completely transformed the natural conditions of the territory. The slow but steady natural process of land formation and land rise changed into land erosion and land subsidence; extensive flood plains changed into narrow channels; gradual transitions of fresh to brackish to salt water zones changed into sharp separations between fresh and salt water. Rivers lost their room to expand during peak discharges; the consequences of floods became more serious because of land subsidence; ecosystems were destroyed because of the loss of sediment and nutrients. Estuaries and deltas, which represent some of the world’s richest ecosystems, are threatened seriously with the loss of their richness.3 All these urbanized lowlands are dealing with similar problems; however, it would be naive to think that there is one single solution for all delta regions. We can see that every delta and delta-like region has been formed by specific natural conditions. Some deltas have been formed by sediment de-
1 UN-Habitat 2 Nichols and Cazenave 2010; Kabat and Vellinga 2011 3 Costanza et al. 1997, Saeijs 2006
7
posited by rivers; other deltas have been formed by sediment transported by tidal currents of the sea; and some have been formed by a combination of these powers. In each delta and delta-like region, the balance between the power of river, sea, wind, and tide is different, resulting in different natural conditions. As a result, it should be clear that it is not possible to use the same solution for every delta region. URBANIZATION Another reason it would be inappropriate to strive for a single type of solution is the broad variety of urban patterns in delta and delta-like regions. The eight examples presented in this book show eight completely different types of urban patterns. By ‘urban’ we not only mean the dense concentrations of people in cities, but also the intensive agricultural, industrial and port-related land use encountered in delta regions. The different urban patterns are related to different territorial conditions. In every delta or delta-like region, the first urban settlements started on higher and relatively safe locations, without protection by floodwalls. Sometimes these higher grounds were found at the edges of the delta on the older Pleistocene land, like Buenos Aires, Lisbon and Hamburg. In other cases, these higher grounds were found on natural levees, formed by century-long sediment deposits on the river embankments, like many Dutch cities in the Rhine-Meuse-Scheldt Delta and New Orleans in the heart of the Mississippi River Delta. And, in still other cases, the higher grounds were created by people, building mounds (in the Netherlands) or raising islands (around Venice) or on the small dikes along the irrigation canals of the Mekong Delta. And sometimes the lowland was regarded as safe enough, protected by a series of barrier islands, which are supposed to absorb the first 4 Brand 2012, Taverne et al. 2012 5 Mitchell 2009a, Mitchell 2009b 6 Scheffer 2009 7 McHarg 1969, see also Meyer and Nijhuis 2013
8
blow in case of a storm surge (Houston and Galveston Bay). In addition, the main economic reasons for exploitation and settlement in a delta vary. New Orleans, Houston, Buenos Aires owe their existence mainly to their strategic position for trade, transshipment and navigation; on the other hand, the spatial land-use pattern of the Mekong Delta is mainly a result of the agricultural exploitation of the lowlands, which has made Vietnam one of the worlds’ largest rice exporters. The Dutch Delta, Hamburg and Lisbon represent different combinations of port-oriented cities surrounded by agricultural land. Venice is an interesting example of a single port-city in the centre of a lagoon, while the lowlands of the Veneto provide food for the city. A final reason that no single solution can be applied concerns the different societal conditions and different historic pathways of the delta areas. The poly-nuclear urban structure of the Netherlands is strongly related to the decentralized political power of this country as a ‘land of cities’ since the 16th century.4 The form and position of Lisbon and Buenos Aires are related to their roles as the seat of centralized power structures in Portugal and Argentina. Taken together, we see a huge differentiation of urban patterns, varying from large mono-central metropolises like Buenos Aires and Houston to the fine-grain sprawled patterns of the Mekong Delta and the Veneto. TRANSITION In this book, transition refers to the character of an urbanized delta as a complex system. According to complexity theories 5, a complex system is defined by a large number of subsystems, each with its own characteristics and dynamics, influencing each other and influenced by external conditions, which have their own dynamics as well.
The evolution of a complex system is the result of the continuous interaction of subsystems and of the continuous interaction with the dynamics of the external conditions. This evolution is often rather arbitrary, non-linear and unpredictable. A complex system can be regarded as being in a relatively stable equilibrium when it is able to deal with sudden changes of one subsystem or with a structural change of the context. When a system is able to protect itself against sudden extreme events, we call it a robust system. When a system is temporarily disordered by a sudden extreme event, but able to recover relatively quickly, we call it a resilient system. When a system is able to adapt to a changing context, we call it a complex adaptive system. Complex systems which are facing extreme events or a changing context, and which are not able to deal with these changes, find themselves in a critical transition.6 They have to find a new equilibrium, which means that the different subsystems not only have to redefine themselves but also have to create new relations with each other. That is exactly what is necessary in urbanized deltas and delta-like regions today: a transition to a new ‘state’ of the urbanized delta, one that is able to adapt to changing conditions in the immediate future but also in a far future which is still rather uncertain and unpredictable. This idea of a complex system is very relevant for urbanized deltas, building upon the work of people like Ian McHarg, who considered urbanized landscapes as layered systems.7 The layers of McHarg (the natural substratum, the infrastructural networks, and the urban land-use patterns) represent the subsystems, each with its own rhythms and dynamics, but also related to and influenced by the other layers or subsystems. The evolution of all the deltas and delta-like regions presented in this book has followed a similar historic pathway: first, the period dominated by
land-formation by natural forces, followed by a transition to a second period of the first human interventions and first urban settlements, still rather modest on account of the level of technology, and political and financial limitations. In most of the deltas, a third period starts in the nineteenth century, when technology and the power of nation states enabled structural interventions in the system of the delta, making it possible to change, manipulate and control the system. Actually, though, we should say: nation states tried to manipulate and control the delta system. The on-going and intensified urbanization, draining, dredging, reclaiming and diking during the twentieth and early twenty-first century brought us to our current impasse: the increasing loss of control of natural powers. It is thus necessary to make the transition to a fourth period, looking for a new balance between the different subsystems or layers of the delta systems. Instead of considering these different systems as competitive, the new paradigm considers them as complementary and potentially supporting each other. ‘Building by Nature’ and ‘Working with Water’ are new mantras which express a new approach, trying to use the energy and dynamics of natural powers instead of merely resisting them. The development of the program ‘Room for the River’ in the Netherlands (2005 – 2015) is an example of this new approach, which tries to create more room for expanding rivers, and to use this new room also to realize new spatial and environmental qualities.8 The new strategy of coastal defence, building the coast seaward using sand-nourishment by a ‘sand-engine’, is another example of this new approach.9 In the USA, new strategies are being prepared after the disasters of Katrina in New Orleans (2005) and Sandy in New York (2012). Greater New Orleans has developed a new urban water management strategy 8 Kwaliteitsteam Ruimte voor de Rivier 2012 9 Zandmotor 2014 10 Living with water 2014 11 Changing course 2014
to stop the process of land subsidence 10; the Mississippi River Delta is the subject of a competition, which aims to restore the sediment supply in order to stop the erosion of the wetlands 11. The mayor of New York announced that the city should become ‘stronger and more resilient’, and organized the competition ‘Rebuild-by-Design’ in collaboration with the federal government.12 All these examples show two things: first, there is not yet a single approach for making urbanized deltas more sustainable, resilient and adaptive, and we are still in a process of experimenting, searching and finding. And, second, design plays an important role in this process of experimenting, searching and discovering new perspectives. UNDERSTANDING, DESIGNING, GOVERNING With this book 13 we want to contribute to the transition towards new relationships for understanding, designing and governing urbanized deltas. This book focuses especially on understanding and designing: understanding by systematically collecting and comparing data and elaborating these data in mapping analysis. New technologies like GIS offer fantastic possibilities for getting new insights into what is happening in urbanized deltas. This understanding is indispensable for designers, planners and policy-makers in delta regions. By presenting and discussing recent designs for the eight urbanized deltas, we show new possibilities and opportunities for future development, aiming to make the urban delta more adaptive. The task of design is to discover new possibilities, to show and to test solutions which are unexpected and might seem unlikely at first sight, but which can address new opportunities for land use, spatial composition and governance. This last issue, governance, is not the explicit concern of this book, but it is important as well: new spatial strategies might require new governance
arrangements. Also in the Netherlands, where flood defence became the special responsibility of the nation state during the twentieth century, the monopoly of the state is no longer self-evident. Local communities like the City of Dordrecht and NGOs like the nature organizations Natuur monumenten (the Dutch Nature Foundation) and World Wildlife Fund are getting involved in the search for new solutions and are taking responsibility for parts of new flood defence strategies in the Dutch Delta. A creative combination of understanding, designing and governing can result in new, unexpected spatial solutions as well as in new, unexpected governance solutions. URBANIZED DELTAS IN TRANSITION This book aims to contribute to a comparative analysis of urbanized deltas in transition. The method and techniques of the comparative mapping analysis will be explained in more detail in Chapter 2. The following eight chapters focus in detail on the eight urbanized deltas. Each of these chapters follows the same structure: First, it describes how the natural powers of currents, sediments, wind and vegetation formed the specific deltaic landscape. Second, it explains how urbanization patterns used the specific landscape conditions of the delta, but also how these patterns contributed to essential transformations of the landscape. Each chapter discusses how the relation between urban patterns (including hydraulic infrastructures) and the delta landscape resulted in a relatively stable balance during some periods, and led to critical transitions in other periods. Finally, each chapter discusses the current state of the art of the urbanized delta and what should be done to improve the sustainability and adaptivity of the delta, showing how design research and research-by-design can contribute to finding new approaches.
12 City of New York 2013 13 and the related exposition and symposium
9
1
2
1 An early example of comparative research by means of maps and charts. Comparative heights of the principal mountains and lengths of the principal rivers of the world by William Gardner, 1823 (source: Bibliodyssey 2014) 2 Winand Staring, the founding father of soil science in the Netherlands, used a diagram to explore and delineate tidal processes in relation to silting-up of land, in order to understand the natural growth of land by sedimentation (source: Staring 1856)
10
Mapping urbanized deltas STEFFEN NIJHUIS AND MICHIEL POUDEROIJEN
“The earth and its inhabitants stand in the closest mutual relations, and one element cannot be seen in all its phases without the others” Carl Ritter (1779-1859)
Mapping is an important activity in delta urbanism. It is a means to generate knowledge for planning and design in urbanized deltas. This implies a strong forward-looking action from a perspective of sustainable development, so as to guide, harmonise and shape changes, which are brought about by social, economic and environmental processes. Systematic study of urbanized delta landscapes is essential and constitutes description, comparison and classification as a basis for knowledge-based planning and design. It utilizes the power of Geographic Information Systems (GIS) to acquire knowledge via modelling, analysis and visual representation. This chapter provides some background on comparative research, elaborates on maps and mapping as tools for analysis, and discusses the availability and use of global datasets concerning environmental conditions and human activities in urbanized deltas. DESCRIPTION, COMPARISON AND CLASSIFICATION The 19th century founding fathers of geography like Alexander von Humboldt and Carl Ritter recognized the landscape as a complex system of systems.1 In their opinion, the earth was an inseparable organic whole, all parts of which were mutually interdependent, including man. In order to get a grip on the great complexity of the landscape, they used graphic techniques to catalogue, define, compare and reason through the collected scientific data. Their published work is full of illustrations, maps and charts, many of which were very influential.2 Particularly, maps like the one made by William Gardner are strongly influenced by their work and are among the earliest examples of comparative research by means of 1 Kilpinen 1996, Martin 2005 2 Brown 2014 3 Tooley et al. 1999 4 Moudon 1994, 1997, Picon 2003 5 e .g. Steenbergen et al. 2009, Hoeferlin et al. 2010, Tossi 2013
maps and charts 3 (Figure 1). In Gardner’s map, rivers and their natural contexts are compared and classified in order to discover similarities and differences in a visual way. In the urban realm there is also a long tradition using maps and comparative research.4 Recently, deltaic landscapes have become the subject of this type of research 5, employing mapping and comparative research as a means to understand the how and why of successes and failures in coping with deltaic circumstances and to determine future directions for development. The main objective of mapping urbanized deltas is to address the problematic situation of intensive cultivation and habitation in floodprone lowlands. In order to explore the similarities and dissimilarities, description and classification are useful as an important source for knowledge-based planning and design. Description is here defined as an intensive study of a single delta, aiming to generalise to other deltas.6 This type of research is widely acknowledged for complex, multifaceted investigations, the goal being to answer research questions and develop propositions for further inquiry.7 Classification is a means to group the observed differences and similarities according to their common characteristics. It aims to understand urban delta systems based on their formal (or physical) expression of social, economic, ecologic and spatial processes.8 Deltaic landscapes can be classified based on the internal coherence between landscape factors, form and functioning; on the human influence on the landscape; or on the visual appearance (physiognomy) and experience of landscape, respectively called biophysical, anthropic and visual landscape classifications.9 In addition, there are classifications which identify different deltaic systems based on their morphology and sediment characteristics.10 However, the classification
6 cf. Gerring 2004, 2007 7 Deming and Swaffield 2011, Flyvbjerg 2011, Yin 2009 8 Sauer 1925, Steenbergen et al. 2009 9 Berendsen 2000, Groom 2005, Nijhuis and Reitsma 2011
10 e .g. Galloway (1975) identified fluvial, wave, and tide-dominated delta systems 11 Penland and Kulp 2005 12 Ibid. 13 Pethick 1984, Bird 1972
proposed here aims to explore the coherence between natural conditions and human interventions more precisely. While combining aspects of biophysical and anthropic landscape classification, this work focuses on four variations of urbanized deltaic landscapes: - Mudflat: A delta where silt (potentially) builds up. These continental-shelf margin deltas are typically formed by rivers with very large sediment loads.11 With sufficient sediment load, these deltas continue to build seaward, extending the continental margin into deeper waters.12 Urban settlements are concentrated on the higher grounds in (e.g., natural levee deposits) or next to the delta, which further mainly consists of wetlands. Examples include the Mississippi River Delta (USA) and Paraná Delta (Argentina); - Plain: A delta with a large deltaic flood plain. These deltas are characterized by a large alluvial plain which is mainly used for agriculture and by a sprawled pattern of human settlements and concentrated cities. Examples include the Rhine-Meuse-Scheldt Delta (NL) and Mekong Delta (Vietnam); - Estuary: A tidal mouth of a river, widening as it enters the sea 13 with almost no deltaic floodplain. Estuaries are typically drowned river valleys 14 and usually have a concentrated large city on the adjacent higher grounds and agriculture in the lower areas. Examples include the estuaries of the Elbe (Germany) and Tagus (Portugal); - Lagoon: A delta or part of a delta protected by barrier-island systems or topographical remnants.15 Lagoon or bayhead deltas are usually part of a bigger coastal and/or deltaic zone.16 Cities are located at the river mouth, on islands or peninsulas. The coastal floodplain consists mainly of wetlands. Examples include Galveston Bay (USA) and the Venetian lagoon (Italy). 14 Healy 2005 15 Penland and Kulp 2005 16 Ibid.
11
3
4
12
5
3 During WWII extensive areas of the Dutch lowlands were badly drained due to a lack of fuel for the pumping engines or because the Germans had flooded them. This situation was considered a useful source of aggregated knowledge on the effect of restrained water management on the humidity of the landscape. Red-blue map of the northern Dutch regions by Cornelis von Frijtag Drabbe, 1954 (source: TU Delft, montage by Nijhuis and Pouderoijen) 4 Overlay analysis is used to study spatial relationships. Thematic map overlay of relief, rock types, communication, farmland, etc., resulting in a synthesis map pointing out the characteristics of the landscape. Example used by Jacqueline Tyrwhitt to explain overlay as an analytical operation (source: Tyrwhitt 1950, montage by Nijhuis and Pouderoijen) 5 Cross-reference mapping connects understanding with design thinking. This ‘suggestive’ cartography offers alternative readings of a landscape and explores certain relationships while integrating thematic maps with statistical information, photographs, diagrams, sections. ‘Engineered Curves’ by Anuradna Mathur and Dilip Da Cunha (University of Pennsylvania) is an application of this mapping technique to study the dynamics of the Mississippi in relation to human interventions (source: Mathur and Da Cunha 2001)
The most dominant features of the genesis and morphology of the delta are used as a key to determine its type. This preliminary classification needs to be further elaborated in order to become a comprehensive classification which integrates biophysical aspects with urban form and networks. Such a comprehensive classification can serve as a basis for delta-specific strategies for sustainable urban development. MAPPING AS A WAY TO STUDY Maps and mapping play a decisive role in studying urbanized deltas. They are used as a tool to understand the different types of design challenges. For example, an urban settlement entirely located in the lowlands requires a different design strategy than one that originated on higher grounds and partially extends into the lowlands. To determine these and other characteristics, visual representations like maps, sections and three-dimensional drawings, as well as info-graphics and scale models, are natural tools for visual thinking and visual communication.17 Visual thinking is a way of generating information by creating, inspecting, and interpreting a visualisation of the previously non-visible (seeing the unseen), while visual communication refers to the effective distribution of information in visual form.18 Maps as a product and the process of mapping are both important means for visual thinking and visual communication in order to understand delta landscapes. Maps help us to reflect upon emerging insights, appraise the landscape in its totality, and observe the relationships between the parts and the whole 19 (Figure 2). Maps have served as tools for handling spatial data for millennia; they are informative as well as persuasive and are therefore important means of knowledge acquisition.20 17 e.g. Tufte 2000, Lima 2011 18 DiBiasi 1990, cf. Zube et al. 1987 19 Nijhuis and Stellingwerff 2011, cf. MacEachren 1995 20 Dorling and Fairbairn 1997, Harley and Woodward 1987
Maps facilitate a spatial understanding of things, concepts, conditions, processes or events in the human/natural world.21 Mapping is an activity of constructing and communicating spatial knowledge, and the map is a result of that. The physical creation of maps is the process of map-making. This can be distinguished from information acquisition and the processing of spatial data which is termed mapping.22 Mapping entails exploration, analysis and synthesis of data and information in a visual way. It refers to a process, rather than a completed product.23 The process of mapping helps us acquire new or latent information, which is the basis for generating spatial knowledge.24 Cornelis von Frijtag Drabbe, former head of the Dutch topographic survey, can serve as an example. He interpreted WWII aerial photographs as an empirical source to create maps known as ‘red-blue maps’. These maps delineate which parts of a landscape were wetter or drier as a result of the reaction to a variety of local conditions such as height differences, soil absorption capacity and vegetation, at a period when water management was lacking 25 (Figure 3). Mapping allows for an understanding on multiple levels because it is not restricted to a method of digital or analogue visual representation. It is first and foremost an act of cognition, a human ability to develop mental representations that allow us to identify patterns and create or impose order.26 Mapping allows us to ‘digest’ information in a rational and systematic way, which is a personal process influenced by the choices and judgements made by the interpreter. At the same time, these findings are made transferable via visual representation, which showcases relationships, structures and patterns. Geographic Information Systems (GIS) combine mapping with information technology 27, thus transfering control of the mapping process
21 Harley and Woodward 1987 22 Dorling and Fairbairn 1997 23 Cosgrove 1999, Abrams and Hall 2006 24 Corner 1999 25 Von Frijtag Drabbe 1954: 7 26 MacEachren 1995
from the cartographer to the researcher. GIS offers researchers a platform where they can deal with complex spatial environments, modelling, analysing and representing them. It requires the researcher to understand the mapping process in relation to the possibilities and limitations of datasets. The wide range of possible applications in urban planning and design makes GIS a vital instrument in urbanism.28 Analytical operations Map dissection, map comparison, and automated map analysis are useful analytical operations. Map dissection is about discovering spatial patterns by selection and reduction, and often serves as the basis for spatial association analysis, which explores the relation between different patterns. Techniques for spatial association analysis are overlay analysis and cross-reference mapping. Overlay analysis is employed to derive relationships by applying thematic overlays to geographic location. Although this technique was already applied by the 19th century landscape architects Warren Manning and Charles Eliot, it was Jacqueline Tyrwhitt, mother of planning, who was the first to describe the overlay technique in an academic setting. “Possible maps should be drawn on transparent paper, so that when completed the maps to the same scale can be ‘sieved’, i.e. placed one on top of another in turn so that their correlations or their absence can be noted. Where relevant these sieve maps should be made bringing out the degrees of correlations noted on certain matters” 29 (Figure 4). Later, this method was further developed for suitability mapping by Ian McHarg 30 and had a major influence on the development of GIS. In mapping urbanized deltas, overlay analysis by means of GIS is used to explore such things as the correlations between environmental conditions and
27 Fisher and Unwin 2005, Dodge et al. 2008, Longley et al. 2010 28 Nijhuis 2013 29 Tyrwhitt 1950: 157 30 McHarg 1969
13
6
Period of polder-construction
7
8
14
6 Mapping of change in space and time via overlay. Different time-slice snapshots from different eras of the land-water contour are combined in a composite space-time map in order to show the dynamics and development of the southwest Dutch Delta (map by Nijhuis and Pouderoijen 2013) 7 The development of the landscape expressed in attributes. The development of the polder system in the southwest Dutch Delta; the gradient in dark to light blue expresses the period of origin of the polders from 1250 AD until 2000 (map by Nijhuis and Pouderoijen 2013) 8 Mapping spatial and temporal chances via a map series. The development of the southwest Dutch Delta in four time-slice snapshots: 1850, 1900, 1950 and 2000 (maps by Nijhuis and Pouderoijen 2013)
patterns of land-use and human settlements. A recent variation of overlay analysis is cross-ref erence mapping. Here, location-specific information is superimposed or merged with other layers of information (Figure 5). This ‘suggestive’ cartography offers alternative readings of a landscape and explores certain relationships while integrating thematic maps with statistical information, photographs, diagrams, sections. This type of mapping connects understanding with design thinking and involves a high degree of subjectivity.31 However, in this work, the emphasis is on understanding and we therefore draw on ‘conventional’ use of maps. Map comparison is about finding similarities and dissimilarities in space, time, and theme between the different urbanized deltas, as well as within the individual delta. Since spatial dynamics and changes over time are hard to express in a static map, different time-slice snapshots need to be mapped in order to delineate the development of a particular delta landscape. These time-slice snapshots can be combined in several ways: via overlay (Figure 6), attributes (Figure 7) or in a series (Figure 8). However, it was not possible to create multiple time-slice snapshots for each urbanized delta, since the information was lacking or only available in analogue form. Automated map analysis is employed to explore the available digital datasets, to calculate elevation zones, as well as land-use within different elevation zones, and to summarize quantities such as precipitation or river discharge. MAPPING ENVIRONMENTAL CONDITIONS AND HUMAN ACTIVITIES Urbanized deltas are the result of the action and interaction of both natural and human factors.32 The landscape is a mediator between nature and society, based on a material space that exists as 31 e.g. Corner 1999, 1992 32 cf. Council of Europe 2000 33 Burel and Baudry 2003 34 Zonneveld 1995 35 De Jong 2007 36 Ibid.
a structure as well as an ecological system, and which is independent of perception; landscape is a level of organisation of systems.33 From this point of view, the urbanized deltas comprise functions with spatial and temporal dimensions. In order to comprehend the heterogeneity of this composition in space and time, it is important to study the chorological (horizontal) and topological (vertical) relationships.34 The relationships between environmental conditions and human responses and interventions can be explored by decomposing the landscape in different layers, stratifying them according to the level of influence and dynamics of change. Layers with a low dynamic of change are substratum and climate. These environmental conditions are regarded as the most influential conditions for land use (first tier conditions). Transportation networks are also important conditional factors for land use, but develop faster than the environmental conditions (second tier conditions). Together, these conditions pave the way for the development of agricultural land use and urban settlements. Levels of scale The level of scale of a territory under study is important, because any size larger than that of the study area supposes a ‘larger context’, but any size smaller than that of the smallest detail supposes context as well.35 This implies that the delta area under investigation has an upper and lower limit, called frame and granule, and is best indicated by its approximate radius and level of detail.36 In order to map the environmental conditions and human activities, the following three levels of scale are used: - Delta region: ≈200 km radius, with a level of detail of 1:500,000-1:2,000,000; - Delta metropolis: ≈50 km radius, with a level of detail of 1:50,000-1:200,000;
- Delta city: ≈10 km radius, with a level of detail of 1:5,000-1:20,000; Most maps created for this book are at the Delta region and Delta metropolis scales. However, in the following chapters the Delta city scale will also be addressed, and the complex interdependency of issues on different scale-levels will be stressed, since urbanized deltas can only be understood by working through the scales. Availability and quality of global datasets Since we investigated urbanized deltas all over the world, it was important to find worldwide datasets with a sufficient spatial resolution to make it possible to analyse and compare the deltas in a consistent and systematic way. However, a major constraint for global datasets is the availability, quality, and consistency of data.37 Despite continuous improvements in data acquisition, storage, and processing techniques, global datasets still suffer from limitations, such as inconsistencies in data coverage, variable data quality for different geographic regions, and uncertainties in data accuracy, due to the data acquisition methods.38 However, a number of global elevation and land-use datasets were deemed suitable for a synoptic global comparison, showing sufficient resolution for regional analysis.39 Each of these maps approaches natural features and human land use from a unique perspective, employing methodologies that draw on a sometimes-overlapping pool of remote sensing imagery, groundbased census results, GIS-data layers, and other global maps.40 While employing high-resolution global datasets it was possible to model, analyse and visually represent each urbanized delta in a comparable manner on the following aspects: substratum, climate, agricultural land use, transportation networks and urban settlements (Figure 9).
37 Nicholls, Tol and Vafeidis 2008 38 Vafeidis et al. 2008, Lichter et al. 2011 39 Gamba and Herold 2009, Lichter et al. 2011 40 Potere 2009
15
Transportation networks
Agricultural land use
Climate
Substratum
Urban settlements
Mississippi River Delta USA
16
Paraná Delta Argentina
RMS Delta Netherlands
Mekong Delta Vietnam
Tagus Estuary Portugal
Galveston Bay USA
Venetian Lagoon Italy
Transportation networks
Agricultural land use
Climate
Substratum
Urban settlements
Elbe Estuary Germany
9 Mapping environmental conditions and human activities: substratum, climate, agricultural land use, transportation networks and urban settlements. Legend on the front-flap (maps by Nijhuis and Pouderoijen, see text for the used geodata)
17
ELBE ESTUARY RHINE-MEUSE-SCHELDT DELTA TAGUS ESTUARY MISSISSIPPI RIVER DELTA
VENETIAN LAGOON
GALVESTON BAY
MEKONG DELTA
PARANA DELTA
10
RIVER NAME
LENGTH (KM)
BASIN AREA (10^3 KM2)
MISSISSIPPI RIVER DELTA
Mississippi
5900
3300
15540
210
PARANA DELTA
Paraná
4800
2600
16806
90
Uruguay
1500
370
4439
10
Rhine
1400
220
Meuse
920
36
320
0.7
Scheldt
430
22
190
0.75
MEKONG DELTA
Mekong
4800
800
14800 1
110-150
ELBE ESTUARY
Elbe
1100
150
760-868 2
0.84
TAGUS ESTUARY
Tagus
1000
80
304
0.4
GALVESTON BAY
Trinity
960
46
222
1.3
Brazos
2000
120
191
9.2
Po
680
74
1460
10-15
Brenta
160
1,6
73
0.19
Adige
410
12
231
1.6
RMS DELTA
VENETIAN LAGOON
AVERAGE DISCHARGE Q (M3/S)
2200
SEDIMENT LOAD QS (MT/YR)
0.07
3
11
MISSISSIPPI RIVER DELTA
ELBE ESTUARY
12
18
PARANÁ DELTA
TAGUS ESTUARY
RHINE-MEUSE-SCHELDT DELTA
MEKONG DELTA
GALVESTON BAY
VENETIAN LAGOON
10 The location of the urbanized deltas in their natural setting. The elevation zones represent different morphological classes varying from deltaic flood plain to high mountains (map by Nijhuis and Pouderoijen, based on SRTM-Elevation data and SRTM-Water body data) 11 Characteristics of the rivers related to the selected deltas (data derived from: Milliman and Farnsworth (2013); complementary sources: 1 Wohl (2007); 2 Tockner et al. (2009); 3 Rijkswaterstaat (2013)) 12 Precipitation patterns in the drainage basins related to the selected deltas (graphic by Nijhuis and Pouderoijen, based on GRDC-Major river basins of the world and WorldClim-data period ~1950-2000)
Substratum and climate Important environmental conditions influencing human activities in each delta are related to its substratum and climate. Topography, soil, precipitation, and temperature have a great impact on the fluvial system and the possibilities for land use. In particular, elevation can serve as a surrogate for a variety of factors determining drainage patterns, suitability for vegetation growth, and the construction of transportation networks and urban settlements. The dynamics of change is very slow. Substantial changes take place in the course of centuries, with an order of magnitude of 100-500 years. High-resolution global elevation data 41 served as the basis to delineate the substratum; this was complemented with bathymetric 42 and world water body data 43 (Figure 10). The characteristics of the fluvial systems are derived from a recent global river database 44 combined with data on the major river basins of the world 45 (Figure 11). To identify the deltaic lowland, the zone less than ten meters above sea level was determined, which indicates the territory vulnerable to significant sea level rise and the risk of flooding by rivers. 46 Precipitation, temperature and wind exert a great influence on the fluvial and coastal system, as well as the possibilities for agricultural land-use. Mean annual precipitation and mean temperature of the warmest and coldest month are derived from global climate data 47 (Figure 12). The prevailing wind directions are based on 15 year statistics of selected weather stations
41 Shuttle Radar Topography Mission (SRTM) with a resolution of ~90 meters (Farr et al. 2007) 42 General Bathymetric Chart of the Oceans (GEBCO) 43 SRTM-Water body data by NASA/ US National Geospatial-Intelligence Agency (NGA) 44 Milliman and Farnsworth 2013 45 Global Runoff Data Centre 2007 46 Also known as the low-elevation coastal zone (McGranahan et al. 2007, Nicholls and Cazenave 2010) 47 WorldClim (period ~1950-2000) (Hijmans et al. 2005) 48 US NOAA-National Climatic Data
and, where applicable, combined with tropical cyclone tracks.48 Transportation networks and land-use Infrastructure networks are another important factor, creating conditions for settlement, economic activities and mobility. For this work, global datasets of transportation networks such as roads, railroads 49 and shipping routes 50 are employed. In addition, important hubs such as harbours and airports are delineated and classified according to importance using the world port index 51 and world airports database 52. Because of the technological complexity and expense of infrastructure networks, the transformation frequency is much lower than the urban system, but faster than the natural system (≈50100 years). Patterns of land use and urban settlements emerge depending on the various environmental conditions we mentioned before. Here the dynamics of change is usually very high: substantial extensions or transformations can take place in less than 50 years. A few global datasets deal with land use, generally multi-class land cover maps that include an urban class.53 To obtain global land cover data, we relied on the most current satellite imagery with the highest spatial resolution. 54 This data allows one to analyse aspects of the rural landscape such as agricultural land use. Agriculture is one of the dominant and most important land uses in deltas, supplying food and acting as an economic driver, and it has significant effects
Center 9 Both ESRI data & map 10 4 50 National Center for Ecological Analysis and Synthesis (NCEAS) 2005 51 US National Geospatial-Intelligence Agency (NGA) 52 ESRI data & maps 10 53 Vector Map level Zero (VMAP0) (Danko 1992), Global Landcover 2000 (GLC00) (Bartholome et al. 2005), GlobCover (GLOBC) (Arino et al. 2007; ESA 2008) 54 GlobCover (GLOBC) with a resolution of ~300 m (Arino et al. 2007, ESA 2008) 55 Vink 1975, OECD 1999, Milliman and
on the environment and fluvial system. Different types of agriculture each have their own impact on resources such as soil, water, air, biodiversity, habitats and landscape.55 In order to compare the vulnerability of land use to flooding, the land-use area is calculated for the territory less than five meters above sea level (Figure 13). This five-meter zone is considered an important indicator for flood hazard analysis and refines the previously mentioned ten-meter zone, which is considered exceedingly high for assessing the risks of twenty-first century sea-level rise.56 To analyse the vulnerability, the land-cover dataset was re-projected into an equal area projection and recalculated into a hundred meter raster. Urban settlements Urban settlements are an important form of land use, and are crucial for this work. The density, spatial distribution, and physical characteristics of urban settlements are important drivers of social and environmental change at multiple scales.57 In addition to the multi-class land cover maps, there are several global datasets which are entirely devoted to urban settlements.58 Since there is no generally accepted set of criteria for creating a binary urban-rural classification, these maps do not use a consistent operational definition of urban areas.59 These maps tend to overestimate the spatial extent of urban areas to a greater or lesser extent (e.g., by ‘over-glowing’).60
Farnsworth 2013 56 De la Vega-Leinert et al. 2000, Eden hofer et al. 2012, Saxenaa et al. 2013 57 Massey 2005 58 These include, (1) Binary maps: MODIS Urban Land Cover 1 km (MOD1K) (Schneider et al. 2003, 2005), MODIS Urban Land Cover 500 m (MOD500) (Schneider et al. 2009) and Global Rural-Urban Mapping (GRUMP) (CIESIN 2004). (2) Continuous maps: Global Impervious Surface Area Map (IMPSA) (Elvidge et al. 2007) and History Database of the Global Environment (HYDE3) (Goldewijk 2005). Night-time illumination maps: LandScan 2005
(LSCAN) (Bhaduri et al. 2002) and (3) Nighttime Lights (LITES) (Elvidge et al. 2001). See Potere 2009 and Potere and Schneider 2009 for a comparison and discussion 59 Potere 2009, Potere and Schneider 2009 60 Ibid.
19
MISSISSIPPI RIVER DELTA
km2
%
PARANÁ DELTA
km2
RMS DELTA
%
km2
Forest
4533.6
25.2
1570.7
10.5
Wetland
6804.9
37.8
9219.0
4.7
0.0
109.9
Water body
4780.3
26.5
Agriculture
1784.1
9.9
Sparsely vegetated
Urban area TOTAL
MEKONG DELTA
%
km2
ELBE ESTUARY
%
km2
%
km2
2052.7
10.3
4194.8
9.1
324.4
9.0
61.5
12.3
0.1
225.7
0.5
0.0
0.7
155.7
0.8
18.7
0.0
6.4
2543.4
17.0
743.1
3.7
4216.1
9.2
1541.7
10.3
15469.8
77.3
37325.4
81.1
GALVESTON BAY
%
km2
VENETIAN LAGOON
%
km2
29.9
5.9
499.8
22.7
0.0
3.6
0.7
1179.6
0.2
18.6
3.7
4.1
218.8
6.1
35.9
7.1
2959.9
82.2
401.4
79.1
%
372.1
4.5
53.6
18.4
0.2
0.2
333.1
4.0
0.0
0.0
396.9
4.8
482.3
21.9
6623.0
80.1
112.9
0.6
8.3
0.1
1578.8
7.9
27.3
0.1
90.3
2.5
18.0
3.5
34.9
1.6
525.5
6.4
18020.5
100.0
14992.9
100.0
20012.4
100.0
46008.0
100.0
3599.7
100.0
507.3
100.0
2200.6
100.0
8269.0
100.0
MISSISSIPPI RIVER DELTA
ELBE ESTUARY
PARANÁ DELTA
TAGUS ESTUARY
RHINE-MEUSE-SCHELDT DELTA
GALVESTON BAY
MEKONG DELTA
VENETIAN LAGOON
13 The territory below five meters elevation for each delta and comparison of land uses in the urbanized deltas in the territory below five meters elevation (map and graphic by Nijhuis and Pouderoijen)
20
TAGUS ESTUARY
Forest
Water body
Wetland
Agriculture
Sparsely vegetated
Urban area
GREATER NEW ORLEANS USA
RANDSTAD-HOLLAND NETHERLANDS
VENETO ITALY
GLOBCOVER + VMAP0
VMAP0
GLOBCOVER
MODIS 500
EARTH AT NIGHT
LANDSAT 7
BUENOS AIRES ARGENTINA
14 Comparison of the differences in spatial extent of urban areas from selected global datasets, addressing different types of urbanization in metropolitan areas (≈50 km radius). As this comparison shows, the definition of human built environment cannot be grasped by a single binary definition of urban/rural. Hence the maps over- or underestimate the spatial extent of urban areas depending on the sensor used and the purpose of the map. Urban land cover maps tend to overestimate the urban fabric, such as the popular Earth at Night map does to a greater extent (“over-glow”) and MODIS Urban Land Cover to a lesser extent. To provide a balanced impression of urban settlements in relation to other forms of land use, it was decided to use the urban class from GlobCover. This data is combined with VMAP0 to correct underestimation common to these multi-class land cover maps (compilation by Nijhuis and Pouderoijen)
21
61 GlobCover (GLOBC) 62 Vector Map level Zero (VMAP0) (Danko 1992)
22
9 8 7 6 5 4 3 2 1
ON
Y
GO
BA N
UA
15 Comparison of urban area in the territory below five meters elevation (graphic by Nijhuis and Pouderoijen)
AN TI NE VE
GA
LV
ES
LA
TO
ST SE GU TA
EL
BE
ES
TU
DE G ON EK M
RY
Y AR
A LT
TA EL SD RM
DE NÁ RA PA
SI
SS
IP
PI
RI
VE
R
DE
LT
LT
A
A
0
IS
IN CONCLUSION This chapter has provided some important clues and background for mapping and comparing urbanized deltas worldwide. It stressed that systematic study of urbanized deltas is essential and that describing, comparing and classifying them is the basis for knowledge-based planning and design. It utilized GIS as a tool for acquiring knowledge, using modelling, analysis and visual representation of high-quality global datasets. The synoptic overview of environmental conditions and human activities which has been presented here will be augmented by in-depth elaborations of each delta under investigation in the chapters to follow, stressing the interdependency of issues on different scale-levels. The combination of a synoptic overview and in-depth knowledge enables researchers to explore the similarities and differences of the various deltas as complex systems. Mapping urbanized deltas helps to understand mutual relations among the different components within and between different deltas, providing new perspectives on how to enhance their adaptability and sustainable urban development.
% URBAN AREA < 5 M ELEVATION
M
In order to provide a balanced impression of urban settlements in relation to other forms of land use, it was decided to use the urban definitions from the global land cover data.61 Since these maps tend to underestimate the spatial extent of urban areas, they were complemented with data from a consistent worldwide vector map 62 (Figures 14 and 15).
Mississippi River Delta USA RICHARD CAMPANELLA
The restoration of conditions for fluidity will be the only way for this region to survive in the long term. 23
Mississippi River Delta USA
Alexandria
Baton Rouge
Lafayette New Orleans
0 Originally started on the natural levees of the Mississippi River, the Greater New Orleans Region has been developed into an urban enclave in the middle of the swamps of the delta with 1.4 million inhabitants (map by Nijhuis and Pouderoijen, TU Delft)
24
50 km
Environmental conditions and human activities (maps by Nijhuis and Pouderoijen, TU Delft)
Substratum
Climate
Agricultural land use
Transportation networks
Substratum The Mississippi River Delta is part of a 18,000 km2 floodplain (< 5 m Mean Sea Level). The Mississippi is the 4th longest river of the world, with a length of about 6,000 km, draining 41% of the US mainland. The river discharges 15,500 m3/ sec on average and has a high sediment load of 210 Mt/year, which caused the development of the typical ‘bird-foot’ form of the delta. Because of canalization of the river and oil- and gas-extraction, the wetlands of the delta are disappearing. Since 1930, 5,000 square kilometers have been lost.
Climate The delta is located in a humid temperate region with an average annual precipitation of 1,500 mm produced by a mix of winter snowfall, frontal and convective storms, but with the maximum runoff in spring. The average temperature varies from 3 °C in winter to 32 °C in summer. Occasionally, hurricanes threaten the region with extreme winds and high water.
Agricultural land use The coastal plain is dominated by wetlands and fresh water bodies and there is only 10% agricultural land use, mainly grassland. The delta has a flourishing fish- and shellfish-industry.
Transportation networks The Ports of New Orleans and South Lousiana form the 2nd largest port-complex of the US. The Louisiana Offshore Oil Port (LOOP) is a deep water port in the Gulf of Mexico off the coast of Louisiana near the town of Port Fourchon. The Gulf of Mexico has a dense network of oil-platforms and pipelines.
25
3
4
3 New Orleans between Mississippi River (right) and Lake Pontchartrain (left), looking to the east (source: Joan Hoal H3 Studio, 2008) 4 Outfall canal with flood walls; downtown New Orleans in the background
26
Understanding how humans have urbanized the delta of the Mississippi River rests upon an appreciation of how this system formed and how it responded to intervention.1 Once we peer below the humanized overlay to the underlying alluvium, it becomes apparent that every sediment particle is associated with ground water, and the ground water with the adjacent river. Deltas being products of their hinterlands, the muddy fresh current arriving from upcountry becomes equally relevant, and because oceans also shape deltas, so too do their tides, currents, depths, and salinities. Fluidity, volatility, and the eternal ebb-andflow of liminal conditions characterize the deltaic environments of the world; they are the bellwethers and microcosms of larger spaces and forces. This chapter presents the Mississippi River Delta, with New Orleans as its primary metropolis, as an example of a river delta “hardened” by human intervention from a situation of fluidity to rigidity. This change occasioned a century of geophysical deterioration climaxed by the disastrous effects of Hurricane Katrina in 2005. The restoration of conditions for fluidity will be the only way for this region to survive in the long term.
FLUIDITY: THE FORMATION OF A DELTAIC LANDSCAPE Over eons, what is now southern Louisiana alternated between terrestrial and aquatic states as sea levels fluctuated with global climate changes. When temperatures cooled, water froze into glaciers and lowered sea level, dewatering shallow coasts and turning them into plains. When temperatures warmed, water released from the glaciers flowed back into the world’s oceans and returned coastal lowlands to the hydrosphere. At glacial maximum, eighteen thousand years ago, vast quantities of water lay frozen upon earthen surfaces at the expense of the world’s oceans, stretching in North America as far south as present-day Cairo, Illinois. As the ice sheets receded with rising temperatures, they resculpted the Missouri drainage system to the west, the Upper Mississippi to the north, and the Ohio to the east, and the three systems merged to form the lower Mississippi River. Most of its sediment load derived from the drier prairie and mountains of the West, whereas most of its water volume came from the moist hardwood forests of the East. At the apex of a down-warping of the Earth’s crust known as the Mississippi Embayment, this dramatically augmented river delivered increasing quantities of sediment-laden water toward the Gulf of Mexico. Because sea level continued to rise, the river gradient weakened, water velocity slowed, and alluvium settled to the bed, sedimenting the embayment. What resulted was a marshy landscape of meandering and braided channels. It was, however, a valley and not a delta, because bluffs and terraces constrained the channel to a broad meander belt. These are the bottomlands of the present-day states of Arkansas, Tennessee, Mississippi, and Louisiana (Figure 5). That meager topography petered out south of present-day Baton Rouge, where, as recently as seven thousand years ago, the Mississippi disembogued into the Gulf of Mexico. When the water column suddenly hit the Gulf, it dumped its alluvium upon the hard compacted clay sea floor, until the deposition rose and broke the sea surface, transforming it to saline marshes and eventually to freshwater swamps laced with ridges. Because of the immense water volume and sediment load vis-à-vis relatively weak tides and waves, the river overpowered the Gulf and extended the coastline outward. It helped also that global warming slowed somewhat in these millennia, giving a chance
for sediment consolidation to outpace the level of the sea. The mouth of the Mississippi River extended farther and wider into the Gulf of Mexico, creating a network of active and abandoned deltaic complexes—a deltaic plain—that would eventually become southeastern Louisiana and home to New Orleans. Delta-building also occurred along the river’s flanks. Springtime overflows spread a thin sheet of excess water across the plain, enriching swamp and marsh ecosystems by pushing back salt water and adding new sediment. By the time of European contact, areas closest to the Mississippi River had risen about three to five meters above sea level (natural levees), while those far from the river lay only a dozen centimeters above a brackish tidal lagoon that French colonials described as a lac and named ‘Pontchartrain.’ Rich alluvial soils and a subtropical climate fostered verdant flora and abundant fauna on the deltaic plain. For this reason, humans occupied it at surprisingly high populations. Evidence that indigenous peoples cleared forest, burned fields, transported species, and raised crops prevails in archeological records as well as historical accounts; the delta was not the forest primeval. Natives negotiated the watery semi-earth by shoring up elevations through middens and other anthropogenic topography; mostly, however, they adapted to it by shifting their encampments to higher ground when high water came. Given their technological limitations, they viewed deltas as conditions to which one must conform, rather than problems to be fixed. Adapting to deltaic fluidity represented an occasional cost associated with the benefits of copious natural resources. Such a strategy aligns with the needs of semi-nomadic hunter-gather societies. It does not, however, serve the aims of agricultural and resource-extraction-based societies seeking to expand hinterland-foreland domains, subordinate natives, and elbow-out similarly motivated competitors toward the establishment of mercantilist nodes. For these societies, deltaic fluidity represented an intolerable problem that demanded a solution. And the premier tool to introduce order to this disorderly environment was the one feature utterly absent in deltas: the hard line.
1 This chapter is an adapted version of the article by Richard Campanella (2014), ‘Fluidity, Rigidity and Consequence. A Comparative Historical Geography of the Mississippi and Senegal River Deltas and the Deltaic Cities of New Orleans and Saint-Louis’, Built Environ ment Vol. 40 no.2.
5 M ississippi River watershed and key features (map by Richard Campanella)
27
6 New Orleans 1863. Urban street patterns on the natural levees of the meandering Mississippi River. North of the city the marshlands and Lake Pontchartrain. Map by Henry L. Abbot, US War Department (source: New Orleans Historic Collection)
RIGIDITY: URBANIZATION AND ENGINEERING New Orleans’ triumphs and troubles began with its geographical siting. French colonists established New Orleans in 1718 upon an active deltaic plain roughly 150 kilometers above the river’s mouth. From the European standpoint, hard lines and orthogonal angles introduced order to disorder, civilization to wilderness, godliness to the heathen, and the power of the crown to the cowering native. While the selected site (low in elevation, high in soil water, flooded regularly by the Mississippi and occasionally by gulf storms) appeared precarious, its geographical situation (that is, how it connected with the rest of the world) seemed enticingly strategic. A city near the mouth of North America’s greatest river perfectly positioned French colonials to defend and exploit the unknown riches of the vast Mississippi Valley from Spanish and English interests. Other potential sites were either more precarious, or markedly less strategic. Should New Orleans be built on the safest site, despite its inconvenience? Or should it exploit the most strategic situation, despite its hazards? French authorities opted for the latter, setting the stage for three centuries of blessings and curses.2 Under American rule, New Orleans saw its population double roughly every fifteen years. Accompanying the growth were myriad alterations to New Orleans’ physical environment. Government and private entities excavated canals for both navigation and drainage, making the city more economically viable but allowing salt water to intrude inland. Former sugar plantations were urbanized and incorporated into the city limits. As Figure
28
6 shows, in 1863 the city comprised a series of gridiron street patterns following the natural levees of the meandering river (Figure 6 ). Recognizing flooding concerns but principally interested in navigation, the federal government funded two surveys in the 1850s to understand how the Mississippi River might be controlled. One was led by the military engineer Andrew Atkinson Humphreys, who theorized that a river restrained strictly by levees would dredge its own bed and thus create storage space for the excess water. Humphreys, in short, recommended rigidity. Charles Ellet, on the other hand, was a civil engineer and suggested a comprehensive approach that included levees but also outlets and reservoirs to allow excess water to be stored laterally—in effect, conceding to fluidity.3 After Congress federalized levee construction and control of the Mississippi in 1879, it officially adopted the ‘levee-only’ policy advocated by Humphreys in the 1850s, and proceeded to seal off all outlets and distributaries. What they eschewed, to their later regret, were all forms of spillways and lateral water storage recommended by Ellet. While the massive earthen wall arising around New Orleans during the 1890s-1920s gave citizens a sense of security, the levees-only policy grew increasingly problematic geophysically. Humphreys thought a leveed river would scour out its bottom and make room for excess water; in fact, the river dropped its suspended sediment into the bedload and raised the bottom— which thus raised the top, which required levees to be height-
2 C ampanella 2006, 2008, 2010 3 Barry 1997
GONZALES
LAKE MAUREPAS
LAKE PONTCHARTRAIN
LAKE BORGNE
M IS SI SS
IP PI
NEW ORLEANS
LAC DES ALLEMANDS
LAKE CATAOUATCHE
LAKE SALVADOR
HAUMA
0
10 KM
7
MISSIS SIPPI
AT CH
PONTCHARTRAIN GULF CLOSURE (PLAN)
AF AL AY A
SPILLWAY
NEW ORLEANS
DIVERSIONS (SEDIMENT FEEDERS)
E
R O
S
DIVERSIONS (SEDIMENT FEEDERS)
I
O
D
N
E
P O
S
I
T
O
R
N
O
S I O
N
E R O
S
I O
E
I
N
0
25 KM
WATER SYSTEM MISSISSIPPI
8
7 Urban patterns in the Mississippi River Delta (map by Must Urbanism) 8 Mississippi River Delta: water system (map by Must Urbanism)
29
9 New Orleans current situation. Two zones of gridiron patterns: On the natural levees alongside the river, and in the drained marshes along Lake Pontchartrain. In between a vast peripheral zone (Map by Palmbout Urban Landscapes, for GNO Urban Water Plan 2013)
ened, which iterated the cycle. Higher and stronger grew the levees, raising the entire river dangerously above the landscape. A sufficiently massive rainstorm finally occurred in 1927, leading to epic flooding throughout the Mississippi Valley. Commercial interests and state allies, worried about potential flooding in New Orleans, strong-armed reluctant federal authorities to dynamite a levee at the expense of thousands of poor rural folk. The blast, which diverted excess water in the form of an emergency spillway, dramatically ended the levees-only policy. Ellet was right: humans should accommodate the Mississippi by allowing some level of fluidity. The 1927 deluge inspired passage of the Mississippi River and Tributaries Act and the Flood Control Act, which cemented the federal government’s commitment to a massively augmented flood control system. Even as artificial levees were being raised circa-1900 to prevent the Mississippi overtopping, the vast majority of the New Orleans population remained on the higher natural levee and eschewed the backswamp. Historically New Orleanians loathed the lowlands, associated them with miasmas and perceiving them as inhospitable and unsightly. Technological breakthroughs in the Progressive Era changed that mindset; increasingly, residents viewed swamps as potential land for modern neighborhoods, while authorities saw taxable real estate and bankers saw lucrative house-building and mortgage-lending opportunities. Following research and design during 1893-1895 and financing in 1899, the Sewerage and Water Board proceeded to build a world-class municipal system to drain the backswamp. It used natural topography to collect runoff in low spots, and pumps to propel the water out newly excavated and/or widened outfall canals and into Lake Pontchartrain. The promethean drainage intervention allowed citizens to move northward into former lowlands, confident
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that topographical and hydrological restraints had been ‘fixed.’ So secure were New Orleanians in their technological salvation that the tradition of building houses raised on piers was abandoned by mid-century in favor of cheaper slab-at-grade foundations. The intervention, however, came at a cost. Drainage and levees removed the water component from the soil body, which allowed organic matter to decompose. Fine alluvium settled into the air spaces, compacting the soil and lowering its elevation. Starting in the early 1900s, parts of New Orleans began to subside below sea level. Pumps, once located behind the populated area, but now surrounded by it, expelled runoff into the lake through outfall canals which increasingly rose above the adjacent neighborhoods—even as they grew in population. While the vast majority of New Orleans’ 287,104 residents lived above sea level in 1900, only 48 percent remained above sea level in 1960, when the city’s population peaked at 627,525. Fully 321,000 New Orleanians by this time resided in the twentieth-century subdivisions built on lakeside low-lands—which had already dropped by one to two meters below sea level. The drainage and urbanization of the swamps had enormous consequences for the spatial structure of the city. The new suburban areas in the former marshlands formed orthogonal plats aligned with the bight of Lake Pontchartrain. Between this 20th-century lakeside suburb and the 19th- and 18th-century meandering patterns on the natural levees by the river, an interstitial area of amorphous ingresses and egresses can be found. This in-between zone is dominated by highways, railroads and industrial buildings and has a rather chaotic and peripheral character, confusing visitors and even locals who enter it (Figure 9). In the 20th-century areas within New Orleans itself, such as Lakeview and Gentilly, the outfall-canals, necessary for the discharge of
10 Coastal land loss on the Mississippi River Deltaic Plain of southern Louisiana. All areas in red have eroded into the Gulf of Mexico within a single human lifetime (Map by Richard Campanella)
storm-water to Lake Pontchartrain, rise high above the houses because the adjacent lands subsided below sea level on account of the drainage. Because of the direct connection of these canals with the lake, the canals had to be lined with concrete flood walls, barricading runoff as it drains from the city but also separating adjacent neighborhoods from each other (Figure 4). A century of coastal manipulation, meanwhile, had brought gulf waters to the door of the sinking metropolis. Three major navigation canals —the Industrial (1918-1923), the Gulf Intracoastal Waterway (1930s-1940s), and the Mississippi River-Gulf Outlet (MR-GO, 1958-1968)— were constructed to improve accessibility of the Port of New Orleans as well as the adjacent Port of South Louisiana, which stretches almost 100 km along the Mississippi and is the largest port complex of the USA. But the new canals also allowed salt water to lap against the perimeter of the bowl-shaped metropolis. The salinity killed cypress swamps and allowed surge-prone waters to encroach close to populated areas. So too did an extensive network of coastal oil and gas canals, which increased land/water interfaces, ergo opportunities for erosion, intrusion, and swamp die-off. Their attendant guide levees and spoil banks channelized storm surges and impounded salt water. Concurrently, the near-total control of the Mississippi through artificial levees had starved the delta of replenishing freshwater and sediments. As a result, Louisiana lost nearly 5000 square kilometers of coastal wetlands—about one-third of the Mississippi Delta— since the 1930s. Eighty square kilometers disappeared annually during the 1970s-1980s, a loss over twenty times swifter than the Mississippi took to build those wetlands in the previous 7200 years. Coastal wetlands protect New Orleans because they buffer hurricane-induced gulf surges from reaching the city: every five to fifteen linear kilometers of wetlands absorb roughly one vertical meter of storm surge. Loss of that critical natural buffer existentially threatens New Orleans (Figure 10). On August 29, 2005, Hurricane Katrina’s residual Category-5 surge overtopped, undermined, or disintegrated certain levees and floodwalls, transforming the otherwise weakening Category 2-3 wind event into a catastrophic deluge. After a harrowing week, stranded citizens were finally evacuated to safety; fatalities eventually totaled nearly 1600. New Orleanians today are quick to point out that failure of federal levees, not Hurricane Katrina per se, flooded their city, and that the tragedy constitut-
ed a manmade and not a natural disaster. In truth, Katrina was a naturally triggered surge that humans planned to resist, engineered to resist, and failed to resist—because of shoddy and underfunded workmanship but also because a century’s worth of anthropogenic deltaic deterioration had made that surge so much harder to resist.
CHALLENGES AND FUTURE PERSPECTIVES After the 2005 catastrophe, the US Army Corps of Engineers immediately focused on repair, reinforcement and extension of the flood walls surrounding New Orleans, including a new storm surge barrier in the “funnel” of the two navigation canals at the east side. But in the long term this structural risk-reduction device will reduce less and less risk and will eventually become neutralized. The Mississippi Delta is dangerously out-of-equilibrium with its constitutional forces and environs. If radical coastal restoration does not create new land at a pace faster than the sea is rising within the next two decades, it may be fighting a losing battle and face disappearance in the 2100s. It is necessary to restore deltaic processes—by, essentially, reintroducing a sort of controlled fluidity. While this argument, which was addressed in 1990, has hardly garnered national prioritization, it is gaining momentum. The State of Louisiana took the initiative to consolidate numerous agencies into the Louisiana Coastal Protection and Restoration Authority (LACPRA), which enabled federal authorities and funding to flow into a single organizational entity. LACPRA has since produced a Master Plan detailing scores of ‘fluidity’ projects dispersed throughout key eroding areas. They range from river diversions, to sediment dredging and pipelining projects, to shoreline protection, to barrier island restoration. In 2014, a design-competition ‘Changing Course’ has been organized, aiming to elaborate the Master Plan in concrete projects. Within New Orleans, local professionals took the initiative to form a team combining Dutch hydrological engineers and designers with local experts with the aim of envisioning a drainage system for the metropolitan region that slows, stores, and utilizes as much rainwater as possible before pumping out the excess, with the goal of recharging the groundwater and slowing further subsidence. The vision, originally nicknamed ‘Dutch Dialogues’ and now elaborated as the Greater New Orleans Ur-
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11 Bird’s-eye view of New Orleans as a restored deltaic city, after implementation of the GNO Urban Water Plan (Drawing by Palmbout Urban Landscapes, for GNO Urban Water Plan 2013)
ban Water Plan, endeavors to demonstrate its viability through a series of pilot projects.4 Instead of directing the whole drainage system to Lake Pontchartrain, the GNO Urban Water Plan proposes considering the Gentilly Ridge (an old riverbed crossing the city from west to east) as a watershed, and discharging the water south of it to the Mississippi and north of it to Lake Pontchartrain. This implies a total reorganization of the drainage system, but it will also provide the opportunity to transform the aforementioned interstitial zone between the historic and modern street grids into a central park system with plenty of water-storage capacity. The plan also proposes lowering the flood walls of the outfall canals and transforming the beds into attractive amenities enhancing and connecting adjacent neighborhoods instead of separating them with an unsightly nuisance. All together, the GNO Urban Water Plan aims not only to create a more sustainable urban water management system, but also to improve the spatial structure of the city. It is hoped that New Orleans will shift from a posture of resisting the fluidity of the delta, to a deltaic city embracing and contributing to the region’s natural fluidity (Figure 11). Can the Mississippi Delta be restored so that its principal deltaic city may persist? Yes, but not without some pain. Whereas a problem typically ends with a solution, a dilemma ends with a choice—a difficult value judgment that yields at least some unpleasant consequences and unhappy stakehold-
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ers. Saving deteriorating deltas will mean that some human communities, despite their historical, cultural, and economic significance, will have to relocate to minimize future loss and allow aggressive coastal restoration to proceed. Resistance will be passionate and often imbued with social tensions and historical distrusts. But the geophysical realities of sea-level rise demand that we make mature decisions about where and how humans inhabit deltas—or else they will be made for us.
4 Waggonner Ball 2013
Paraná Delta Argentina VERONICA ZAGARE, WOLBERT VAN DIJK
The fragmented metropo litan expansion collides with a growing delta in constant transformation. 33
Paraná Delta Argentina
Rosario
Buenos Aires
0 Buenos Aires is located at the edge of the higher grounds next to the mudflat. The metropolitan region is home to 12 million people, one third of the population of Argentina. The mudflat of the delta is increasingly used for both shanty towns as well as gated communities (map by Nijhuis and Pouderoijen, TU Delft)
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50 km
Environmental conditions and human activities (maps by Nijhuis and Pouderoijen, TU Delft)
Substratum
Climate
Agricultural land use
Transportation networks
Substratum The delta consists of a floodplain of almost 15,000 km2 (< 5 m Mean Sea Level). The Paraná is the main river, 4,800 km long, with an average discharge of 16,806 m3/sec and a sediment load of 90 Mt/year, which mainly determines the growth of the mudflat at a rate of 50-100 m per year.
Climate The Paraná Delta is located in a subtropical, sub-arid region with hot summers and mild winters with a prevailing south-eastern wind, a mean annual precipitation of 1,146 mm throughout the year, and temperatures varying from 6 °C in winter to 30 °C in summer.
Agricultural land use There is only 10% agricultural land use in the floodplain, which mainly consists of wetlands and fresh water bodies.
Transportation networks The delta is crossed by only two main roads, connecting the cities where the ports and airports are located; local roads penetrate the wetlands and several small ports support local fleets.
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3
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3 View of Buenos Aires from the coast of the Rio de la Plata towards the Lower Parana Delta, 2013 (photograph by Zagare) 4 Panoramic section of the waterfront along the public space called “Paseo Victorica” in Tigre, 2013 (photograph by Zagare)
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The Paraná Delta presents a dichotomy between the wild and changing condition of its islands and the urban growth along its edges. This chapter analyses the spatial development of the area, especially in the Lower Paraná Delta, where the Paraná River flows into the Rio de la Plata. In this section of the delta, the contrasts intensify due to the proximity to the Buenos Aires Metropolitan Area, which is the major conurbation of the country. There, the unplanned growth of the metropolis has led to the privatization and polarization of the space, limiting the relation of the citizens with water and increasing their vulnerability to floods. In other words, the fragmented metropolitan expansion collides with a growing delta in constant transformation, creating an imperative need for an integral management of the delta related to urban development in a context of governance.
LANDSCAPE AND GEOMORPHOLOGY The Paraná Delta is a complex estuarine model because, unlike most other deltas, it does not discharge its sediments directly to the sea, but through the estuary of the Rio de la Plata.1 From a geographic perspective, the delta was originally restricted to a 15,000 km2 plain which spreads over three provinces of Argentina (Buenos Aires, Santa Fe and Entre Rios) (Figure 5). However, from a geomorphologic point of view, the delta can be analyzed together with the estuary due to the interaction between the delta plain and its natural limit, the Rio de la Plata.2 Following the distinction of the components of deltas developed by Hori and Saito (2003), it is possible to observe that the subaqueous part of the Paraná Delta overlaps with almost the entire Rio de la Plata riverbed. This indicates the influence of the sedimentary processes that form the Delta over the estuary and its coastline. In fact, the Paraná River has a discharge of 18,000 m3/sec and transports around 160m tonnes of sediment per year (28% clay, 56% mud and 16% sand). The sand which is deposited at the river mouth increases the length of the delta, while the mud collects and contributes to banks that emerge and become islands.3 The front of the sub-aerial delta is advancing at a rate of 50-100 m per year at the sub-front of Paraná de las Palmas,
which means that it is expected to reach the city of Buenos Aires in 110 years, altering the morphology of its coast and changing the relation between the city and the water (Figure 6).4 Three zones can be distinguished along the 320 km of delta extension: upper, middle and lower (the river mouth). While the hydrology in the upper and middle sections of the delta is based on the pulses of floods and droughts caused by the variability of the river and its tributaries’ flows, the Lower Paraná Delta is also influenced by tides and the phenomenon known as Sudestada, which refers to the persistent southeast winds coming from the Atlantic Ocean.5 Consequently, the risk in the lower delta is associated with the rise of the level of the Rio de la Plata, due in part to sea level rise, but mostly due to the action of the winds which push water into or out of the estuary, thus altering the level of the river. These factors, combined with recurrent heavy rains associated with climate change, block the natural and artificial drainage of the rivers, producing severe flooding along the coasts and along the water courses. Relevance of the system and its ecological services The Paraná Delta is part of a large system which has a vital role not only for the region but also for South American continent in terms of hydrology, natural resources and economic development. The delta drains the second largest river basin of South America (after the Amazon), an area covering 3.1 million km2 in five countries (Argentina, Brazil, Bolivia, Uruguay and Paraguay). According to the Intergovernmental Panel on Climate Change,6 the Rio de la Plata, the Amazon and the Orinoco carry more than 30% of the world’s renewable freshwater into the Atlantic Ocean. From a regional perspective, the Paraná Delta, like other wetlands, provides important ecosystem goods and services. The ecosystem functions are hydrological regulation (flood control, groundwater replenishment and water retention), biogeochemical regulation (transformation and degradation of nutrients and contaminants) and other ecological functions (primary, secondary and tertiary production and maintenance of diversity).7 However, the delta not only regulates the natural dynamics of the system and provides services for the communities along its path, but it also represents a high value in terms of cultural identity.
1 Parker and Marcolini 1992 2 Parker and Marcolini 1992, Cavalotto and Violante 2005 3 Sarubbi et al. 2004 4 ibid. 5 Barros et al. 2003, 2006 6 Magrin et al. 2007 7 Kandus et al. 2010
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5 Geomorphology of the delta and main urban agglomerations (Map by Zagere based on Parker 1992 and Cavalotto and Violante 2005) 6 Advance of the front of the delta (observed and expected) (Map by Zagere based on Sarubbi et al. 2004 and Sarubbi 2007)
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URBAN DEVELOPMENT The Buenos Aires Metropolitan Area A whole network of cities of different sizes and with different specializations is located along the edges of Paraná Delta. Among them, four large urban agglomerations can be distinguished: the Buenos Aires Metropolitan Area – the largest conurbation of Argentina, with a population of around 13 million inhabitants the Gran Rosario Metropolitan Area, La Plata City, and Santa Fe. These agglomerations constitute the wealthiest and more populated economic corridor of the country and converge with the key commercial route of the Mercosur, which connects Santiago de Chile (Chile) with Sao Paulo (Brazil). The Lower Paraná Delta is influenced by the urban development of the Buenos Aires Metropolitan Area, which exerts pressure because of its size, its level of productivity and its elevated growth rate. The metropolis is home to 31% of the national population and contributes 53% of the country’s GDP (Gross Domestic Product) despite the fact that it covers less of 1% of the country’s surface.8 While agricultural activities are relevant, the major importance of the region is linked to industrial activities as well as services, due to the proximity to the Buenos Aires city core and to the ports of Paraná River and Rio de la Plata. Historical evolution of urbanization Before the Spanish colonization, the delta and the coasts of the estuary were inhabited by aboriginal communities. The city of Buenos Aires was settled by the Spanish (first in 1536 and again in 1580) on the bank of the Rio de la Plata. Though it did not have direct contact with the delta, the choice of location was influenced by the navigable waterway of the Paraná River, which was the main route to Paraguay (Figure 9). Years later, the islands of the Lower Paraná Delta were settled by Europeans who cultivated fruits there and logged the forests.9 These settlements were unplanned, disperse and precarious, and the access was difficult because of the lack of infrastructure. The possession and distribution of the plots on the delta was not regulated by the state and at first the area was considered a non-produc tive natural beauty. It was not until the end of the nineteenth century that the lands of the Lower Paraná Delta were measured and legally distributed, with 55% of the islands being transferred to private owners. By that time, the economy of the islands was based on small-scale units of production (family economy) focused on fruits, vegetables and forestry. Meanwhile, from the middle of nineteenth century, Buenos Aires expanded rapidly as a metropolis, due to its incorporation into the international market. The agricultural-export model and the high British demand for raw materials and food led to the growth of the city and the port (until the world economic crisis of 1929). A decade later, a vigorous industrialization process encouraged the development of new urban centres relatively close to the city centre (from five to twenty km). These new centres offered commercial spaces, banks, and health and education services.10 Industrialization had a radical impact on the productive system of the Lower Paraná Delta as the size of production increased, and as forestry gained in importance. This change implied new kinds of producers, new technologies, and different working processes. The new actors involved in the delta were large companies or wealthy entrepreneurs who bought the land from the original owners, who migrated inland to find new opportunities.11 In the last quarter of the twentieth century, the metropolitan expansion of Buenos Aires was characterized by a model of urban growth of spatial dispersion but global integration,12 which led to a social, economical and urban restructuring.
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That process exacerbated during the 1990s, when the liberal economic model led to the expansion of new urban centres, establishing a more complex network and creating new spatial relations along highways, instead of along the old railway system. Those years were characterized by structural political and economic changes such as state reform, economic deregulation, monetary stabilization (making the currency convertible), construction of transportation infrastructure, privatization of public services, and new urban laws.13 The withdrawal of the state as regulator of territorial planning encouraged foreign investors to finance private urban developments, changing occupation patterns and leading to a new configuration of the space. Large plots were appropriated by private investors near the river, especially in the Lower Paraná Delta, where they then developed gated communities (neighbourhoods with a closed perimeter, isolated from the rest of the urban fabric). Directed towards upper-middle and higher income groups, these developments were certainly successful. The number of private urbanizations increased from 100 to 350 between 1995 and 2000 and today has reached 400. According to Ciccolella (2002) and Cohen (2007), the surface area of gated communities is nearly 500 km2 (2.5 times the area of Buenos Aires city). In 2001, the end of currency convertibility caused a national political and socio-economic crisis. This led to negative effects such as increased unemployment and the rise in the number of informal settlements, usually called villas or asentamientos, according to their internal structure and origin. These are settlements on land without infrastructure or services, illegally occupied by lower socio-economic groups to fulfil the demand for residential space. It is estimated that between 2001 and 2005, 6 of every 10 new inhabitants of the Metropolitan Area established themselves in an informal settlement.14 The result of the historical process of occupation of the mainland metropolitan area is a polarised scenario of spatial segregation and social inequities. Exclusive gated communities, traditional urban areas, and informal settlements are located next to each other, on lands sensitive to flooding. The banks of the main water courses are mostly privatized, so the traditional urban fabric does not have much contact with the water except in certain places in public areas. Furthermore, due to the lack of an integral public flood defence, private landlords protect their plots by building their own dikes or embankments, which can negatively affect surrounding constructions, which remain under the flood level. On the islands, the expansion of this metropolitan pattern is expressed in the intrusion of typologies related to the gated communities which modify the natural topography of the land and the water courses, affecting the biodiversity and introducing foreign species to the environment. In addition, a contrasting situation has developed between the first and second sections of islands. While the first section (part of the Municipality of Tigre) has gained popularity thanks to tourism and recreation activities, the second section (part of the Municipality of San Fernando) has lost population due to the lack of accessibility and decrease of productivity.
CHALLENGES AND FUTURE PERSPECTIVES The Paraná Delta is divided by a multiplicity of boundaries into often overlapping jurisdictional authorities, with 3 sub-national jurisdictions (provinces) and 18 local governments (municipalities). The overlapping of governments, the lack of coordination and their conflicting visions on the area’s role makes designing and implementing management policies and strategies inade-
8 AABA 2010 9 Galafassi 1996, Sierra 1967 10 Ciccolella 2002 11 Galafassi 1996 12 Ciccolella et al. 2006 13 Ciccolella 2002, 2006, AABA 2010, Zagare 2012 14 Cravino et al. 2009
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7 Urban patterns related to the Paraná delta (map by Must Urbanism) 8 Water system (map by Must Urbanism) 9 Growth of the Buenos Aires Metropolitan Area (Map by Zagere based on Vapñarsky 2000)
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10 Possible future perspective of the Buenos Aires waterfront and Parana Delta. The new silted-up land in front of the city might be used for a new waterfront park system, connecting the city with the delta landscape (drawing by Wolbert van Dijk)
quate, fragmentary and unsuccessful.15 In the last decades, the power to decide over territorial matters was transferred to the local level. This placed extra pressures on municipal governments due to their lack of funds, but also led to the development of local strategic plans and new tools for citizen participation. In the case of the Lower Paraná Delta, the local scale seems to be the ideal stage for overcoming the challenge of developing accurate territorial plans to encourage stakeholder participation and inter-municipal cooperation in a context of governance. It should also be a good starting point to understanding, communicating and adapting environmental policy to integrate it with legislation and plans at the local level. Another challenge for the area is finding innovative solutions to the present spatial conflicts caused by lack of connections. Spatial barriers block the connections between the different landscapes and also between social groups. The city does not have many connections with the water in terms of public space. Almost the entire waterfront is privatized and utilized for ports, industries, recreation areas, and private marinas, leaving few spaces where social groups can interact. In the past, in the city of Buenos Aires and in some other municipalities along the delta, the limit between the city and the river was a cliff, also called the Barranca, which served as a natural protection to sea level rise. Then, the city grew down the cliff, together with some urban elements such as the Recovas. Those original spaces, which were totally integrated into the urban fabric, encouraged public use and were representative enough to become the identity of the water front. At present, a possible action to increase spatial connections and face the changing coastline is to revise traditional urban elements and propose innovative spaces to deal with the advancing waterfront and increase social cohesion through territorial decisions. The new islands consolidated by the sedimentation process are called land in formation and must be considered a reserve with high potential to create public spaces of
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wetland restoration, which could be integrated into the existing protected areas, such as the Biosphere Reserve of the islands of San Fernando. On the mainland, spatial planning should consider ways to develop and implement legal instruments to decrease spatial barriers and balance land uses, since the increase of gated communities has diminished the internal relations within the traditional urban patterns. The need to improve fluvial transportation coverage is another key-issue in order to guarantee equal conditions to the islands of the first and second sections of the Lower Paraná Delta, and so equalize their possibilities for social and economic development. When we considering the impact of climate change, given the fact that the area is mainly affected by floods along the coasts, around the water courses, and in the low lands between privately made embankments, increasing the adaptive capacity of the area should also be considered a priority. A future vision could include a system of public green spaces which help to connect the unconnected while at the same time increasing rainwater storage during extreme climate events. These spaces could become a new urban element that contributes to the identity of the area. Although some of the issues we have mentioned are spatial matters, many other associated challenges face this area, such as guaranteeing all social groups access to lands with appropriate infrastructure, providing sufficient services to all areas of the territory, improving productive activities and port development while taking their environmental impacts into account, and articulating new spaces of dialogue between stakeholders. Local governments have to deal with daily problems and future challenges at the same time. Universities, as relevant actors, can play an important role in analysing the historical processes and present situation, and also in proposing different possibilities or visions for the area in order to resolve the cross-sectoral discussion (Figure 10).
15 Zagare 2012
Rhine-MeuseScheldt Delta Netherlands HAN MEYER, STEFFEN NIJHUIS, ROBERT BROESI
In the Rotterdam region and the Southwest delta, flood defence, urban development, environmental issues and port economy are interwoven with each other in a complex way. 41
Rhine-Meuse-Scheldt Delta Netherlands
Amsterdam
Rotterdam
Ruhr region
Antwerp
Cologne Brussel
0 The Rhine-Meuse-Scheldt Delta contains a pattern of compact mid-size cities, resulting in Randstad-Holland as a main agglomeration with 6.5 million inhabitants (map by Nijhuis and Pouderoijen, TU Delft)
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50 km
Environmental conditions and human activities (maps by Nijhuis and Pouderoijen, TU Delft)
Substratum
Climate
Agricultural land use
Transportation networks
Substratum The delta is located in the second largest deltaic plain of this series and consists of about 20,000 km2 (< 5 m Mean Sea Level). The Rhine is the main river and with a length of 1,400 km the second longest river in Europe; the river has an average discharge of 2,200 m3/sec and a low sediment load of 0.07 Mt/year. The decrease of sedimentation-transport has resulted in an increasing erosion of coastline and estuaries, and the centuries-long drainage of the polders has resulted in substantial land-subsidence
Climate Climate variability is determined by a humid and temperate oceanic climate caused by the prevailing south-western wind; precipitation occurs throughout the year with a mean annual amount of 780 mm; average temperatures vary from 0 °C in winter to 21 °C in summer
Agricultural land use The floodplain consists of 77% agricultural land, mainly in use as grassland and arable land. A relatively small part of the agricultural land is used for greenhouses, which have a relatively large share in the total agricultural productivity
Transportation networks The delta is characterised by a dense transportation network of different modalities and transportation hubs such as the port of Rotterdam, which connects the Rhine, as the most important economic artery of Europe, to the rest of the world
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3
4
3 A erial photograph Rotterdam, from east to west (source: Dick Sellenraad Aeroview 2005) 4 Rotterdam riverfront. View from west to east. At right, the ‘Kop van Zuid’ area, with ‘De Rotterdam’-building under construction (source: Han Meyer 2013)
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Through the centuries, urban development and water management have been strongly related to each other in the Dutch delta of Rhine, Meuse and Scheldt (RMS-delta). Urban and economic development resulted in the formation of a number of important port cities: Amsterdam, Rotterdam, Antwerp, as well as a series of smaller port cities (Figure 5). In 2008 the Dutch government installed a Delta committee, which recommended a fundamental update of the flood defence system in the Netherlands 1, which should result in a new ‘delta program’. One of the most urgent problems to be solved in this delta program is the future of the Rotterdam region and the Southwest delta, where flood defence, urban development, environmental issues and port economy are interwoven with each other in a complex way. This chapter addresses the need for a fundamental transition towards a new approach to delta management, which will also create new opportunities for urban development.
LANDSCAPE AND GEOMORPHOLOGY The situation of the Rhine, Meuse and Scheldt Delta is defined by the transport of river sediments, combined with strong tidal movements and sea currents. The result is a delta with a sand barrier coastline of beaches and dunes in front of the alluvial wetlands. This coastline has been formed of marine sediments, transported by the dominant Gulf Stream and tidal currents. Between this sand barrier coastline and the alluvial wetlands, a lagoon came into existence. The northern part of the Netherlands still shows this model of a lagoon behind a series of sand barrier islands. Over many centuries, the western part of the lagoon was filled up by vegetation, resulting in layers of peat, four to six meters thick. This peat landscape was interwoven with a vascular network of creeks and small rivers, which functioned as a natural drainage system 2 (Figure 6). The result is a delta which can be defined, according to the delta typology mentioned in the introduction, as a sea dominated delta. The Rhine (the present Oude Rijn) played a main role: first, the river was the central axis of the complex of drainage systems in the whole region. All the superfluous water from the peat-lands of central Holland and Utrecht was transported to and drained into this river by newly dug drainage systems. Second, because of the growing population and increasing economic activity in the region, the cities along the river gained in importance as regional and trade centres. During the 10th and 11th centuries, important changes took place in the water system. What had been the mouth of the Rhine (the current ‘Oude Rijn’) silted up. Moreover, heavy storms created new sea inlets in the Southwest, and Lake Almere came in open connection to the sea, which created the Zuiderzee. In this process, the river Rhine found a new outlet to the sea to the south, interweaving with the river Meuse and creating a landscape of estuaries, wetlands and islands which we call the Southwest Delta today.
URBAN DEVELOPMENT Polders and cities as hydraulic constructions The new sea inlets of the Zuiderzee and the Southwest Delta offered new opportunities for trading routes as well as for discharge of the drainage systems. In order to profit from these opportunities, a complete reorientation of the drainage system as well as of the spatial structure of the urban system was necessary. At the same time, it was necessary to create a defence against flooding from the IJ and from the Meuse mouth. The
5 5 The Dutch Delta, looking from the South to the North. Top-right Amsterdam; in the middle Rotterdam, at the bottom Antwerp, 2006 (source: Atlas Rijn-Schelde delta) 6 Paleogeographic reconstruction of the Dutch Delta in 800 A.D. (source: Meyer and Nijhuis, 2013) 7 The Netherlands 1600. The emphasis of urban development has moved to the edges of central Holland, linking to the Zuiderzee (Amsterdam) and Meuse-mouth (Rotterdam) (source: Meyer and Nijhuis, 2013)
6
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1 Delta committee 2008 2 Van de Ven 2004, Nijhuis and Bobbink 2010
45
8 T he growth of the polder-islands of the Southwest Delta, with towns and canals (map by authors) 9 Fragment of the island Goeree-Overflakkee, with different ‘generations’ of polder-units and polder-towns (map by Pouderoijen, TU Delft)
Maassluis Schiedam Vlaardingen
Brielle
Ridderkerk
Heenvliet Geervliet Abbenbroek
Heerjansdam
Hellevoetsluis Goedereede
Simonshaven
Zuidland
Stellendam Piershil Goudswaard
Maasdam ‘s-Gravendeel Klaaswaal
Middelharnis Dirksland Scharendijke
Strijen
Stad aan ‘t Haringvliet
Numansdorp
Brouwershaven
Schelphoek Oude - Tonge Burghuis
Hooge Zwaluwe
Ooltgensplaat Sirjansland Klundert Zierikzee Zevenbergen
Oosterhout
Dinteloord
Colijnsplaat Stavenisse
Steenbergen
Kamperland
Domburg
Korgene
Veere
St. Maartensdijk Scherpenisse
Westkapelle
Tholen Wemeldinge Zoutelande
Arnemuiden
Goes
Middelburg
Yerseke
Vlissingen
Typologie stedelijke patronen
Hansweert
Hoedekenskerke
Stedelijke kernen gerelateerd aan sterke zeestromingen
Breskens
- diepe geulen zorgen voor extreem toegankelijke havens maar ook permanente reperatie
Ellewoutsdijk
Hoofdgeulen met sterke stroming langs de kust
Hoofdplaat
Terneuzen
Stedelijke kernen gerelateerd aan aan-en opslibbings processen
Sluis
- veranderende water-land relatie maakt de aanleg van havenkanalen noodzakelijk Philippine
Hulst
Havenkanalen Nieuwe land
Stedelijke kernen gerelateerd aan afdammings processen
- lange waterverbindingen zijn afgesneden of onderbroken door sluizen
Afdamming Afgedamd watersysteem
8
drainage systems were reorganized and linked to the IJ and the Meuse, which gained a new role as the main discharge channels of central Holland 3 (Figure 7). Land owners and local communities started to reclaim the swampy peat lands by constructing drainage systems. This drainage technology led to a drastic subsidence. During seven or eight centuries, some parts in the deltaic area subsided six to eight meters due to drainage, resulting in land five to six meters below mean sea level.4 The central part of Holland (the current ‘Randstad’ area) was transformed from a wet lagoon into a drained and rationalized landscape, surrounded by a main dike ring. Amsterdam at the northern edge and Rotterdam at the southern edge of this dike ring became the most strategic ‘edge-cities’. South of Rotterdam, the Southwest Delta became an archipelago of islands, as a result of the combination of natural sedimentation and man-made polder-constructions. Islands were created by deposits op natural sediment; men started to colonize these islands and surrounded them with dikes to protect the new land against high waters. Outside the flood protected land behind the dikes, the new outer-dike areas grew because of ongoing sediment deposits along the embankments. As soon as the new silted-up land was high and dry enough, the new land was added to the polder-area by constructing new dikes along the edges. This process was repeated several times, resulting in a moving landscape of growing islands. Because of this process, water-oriented towns had to dig canals through the new polder-areas, in order to maintain contact with the open water. Figures 8 and 9 show this process in the Southwest Delta, zooming in on the island of Goeree-Overflakkee. The situation in the Dutch Delta in the early 19th century can be regarded as a mosaic of polders which had transformed almost all the alluvial wetlands into an engineered landscape, defined by dikes, ditches, drainage arteries and dams. Urban settlements were an integral and crucial part of this engineered landscape. The natural dynamics of the delta landscape were used as the fundament for the new infrastructural networks of
46
9
dikes and drainage canals, developed in combination with new urban structures. However, the river channels and estuaries of the Southwest Delta were narrowing and silting up because of the on-going process of sedimentation. As a result, the Dutch rivers flooded frequently because of the lack of discharge possibilities during extreme supply of water.5 Moreover, because of the sedimentation, the rivers and estuaries became too shallow for modern navigation. National regulation of the delta: The controlled delta as a modern project From the second half of the nineteenth century, a fundamental transition took place in the system of the delta. This became possible thanks to the rise of new conditions. The most important condition for these interventions was the birth of the nation state. The brand new nation state of the Netherlands (founded in 1814) considered the water system of the delta as the key to the national economy. A second condition was created by the spectacular developments and innovations in science and technology, which enabled engineers to build flood defence constructions and drainage systems on a gigantic scale.6 The state took the lead in national projects concerning flood defence and river improvements: During the Napoleonic period, Rijkswaterstaat (RWS, National Water Management Agency) was founded as a civic institute in 1798.7 The river system was reorganized by digging new channels like the Nieuwe Waterweg and Noordzeekanaal in the 19th century (Figure 12). This led to an artificial fixation of the main flow of the rivers through the Nieuwe Waterweg, resulting in an improved discharge capacity of the delta area and an improved accessibility of the port of Rotterdam, but also to an increased influence of the sea (and of high water levels of the sea) on the city of Rotterdam.8 In the twentieth century, two serious floods in the northern parts of Holland (1916) and in the Southwest Delta (1953) were the reason for two major hydraulic works, initiated by the national state: The Zuiderzee works and the Delta works.
3 Van Tielhof and Van Dam 2006 4 Van de Ven 2004 5 Buisman 2011 6 Van de Ven 2004 7 Bosch and Van der Ham 1998 8 Van de Ven 2008
ROTTERDAM
NORTH SEA DORDRECHT
HARINGVLIET GREVELINGENMEER
HOLLANDS DIEP
GREVELINGEN
VOLKERAK ZOOMMEER
OOSTERSCHELDE BREDA
VLISSINGEN WESTERSCHELDE
ZEEBRUGGE
BRUGGE 0
ANTWERPEN
10 KM
10
Aanleg Nieuwe Waterweg 1866-72
AMSTERDAM
IJ S
Voornskanaal (1829)
SE
Nieuwe Merwede (1861 - 1874)
L
UTRECHT ARNHEM ROTTERDAM
Bergsche Maas (1888 - 1904)
Wilhelminakanaal (1923)
NIJMEGEN
DELTA WORKS
Prins Hendrikpolder (1910)
Kanaal door Walcheren (1873)
Afdamming Sloe (1872)
Kanaal door Zuid Beveland (1865)
RUHR REGION Afdamming Oosterschelde Westerschelde (1868)
ANTWERPEN
Kanaal van Schipdonk (1860) Inpolderingen rond de Braakman (1845-1918)
Kanaal Dessel-Turnhout-Schoten (1875)
EU
SE
T
Boudewijnkanaal (1905)
M
LD HE SC
BRUGES
Leopoldkanaal (1847)
RH
Kanaal van Gent naar Terneuzen (1827) verbreding (1885)
IN
E
kanaal Brugge-Oostende
Maas-Scheldekanaal (1846)
Kanaal Gent-Brugge Netekanaal
Albertkanaal (1938)
12 0
25 KM
11
10 Urban patterns in the Southwest Delta (map by Must Urbanism) 11 Rhine-Meuse-Scheldt Delta: water system (map by Must Urbanism) 12 River regulation projects in the Southwest Delta, 2nd half 19th century (map by authors)
47
~ 99% - 75%
~ 0% - 20%
~ 1% - 5%
~ 100%
13
14
15
13 Southwest Delta with Delta works, 2000 (map by authors) 14 Rotterdam region: elevations of inner and outer dike areas (source: Meyer and Nijhuis, 2013) 15 Three options for coastal defence approaches and urban development in Scheveningen (source: Atelier Kustkwaliteit and DeFacto) Top: City at the Sea. Hard seabound; flood defence by quay constructions and sheet pilings; dense urban pattern with sea-front boulevard Middle: City behind the Dunes. Soft seabound; extension of beach and dunes in the sea, with ‘urban villas’ in the new dunes Bottom: City in the Sea. Hard seabound. Construction of two right-angled breakwaters; the natural deposits of sand will result in a new ‘urban bay’
48
The construction of the Afsluitdijk (Closing dike) resulted in a shortening of the coastline and a transformation of the Zuiderzee into a fresh water lake. The new Ijsselmeer polders became the prestigious and exemplary model of modern agriculture, showing a new type of efficiently parcelled and extremely fertile agricultural land. But it also provided an opportunity for an experiment in comprehensive spatial planning. A system of new towns and villages was carefully planned and designed. The ambition to define a harmonious spatial relationship between townscape and (polder) landscape played an important role in these plans.9 With the Delta works, the Southwest Delta was transformed from a poor and peripheral series of isolated islands to an industrialized, wealthy and integrated part of the nation (Figure 13). The New Waterway increased in importance; instead of an entrance, it became the central axis of a 100 km2 industrial port area, with the largest port of Europe and the 2nd largest petrochemical refinery centre of the world. Several new industrial areas were also developed in other parts of the Southwest Delta, while agriculture benefited from the new fresh water basins in the area because of the damming of the estuaries. Moreover, the Southwest Delta became an important destination for tourism and recreation. The total result of the Zuiderzee works and Delta works was a shortening of the Dutch coastline from 1400 km in 1930 to only 400 km in 2000.10 The Zuiderzee works and Delta works were the two major parts of the ‘modern project’ of the Dutch state, which aimed to transform the Dutch nation from a fragmented bundle of cities, provinces and islands into a unified, industrialized and prosperous welfare-state. The Zuiderzee works and Delta works were strongly based on the idea that it was possible to regulate and to steer not only the water system, but also the system of urban and agricultural land-use and the natural (biotic) system. This idea of a total, ‘hermetic’ integration of different systems evaporated in the 1980s. Urban land use developed in another direction than was planned. The building of large-scale New Towns in the Southwest Delta, foreseen as necessary in the 1950s and 1960s, was cancelled in the 1970s. Currently, the region is struggling with a shrinking population. Local communities are looking desperately for new opportunities for urban renewal. The strong relation many cities had with the water disappeared and was substituted by an orientation to the road networks. In the urban area of Rotterdam, the new dikes, constructed in the 1950s and 1960s, meant an increased separation between city and river, and between urban and port landscape.11 In the course of the 19th and 20th centuries, the outer dike areas have been raised to a level of 3.20 – 4.00 meters above average sea level. Altogether this development created the strange situation of a river plain area with large and relatively high outer dike area, as an artificial ‘super levee’, containing port facilities and some urban enclaves. Next to this ‘super levee’ we find the urban and agricultural areas, mainly below sea level. The result is the remarkable difference in elevations as shown in Figure 14. The damming of the estuaries resulted in a serious decay of the ecosystems. Many species of fish, shellfish, birds and plants disappeared.12 The environmental decay of the delta became an issue of public and political concern. The first sign of the influence of this attention to the environment in the Netherlands was the changing concept for the East Scheldt storm surge barrier in the 1970s, maintaining the East Scheldt as a brackish and tidal sea arm.13 At present, the repair of the estuarine nature in the whole delta is a central matter of attention for NGOs like the World Wildlife Fund.14 The role of the ports is also changing. Instead of competing with each other, the ports in the
16 Two options for discharge of the river water. Left: Continuation of the role of the NewWaterway as main discharge artery. Right: Closure of New Waterway, emphasis on Haringvliet as main discharge artery (maps by H+N+S Landscape Architects and Delta program Southwest delta)
delta are increasingly looking for possibilities for collaboration. This requires intensification of the navigation network in the delta, connecting the different ports with each other.15 Finally, the modern flood defence systems have not been able to deal with changing conditions. Some extreme high water situations in the Dutch rivers in 1993 and 1995, as a result of unforeseen high peak discharges, addressed the need to update the quality of the flood defence structures in the Netherlands.
CHALLENGES: RESEARCH BY DESIGN In 2005 an ambitious program was started by the government, ‘Room for the River’, followed by the Delta program in 2008. For both programs the question remains how to deal with the different issues concerning environment, urban development and economic development in relation to an overall flood defence program. Both programs created strong conditions for new experiments. Room for the River can be considered as a preliminary laboratory to test new concepts. A new system of dikes and bypasses was presented as a framework, which creates conditions for the development of local projects for ecological as well as for urban development. The Delta program addresses the need for an approach which emphasizes, even more than the Room for the River program, the fundamental uncertainty of climate change as well as societal changes in the long term. In addition, the basic framework must be able to adapt to changing conditions in the far future. At the same time, it is worthwhile to investigate how the type of flood defence approach will influence the possibility for urban development. The Studio Coastal Quality was an initiative of research and public debate on this question in 2011 – 2013. Designers, hydraulic engineers, and environmental scientists investigated different options for reinforcing the coast, and tested the consequences for urban and environmental development. Figure 15 shows the results of this approach of research-by-design for Scheveningen (the sea-front resort of The Hague), with three different options for strengthening the coast, resulting in three different urban qualities. The method offers a more extensive assessment framework for the public and political debate on the preferred solution for coastal defence.16
9 Van der Wal 1998 10 Stive and Vrijling 2010 11 Meyer 1999, Duursma 2001 12 Saeijs 2006 13 Saeijs 2006, Schipper 2008 14 WWF 2010 15 Port of Rotterdam 2012 16 Brand et al. 2014
49
Robuust Adaptief Raamwerk (RAR) Primaire dijk
Secundaire dijk
Secundaire dijk
Secundaire dijk Landbouw
Primaire dijk
Recreatielandschap
Natte Natuur Primaire dijk
RAR - CONCEPT
Sluis
RANDVOORWAARDEN
Haringvliet
Haringvliet
Haringvliet
1. Zone tussen water en land
1. Primaire waterkeringszone (veiligheidsnorm 1/4000) 200m tot enkele km
Secundaire dijk
Secundaire dijk
Verlagen tot zomerdijk
Primaire dijk
Sluis Haringvliet
Waterberging buitendijks
Recreatiehaven
Primaire dijk
1 jaar tot 100 jaar
2. Robuust (veiligheidsnorm 1/4000)
Sluis Haringvliet
2. Inspelen op tijd
Verhogen tot primaire dijk
Kanaal
Waterberging binnendijks
Haringvliet
3. Voldoende ruimte voor water
%
4. Activiteit stimuleren
3. Adaptief 5. Integrale gebiedsontwikkeling
6. Functies hoogwaterbestending
ADAPTIEVE GOVERNANCE 1. Hiërarchische sturing
(basisbelangen – waterveiligheid)
RUIMTELIJKE PRINCIPES 1. Dijkverhoging primaire dijk
2. Dijkverhoging secundaire dijk
2. Netwerksturing
(collectieve belangen – natuur)
3. Dijkteruglegging
4. Beperkt bouwen op terpen 3. Zelfsturing
(ruimte voor private initiatieven) %
5. Integraal ophogen - (voormalige) haven
17 Robust Adaptive Framework. The sections show the multiple possibilities for development of the zones between the primary and secondary dikes in the areas south of Rotterdam (map by authors)
The research project IPDD (Integrated Planning and Design in the Delta) elaborated the need for adaptive design methods and investigated the possibilities using historic analysis, registering current ideas and plans of actors in the region, and developing scenarios for possible future trends. The result is a proposal for a new plan, a ‘Robust Adaptive Framework’. The idea is to define a spatial framework, which can be developed as a robust and adaptive system in different respects: both with regard to flood defence, climate change and sea level rise, as well as environmental qualities, the port economy, and urban development. The Rotterdam region functioned as the laboratory for the development of this approach. In this region one of the most urgent long term and large scale questions that needs to be addressed in the coming fifty years is whether the Nieuwe Waterweg (the result of 19th century interventions) should be maintained as the main discharge channel of the rivers Rhine and Meuse. The alternative would be that the Haringvliet branch (south of the region) would acquire the role of main discharge channel (Figure 16). This choice will have serious consequences for all systems: it will have consequences for the type of flood defence systems alongside the Nieuwe Waterweg and Haringvliet; for the functioning of the port of Rotterdam; and for the possibilities for new urban patterns along the waterfronts of both branches. The proposed framework delivers conditions for adaptation to long term changes in water levels and river discharges, as well as for short term changes in land use for environmental, agricultural or real estate purposes (Figure 17). In the urban-
50
ized and industrialized area of Rotterdam and the port, the raised outer-dike areas are part of the framework. They can be considered as part of a (robust) flood defence system which protects the hinterland, and can be adapted to changing water conditions in the future. In the rural areas, the historic secondary dikes should also be regarded as part of the robust flood defence system. The areas between the primary and secondary dikes can be used for nature, new agriculture or small scale residential projects, as well as for water storage in times of extreme discharges. This framework provides a common ground for different actors. Conclusion A renewal of the water management and flood defence system can function as the engine to reconfigure urban structures, environmental systems and economic structures, this time by strengthening the metropolitan regions of Amsterdam and Rotterdam – The Hague. This might also contribute to the development of a new balance between central state responsibilities and local or regional ones – both concerning spatial planning as well as hydraulic engineering. This will be made possible by the introduction of plans like the robust adaptive framework. The essence of such a framework is that is can build upon historic patterns and that it creates possibilities for collective action by different actors. Design research (the analysis of previous designs and patterns) and research by design (testing different possibilities for an area) both play an important role in this approach.
Mekong Delta Vietnam MARCEL MARCHAND, DIEU QUANG PHAM AND TRANG LE
What is the future role of urban planning in contemporary flood risk management? 51
Mekong Delta Vietnam
Phnom Penh
Tây Ninh
Ho Chi Minh City
0 The Mekong Delta has a population of 16 million people, living in a sprawled pattern of agricultural settlements and a few large cities such as Can Tho and Ho Chi Minh City (map by Nijhuis and Pouderoijen, TU Delft)
52
50 km
Environmental conditions and human activities (maps by Nijhuis and Pouderoijen, TU Delft)
Substratum
Climate
Agricultural land use
Transportation networks
Substratum The Delta is located in the largest floodplain which consists of about 46,000 km2 (< 5 m Mean Sea Level). The Mekong is the main river with a length of 4,800 km, an average discharge of 14,800 m3/sec and a sediment load of 110-150 Mt/year. Because of frequent floods, the land is rising with the same speed as the sea-level. This process is threatened by the construction of dams upstream in Laos, Cambodia and China.
Climate Climate variability is determined by a tropical climate with high humidity and distinct wet and dry seasons, with average temperatures varying from 19 °C to 32 °C and a mean annual precipitation of 1,672 mm, mainly by monsoon rainfall in summer.
Agricultural land use The coastal plain consists 82% of agricultural land, mainly in use for rice cultivation and grassland. Thanks to the Mekong Delta, Vietnam is the second largest exporter of rice worldwide.
Transportation networks The transportation network is determined by a few main routes and a dense system of local routes. The Mekong is little utilized for navigation, irrigation or power generation.
53
3 The city of Can Tho with Can Tho River, looking to the east (photo: Han Meyer)
54
The urban pattern of the Mekong Delta is strongly related with an extensive network of canals. This has contributed to the development of the delta, which is currently one of the largest rice-production areas of the world. Flooding is still an annual event over large parts of the delta. It brings new sediments and nutrients to the fields, benefiting both the rice production and the long term sustainability of the delta by counterbalancing sea level rise. However, increasing salt-intrusion from the sea, on-going industrialization, and intensification of rice cropping are reasons to construct or heighten dikes along the rivers and to consider dams or barriers in the river mouths. The long-term sustainability of this approach can be questioned, since natural sedimentation processes will be disturbed and water levels in the main rivers will increase. Other approaches should be investigated. A central question addressed in this paper concerns the future role of urban planning in contemporary flood risk management.
LIVING WITH WATER, BUT FOR HOW LONG? Every year the Mekong River deposits some 160 million tons of sand and silt, and it has been doing this for more than 3000 years.1 This has created a delta stretching out over around 5.5 million hectares. Because of the interplay of river, tide and waves, a complex landscape has evolved with large differences in soil structure and elevation (Figure 4). Since ancient times the beach ridges and river levees have been suitable places to settle.2 Alongside the two main river branches, the Bassac and Mekong, large floodplains exist which are inundated every year as deep as three meters. These physical conditions have largely shaped the human occupancy of the delta, but interventions have also influenced these conditions. Understanding the interactions between human occupation, infrastructure network and the physical conditions as three spatial layers 3 is necessary in order to interpret the challenges in water management and urban development that face the Mekong Delta today. This chapter focusses on the part of the Mekong Delta that falls within Vietnam and in which flood management strategies
are currently being debated. Since floods determine to a large extent where people live, the issue is also relevant to explain urban development. However, there seems to be a tipping point here: the age-old strategy of living with the floods no longer seems to hold. Cities are turning their backs to the water and higher rice production policies demand higher dikes. This centralized, modernist, flood control oriented approach can be traced back to the first Mekong Delta Development Plan from the 1960s, but it materialized mostly in large-scale water control systems in the 1990s 4 (Figure 5). Future economic development combined with growing concerns regarding climate-induced sea level rise further fuels the demand for flood protection and salinity control measures, such as the idea to close off the main estuaries with large dams.5 Both environmental and social concerns have questioned the current development approach in the Mekong Delta.6 A new, more ‘adaptive’ approach towards more diversification and environmentally friendly options is needed. But what are these options, which seem cheaper, more ecosystem friendly, socially acceptable and more robust to climate change? And how can these become incorporated in (urban) planning approaches and practices? Could the age-old tradition of ‘shaking hands with the floods’ 7 be revitalized? To answer these questions we will focus on the urban planning and water management in the Delta, using Can Tho as an example.
URBAN DEVELOPMENT Can Tho, the largest city in the Delta, is situated on the Mekong River. It is a prime example of the urbanization process in the Delta, whereby increasing numbers of inhabitants get exposed to flooding. Can Tho has a diverse topography, ranging from urban areas at the bank of a crevasse channel leading from the Mekong into a floodplain area, to a mainly agricultural and rural area with a system of canals in the south. Because of the favorable conditions for trade and transportation, Can Tho developed into a center for cultural and economic exchanges. Similar to other cities in the Mekong Delta, Can Tho has experienced rapid changes in recent decades (Figure 6). Especially after the introduction of economic reforms in the mid 1980s,
1 Nguyen et al. 2000, Ta et al. 2002 2 Biggs, 2005 3 McHarg 1969, De Jonge 2009 4 Käkönen 2008 5 Marchand et al. 2011 6 Käkönen 2008 7 Miller 2006
4 Map of the Mekong Delta with flood extent and provinces (map by authors) 5 The Mekong Delta in 2000: the whole delta as a hydraulic system (map by authors)
55
6 Development of Can Tho City (1964-2006) (maps and sections by authors)
the city’s population has increased rapidly, from 180,000 in 1979 to approximately 1.1 million inhabitants in 2006. As a result of the increasing population and economic development, the urban landscape transformed completely. During the 1990s, economic liberalization led to the establishment of new planning modes, whereby housing demands were fulfilled along highways. Within just the last twenty years, the urban surface has doubled; many new urban areas have been developed on low-lying marsh land. Today, approximately 70 percent of the urban area is located less than 1 m above sea level, which makes such areas highly vulnerable to the projected rise in sea level. The city of Can Tho is threatened by recurrent floods, which have three causes: high river discharges, marine tidal and storm surges, as well as heavy local precipitation. In the long term, flooding will be enhanced by subsidence, due to both natural compaction and increased water abstraction. This lowering of the soil will add directly to the flood problem. Extreme rainfall events can yield more than 100 mm in a couple of hours.8 Evidently, when these factors are combined at the same time, the most critical flood situations will be created. If climate change results in a significant sea level rise and more intense rainfall incidents, the flood risks could become unmanageable for the city if no countermeasures are taken. Flood control by dikes alone will evidently not work: dikes may keep the river water out, but they are useless against heavy rainfall. Furthermore, the existing sewage pipes already act as negative drainage systems during high tide. Therefore, there is ample reason to broaden the scope of solutions with a ‘climate proof’ urban planning philosophy which relates to the existing landscape and water network: green open spaces with water storage capacity along existing and restored creeks, waterfront development combining residential/business development with recreational and flood protection functions, wadis in combination with helophyte filters for water purification and increased infiltration, etc.9 There seems to be a window of opportunity for
56
these ideas because of the current plans for urban expansion; the high levels of local awareness are evidenced by a specially installed climate change centre at the People’s Committee of Can Tho.10
FUTURE CHALLENGES For a successful sustainable policy towards flood risks in Can Tho City, integrating urban planning with water management in the entire Mekong Delta seems crucial. To a large extent, urban development depends on economic and flood management planning decisions made at a high level, whether regional or national. For instance, in 2005 the Ministry of Agriculture and Rural Development (MARD) executed a master plan study on integrated water resources planning for the Mekong Delta to promote local socio-economic development. The study proposed a long-term development plan to adapt to critical dry season situations caused by upstream developments. Also a number of proactive adaptation measures were recommended (especially with regard to salinity intrusion), including improvements in sea dikes, water diversion channels and large sluice gates at the river mouths.11 The interactions between various regions within the delta also play a role. The choices in flood protection in the upstream provinces of An Giang and Kien Giang will have an effect on the flood risk in downstream Can Tho. Raising the dikes in the Long Xuyen Quadrangle and Plain of Reeds, the two main rice granaries of the Mekong Delta, could lead to higher water levels downstream. But there are many alternative strategies possible to deal with the flood waters in the Delta. For instance, the land area between the main branches of the river, the Bassac and Mekong, could be used for retention during extreme floods, following a ‘Room for the River’ concept. In addition, the flow ratio between the two main rivers can be manipulated, so that during high discharges, water flows through dedicated areas
8 Konings 2012 9 Ibid. 10 pers. comm. mr. Ky Quang Vinh, 2012 11 Marchand et al. 2011
LONG XUYÊN
SA ÐÉC
SÔ
NG
` SÔNG TIÊN
HÂ
.U
CAN THO’
0
10 KM
7 >16 WEEKS FLOOD DURATION
` HÔ ` CHÍ MINH THÀNH PHÔ
LONG XUYÊN
~ MY THO
12 -16 WEEKS
V ĨNH LONG
` THO’ CÂN
4 -12 WEEKS
< 4 WEEKS
0
25 KM
8
9
7 Urban patterns related to the Mekong Delta (map by Must Urbanism) 8 Mekong Delta: water system (map by Must Urbanism) 9 Two alternative strategies to deal with the floodwaters in the Delta and possible plans of urban patterns. Left: ‘Closed system’, with closure of estuaries and dikes along rivers. Right: ‘Open system’, with open estuaries and room for the rivers
57
10 City structure plan for District 3 of Cao Lanh: design study on possibilities of an ‘open system’. Parts of the agricultural area will be flooded in case of extreme high water (source: Trang 2013)
only, relieving the flood risk of critical areas. Alternatively, a full protection strategy could be opted for, whereby estuaries are closed and dikes are raised along the main rivers and the coast (Figure 9). Since these strategies and plans focus on the medium to long term, a city such as Can Tho cannot wait for the outcome of these planning processes. The immediate and near-future threat of floods is simply too great. Therefore, no-regret approaches and solutions are needed, ones which can adapt to future changes. Raising the land for new town extensions through landfill is a robust measure to reduce flood risk as it makes the city less dependent on external flood protection measures. Another no-regret measure would be water retention within the urban fabric, delaying the discharge for several hours so that excess water can be released during low tide by gravity. Otherwise, heavy pumps need to be installed. Spatial planning which allows for increased infiltration and retention areas in new town sectors looks promising.12 For Cao Lanh City, a town in the Delta similar to Can Tho, an alternative urban extension plan was developed by L. T. Trang (2013). It is based on two principles: Transit Oriented Development (TOD) and Room for Water. After construction of the public transport network in the new districts, areas surrounding transit stations will become new urban nodes. By careful planning of this network along higher parts, the flood risk will be minimized and the central lower part of the new district will remain open. This could become a river parkland offering recreational facilities, community gardens, orchards and fish ponds as well as providing room for water during high river discharges or heavy rainfall (Figure 10 ).
58
Conclusion The Mekong Delta provides unique examples of adaptations to floods. Adaptations started with the first inhabitants many centuries ago and still continue today. It is often stated that the Mekong Delta is one of the most vulnerable deltas to climate change. But this is only part of the story. More decisive for the future is the combination of climatic impacts with current economic and demographic developments. Indeed, vulnerability is determined by a combination of spatial planning, water infrastructure and social networks. And these are fields in which choices can be made. There is still time for a development which leaves room for underlying physical processes. Such a revival of living with floods could turn the Delta into a champion of climate change adaptation. This requires that urban planners and water managers share a vision on the future of the Mekong Delta, which can be translated into short and medium term measures and developments that allow for flexibility and adaptation. History has shown a strong path dependency of the network layer (canals, roads, dikes) upon the urbanization pattern as occupation layer. Future urbanization can be made more flood resilient by using the network in a ‘flood-wise’ manner, as the alternative plans for Cao Lanh and Can Tho cities show. These are examples of so-called casco-planning 13, by which robust infrastructure and landscape elements are used as a basis for land use and urban development to evolve in an organic and flood resilient way. They also show that bottom-up approaches to flood risk management are equally important as large scale flood master plans and deserve to be heard in the planning discourse on the future of the Mekong Delta.
12 Konings 2012 13 Sijmons 1991
Elbe Estuary Germany DIRK NEUMANN
It is necessary to find a new and sustainable balance between port development, environmental management, flood defence policy, and urban development. 59
Elbe Estuary Germany
Lubeck
Hamburg
Bremen
Hanover
0 Hamburg is the main city in the region. Urban development started at the edge of the estuary on higher land. Later, the lower embankments were also used for port development. The Hamburg Metropolitan Region is inhabited by 5 million people (map by Nijhuis and Pouderoijen, TU Delft)
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50 km
Environmental conditions and human activities (maps by Nijhuis and Pouderoijen, TU Delft)
Substratum
Climate
Agricultural land use
Transportation networks
Substratum The coastal flood plain of the Elbe estuary is 3,600 km2 (< 5 m Mean Sea Level). The Elbe has a length of 1,100 kilometres, an average discharge of 870 m3/sec and a low sediment load of 0.8 Mt/year. The river mouth is dominated by tides. Because of canalization and dredging, the average difference between low and high tide has been increased from 1.90 to 3.60 meters during the last two centuries, resulting in greater vulnerability to floods.
Climate The Elbe estuary is located in the humid temperate regions with a mean annual precipitation of 750 mm with a maximum runoff in winter, a prevailing western wind and average temperatures varying from -3 °C in winter to 23 °C in summer.
Agricultural land use The coastal floodplain consists 80% of agricultural land, mainly used as grassland or for crops.
Transportation networks Hamburg is well connected to the rest of Europe via the dense network of German highways. The Port of Hamburg remained beside the city of Hamburg, and was never moved to the sea-mouth because of the autonomous position of the Free and Hanseatic City Hamburg.
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3 Aerial view of the Elbe River over the HafenCity towards the mouth of the Elbe (photo by Andreas Vallbracht)
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This chapter describes how the tidal Elbe River with its water system has influenced the spatial developments of the Hamburg Region in the last eight centuries with a focus on recent developments. The chapter argues that it is necessary to find a new and sustainable balance between port development, environmental management, flood defence policy, and urban development.
LANDSCAPE AND GEOMORPHOLOGY The river Elbe, with a length of 1,094 km, arises in the Czech Republic, and its watershed covers the majority of the Czech Republic and large parts of north and east Germany. It runs through Dresden, Magdeburg and Hamburg and finally flows into the North Sea at Cuxhaven.1 This chapter will focus on the estuary of the Elbe between Hamburg and the river mouth to the North Sea at Cuxhaven. The Elbe is dominated by strong tides, which invade 180 km landwards into the estuary. The influence of the tides is artificially blocked by the weir at Geesthacht. The Elbe is the only waterway to reach the seaport of Hamburg. The port is located on the island Wilhelmsburg, which splits the Elbe into two courses, the Norderelbe and the Süderelbe. 20,000 years ago the valley of the Elbe was created by glaciers. The melting water streamed through this valley towards the North Sea and formed a glacial landscape. The Holocene river landscape is situated between higher sand ridges of the Pleistocene landscape. Differences in height as great as 70 meters can be observed between the high sand ridges and the wide wetlands of the Elbe (Figure 4). Due to erosion and sedimentation, large amounts of sediment have been relocated, a process accelerated by storm surges. The formation of sand banks, islands and dunes was continuously changed by discharging river channels and changing river widths. Additionally, the water quality conditions changed, with fresh and brackish water creating conditions for a large variety of aquatic flora.2
URBAN DEVELOPMENT A nature-dominated system (1200-1800) In the 11th -12th centuries, the natural landscape was slowly cultivated. The first settlements were located on the higher
sand ridges close to the Elbe and at the tributary waters, which were rich in fish. In summer time, the fertile meadows along the river were used to graze cattle. In the winter, the land flooded again. The still unregulated natural dynamics of the Elbe forced settlers to adapt to the different water conditions. The first settlers of Hamburg took advantage of the special geographic conditions. Along the path following the Elbe, the Elbuferhöh enweg, the settlers found a flood free sand ridge located next to the Alster, with a perfect water access to the Elbe (Figure 5). The site offered the opportunity to establish a convenient harbor and a ‘dry’ access to the strategically important Alster ford.3 In the 12th century, Hamburg consisted of two castles. The Alster was dammed at the Jungfernstieg, which generated the well-known artificial lakes of inner and outer Alster. The Alster mouth served as a port and was protected against flooding by dykes. By the 16th century, the Alster marsh south of the Jungfernstieg was drained, reclaimed and urbanized, and a protected port was created on the banks of the Elbe.4 The first land reclamation projects took place during the 13th century. From then on, more and more dykes were built to protect land which had previously flooded regularly. Nevertheless, several storm surges overtopped the low dykes and destroyed the water constructions. For example, the Allerkind leins flood in 1248 destroyed Gorieswerder and created several islands on the site of today’s Wilhelmsburg. In the 15th -17th centuries, the Elbe changed from a natural river estuary with large wetlands into a more regulated river where the wetlands were mainly cultivated and protected by dykes. The techniques of water infrastructure were already developed to a high standard. Tributaries of the Elbe were closed by dams and integrated into the water system of the reclaimed land. These polders along the Elbe were well protected against regular flooding and supplied the growing city of Hamburg with grain, vegetables and milk. The regulated waterways of the Elbe were used for transportation of products. In the 18th century, drainage techniques were further developed, including the use of windmills to pump water out of the polders. The polders attracted more and more settlers, with permanent settlement on the edges of the sand ridges (Geesthänge) and along the dykes, which led to long linear villages with a relatively open building structure.5 The remaining flood plains still covered large surfaces along the Elbe. The interventions of land reclamation hardly affected the
Alster
1 Tockner et al. 2009: 533 2 Glindemann et al. 2006: 4 3 Bracker 1987: 9 4 Ibid., 57ff 5 Landschaftsbild 2005: 14ff
Elbuferhöhenweg
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4 View from Blankenese to the River Elbe (photo by author) 5 Ground relief map with the settlement of the Hammaburg and the probable course of the Elbuferhöhenweg (after Bracker 1987)
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6 View from the Landungsbrücken to the HafenCity and on the other side of the Elbe River, the port of Hamburg (photo by author)
daily tide level difference of about 1.90 meter between 1200 and 1800. The dykes were mostly not strong enough to withstand bigger storm surges; therefore, settlers were regularly forced to give reclaimed land back to the river. River regulation and port domination (1800 – 2000) In 1842 a great fire destroyed large parts of the center of Hamburg. This was a good opportunity to get rid of the very narrow city center and the dirty, silted-up canals. William Lindley realized his reconstruction plan and created a new water system with more efficient sluices as part of a more rational urban layout.6 About 20 years later, the port was fundamentally renewed and extended. John Dalmann designed new docks on the Elbe islands south of the Binnenhafen. He used the tide and stream conditions of the Norderelbe to avoid siltation in the new harbor basins. A good railway connection made the logistical processes of loading and unloading more efficient and competitive.7 Since then the area has been transformed and is now known as the Speicherstadt and the HafenCity. From the 18th/19th century on, the harbours of Hamburg, Altona and Harburg were competing against each other, accessibility a recurrent bone of contention. Already in the 13th century, several tributaries of the Elbe were cut off to get more water into the Norderelbe in order to improve the accessibility of the harbour of Hamburg. When Hamburg led more water towards the Norderelbe with engineering works, the accessibility of Harburg, situated on the Süderelbe, was threatened. The contracts of Köhlbrand (1868-1908) between Prussia and Hamburg contained measures regarding the canalization, relocation and deepening of the Norderelbe and Süderelbe. After the completion of the engineering works, all three ports were accessible for modern steam ships. In 1937 the three cities were unified in the state of Hamburg, thus ending the competition. Human interventions in the 20th century had enormous consequences for the tidal hub, hydraulic behaviour, sedimentation, and water quality of the Elbe. For coastal protection, the dyke length was shortened and more and more foreshore areas were reclaimed. The enormous impact of the flood in 1962, where 28,000 houses were destroyed, was the reason to improve the flood risk management. The dykes along the Elbe estuary had to be raised from 5.70m to 7.20-9.25 meters. Since 1976 all tributaries of the Elbe estuary have been cut off by flood barriers. Since 1955 about 209 square kilometres inter-tidal area have been lost to land reclamation.8 The tributaries and the foreshore areas served as an enormous buffer, which could absorb the force of the tidal energy. However, today the space of the main stream is so constricted that the tide can continuously stream deeper inland. The tidal hub is constantly increasing -- in the last 100
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years by about 160 centimeters.9 While the tidal energy transports more and more sediment deep into the estuary, the low tide is less strong and cannot transport the sediment back. This effect is called ‘tidal pumping’. The result of this phenomenon is increasing siltation, mainly in the harbour area of Hamburg. The Port of Hamburg is a tidal harbour, which means that the port and its basins are influenced by daily changing water levels. The average difference between high and low tide is 3.62 meters. At high tide, ships with a draught of 13.5 meters can pass the waterway. Because of ‘tidal pumping’ the Port Authority has to dredge about 8 million cubic meters of sand per year to guarantee the depth of the waterway.10 There are plans to deepen the channel to 15.9 meters, but the government cannot give permission, because nature protection areas could be damaged.11 The economy of Hamburg’s harbour is important for the state of Hamburg, with the port generating about 14% of the state’s total gross domestic product (GDP). 155,000 people in the Metropolitan Region of Hamburg work in port-related jobs.12 The location of the harbour is remarkable, since the port is constantly visible from the centre of Hamburg and contributes to the image of the city (Figure 6).
NEW PERSPECTIVES There are a variety of different new spatial strategies for the Hamburg region, following the idea of giving the ‘dynamic’ river more space. The Tidal Elbe River Concept In 2006 the Hamburg Port Authority (HPA) and the Federal Administration for Waterways and Navigation published a concept for a sustainable development of the Tidal Elbe River. The concept proposes three main interventions to reduce the siltation and the tidal hub of the estuary.13 The first step is to reduce the tidal energy present at the mouth of the Elbe nearby Cuxhaven. Current research by the Strombau project group 14 shows that narrowing the mouth of the Elbe would reduce the incoming tidal energy. This can be achieved by building sandbanks or sand fills or by building a partial dam.15 The second step is to create flooding areas along the Elbe estuary between Geesthacht and Glücksstadt, which would allow the water to spread out and lose its force. The third step is to optimize the sedimentation behaviour in the whole estuary. One intervention could be to make the riverbed rougher, for example by building grooves. The expected tide elevation after these interventions is around 50cm lower than the current elevation. In addition, these interventions should reduce the sediment transport down streams and reduce tidal pumping.16 The Tidal Elbe River Concept is projected to have effects and synergies on several sectors like economy, flood risk control, urbanized areas, nature systems, tourism and recreation.17 The interventions should also reduce the siltation in the harbour areas, permitting better and sustainable accessibility for large ocean-going ships to the harbours along the Elbe estuary. The enormous costs of constantly digging out the waterway would be reduced. The interventions to reduce the tidal energy would also have positive effects on flood management and are more sustainable than raising the dikes. More floodplains, inter-tidal and foreshore areas will make the natural system of the Elbe estuary more robust. The fragile dynamic water processes can develop better and with a more stable balance. Ultimately, the Elbe estuary with its unique natural and cultivated landscapes can improve the sustainable living area of the Hamburg metropolitan area.
6 Bracker 1987:169ff 7 Ibid.,188ff 8 Glindemann et al. 2006: 6 9 Ibid., 8 10 Stokman et al. 2008: 29ff 11 Spiegel online, 2012 12 Hafenentwicklungsplan bis 2025, 2013: 8ff 13 Glindemann et al. 2006: 11 14 The Strombau project group consists of experts from Wasser und Schifffahrts ämter (WSA) Hamburg and Cuxhaven, WSD Nord, Hamburg Port Authority, Bundesanstalt für Wasserbau (BAW) and Bundesanstalt für Gewässerkunde (BfG) 15 Ohle and Marušić 2007: 4ff 16 Ibid., 7ff
NEUMÜNSTER NORTH SEA
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7 Urban patterns in the Elbe estuary (map by Must Urbanism) 8 The water system of Elbe estuary (map by Must Urbanism) 9 Kreetsand Tidal Park – Landscape design Rabe landschaften and Studio Urbane Landschaften (source: Hamburg Port Authority, Studio Urbane Landschaften Hamburg / OSP)
9
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Hafencity Hamburg Hafencity Hamburg is an urban development project on the Elbe River front (Figure 3). The planning area of 157 hectares can be seen as an expansion of the inner city of Hamburg. In the former harbour area the Hafencity Hamburg GmbH is developing around 4,000 apartments and offices providing space for 45,000 workers.18 Hafencity Hamburg is worth mentioning because of its special relationship to the dynamic water of the Elbe. The whole area is situated outside the public flood protection. Thus what are the reasons for not protecting Hafencity with dykes? First of all, a main dyke would cut off the relationship to the water and destroy the spatial qualities of the approximately 10 kilometer-long promenade along the harbour basins, and second the investment required to build a flood protection for the whole area in the beginning of the planning process would be too high.19 Private developers of buildings are responsible for their own flood protection. Every building is built with raised basements, which are waterproofed and are provided with flood doors. Normally, it is strictly prohibited to live outside the primary flood protection, but because of the Hafencity project, the state of Hamburg modified the water law of Hamburg, permitting the government of Hamburg to identify areas with exceptional regulations. In case of flooding, the area will still function and be accessible for emergency services and evacuation. That is why infrastructure like bridges and streets are elevated to a level of 7.5 meters above sea level. This flood protection strategy has the disadvantage that the unembanked areas of the Hafencity are difficult to adapt to rising water levels in the future, because raising the existing buildings is almost impossible.20 Governance system and the IBA Hamburg The Elbe estuary belongs to the states of Lower Saxony, Schleswig-Holstein and the Free and Hanseatic City of Hamburg, which are responsible for urban and regional planning and for coastal protection. The Federal Administration for Waterways and Navigation of Germany is responsible for the Elbe waterway. Thus, four sovereignties share responsible for the Elbe estuary. An excellent example for cooperation between knowledge, design and governance is the IBA Hamburg (International Building Exhibition). The IBA Hamburg facilitates the development of new spatial strategies to design spaces capable of dealing with climate change. The exhibition can be seen as a laboratory to experiment with new planning methods, innovative urban spaces, and architecture that can adapt to the dynamics of water in and around the island of Wilhelmsburg, situated south of the inner city of Hamburg. The water projects for the island Wilhelmsburg were developed by several organizations, like universities from Hamburg and Hannover, urban planners, landscape architects, the responsible departments of the state Hamburg, and the Hamburg Port Authority. The IBA is able to integrate these specific projects into the overall development of the island. The Institute of River and Coastal Engineering at the University Hamburg-Harburg developed a new flood risk management strategy for Wilhelmsburg. This strategy proposes applying flood risk management instead of raising the dykes. The proposal seeks to control flooding mainly by the use of compartments behind the main dyke, which consist of old sleeping dykes, higher infrastructure lines (highways and railway tracks) and mobile walls to be erected just before the storm surge. This strategy can protect the main urban areas. This flood risk management strategy scores better compared to building higher dykes, because it is cheaper and has more redundancy.21
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The Leibniz University Hannover did research on the relationship of water dynamics of the Elbe and the new possibilities of spatial planning on the island of Wilhelmsburg. Land-water typologies, like inter-tidal zones, regulated polder landscapes, and harbour areas are adapting to water dynamics such as regular flooding, water retention, different water levels (tide), and storm surges.22 The Deichpark Elbinsel project of the IBA Hamburg can be considered as an already existing cultural park of dykes and water protections around Wilhelmsburg and as a laboratory for an innovative implementation of new water strategies. One of the pilot projects is Kreetsand (Figure 9): IBA Hamburg and the HPA are realizing a new inter-tidal zone at the east side of Wilhelmsburg, which combines nature with recreational functions. The area will be partly accessible for visitors, who can experience the dynamic water behind the main dyke. Conclusion The Tidal Elbe River project is a good example of a different mindset for dealing with the Elbe estuary. The concept’s goal is still to control the water of the Elbe River to avoid negative effects like the siltation in Hamburg’s harbour. But the solutions apply new strategies for dealing with the natural processes of water dynamics in the estuary. For example, increasing the tidal volume capacity by realizing more flood-plains around the Elbe and reconnecting former tributaries are both clear signs of a changing attitude. The Tidal Elbe River project shows significant awareness for the Elbe estuary as a system. The estuary is an artery for the whole Hamburg region. The authors of the concept are searching for solutions with positive effects on different sectors (thus developing a win-win strategy). Increasing flood-plains and inter-tidal zones in the estuary not only has positive effects on the siltation in the harbour of Hamburg, but makes the entire ecological system more robust, reduces the flood risk, and enhances the nature reserves as well as the quality of the living environment. These integrated projects enjoy a broad public support and have a greater chance of being implemented. In the current developments of Wilhelmsburg (IBA Hamburg), the spatial quality of the Elbe River with its dynamics is integrated into the urban concept. In the designs for the Deichpark and the Kreetsand flood plain, the relationship to the water, the accessibility of the dykes and foreshore areas, and its spatial quality are significant parts of the planning process. The city renewal projects in Hamburg are dealing with the dynamics of the Elbe River and its spatial qualities. The planners of the Hafencity project have chosen for high quality public spaces along the quays with a direct relation to the water of the Elbe. These areas can be flooded, which even reinforces the experience of the water dynamics. The current spatial projects in the Hamburg region are indicators of changing attitudes towards river and water management. The idea that water needs more space and attention in spatial planning is beginning to be accepted. Both the whole estuary system of the Elbe and smaller scale projects along the Elbe are influenced by this attitude. There is a broader acceptance that the river is a natural dynamic system, and that controlling and restricting the ‘wild’ water is not the right answer to contemporary problems.
17 Glindemann et al. 2006: 13 18 HafenCity 2013 19 Ibid. 20 Müller 2013 21 Pasche 2007: 3ff 22 Stockman et al. 2008: 113ff
Tagus Estuary Portugal JOÃO PEDRO COSTA, JOÃO FIGUEIRA DE SOUSA
This area hosts a complex and intricate system, one encompassing heavy productivity and diversity. 67
Tagus Estuary Portugal
Lisbon
0 The Lisbon Metropolitan Area, with 2.8 million inhabitants, is mainly on the higher land next to the estuary. A small part of the urbanized area is located in the floodplain (18 km2: 3.5%), including the historic centre of Lisbon (map by Nijhuis and Pouderoijen, TU Delft)
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50 km
Environmental conditions and human activities (maps by Nijhuis and Pouderoijen, TU Delft)
Substratum
Climate
Agricultural land use
Transportation networks
Substratum The Tagus Estuary contains a small coastal floodplain of 507 km2 (< 5 m Mean Sea Level). The Tagus is 1,000 km long, has an average discharge of 304 m3/sec and a sediment load of 0.4 Mt/year.
Climate The Tagus Estuary is located in a temperate humid region with hot summers and mild winters, a mean annual precipitation of 774 mm with maximum runoff in winter, a prevailing northwest wind and average temperatures varying from 8 °C in winter to 29 °C in summer.
Agricultural land use The relatively small floodplain is mainly used for agriculture (80%) in the form of rice cultivation.
Transportation networks Lisbon has one of the largest container ports on the Atlantic coast of Europe. The Tagus Estuary is crossed by two of the most important national highway-arteries.
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3 The Tagus Estuary from the southwest with Lisbon on the left (source: João Ferrand, Administration of the Port of Lisbon)
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Located in Portugal, the Tagus Estuary comprises a water surface with an area of 320 km2. The estuary includes 14 municipalities, with a population of 1.70 million inhabitants 1, approximately 15% of whom live within 500 meters of the estuary.2 It is located in the centre of the Lisbon region and the Tagus Valley, with 3.65 million inhabitants, and in the metropolitan area of Lisbon with 2.82 million inhabitants.3 This area hosts a complex and intricate system, one encompassing heavy productivity and diversity combining urban, industrial, military, leisure and recreation activities with fluvial traffic, agriculture, fishing and salt extraction. These functions occur in the context of an essential ecological dimension, with 25% of the estuary classified as a protected area 4 in accordance with the Ramsar Convention.
LANDSCAPE AND GEOMORPHOLOGY The Tagus Estuary has witnessed a dynamic human appropriation through its history. Its natural setting has been the site of human occupation for millennia, including Phoenician and Roman settlements. The traces of these settlements testify to the attractiveness of the Estuary’s water system, as well as its strategic importance. Activities associated with agriculture, forest, fishing, and salt extrapolation contributed to its development in ancient times, and eventually supported the construction of the navies which permitted the Portuguese overseas discoveries during the 15th and 16th centuries. Consequently, port activities have had a long and intricate relationship with the estuary, both for fluvial and overseas commerce. As occurred in other deltas and estuaries, industrialisation had significant impacts on the Tagus. This proceeded in two phases: (i) the first industrialisation, centred on the municipality of Lisbon, primarily along the city’s central and western waterfronts; and, (ii) the second industrialisation, mainly located on the northeast and southern banks (with a large port, industrial companies, and military infrastructure located in Almada, Seixal, and Barreiro). Contemporary economic forces have led to a process of deindustrialization, which has forced the reinvention of economic activities, focussing now on tourism, leisure and recreation. At the same time, and equally important, urban waterfronts have been regenerated and reinvigorated, acquiring new functions as urban areas. The Tagus Estuary is one of the largest estuaries in Europe, ranging from the river’s mouth upstream to Vila Franca de Xira, the upstream limit of saline water intrusion under normal hydrological conditions. It “…can be divided in two distinct regions, the upper and lower estuary, that present different morphologies and properties.” 5 And it “…can be partially stratified or vertically mixed, depending on the interaction between tide and river flow.” 6 The estuary has several alluvial plains as a result of river erosion, transport, deposition and accumulation of matter. It is also important to take into account that “the estuary is subjected to constant silting, requiring occasional dredging to maintain the navigational channels.” 7 Tidal action has a “…dominant semidiurnal period and maximum amplitude of 2m in spring tides.” 8 Tidal cycles are a significant factor in the Tagus Estuary, since the average tidal volume 9 is substantial compared to the water volume below the low-tide level.10 This estuary can be characterised as a “positive type” estuary, and also as a partially stratified estuary.11 The tidal range and the geomorphological characteristics (both at the upper and lower estuary) allow the Tagus Estuary to be considered in the class of meso-tidal estuaries.
The Tagus Estuary is also an important area for nature conservation, having an important biological potential, and serving as a central environmental element in the metropolitan area of Lisbon. It is accepted that “its natural values stem, particularly, from its size and functional diversity, from the richness of the fauna and flora and, in a general way, from the diversity of ecosystems that can be found within it.” 12 In fact, it is a region marked by an extraordinary diversity of landscapes as well as high biodiversity, of both flora and fauna. Nevertheless, this natural heritage is extremely fragile, and these areas are classified and legally protected. The mid and upper estuary areas have been given national, European and international conservation status: the Natural Reserve of the Tagus Estuary, located in the estuary’s most upstream section, has an area of 14,192 hectares. This includes a large surface of estuarine waters, alluvial deposits, alluvial islands, salt production fields, salt marshes and marshlands. The central part of the estuary is permanently submerged and is essential for the survival of coastal fish populations. The alluvial deposits are large expanses of mud that are influenced by tidal dynamics, created through the deposition of very fine suspension particles carried by the water. These deposits are frequently colonised by various benthic macro-invertebrates. The salt marshes have an equally important role as fish nurseries, and the salt production fields are an optimal location for some fish species. The marshlands cover flat land that has become part of the estuary’s bed. Altogether, the Natural Reserve of the Tagus Estuary has a wintering bird population of over 10,000 anatids and 50,000 waders. As a result, this makes it the most important wetland in Portugal, and one of the most noteworthy in Europe. To summarize, the classification of the Tagus Estuary as an exceptional natural heritage site is based on the role it plays in accommodating a rich variety of interrelated ecosystems. Although the bird population is significant, there is also a noteworthy amount and variety of fish and plant species. Thus, recognising the estuary’s environmental value, it is essential that strategic land use planning options also aim to “preserve the natural habitats of the estuary´s margins, bays and adjacent creeks, particularly salt marshes and other wetland areas.” 13 Only this can assure the sustainability of the Tagus Estuary in future years.
URBAN DEVELOPMENT WITH LISBON AS EXAMPLE The resident population of the 14 municipalities which are located on the edge of the Tagus Estuary is 1.7 million inhabitants. In the metropolitan area of Lisbon, the north bank accommodates 68.8% of this population, with the greatest concentration in Lisbon proper, with 547,000 inhabitants. On the south bank, the greatest concentration is in the Almada-Seixal-Barreiro area, with 411,000 inhabitants. Since 2001, the population of the Tagus Estuary Region has increased 5.2%.14 This overall figure obscures different growth patterns: the northern bank grew 4.0%, and the southern bank 7.9%.15 On the other hand, the Tagus Estuary occupies a strategic location which, allied with its natural system, has allowed it to become, over time, an important economic catalyst, contributing to the development of various economic activities related to the use of the estuary and adjacent areas. The most important of these are agricultural activities, fishing and aquaculture, forestry, recreation/leisure activities, shipping, naval construction, industry, transportation. This large scope of activities expresses and articulates itself in numerous ways, namely:
1 Censos 2011 2 POE 2011 3 Censos 2011 4 RNET – Natural Reserve of the Tagus Estuary 5 Dias et al. 2011 6 Cabeçadas 1999 7 Gomes 2008 8 Canas et al. 2009 9 600x106 m3 10 1900x106 m3 11 Cf. ICN 2002 12 Fonseca Ferreira and Vara 2002: 42 13 Almeida et al. 2010: 48 14 i.e. by 90,595 inhabitants 15 INE 2001, INE 2011
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- The multifunctional land use of the Tagus Estuary. For example, the city-port articulation considers underused port areas available for urban renewal, leisure/recreational uses, and reconversion projects related to port activity. The administration of the Port of Lisbon has recognized that there are areas for which no port activity is planned and has made agreements to transfer these areas to town councils. At the same time, these visions and projects for port development have led to public debate, and will continue to. The Regional Plan of Lisbon’s Metropolitan Area, which is in the final stages of its 2012 revision, could eventually allow a new port to be built at Trafaria (located on the south bank of the river mouth. However, consensus with the municipality of Almada has yet to be reached, and the future of the area, combining urban renewal and e environmental improvements, is still unclear (Figure 6). - The coordination of such diverse activities causes negative externalities, and incompatibility among the activities themselves. Examples include (i) the effect of industrial residues and contaminants (largely produced during the second half of the last century by the large industrial complexes lining the estuary); and, (ii) the agricultural runoff in the estuary, and its impact on the environmental quality, including that of primary activities (e.g., oyster farming). - The regeneration of the margins of the estuary, resulting from the evolution of activities, for example the disused and/ or abandoned areas that resulted from the decline in industrial activity (mainly in the 1980s). This has thus generated the need for reconversion, particularly on the south bank, with several hundred hectares of abandoned territories that were once essential to the second industrialization. To this end, the Arco Ribeirinho Sul Strategic Plan was approved in 2009 16, stating that “the renewal of the old industrial complexes of Margueira, Siderurgia Nacional, and CUF/QUIMIGAL presents itself as an opportunity to support the development of the south bank in the context of the Lisbon Metropolitan Area”. The environmental problems and soil contamination in these areas is also an intricate issue to solve. More recently, the project was abandoned due to economic constraints. - The planning and public governance of the estuary reflects its complexity, with a high number of instruments for territorial and estuarine management, as well as a high number of qualified institutions (e.g., licensing, spatial planning, maritime safety, etc.). - The debate concerning new key infrastructures, reflecting the urban pressure on the margins of the Tagus Estuary and adjacent areas, which hold approximately 16.6% of Portugal’s population. In particular this refers to planned large-scale investments in transport infrastructure and logistics including plans for: (i) the New Lisbon Airport, (ii) the third bridge over the Tagus Estuary, (iii) the Poceirão Logistic Platform, and (iv) the Castanheira do Ribatejo Logistic Platform. - The attention to some environmental problem areas, such as the numerous sources of water pollution from urban, industrial and agricultural origin on both sides of the Tagus Estuary and its tributaries. For example, it was only in 2011 that raw sewage from domestic dwellings finally stopped being discharged into the Tagus Estuary. - The integration of these activities with natural dynamics, such as (i) erosion problems on the estuary’s margins and beds caused by the decrease in sediment flow carried by the Tagus River, (ii) the extraction of sand from the river bed due to urbanisation processes, and, (iii) the wave turbulence caused by increased shipping in the estuary. This turbulence is the
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result of waves generated by catamarans used for passenger transport. These waves affect sediment transport, increasing the erosion process, and threaten both the environment and the man-made heritage. To sum up, being a strategic location for various economic activities, the complexity of the estuary stresses the need for coordinated action, particularly in processes of urban development. Conflicts between uses, activities, occupations, planning and management tools are part of everyday life in the estuary. Still, these conflicts reinforce the estuary’s main characteristic: its capacity to incorporate and sustain diverse urban functionalities due to its naturally opulent characteristics.
CHALLENGES AND FUTURE PERSPECTIVES The Tagus Estuary plays an important role at a regional and national level for two main reasons. On the one hand, it is a crucial environmental element in Lisbon’s metropolitan area, as a result of its biological potential, and the richness of its natural and cultural heritage. On the other hand, it also sustains a variety of uses, such as tourism, recreation, and leisure. Equally important are the economic and social functions of the estuary, and the delicate balance upon which all these factors together depend. The variety and high quality of the ecosystems, and the multifunctional land use of the Tagus Estuary, has led to three main problems that have to be solved: (i) the conflict between uses and activities; (ii) the disused and/or abandoned facilities; and (iii) the urban pressure, which is one of the main causes of water pollution. These problems might be solved by developing an integrated estuary management system, which promotes a balanced approach to planning and management, with a focus on sustainability, competitiveness and integration. It is equally important to ensure an integrated land use planning and management, and to balance the economic activities (port, industrial, and urban) that are essential to the estuary. Last but not least, any plan needs to protect the biodiversity and natural resources that have served and enriched urban life, and shall continue to do so. An important challenge lies in creating projects that integrate port uses and urban uses, bearing in mind the balance needed between such uses, without compromising the efficiency and economic profitability of strategic port activities. The participation of all citizens and interested entities (as well as riverfront municipalities) in producing these solutions is crucial to ensuring their success. A vision for an integrated estuarine development should integrate realistic solutions for the respective obstacles. In this way, one can not only ensure the sustainability of estuarine ecosystems, but also integrate the instruments for territorial management, applying plans and programs of local, regional and national interest. This objective will require greater coordination and consultation between the different entities which are directly and indirectly involved in the planning and management of the Tagus Estuary: local, regional and national governments, economic sectors, environmental and community organizations, etc. Examples of some of these entities and the role they have in coordinating and implementing a plan for sector and/or territorial guidelines affecting the Tagus Estuary include the following: - The Regional Coordination and Development Committee of Lisbon and the Tagus Valley, responsible for elaborating and implementing the Lisbon Metropolitan regional plan, currently under revision. The plan’s territorial strategy centres on four main objectives: (i) to re-centralise the metropolitan area on
16 Resolution of the Council of Ministers no. 65/2009 (August 7th, 2009)
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4 Urban patterns related to the Tagus Estuary (map by Must Urbanism) 5 The Tagus Estuary: water system (map by Must Urbanism)
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6 Regional Plan of Lisbon Metropolitan Area, 2012
the Tagus Estuary, preserving the natural values and protected areas; (ii) to develop Greater Lisbon, a city of two banks, centred around the city of Lisbon; (iii) to develop a more polycentric regional urban system; and (iv) to value the territorial diversity by correcting existing imbalances.17 - The Portuguese Environmental Agency, responsible for the Tagus Estuary Region Basin Management Plan, currently being developed. This document emphasises the importance of the estuary, both ecologically and for its economic and social functions, aiming to protect the water, beds and shoreline; moreover, it is intended to defend enclosed ecosystems, as well as social, economic, and environmental valuing of the surrounding terrestrial areas. - The Institute for the Conservation of Nature and Forestry, responsible for managing the Tagus Estuary Nature Reserve, aims to balance economic activities that take place inside this protected area. This shall be done through nature conservation and the preservation of natural values, including activities such as commercial fishing, recreational fishing, aquaculture, buildings and infrastructure, nature tourism, scientific research and monitoring, and military exercises. - The Port of Lisbon Authority, whose guidelines prioritize the structuring of port activity into three areas of business: containers, foodstuffs, and tourism, recreation and leisure.18 - The town councils of the riverfront municipalities, which constitute important institutional actors within the estuary. The Municipal Master Plans are determinant factors in the organization, use and occupation of the surrounding areas concerning the estuary’s water plan. These must be linked to the Lisbon Metropolitan Regional Plan, as well as to the various sector plans.
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To conclude, concrete steps are being made towards an integrated approach regarding the Tagus Estuary. This addresses the planning and management of the estuarine space, namely through the elaboration of the Tagus Estuary Management Plan. Although the plan needs to be further integrated at different government levels, the Tagus Estuary Management Plan is an instrument designed to promote change, reconciling land use and occupation of the territory, and identifying spaces of coordination, collaboration and institutional mediation. Only by developing an integrated approach such as this is it possible to deal with the very dynamic development of urbanisation, economic activities, infrastructure, natural values, and technological risks faced by delta and estuary regions in Europe.
17 Cf. MAOT 2002 18 Cf. APL 2007
Galveston Bay USA THOMAS COLBERT
This emerging new American landscape will require new paradigms for coastal and urban analysis, planning, and management. 75
Galveston Bay USA
Houston
Galveston
0 Houston Metropolitan Area has a population of 6.2 million and is still growing rapidly. 35 km2 (1.6%) of the urban area is located in the floodplain (map by Nijhuis and Pouderoijen, TU Delft)
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Environmental conditions and human activities (maps by Nijhuis and Pouderoijen, TU Delft)
Substratum
Climate
Agricultural land use
Transportation networks
Substratum Galveston Bay is part of a coastal flood plain of about 2,201 km2 (< 5 m Mean Sea Level). The Trinity is the main river with a length of 960 km, an average discharge of 222 m3/sec and a sediment load of 0.4 Mt/year
Climate Galveston Bay is located in a humid subtropical region, with a mean annual precipitation of 1,260 mm with maximum runoff in spring, a prevailing south and south-east wind bringing heat, and average temperatures varying from 7 °C in winter to 33 °C in summer. Hurricanes are a yearly threat.
Agricultural land use The coastal floodplain consists mainly of wetlands and forests; only 22% is in use for agriculture in the form of grassland.
Transportation networks The main routes radiate from Houston over the region. The Port of Houston is an important logistic hub and has the largest petrochemical complex in the world. Moreover, it handles about 70% of the container cargo of the US. The Houston Ship Canal through Galveston Bay is therefore one of the busiest waterways.
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3 V iew from Galveston Bay to the west, with petrochemical plants in the foreground and downtown Houston in the background (courtesy: Hartman)
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This chapter concerns the development, spatial characteristics, and future of the upper Texas coastline of the United States. It focuses on the region around Galveston Bay. Over the last hundred and fifty years this region has developed from a sparsely settled agricultural and fishing hinterland into one of the most important industrial and urban concentrations in the world. Its population, economy, and industrial infrastructure continue to grow at a remarkable rate. The pressure of population growth and industrial expansion have pushed urban and industrial development into previously undeveloped agricultural and wilderness areas, as well as low-lying coastal and riverine flood zones. As this process continues in a substantially unregulated manner, the region faces unprecedented ecological, life safety, and economic risks. In an era of limited support for governmental programs, public policy makers are faced with increasing challenges with respect to these risks. This emerging new American landscape will require new paradigms for coastal and urban analysis, planning, and management.
LANDSCAPE, WEATHER AND GEOMORPHOLOGY Seven rivers serve the upper Texas coastline. These rivers, the Sabine, the Neches, the Trinity, the San Jacinto, the Brazos, the San Bernard, and the Colorado empty into a string of bays behind barrier islands. The thick layer of clay and sand that underlies the region was laid down over countless centuries as the ancestors of these rivers carried sediment from the Rocky Mountains to the sea. The land is overwhelmingly flat. It slopes from the center of Houston toward the Gulf of Mexico at a rate of one in five thousand (Figure 4). It slips into the sea falling gradually to form a notably broad and shallow continental shelf. In many places it is hard to say where land begins and sea ends. Mats of grass and coastal plants merge seamlessly into the water, creating a sponge-like habitat that is teeming with tiny fish and shellfish and covered with birds of different species depending on the season. If you reach into these wetlands with your hand you will pull up a crawling mass of life. This is the
Gulf of Mexico’s nursery. Underneath the surface layers of silt, sand, and clay are deeper layers of shale. Under these are pools of oil and gas that have sustained the region’s economy for a hundred years. The abundance of these mineral reserves near nascent port facilities and rail lines led to the development of the greatest conurbation of networked refineries, ports, and pipelines in the world. From New Orleans, Louisiana to Corpus Christy, Texas there stretches a vast network of refineries and pipelines carrying basic chemicals and refined petrochemical products and natural gas. This network is centered at the top of Galveston Bay in the Houston Ship Channel.1 The network fans out to the far reaches of North America, bringing raw materials to the Gulf Coast and supplying refined fuels and chemicals in return. The entire upper Texas coast is essentially one giant industrial plant that is woven into the landscape, cities, water, and air along its path. The adjacencies can be startling. Oil pumps rock up and down beside grazing cattle, alligators, and pink fields of roseate spoonbills. Oil tankers ply the same dredged shipping lanes as fleets of shrimp boats, with oyster boats in nearby shallow waters. Old men fish with bamboo poles beside fields of chemical storage tanks. Migrating ducks, hawks, and butterflies follow the trails of pipelines as they move north in the spring filling North America with wildlife and energy. The flatness of the land in proximity to a warm sea puts the region at risk of severe weather events as the Great Hurricane of 1900 and the many other hurricanes since have repeatedly shown. But the region is threatened with other sorts of severe weather as well. Rain falls at a rate that is unknown in other regions. Two hundred and fifty millimeters of rain in a single day is not uncommon. The record rainfall for the region occurred in July 24, 1979 when fourteen hundred millimeters of rain fell on Alvin, Texas in a twenty-four hour period.2
Geological History Twenty thousand years ago, ice sheets covered more of the earth’s surface than at any subsequent period. Sea level near present day Houston, Texas was at that time approximately one hundred and seven meters lower than it is today. The coastline
1 Mankad 2009 2 NOAA 2013a
4 Geomorphology & urbanism shown in relation to projected 7.6 meter surge tide inundation zone
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5 Prime ecosystems (Data courtesy Dr. John Jacob, Texas Sea Grant), 100 year rainwater flood plain, and 7.6 meter surge zone
was located some one hundred and thirty kilometers to the south of its present location. Texas’ rivers had carved deep valleys into the land as they made their way to the sea. As the earth warmed, many of these valleys were filled with rising seawater, creating the series of bays that defines the upper Texas coastline. At the height of the ice age, the Trinity and San Jacinto rivers came together near the center of present day Galveston Bay. They had carved a valley that was up to fifty-two meters deep under what is now the City of Galveston. The location and shape of the bay has changed as sea level rose and sediment was deposited. Today the average natural depth of Galveston Bay is only two to four meters. Galveston Island began to form about 2,500 years ago. With the creation of Galveston Island and her younger sister, Bolivar Peninsula, Galveston Bay was substantially separated from the sea. Fresh water from the Trinity and San Jacinto rivers began to have greater influence. Over the last 1,200 years, due to sea level rise, Galveston Island, the Bolivar Peninsula, and the coastal shoreline have been migrating landward at an average rate of about one to one and a half meters per year, and almost two meters per year on the west end of the Galveston and east end of Bolivar. Both Galveston Island and the Bolivar Peninsula today only average a few feet above sea level.3 Sea level rise in the region has been exacerbated by subsidence due to the extraction of ground water and oil. This is particularly evident in the upper Galveston Bay area and especially at the Houston Ship Channel, where subsidence in some areas exceeded three meters in the years prior to 1978.4 While subsidence has been substantially alleviated in many areas by bans on the use of ground water, the profile of the land has been permanently altered throughout the region. This combined with continuing sea level rise has left many historically safe areas at substantially increased risk of flooding. The Living Landscape Vast wetland areas dominate the lower reaches of the coastline, including its barrier islands. Progressing from salt water to brackish to fresh water dominated ecosystems as land rises
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from the sea, the region is a vital resource for all sorts of fish and shellfish in the bay system and in the Gulf of Mexico. It is also an essential way station for migratory birds as they traverse the region twice a year. The Texas coast has one of the highest migratory bird counts in the world. Birds from the central and eastern regions of North America are funneled through these wetlands as they head south and then either follow the coastline to Mexico or make the jump directly across the Gulf of Mexico to Yucatan and back. For birds that use the area as a jumping-off point, the presence of these rich feeding grounds along the Texas coast is essential (Figure 5). Galveston Bay is a shallow estuarial bay. Its one thousand six hundred square kilometer area makes it one of the largest bays in North America. After the Chesapeake Bay, it is the second most productive bay in the nation. Sport fishing, commercial fishing and recreational activities have an overall impact of over one billion dollars a year.5 An estimated ninety-seven percent of all commercial fishing and shell fishing in the Gulf of Mexico are dependent on wetlands of this sort at some point in their life cycle.6 Galveston Bay and the region surrounding it offer a wide range of ecosystems and habitats. Oyster reefs, mud flats, dune systems, wetlands, river deltas, prairies, and riparian forest all provide homes for an abundance of fin fish, shellfish, oysters and birds, as well as diverse mammalian wildlife, alligators and other reptiles.7
URBAN DEVELOPMENT The upper Texas coastline has been settled for thousands of years. After their arrival in the eighteenth and nineteenth centuries, European settlers quickly displaced native people. A notable early European settler was the pirate Jean Lafitte who in the early nineteenth century established Galveston Island and its surrounds as a pirate colony. Later, one of the most important battles of the Texas Revolution was fought at what is now the mouth of the Houston Ship Channel at the upper reaches of Galveston Bay. Galveston later became an important port as railroads began to bring cotton and other agricultural
3 Anderson 2007 4 Melosi 1979 5 Galveston baykeeper 2013 6 NOAA 2013b 7 Jacobs 2000
products for export and imported goods to the rapidly growing region, including large numbers of immigrants and, before the Civil War, slaves. By 1900 Galveston had established itself as an important port and significant urban and cultural center. The Great Hurricane of 1900 destroyed the City of Galveston, resulting in 7,000 - 10,000 deaths. As a result of this storm, the Galveston Sea Wall was constructed and much of the city behind it was raised to 5.2 meters above sea level, the approximate height of surge tide at this location. Recent studies have indicated that the actual surge tide height at Galveston was in fact 6 meters, and established this as the 100 year surge level.8 An ultimately more profound result of this disaster was the accelerated expansion of the now dominant Port of Houston and the Ship Channel leading to it. Since 1900 the City of Houston has grown at a rapid rate (Figure 6). The city grew over 25% (twice the national average) between the 1990 and 2000 census. The current population of the metropolitan area is over six million. Even more rapid population growth appears to be taking place today. Outside of the city limits of Houston, surrounding areas have grown even more rapidly than the city itself, especially over the last thirty years.9 The Buffalo Bayou-Gulf of Mexico Tansect Urban development in the region is centered along the Buffalo Bayou transect. Buffalo Bayou, the last tributary to the San Jacinto River, begins 48 km to the west of Houston. The western end of its watershed is seeing rapid suburban growth. At the center of its length, the bayou runs through the wealthiest residential districts of Houston, then through the city’s commercial core, and after that the Houston Ship Channel. Upstream suburban growth, which is rapidly consuming previously undeveloped natural prairies and agricultural land, threatens to greatly increase the rate of rainwater runoff. Two flood control dams to the west of the city protect the city center and the Ship Channel against upstream rainwater flooding. However, these dams are currently in disrepair. As a result, their allowable detention levels have been substantially reduced resulting in substantial increase in the risk of flooding. The remainder of the transect, the ever more deeply and widely dredged Ship Channel is subject to different pressures and different risks. The Ship Channel runs from just east of downtown Houston to the Gulf of Mexico and then out to sea until navigable depth is obtained. This channel serves the Port of Houston. Already the second most important port in North America, expansion planned for the near future includes major increases in chemical storage tank capacity, expansion of refineries, construction of coal terminals, accommodation of Post-Panamax shipping, and associated transportation infrastructure improvements. While not vulnerable to rainwater flooding, much of this development lies within the twenty-five foot hurricane surge-risk zone. The Clear Lake area and upper western shore of Galveston Bay now has a combined population of over a quarter of a million people living within the twenty-five foot surge-risk zone. Although repeatedly devastated by tidal surges from bay water, the western shore of Galveston Bay continues to be developed as a thriving commercial, residential and recreational sector with NASA Headquarters at its center. Along the lower western edge of the bay, Texas City contains another important population center and additional major industrial and port facilities. Below this, at the mouth of Galveston bay lies Galveston Island. The island suffered substantial and enduring loss of population in 2008 as a result of Hurricane Ike.
6 Map showing urban growth since 1915 (courtesy Dr. John Jacob and Texas Sea Grant)
CHALLENGES AND FUTURE PERSPECTIVES Riverine & surge flood protection Throughout the Houston region, riverine flooding has been a problem since the city’s beginning. The flat topography and occasionally extremely heavy rainfalls have long resulted in widespread flooding. Various engineering responses have been tried. Until recently, channelization of drainage systems was the preferred response. However, increased urban growth resulted in runoff exceeding the design limits of these channels, which were in any case unsightly and sometimes hazardous. More recent responses have included buyouts of repeatedly flooded properties, and removal of vast amounts of soil to increase channel sections and detain water in flood prone areas. Many of these redesigned drainage ways have been developed as recreational lands and wildlife habitat. These measures have been complemented by increasingly strict requirements throughout the region for new construction to detain rainwater on site to approximate natural runoff rates. Although not yet required in all areas, Low Impact Development (LID) requirements are seen as the most promising long-term solution to rain water flooding. However, existing developments, many recently approved projects, and developments in some jurisdictions are not required to meet these new runoff standards. Even so, rainwater flooding remains a secondary threat compared to hurricane-related tidal surges. Although the region has been repeatedly subject to devastating tidal surge flooding, the only structural protections that exist in the Houston-Galveston region are the Galveston Sea Wall, which does not protect the City of Galveston against flooding from bay water to the north, and the almost seven meter high Texas City levee. Although nearly overtopped in the recent Hurricane Ike, this levee has effectively protected Texas City and its associated refineries since its construction. Since the assaults of hurricanes Katrina, Rita, Ike and others, a number of proposals for additional structural and non-structural protections have been developed. These include a proposal for a monumental levee and gate structure known as the Ike Dike, which is intended
8 Needham and Keim 2013 9 Texas A&M Real Estate Center 2013
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7 Urban patterns related to Galveston Bay (map by Must Urbanism) 8 Galveston Bay: water system (map by Must Urbanism) 9 Vulnerabilities and layered defence plan. Green areas, all less than 1.5 meters above sea level, constitute the study area of the LSCNRA. Yellow areas are existing agricultural and native prairie lands. These zones buffer existing and proposed structural defenc es against surge tide and wave action and absorb floodwaters while creating economic and recreational opportunities and protecting coastal ecologies.
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Protected community
Elevated highway and coastal marsh
Elevated Galveston Seawall redesigned
10 Galveston Defence Option 3 showing existing Sea Wall, proposed sea wall expansion, shipping and vehicular gates as well as protective wetlands restoration and urban expansion areas
to run the approximately one hundred and ten kilometers from the western end of Galveston Island to the eastern end of the Bolivar Peninsula, and a proposal for an integrated multi-layered defence system known as the SSPEED Center proposal. These proposals are now entering a period of comparative analysis. The Ike Dike is intended as a singular masterstroke in the tradition of the heroic engineering of the nineteenth and early twentieth centuries. By preventing seawater from entering Galveston Bay during a hurricane, it intends to protect the entire bay against surge flooding. By being placed on the ocean-side beach of the barrier islands, it intends to protect Galveston Island and the Bolivar Peninsula against destructive flooding and wave action. Potential drawbacks include the expense of construction and maintenance, including costs related to accelerated beach erosion, and environmental impacts. Additionally, visual access to the beach would be lost and the threat of bay water flooding during hurricanes may remain a threat. Other proposals that have been put forward include a layered series of local structural interventions and a large-scale non-structural flood control measure. A single gate is proposed to connect escarpments on either side of the mouth of the Ship Channel at the top of Galveston Bay. This would protect the most important concentration of shipping and industrial facilities of the upper Gulf Coast against flooding. At risk in this area are over 1,700 major chemical storage tanks, and approximately 148 billion dollars in direct damage to industrial facilities not including loss of productivity or cleanup costs.10 As with other proposals, concerns exist here as well. ADCIRC studies have shown that in a major hurricane, during a seven and a half meter surge, this gate may cause 75-150 mm of increased flooding in some nearby areas 11 (Figure 9).
To the south of the Ship Channel, it is proposed to construct a levee connecting the Ship Channel Gate to the north to the Texas City levee to the south. Various alignments have been studied. A waterfront levee would protect the entire Clear Lake region and could be designed to provide a park and wetland system that would serve as a regional recreational resource. An alternative location for a levee is provided by nearby State Highway 146, which has sufficient right of way width to contain a levee system without any land purchase being required. Alternative hybrid proposals have also been studied. Each alignment option creates a different set of potential concerns. In one case waterfront homeowners are opposed. In the other, those left outside the confines of the protective levee are concerned about potential surge heights being increased by the construction of a levee. As has been said, Galveston is extremely vulnerable to storm surges from Galveston Bay water. The protection of the densely developed eastern end of the island could be achieved by extending the existing sea wall around the north side of the island. This could be accomplished while at the same time enhancing the urban waterfront as an industrial and recreational destination that will attract future development and help restore the island’s economy (Figure 10). The final component of the SSPEED Center proposal is the creation of the Lone Star Coastal National Recreation Area (LSCNRA). This proposal calls for the creation of a voluntary partnership between private and corporate landowners, government agencies and NGOs. This partnership would create an alternative economy for the most at-risk areas, which also happen to be the most ecologically productive and most historic areas along the upper Texas coastline. The new economy would rest on the coordinated protection, marketing, and devel-
10 Rifai 2013 11 Proft 2013
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12 The LSCNRA Diagram 13 Proposal by Nelda Pereira for a strategic integration of architecture, ecosystem protection, industrial infrastructure, and economic development. An eco-tourist and birding tower and boating-hiking trail access point at the mouth of the Houston Ship Channel, where migratory birds and international shipping cross, on dredge-spoils islands to be linked to the mainland by proposed levee and gate system.
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opment of recreational and ecological resources including the collective marketing of eco-system services. Implementation of this proposal, which can be achieved with or without the implementation of structural protections, would create substantial income for land owners and increase local employment in a sustainable manner while de-incentivizing construction in fragile and at-risk areas. By protecting these lands and their abundant flora and fauna, not only will people and industries be taken out of harm’s way, but also inland areas and Galveston Bay will benefit from continued flood protection.12 (Figure 12) Adaptive Frameworks Research into the various flood protection and economic development possibilities for the upper Texas coast seeks to define the most efficient and beneficial balance of security and growth. The goal is to develop a regional coastal resilience plan that is adaptable to changing circumstances: economic, social, ecological and climatic, including potentially accelerated sea level rise and increasing severity and frequency of severe weather events. In order to strengthen the metropolitan region surrounding Galveston Bay, planning must balance the preservation and enhancement of environmental qualities, urban development, and industrial expansion. These concerns must be understood as an interdependent network of what are normally considered to be independent systems. For this to be possible and for effective
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planning to take place, planners, architects and urban designers, hydraulic engineers and environmental scientists must work together with politicians and business leaders. The responsibilities and capabilities of the state, industry, government and private landowners must be redefined. Regional considerations must be reconciled with local concerns and opportunities. The future of the upper Texas Gulf Coast and the Galveston Bay region is a work in progress. Its future depends on the development of a new paradigm of urban and natural systems integration, one that is based on the coexistence of these essential systems. In the complexity of their dynamic interrelations, urban, ecological and industrial infrastructures can be said to resemble either a machine or an organism, one that is dependent on the proper functioning of all its mechanisms or organs to function smoothly. The apparent interchangeability of these two historically opposed metaphors in the discussion of emerging coastal conditions is emblematic of the need for a non-dichotomous paradigm of urbanism with nature. The urgency and universality of this need is being faced on a daily basis by research and design teams working in coastal and deltaic areas in all parts of the world. The essential multi-disciplinarity of these teams suggests the kind of understanding that will be required to address the many challenges and opportunities facing coastal regions today and in the future (Figure 13). 12 NPCA 2013
Venetian Lagoon Italy PAOLA VIGANÒ
Venice is an extreme case of controlling natural processes, with sophisticated water management covering a vast territory, not only that of the lagoon 85
Venetian Lagoon Italy
Milan Venice
Verona
Bologna
Pisa
0 The coastal plain is characterised by a sprawling urban development. The Padua-Treviso-Venice Metropolitan Area (PATREVE), has a population of 1.6 million people; 60,000 of them live in the historic city of Venice (map by Nijhuis and Pouderoijen, TU Delft)
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Environmental conditions and human activities (maps by Nijhuis and Pouderoijen, TU Delft)
Substratum
Climate
Agricultural land use
Transportation networks
Substratum The Venetian Lagoon is located in a coastal plain of 8,269 km2 (< 5 m Mean Sea Level). The Po is the main river in this region and has a length of 680 km, an average discharge of 1,460 m3/ sec and a sediment load of 10-15 Mt/year. Because of groundwater extraction, the islands in the lagoon (including Venice) are subsiding.
Climate The temperate humid climate is characterised by a mean annual precipitation of 748 mm with maximum runoff in winter/spring and average temperatures varying from 0 °C in winter to 30 °C in summer.
Agricultural land use The coastal floodplain is 80% in use for agriculture, mainly as cropland and some rice cultivation.
Transportation networks The Lagoon has two important hubs: the tourist-destination Venice, and the industrial hub of Venice-Mestre. Roads, railroads and navigation channels connect these hubs to the hinterland and the open sea.
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3 The Venetian Lagoon from the northeast, with Venice protected by a barrier island and in the background the alluvial plain with a diffuse urban pattern, 2011 (source: Photo-MTM, Italy)
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decreased ice coverage
Across the landscape: Between mountains and sea The idea of the transect, of the section across a territory, has a long history; in Histoire d’un ruisseau (The History of a Stream, 1869) Elysée Reclus, an anarchist geographer who moved between France, Switzerland, Belgium and many other countries, follows the stream’s entire path from mountain to lowland, describing how it works, its role, and metamorphosis of the watercourse into a river. Geddes, who held Reclus in great esteem, uses his better-known “section” that defines social and economic roles in relation to the position of activities and dwelling places along the valley. The transect across a mountain-to-lowland landscape is an analytical and design tool for understanding the territory and formulating adaptation strategies to climate change. The territorial transect also allows us to bring the many spatial differences that distinguish one area from another to the fore, establishing necessities and synergies. The transect intersects the plain north of Venice from the mountains in the northwest to the sea in the southeast (Figure 5). Below the mountains it crosses a dry plain to the north where the subsoil is composed of gravel. Here, the difficulty lies in providing water for irrigation, keeping it from immediately infiltrating into the water table and also purifying the infiltrated
5m
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EXTREME TERRITORIES The five meter elevation line identifies lowlands vulnerable to significant sea level rise and risk of flooding (Figure 4). It reveals several “extreme territories” along the European coast, including ancient land reclamation and industrial areas under transformation. This chapter addresses not only the areas which are progressively flooded along the coastline and in the lowest areas of the plain and subject to radical modifications, but also other parts of the drainage basin of the Venetian Lagoon and more generally the metropolitan area of Venice. The information comes from research studies carried out in recent years based on the three hypotheses.2 The first hypothesis is that the logic of the watershed dictates the interrelation of the different parts of the territory, upstream and downstream, in a sequential manner, coherent in space and time and fundamentally process oriented. Only a principle of solidarity and territorial responsibility can alleviate the hydraulic stress of the region’s most at-risk areas. Only by holding back and absorbing the excess water upstream can flood risk be reduced, even if not totally eliminated. Scenarios of adaptation start from the upland dry plain and proceed all the way down to the lagoon. The second hypothesis regards the diffuse urban condition of the territory of the Veneto and its capacity to adapt to climate change. Contrary to the commonly adopted point of view, which considers the territories of dispersion negatively from an ecological and sustainability point of view, we hypothesize that the minute and diffuse water network, as well as the interspersed agricultural areas, houses, warehouses, road networks, together constitute bastions of a resilient settlement structure that can be modified and adapted by resorting to its dense infrastructural substrate. The spatial amplitude of this
urban form, with the presence of open and cultivated areas and diffuse networks, is one of the specific characteristics of a structure capable, if understood, of responding to new conditions. Naturally, the hypothesis of a “project of isotropy” 3, capable of best exploiting this diffuse substrate in order to reduce the water risk, but also for the production of energy and food, requires a detailed and close reading of the possibilities, often lying latent, in the territory: whether this is a question of organizing new forms of mobility less dependent on the automobile, or whether it is one of facing frequent flooding in an increasingly impermeable space, fragmented by large infrastructure. The hypothesis of the project of isotropy and its ecological, economic and political rationality structure this entire work. The third and final hypothesis regards the role of climate change. Climate change will undoubtedly render the territories of Venice even more vulnerable in the future, leading to the making of an “extreme city” from both a morphological and topological point of view. However, it could also be used as connector: between different disciplines and know-hows and between the different parts of the territory, capable of constructing an ideography of the Venetian metropolitan territory. Here new alliances, new projects and planning styles are required.
contour line EEA
Venice is an extreme case of controlling natural processes, with sophisticated water management covering a vast territory, not only that of the lagoon.1 Our studies initially analysed the forms of water management in the Venice metropolitan area, which are highly complex in nature, and traced some threads of the area’s long environmental history during which an amphibious and hydraulic culture was formed. This culture is characterized by a meticulous maintenance of the water network for all its different purposes and by a habitual awareness of risk, though this has partially disappeared during the course of modernization.
1 Bevilacqua 1998, Cosgrove 1990 2 “Landscapes of Water” -research program in 2005 (Viganò et al. 2009), continued with “Water and Asphalt - The Project of Isotropy” in 2006 (Viganò 2008, Secchi 2011, Viganò 2011) and followed by the “Extreme City”-project (Fabian and Viganò 2010) 3 Viganò 2008, Secchi 2011
increased extreme rainfall
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4 The five meter elevation contour line enables the identification of lowlands which are vulnerable to significant sea level rise and the risk of flooding (source: Fabian and Viganò 2010) 5 Territorial section and climate change (source: Fabian and Viganò 2010)
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water in order to decrease current pollution levels. The relation to water is the opposite in the central wet plain with its clay soil, where the problem is drainage. Along the central wet plain, the ancient Roman centuriatio, a system of land subdivision, road and drainage networks, developed by monks in the Middle Ages, weaves its way at different angles to accommodate slopes and allow water to flow away from the impermeable ground (Figure 6). This system of generalized accessibility and water management has structured the growth of the diffuse city, but its efficacy has been compromised by the lack of maintenance as a result of reduced flood risk awareness and the change of primary economic activities. The increasing impermeabilization of the territory due to urban land use makes it even more compelling to restore the system’s efficiency in order to face extreme rainfall events. On-going urbanization and polder making In the 15th century, the Venetian Republic initiated the great diversion of rivers entering the lagoon in order to avoid it filling with sand and gravel from the northern mountains. Rivers were displaced to the east and west of the lagoon in an incredible endeavour that gave origin to the new science of hydraulics thanks to Galileo. During the Fascist period of the 1930s, colossal reclamation works were carried out in the low-lying wetland areas around the lagoon through polderization similar to the Dutch flood defence approach. This transformation was intense enough to completely change the land’s physical and ecological characteristics, using a complex systems of dykes, ditches and pumping stations to create new areas for intensive agriculture.4
The transect illustrates the impossibility of formulating any design strategy without a clear understanding of the different characteristics of various parts of the territory and the unique water, environmental and development problems they face. The difficulty of analysing hydraulic risk is aggravated by interdependencies among the different parts of the territory that climate change renders even more important and visible. Our proposed scenario of mitigation and adaptation focuses on the area between the mountain foothills and the lagoon, with the objective to collect and contain as much water as possible upstream in order to reduce the impact of extreme events downstream in the fragile lagoon ecosystem (Figure 9). Strategy: Slowing down and storing the water The first strategy developed in the scenario proposes exploiting the abandoned gravel pits in the dry plain (the strip of upland plain lying at the foot of the Dolomitic reliefs, featuring a thick alluvial mattress formed following the free expansion of the Piave River) for storing and purifying water, enabling it to infiltrate into the groundwater table and replenish it. As described before 5, if all of the gravel-pits in the dry plain were to be utilised as flood prevention reservoirs collecting excess fluvial flood waters, the quantities of water involved would be considerable. In the province of Treviso alone, close to 80 million cubic meters of water could be collected within the new basins - representing about half the capacity held by the Vajont Dam (150 million cubic meters) 6 and the water deficit of the Piave River resulting from the balance between use and resources, including vital minimum run-off. The holding capacity
4 Bevilacqua 1989, Bianchi 1989 5 Viganò 2009 6 After the tragedy of the Vajont Dam break in 1963, the utilization of the Piave River’s water (for electric energy and agriculture irrigation) went on - as if the available quantities had not changed - and the drawing off a river that was increasingly lacking water continued, especially in the summer months.
6 Water system and geological strips (source: Fabian and Viganò 2010)
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7 Urban patterns related to the Venetian Lagoon (map by Must Urbanism) 8 The Venetian Lagoon: water system (map by Must Urbanism)
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9 A new territorial section. Result of a workshop entitled “Climate change: Scenarios for new territories”, Università IUAV di Venezia, 2009 (Coordinator: P. Viganò, Scenario Is-land? Students: A. Bonadio, A. Curtoni, G. Mazzorin and I. Salmaso) 10 Landscape of water, requalification of a gravel pit as guided flooding basin (source: Viganò et al. 2009) 11 A diffuse park in the gravel pits of the dry plain. Student work by: C. Pisano, C. Roch Saiz, V. Saddi (European post-Master in Urbanism (EMU) - fall semester 2010, coordinated by: P. Viganò and B. Secchi) 9
10
of the existing gravel-pits could be sufficient to guarantee the necessary water for agriculture in periods of drought, significantly reducing drawing upon river waters in the more delicate periods of the fluvial ecosystem. This would also avoid the use of water from the mountain basins during the summer months when they are in demand for recreation and sports activities. Within this scenario, the gravel pits that are higher than the water table could be used as reservoirs. These deep and wide holes in the cultivated plain have often been abandoned and transformed into dumps; in the Treviso area, their capacity is around 77 million cubic meters. If these can be connected in a network to the dense pattern of channels fed by the waters of the Piave River, this would create an integrated new water system, which can reduce pressure from rivers during flood and store water for periods of drought (Figure 10). If we consider that the excavation of gravel, though reduced due to the economic and housing market crisis, has not ceased and will not cease, then a different excavation technique (agrarian reclamation) can generate a less invasive scenario with shallow pits, where agriculture can be restored after the exploitation. In this case, a series of bas-reliefs in the plain, modest depressions, might form the foundation of a new network while also being effective for guiding flood control (Figure 11). The quarries, the canals that would connect them to rivers, the pathways running along them, the tree-lined strips, the enhanced embankments: the exploitation of the gravel and the re-use of the abandoned gravel-pits provide an extraordinary opportunity to re-think the territory, its landscape, its construction modalities, and the activities that involve it directly today. From hidden, fenced off and dangerous places, the gravel pits can be reintegrated into the inhabitable space of the diffuse city. The difficult concept of ecological continuity (an often misused term) is essential to interpreting this territory in design terms. Located at the limit of very different landscapes and
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11
eco-systems, the dry plain land area - situated along the prealpine foothills and the spring line crossed by the rivers - must maintain its role in filtering, as an area for water to percolate from one environment to the other, from north to south and east to west and also through the underground layers. Between the wet and the dry plain the spring line feeds karst spring groundwater to rivers which are a lot calmer than the alpine ones. In recent years, the lowering of the water table has reduced the flow of groundwater rivers and the water available for emergency irrigation in the summer. Reinforcing the role of the permeable plain and recharging the upland plain water table would feed the groundwater rivers. Specifically, structured arboreal systems could be used to manage the water from the rivers, intercepting the excess water in the periods when this is feasible and purifying it. The transitional area defined by the karst springs must be protected from pollution. Here reforestation and ecological agriculture might help redesign the rural landscape and improve its ecological qualities with new agro-forestry models in which trees can purify water. “Filtering woodlands made up of small tracts of land that are cultivated for short-rotation wood crops and crossed by a network of drainage and infiltration ditches, … would allow for the refinement of the surface waters or effluences of the depuration plants”.7 Progressively passing through terrains that are ever less permeable as the water proceeds towards the lagoon, the capacity to slow down and store water becomes ever more crucial. In the recent extreme events (2014 and 2010), press coverage shows that all the concerned parties have become aware that redesigning and maintaining the lesser channels is necessary. During those events, the secondary watercourses were unable to discharge into the rivers, which were already saturated, and not even into the sea, due to continuing high tides.
7 Mezzalira 2009
New dikes for flooding In narrating the metamorphoses observed along the course of the stream, Reclus imagines the watercourses creating a new network of arteries both large and small that transform the plain into an “immense garden”. He argues that the fact that floods fertilize the terrain along with the naturally low areas can contribute to governing and solving the dilemma of water shortages, as well as of excess water. Thus, a careful reading of the microtopography in the low plain, details which are not obvious to the naked eye, but that were always taken into account by ancient settlements, would allow us to conceive of spaces for water along the rivers, in the low-lying areas that in the past had meadows and lowland forests. This approach also allows one to imagine new topographies that use and exploit the minor networks, introducing new systems of slight depressions that can help increase the multifunctionality of the areas. Of course, increasing the flow section of the drainage channels and ditches is not enough; one also needs to clean and reopen these channels to increase the capacity of the basin. This process is not only the responsibility of water boards (consorzi di bonifica) that deal with water resources, but also of the individual owners of the agricultural areas, who have always maintained the water networks and banks that cross their fields - spaces which are common, although not public. These issues have been broached in the case of a natural depression of about 700 hectares called Prà dei Gai, as a means to manage flooding on the Livenza River, which is menaced by its tributary, the alpine Meduna River. The depression, immediately north of the confluence, could be used as a basin to reduce the risk of flooding, but Prà dei Gai is also a vast grass surface along the river around which there are small developments, linear settlements, dispersed industrial activities, agriculture, and old Venetian villas transformed into luxury hotels. Existing dikes and paths are the frontier between this large, mostly empty
area, which currently floods once or twice a year, and the rest of the territory (Figure 12). The interventions to adapt the existing natural depression could lead to the creation of a contemporary park in the process of transforming the depression into a flood containment basin; to achieve this, the depression would need to be separated from the river by a new dike and connected by a new canal. These interventions are based on two main concepts: the first accepts the new dyke configuration and explores the patterns of interaction between the interior and the exterior of the new flood area; the second reverses the engineering concept and proposes using the new dykes to frame the built areas instead of the river and flood basin. The water can find new spaces between the built areas protected by the new dykes, which can also be used to host dwellings and work facilities. A process of phyto-depuration of white and grey water could be integrated along the dykes to solve the current lack of a sewage system in some parts of the area. Although the latter approach extends the amount of territory threatened by flooding, both environmental and hydraulic engineers agree upon the feasibility of this solution. From the spatial point of view, the two concepts define alternative configurations of great interest, in both cases based on the design of border and cross-border devices that mediate the relation between the inhabited areas and those set aside for flooding in extreme events. In both cases, the grassland of Prà dei Gai, through which the Livenza River flows, can now be today interpreted as the empty centre of a wider diffuse area, where a rural society once used to meet for village fêtes and cattle fairs. A final strategy would be to allow the low-lying areas close to the lagoon to be flooded by re-modelling the low wet plain, changing its current use and reversing the reclamation that took place in the last century. This would involve using and reinforcing the existing embankments that protect the settlements,
13
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12 Prà dei Gai (metropolitan region of Venice), concepts for development: dikes along the rivers; dikes around the settlements (European post-Master in Urbanism (EMU), Consorzio di bonifica sinistra Piave (eng. Vincenzo Artico). Workshop coordinated by P. Viganò and G. Zaccariotto) 13 The “Rooms” model. Result of a workshop entitled “Climate change: Scenarios for new territories”, Università IUAV di Venezia, 2009 (Coordinator: P. Viganò, Scenario W/Netlands. Students: F. Arca, A. Cassol, C. Furlan and M. Rossi)
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14 14 The Rooms’ borders as a new structure for a fragile territory. Present conditions and future scenarios. Student work by F. Arca, A. Cassol, M. Rossi, Water borders. Diploma in Architecture, Università Iuav Venezia (Thesis coordinators: A. Aymonino, P. Viganò, with M. Bianchettin, L. Fabian and S. Peluso) 15 Water and asphalt, the project of isotropy in the metropolitan area of Venice (Contribution to X Venice Architecture Biennial 2006 by B. Secchi and P. Viganò with PhD students in Urbanism)
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and enlarging the space of the rivers in the low impermeable plain, as well as using the dyke-system as a support for a new territorial organization. The lower plain consists of a complex network of canals and dykes that divide the plain into sub-basins, “rooms” which sometimes contain an urban centre, but more often corn fields. Instead of trying to resist climate change by building higher dykes, for example in the case of the Piave River dykes which protect the city of San Donà, the idea is to introduce weak points, allowing the excess water to pass through the existing canals to “agricultural rooms” where it can be stored (Figure 13 and 14). With a careful reading of topography, the adaptation to climate change would be gradual, eventually leading to the flooding of most of the reclaimed plain. By that time, the infrastructures will have had to be adapted in all their networks in order to maintain the connections between the various towns and cities; the higher ground will serve as connecting filaments; these higher areas will need to be densified, and a new settlement structure could be conceived. Nevertheless, given the critical condition, small-scale interventions in the low wet plains are also required, such as implementing areas for diffuse water storage and redesigning the network of public spaces.
FUTURE CHALLENGES Although each of the aforementioned strategies can be conceived and put into practice separately without reference to the other, the power of the idea of the transect is to reconnect places and territories within a broader common vision of restoration and improvement. The degree of sea-level rise is still very uncertain, but if the proposed eustatic scenarios come true, the
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entire hydrographic system of the Padana Plain, the Po Delta and the lagoon hinterland crossed by the rivers would undergo heavy modifications. These changes would play havoc with the relations between the hydrographic basin and the lagoon. For this reason, the proposed strategies are highly important not only to protect against the rising sea level, but also to counter the risk of inland flooding, which would circumvent the mobile barrages that are now nearing completion. For obvious historical, cultural and ecological reasons, the Venice lagoon area is regarded as a place that cannot totally give way to water. Flood prevention techniques have been implemented, like raising the level of pavements and walkways in the city or devising mobile barriers against high water, such as the construction of the MOSE – a large barrier project now under completion, as an attempt to combat rising water levels. These flood defence projects improve the resistance of the territory, making it more able to remain undisturbed by events, but the area remains extremely fragile and is highly prone to extreme events. However, in the interior areas of Venice’s metropolitan region, flood risk can be reduced through more resilient strategies, for example by improving the evacuation capacities of minor water systems, conceiving and devising works that adapt temporarily to perturbations to regain their former status over time 8, such as allowing temporary flooding of given places, which are later returned to their regular use. This approach allows an ecosystem to endure and persist, albeit with great heterogeneity and many periods of instability.9 Beyond the case of the city of Venice, we need to reflect on a new balance between resistance and resilience on a regional scale (Figure 15), adapting the existing infrastructure to the new conditions arising from climate change, considering the associated risks as well as contemporary values.
8 Klein, Nicholls and Thomalla 2003 9 Holling 1973
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About the authors
Robert Broesi is Partner and Urban Designer at MUST Urbanism, Amsterdam (The Netherlands) and Cologne (Germany) Richard Campanella is Senior Professor of Geography at Tulane School of Architecture, New Orleans (USA) Thomas Colbert is Associate Professor of Urban Design at the Gerald D. Hines College of Architecture, University of Houston (USA) João Pedro Costa is Professor of Urbanism at the University of Lisbon (Portugal) Wolbert van Dijk is an independent landscape architect based in Rotterdam (The Netherlands) Marcel Marchand is Senior Researcher at Deltares, institute for applied research in the field of water, subsurface and infrastructure (The Netherlands) Han Meyer is Professor of Urban Design at the Department of Urbanism at the Delft University of Technology, Faculty of Architecture and the Built Environment (The Netherlands) Dirk Neumann is Urban Designer at MUST Urbanism, Amsterdam (The Netherlands) and Cologne (Germany) Steffen Nijhuis is Assistant Professor of Landscape Architecture at the Delft University of Technology, Faculty of Architecture and the Built Environment (The Netherlands) Pham Quang Dieu is Lecturer at the University of Ho Chi Minh City (Vietnam) and PhD-candidate at the Delft University of Technology (The Netherlands) Michiel Pouderoijen is Researcher at the Chair of Landscape Architecture, Delft University of Technology, Faculty of Architecture and the Built Environment (The Netherlands) João Figueira de Sousa is Associate Professor of Regional Planning and Geography at the University of Lisbon (Portugal) Trang Le is Lecturer at the National University of Civil Engineering, Faculty of Architecture and Planning, Hanoi (Vietnam) Paola Viganò is Professor of Urbanism at the University of Venice IUAV and a partner of Studio Associato Secchi-Viganò, Milan (Italy) Veronica Zagare is a researcher at the Instituto Superior de Urbanismo of the University of Buenos Aires (Argentina) and PhD-candidate at the Delft University of Technology (The Netherlands)
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URBANIZED DELTAS IN TRANSITION Editors Han Meyer and Steffen Nijhuis ISBN 978-90-8594-054-8 Keywords Delta urbanism, Mapping in landscape architecture and urban design, Urbanization, Resilience, Sustainable urban planning, Comparative research, Design research, Research-by-Design, Geographic Information Systems, Global datasets Copy editing Sören Johnson Graphic design Linda Swaap, Accu grafisch ontwerpers Cover illustration Steffen Nijhuis and Michiel Pouderoijen Printing AD Mercurius, Almere Published and distributed by Techne Press, Amsterdam, The Netherlands www.technepress.nl Acknowledgements This study is part of the Delta Urbanism research program at the Delft University of Technology, Faculty of Architecture and the Built Environment, Department of Urbanism. The research has partly been conducted in the context of Integrated Planning and Design in the Delta (IPDD), a research project conducted by a consortium led by Delft University of Technology and financed by the Netherlands Organization for Scientific Research (NWO). MUST Urbanism was one of the leading partners in this project. The involvement of Delft University of Technology in the Dutch Dialogues project in New Orleans created the opportunity for knowledge exchange with Tulane University (New Orleans). Collaboration with the University of Houston and the University of Buenos Aires, initiated by Diego Sepulveda Carmona, provided the possibility to extend the study with Galveston Bay and the Paraná Delta. Collaboration with the Università IUAV di Venezia in the context of the European Postgraduate Masters in Urbanism (EMU) made it possible to include the Venetian Lagoon in this study. Results of this study have been shown at the Architecture Biennale of Buenos Aires (2013), the International Architecture Biennale Rotterdam ‘Urban-by-Nature’ (2014) and the Biennale of Venice (2014). The chapters on the Mississippi River Delta, Mekong Delta and Paraná Delta are reworked versions of articles published in the journal Built Environ ment, Vol. 40 nr. 2, 2014. Financial support by the TU Delft Infrastructures and Mobility Initiative (DIMI) and the University of Houston made it possible to publish the book.
Copyright © 2014 by the authors and editors, unless otherwise stated. All rights reserved. No part of this publication may be reproduced or stored by any electronic or mechanical means (including copying, photocopying, recording, data storage, and retrieval) or in any other form or language without the written permission from the publisher. The sources used preparing this book have been identified to the best of our ability and permission has been granted to use the materials. If a source has been incorrectly identified or appears without the appropriate permission, please contact the publisher and/or editors.
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URBAN PATTERNS AND WATER SYSTEM reduced tide tide river discharge spillway large river, lake, sea sandbank, riverbank, shoreline wetlands swamp water course, canals and rivers controlled flood area reclamation of wet ground topography dune dam storm surge barrier lock floodgate primary dike, flood barrier highway main road landfill / harbour urban area
Urbanized deltas are highly complex systems. They are the most densely urbanized and industrialized areas in the world; at the same time, they face many threats from climate change, being extremely vulnerable to flooding, erosion, and silting up of ports. At the beginning of the 21st century, most of the world’s urban deltas face a ‘critical transition’, in response to increasing imbalances. Climate changes and societal developments lead to conflicting land use claims, with space for water on the one hand and urbanization, industry and agriculture on the other. In order to survive in the long term, urban deltas need to be approached from new perspectives, as adaptive systems. Urbanized Deltas in Transition compares eight international urban deltas. Exploiting the power of Geographic Information Systems (GIS) and employing high-quality global datasets, it studies the mutual relations among different components in a series of urban deltas, and proposes new perspectives for enhancing the adaptability of these vital regions.
ISBN 978-90-8594-054-8
9 789085 940548
