Using a Multi-Criteria Matrix Approach to Prioritise ...

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Using a Multi-Criteria Matrix Approach to Prioritise Estuary Management Options from a Multitude of Management Plans Louise Howells1, David Rissik2, Scot Hedge3 and Lucy Archer4 Senior Project Engineer, Lawson and Treloar, Sydney, 2Data and Technical Officer, Estuaries Unit, Department of Land and Water Conservation, Sydney, 3Environmental Project Officer, Warringah Council, Sydney, 4Environmental Consultant, KBR, Sydney 1

Abstract: Most Council's face a complex timing issue with regard to the preparation and implementation of management plans under different local and state government programs covering the one natural resource (e.g. an estuary). In some cases, an estuary and its catchment can fall under five or more management plans, which may be area dependent or broad ranging. Warringah Council faced this issue in the management of the Dee Why Lagoon system. An approach to resolve this matter has been utilised for the assessment of potential estuary management options. The approach involves the extraction of all options from each individual plan for assessment into a common format as well as identification of additional options via a gap analysis. Following this, a set of economic, social and environmental criteria is identified to form the basis of a multi-criteria assessment matrix. In the case of the Dee Why Lagoon Estuary Management Study, there were over 200 options, varying spatially and temporally and ranging from education programs through to engineering works identified for the management of the whole system. The approach developed may well prove to be a solution for a number of other estuaries.

INTRODUCTION The management of an estuary is complex task due to the nature of the processes occurring within an estuarine system such as a coastal lagoon. These complexities are further hampered by jurisdictional and legislative issues that result in a variety of management plans for a single catchment and estuary. This issue has been highlighted in the NSW Healthy Rivers Commission of Inquiry into Coastal Lakes [2002]. Catchment processes heavily influence systems such as these. The Commissions findings outlined that integrating all management plans in the catchment enables a 'whole of catchment' approach to be adopted for the management of a coastal lagoon. As such it s essential that all existing plans be integrated for the catchment and a gap analysis of these plans be undertaken. Such an approach has been utilised as part of the Dee Why Lagoon Estuary Management Study to overcome the tyranny of multiple management plans. CASE STUDY - DEE WHY LAGOON AND ITS MANAGEMENT FRAMEWORK Dee Why Lagoon is located on the northern beaches of Sydney within the Warringah Council Local Government Area (LGA). The Lagoon is an intermittently closed and open lake or lagoon (ICOLL). Opening occurs either as a result of heavy rain or by artificial means (authorised or unauthorised). When closed, the lagoon covers an area of approximately 30 ha, has a maximum depth of the order of 1.5 m and has an entrance beach berm that has a managed level of 2.2 mAHD. It has a catchment area of approximately 570 ha. In addition to Warringah Council and the Department of Land and Water Conservation, the Lagoon is accorded value by a number of groups including the National Parks and Wildlife

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Service and NSW Fisheries as well as community groups such as the Friends of Dee Why Lagoon. The Lagoon and a portion of its riparian area make up what is known as the 'Dee Why Lagoon Wildlife Refuge'. Beyond this area the lagoon is surrounded by highly urbanised land. Most of the land use in the catchment is residential with some industrial development in the northwestern parts. The Lagoon has a high conservation value for flora and fauna and provides a valuable area of open space within an urban setting. The main issues for the Lagoon have been canvassed through a number of consultative approaches and through various management planning investigations. The issues were summarised into nine major areas which included aspects such as poor water quality, illegal breaching of the lagoon and the need for protection of the lagoon for ecological value. The management of Dee Why Lagoon is principally undertaken by Warringah Council with assistance from the Department of Land and Water Conservation. This responsibility falls under the umbrella of the Estuary Management Policy for New South Wales, which is defined in the Estuary Management Manual [NSW Government, 1992]. The estuary management manual recommends an eight-step process to implement the Estuary Management Plan, much of which has been undertaken (MHL, 1997; AWT, 2001; Lawson and Treloar, 2002). The next step is the production of the management plan. LAGOON MANAGEMENT OBJECTIVES In the case of such an urbanised catchment, unrealistic environmental objectives for the estuary are unlikely to be met because of existing, largely irreversible, conditions. In light of this issue and given the historical approach to management of the entire system, management objectives were derived on a spatial unit (an area) basis which were identified and mapped where possible. The units were: • Community - not mapped since the community is not confined to a single group or a specific area • Catchment - generally with fixed boundaries, except for some areas where high flow events can cause alternate flow paths to operate, the definition of catchment is inclusive of stormwater assets within the areas referred to as the 'Wildlife Refuge' and 'Other Foreshore' • Tributaries and Corridors - connecting Dee Why Lagoon with other natural resources such as Narrabeen Lagoon, Long Reef Headland and Curl Curl Lagoon • Wildlife Refuge - the majority of the area fringing the Lagoon proper • Other Foreshore Areas - the south-east corner of the Lagoon foreshore • Waterbody - the area covered by water when the Lagoon is filled and the entrance is closed • Entrance - broadly that area dominated by mobile marine sediments • Monitoring/Research - encompasses all units. EXTRACTION AND FORMATTING MANAGEMENT PLANS

OF

OPTIONS

FROM

EXISTING

The management options for the Lagoon were derived from a multitude of existing management plans and strategies including: • Wildlife Refuge Plan of Management [Warringah Council, 2002]

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Sydney Water Sewer Overflow Abatement Program [SWC, 2001] Vegetation Management Plan [Kate Low and Assoc, 2000] Dee Why Lagoon Wildlife Refuge - Summary of Community Values, Issues and Management Proposals Arising from Consultation of November 1998 Stormwater Management Plan [PBP, 1998] Warringah Council Geographic Plan of Management for Coastal Community Lands [Warringah Council, 1998] Warringah Council Recreational Strategy for Warringah's Beaches and Coastal Open Space [Warringah Council, 1998] Dee Why Valley and South Creek Open Space Corridor Geographic Plan of Management [Clouston, 1996] Dee Why Wetland - Rehabilitation and Management Plan [Winning, 1994] Dee Why Urban Design Strategy [Dickson Rothschild, undated].

Over 200 options were identified for possible implementation. Detailed assessments of major options including the feasibility of dredging and the rehabilitation of a tributary creek (Dee Why Creek) were included as part of the study and are reported in detail in Lawson and Treloar [2002]. GAP ANALYSIS Management gaps were identified by extracting all options into a common format to a spatial basis. As a result, the means of identifying where gaps occurred was greatly simplified and areas with few or zero options were identified and addressed. MULTI-CRITERIA MATRIX ANALYSIS A decision making framework was devised in order to subjectively rank each option on the basis of a set of standard criteria. These criteria were: • • • • • • •

Capital Cost Estimate Recurrent Cost Estimate Estimated Life Cycle Cost of Implementation Technical Feasibility Meets Management Objective(s) Flora Impact - Aquatic Flora Impact - Terrestrial

• • • • • • •

Fauna Impact - Aquatic Fauna Impact - Avifauna Fauna Impact - Terrestrial Water/Sediment Quality Impact Human User Impact Community Acceptance Council/State Agency Acceptance.

A score was assigned for each option for each criterion by a team of scientists and engineers based on subjective scales developed. In assigning scores to each of the options it was assumed that construction impacts would be assessed prior to any physical works and that appropriate mitigation measures will be implemented to ensure minimal ecological impact during works. Using the decision making framework all options were ranked on the same basis. Overall, the analysis yielded the following types of options which proved to provide the greatest benefit for their cost including: • policy revision • revision of maintenance practices • placement of signage, and • distribution of education materials.

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The outcomes of the analysis indicate that small scale options (such as policy change and maintenance works) are the most cost-effective solutions where resources are limited. Options involving major capital works such as dredging of the Lagoon and rehabilitation of the creek, whilst resulting in major and observable changes, are less cost-effective in their application. The objectives being addressed by each proposed management action are clearly stated and unambiguous and are suited to performance assessments. Performance indicators for each management action are not addressed at this stage of the management process but will be addressed during the production of the management plan. CONCLUSIONS AND RECOMMENDATIONS Whilst not a complex process, the extraction of management options from multiple plans into a single format is a time consuming task. Most plans are generally not in a common format and are generally not available in an electronic format. Both the entry of all options into a single database and the rationalisation of the options to a common format and elimination of overlaps consume considerable resources. However, the benefits of such an approach recognise the extensive work that has preceded the preparation of an estuary management plan. This approach, rather than 'reinventing the wheel', allows for the collective useful conclusions drawn previously to be utilised and assists with identifying gaps and overlaps in management plans. The use of multi-criteria matrix analysis techniques, whilst subjective, allows for the identification of priorities across a wide range of different types of options. The approach results in a clear direction for natural resource managers to seize upon, in a climate of limited funding and ongoing competition between different stakeholders for the implementation of single-issue management solutions. Acknowledgements The ongoing assistance in the estuary management process for Dee Why Lagoon is underpinned by strong community support from the Friends of Dee Why Lagoon whom are tireless in their enthusiasm to see the Lagoon managed and conserved both now and for future generations. Their assistance is gratefully acknowledged. References AWT, Dee Why Lagoon Estuary Processes Study, prepared for Warringah Council, 2001 Clouston, Dee Why Valley and South Creek Open Space Corridor - Geographic Plan of Management, prepared for Warringah Council, November, 1996. Dickson Rothschild, Dee Why Urban Design Strategy. Prepared for Warringah Council. Healthy Rivers Commission (2002) Independent Public Inquiry into Coastal Lakes: Final Report, ISBN 0 9577 268 6 4, undated. Kate Low and Associates, Draft Vegetation Management Plan Dee Why Lagoon Wildlife Refuge. Prepared for Warringah Council, 46p., 2000. Lawson and Treloar, Dee Why Lagoon Estuary Management Study, Prepared for Warringah Council, Draft, July, 2002. Manly Hydraulics Laboratory (MHL), Dee Why Lagoon Data Compilation Study, Report MHL845 prepared for Warringah Council, May, 1997. New South Wales Government, Estuary Management Manual, New South Wales Government: New South Wales, Australia, 1992. Patterson Britton and Partners (1998) Northern Beaches Stormwater Management Plan. Report prepared for Warringah Council. SWC, 2001 Warringah Council, Geographic Plan of Management for Coastal Community Lands. Adopted 23rd June 1998.

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Warringah Council, Recreation Strategy for Warringah’s Beaches and Coastal Open Space. Adopted 23 June 1998. Warringah Council, Warringah PLAN 2000 - 2003 (Warringah Council Management Plan), 2000. Warringah Council, Draft Dee Why Lagoon Wildlife Refuge Plan of Management (2), 23 April 2002. Winning, G., Dee Why Wetland Rehabilitation and Management. Report prepared for Warringah Council by Shortland Wetlands Centre Ltd and Ecological Management Consultancy, 30 pp, 1994.