Managing Urban Stormwater: Council Handbook · A stormwater management plan is a document that provides the direction for stormwater management within a catchment or sub-catchment.

Managing Urban Stormwater:Council Handbook

Draft

November 1997

NSW Environment Protection Authority

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Acknowledgments

This document is the result of input from a number of sources. The project manager andprincipal author was Mike Sharpin, with significant input from Shane Barter. Thisdocument and the draft document Managing Urban Stormwater: Strategic Framework, onwhich this document is based, benefited from input from various Environment ProtectionAuthority staff, particularly Joe Woodward and Anne Clark. Paul Clark (formerly of theEPA) also provided input into this document and was responsible for guiding a series ofPilot Projects on stormwater management, which have assisted in preparing thisdocument. Eric Hatfield (EPA), Russell Cowell (EPA), Barbara Schaffer, Cathy Gray, ChrisGray and Peter Coupland have also helped prepare previous documents which assistedwith the evolution of this document. Constructive comments have also been receivedfrom reviewers of the draft Managing Urban Stormwater: Strategic Framework document. The assistance of the Ontario Ministry of Environment and Energy, and Ministry ofNatural Resources, Canada, is also appreciated.

For technical information about this report, contact:Manager StormwaterEnvironment Protection AuthorityLevel 15, 59-61 Goulburn StPO Box A290Sydney South 1232Phone: (02) 9795 5000 (main switchboard)Phone: 131 555 (publications and information requests)Fax: (02) 9325 5999

Published by:

Environment Protection AuthorityLevel 15, 59-61 Goulburn StPO Box A290Sydney South 1232Phone: (02) 9795 5000 (main switchboard)Phone: 131 555 (publications and information requests)Fax: (02) 9325 5999

ISBN 07313 2792 6EPA 2001/73November 1997

Printed on recycled paper

iii

Foreword

Urban stormwater management is a complex and challenging issue. There is no singleanswer to our stormwater management problems and we need to derive innovativemanagement approaches using a mix of strategies. The effective management of urbanstormwater is also a shared responsibility, requiring the active involvement of many StateGovernment Agencies, local councils, land developers, building contractors, industry andindividuals.

The preparation of catchment-based stormwater management plans provides anopportunity to involve all stakeholders in the development of an appropriate andcoordinated mix of strategies to address the specific management issues for eachcatchment. These plans will highlight the significant conceptual shift that has occurred instormwater management, focusing on issues that affect the health and amenity of ourwaterways rather than perpetuating the limited and traditional focus on flood mitigationand drainage. Many of the solutions will be found by looking upstream to find ways wecan manage a range of day-to-day activities, rather than focusing on managing thedownstream impacts.

The NSW Government is releasing a series of Managing Urban Stormwater documents toassist local councils and other organisations with urban stormwater managementplanning and improving stormwater management practices.

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Managing Urban Stormwater: Council Handbook

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Managing Urban Stormwater: Council Guidelines

Contents

PART A – STORMWATER MANAGEMENT PLANNING..............................................1

1 INTRODUCTION ....................................................................................................... 31.1 Managing Urban Stormwater.................................................................................... 31.2 Purpose of this document........................................................................................... 31.3 Roles and Responsibilities for Stormwater Management ......................................... 3

2 WHAT IS A STORMWATER MANAGEMENT PLAN? .......................................... 4

3 THE NEED FOR STORMWATER MANAGEMENT PLANS................................... 5

4 STORMWATER MANAGEMENT PRINCIPLES ...................................................... 6

5 UNCERTAINTY.......................................................................................................... 7

PART B – THE STORMWATER MANAGEMENT PLANNING PROCESS................9

6 FRAMEWORK FOR PREPARING STORMWATER MANAGEMENT PLANS.... 116.1 Legal Framework ...................................................................................................... 116.2 Relationship with other Plans .................................................................................. 116.3 Cooperation between stormwater managers .......................................................... 116.4 Consultation.............................................................................................................. 126.5 Council Activities Affecting Stormwater................................................................. 126.6 Stormwater Management under the Local Government Act................................. 13

7 STAKEHOLDER INVOLVEMENT IN THE PLANNING PROCESS..................... 13

8 PREPARING STORMWATER MANAGEMENT PLANS....................................... 14

9 IMPLEMENTATION ................................................................................................ 34

10 MONITORING.......................................................................................................... 35

11 REVISING THE PLAN.............................................................................................. 36

PART C – EXAMPLE STORMWATER MANAGEMENT PLAN .................................39

REFERENCES .....................................................................................................................57


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APPENDIX A – NOTICE REQUIRING PREPARATION OF STORMWATERMANAGEMENT PLANS .....................................................................................................69

APPENDIX B – URBAN STORMWATER AND THE ENVIRONMENT.....................71

APPENDIX C –STORMWATER MANAGEMENT PRINCIPLES................................93

APPENDIX D - LEGISLATION AFFECTING URBAN STORMWATERMANAGEMENT................................................................................................................. 115

APPENDIX E – CATCHMENT AUDITING ................................................................... 127

APPENDIX F - STORMWATER QUALITY MODELLING.......................................... 133

APPENDIX G - STORMWATER QUALITY MONITORING ....................................... 141

APPENDIX H – ASSESSING THE POTENTIAL IMPACTS OF NEW URBANDEVELOPMENTS............................................................................................................. 153

APPENDIX I - STORMWATER MANAGEMENT SYSTEMS.................................... 157

List of Figures

Figure 6.1 – Possible Stormwater Management Structure....................................................12Figure 8.1 – Tasks for Preparing Stormwater Management Plans.......................................15Figure 8.2 – Linkages between catchment values, stormwater management objectives,

issues, causes and management options.........................................................................16Figure 9.1 – Linkages between a catchment-based Stormwater Management Plan and

Council Management Plans ............................................................................................35Figure I.0.1 - The Stormwater Management Process ..........................................................159

List of Tables

Table 4.1 – Stormwater Management Hierarchy ...................................................................7Table 5.1 – Potential Stormwater Management Techniques ..................................................8Table 6.1 – Potential Influence of Council Activities on Stormwater...................................13Table 8.1 – Potential Stormwater Treatment Objectives.......................................................23Table 8.2 – Possible Management Issues and Causes............................................................25Table 8.3 – Potential Management Practices .........................................................................27Table 8.4 – Cost scores for Option Ranking Scheme.............................................................31Table 8.5 – Benefit Scores for Ranking Options Scheme.......................................................31Table 8.6 –Example Options Ranking Sheet..........................................................................33


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PART A – STORMWATER MANAGEMENTPLANNING


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1 INTRODUCTION1.1 Managing Urban Stormwater

This document is part of a package of documents on managing urban stormwaterpublished by NSW Government agencies. The other components of the package are:

• Managing Urban Stormwater: Source Control. This document contains a range oftechniques for managing stormwater at the source, including education and Counciloperations.

• Managing Urban Stormwater: Treatment Techniques. This document contains a range oftechniques for treating the runoff from urban areas.

• Managing Urban Stormwater: Soils & Construction, which describes urban soilconservation and stormwater management of construction activities.

1.2 Purpose of this document

A notice requiring the preparation of catchment-based stormwater management planswas issued to all local councils by the Environment Protection Authority under Section 12of the Protection of the Environment Administration Act 1991. This notice is reproduced inAppendix A. The Sydney and Hunter Water Corporations, the Roads and TrafficAuthority and other State Government agencies with stormwater and/or landmanagement responsibilities are required to cooperate with councils in the preparation ofthese plans.

The aim of this document is to provide guidance to local councils and other organisationson the preparation of catchment-based stormwater management plans in accordancewith this notice. It also provides State Government agencies, developers and otherorganisations with guidance on meeting the requirements of a stormwater managementplan.

This document discusses the process involved in preparing these plans and provides anexample plan which provides a guide on a suitable format of a catchment-based plan.

Where this document refers to a catchment it should be read as also referring to a sub-catchment of a larger catchment.

These guidelines are intended for application in urban residential areas under post-development conditions. The planning process could, however, also be applied to largefreeway projects or industrial/commercial sites. The preparation of Erosion and SedimentControl Plans for construction activities is discussed in Managing Urban Stormwater: Soils& Construction.

1.3 Roles and Responsibilities for Stormwater Management

Stormwater management within a catchment is often undertaken by a number oforganisations. Local councils are generally responsible for the majority of stormwatersystems, although there may be more than one council within a particular catchment. The Sydney and Hunter Water Corporations also have responsibility for major stormwatersystems in some catchments. The Roads and Traffic Authority is also responsible forstormwater systems on freeways and State Roads under their control.

State Government Agencies including the Environment Protection Authority, the


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Departments of Land and Water Conservation and Urban Affairs and Planning, NSWFisheries, the Waterways Authority and the National Parks and Wildlife Service also playa role in stormwater management. Catchment Management Committees and Trusts, Lakeand Estuary Management Committees and other coordinating bodies also have a stronginterest in stormwater management. Decisions and actions in different areas by theseorganisations can strongly influence stormwater management. This includes decisions onthe location and form of urban development.

The process outlined in Part B of this document has been developed to provideinformation on stormwater management needs which can provide input into Councils’Management Planning process required under the Local Government Act. Managementpractices, both non-structural and structural, aimed at addressing stormwatermanagement problems and issues are to be identified and prioritised for each stormwatermanager in the catchment. This information can then be considered and incorporated inCouncil’s development of annual Management Plans. Councils’ Management Plans arerequired by the Local Government Act to describe Council’s principal activities, includingcapital works, services, asset replacement programs and activities aimed at protectingenvironmentally sensitive areas and to promote ecological sustainability. Therecommendations of the Stormwater Management Plan can also be considered whenstormwater managers other than councils are preparing their annual works programs.

2 WHAT IS A STORMWATER MANAGEMENT PLAN?

The primary goal of urban stormwater management plans is to facilitate the coordinatedmanagement of stormwater within a catchment to maximise ecological sustainability andthe social and economic benefits of sound stormwater management practices.

A stormwater management plan is a document that provides the direction for stormwatermanagement within a catchment or sub-catchment. The plan is to:• identify the existing and future values of a catchment• derive stormwater management objectives to protect these values• identify problems and issues that may compromise these objectives• detail a suite of non-structural and structural management practices to address these

problems and issues which have been agreed between all stormwater managers withina catchment.

A stormwater management plan is a framework for action

It is important that the stormwater management plans:• encourage community involvement in stormwater management• encourage the preservation of valuable existing elements of the water environment• maximise the control of stormwater runoff at the source• identify and prioritise an appropriate mix of cost-effective stormwater management

practices to suit the particular requirements of a catchment• link to Councils’ management planning processes, specified in the Local Government

Act.• incorporate monitoring procedures to allow for feedback and improvement of the

plan.

The stormwater management plans are to be catchment or sub-catchment based. A planmay encompass more than one catchment, although the management strategies should be


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based on the characteristics of each individual catchment.

Due to the complexity of the physical, chemical and ecological processes which occurwithin and between catchments, the application of prescriptive management practices isconsidered inappropriate. In addition, the management objectives, problems, issues andcommunity expectations will also vary between catchments.

The preparation of management plans for each catchment enables these characteristics tobe recognised and for appropriate stormwater management practices to be implemented. Decisions on the adoption of these management practices should be based on achievingcost-effective and balanced environmental solutions which reflect these individualcatchment characteristics. An inter-disciplinary approach by stormwater managers isappropriate to achieve these goals.

The focus of the plan is environmental protection through improved stormwatermanagement. The plan should therefore be regarded as a management tool, and theemphasis in stormwater management should be on developing and implementing actions,rather than focussing on producing a high quality ‘glossy’ plan.

In many cases, the stormwater management plan that is prepared to comply with theEPA’s notice will be a council’s first such plan. As the stormwater planning process isnever “complete”, this plan should form the foundation for future plans (refer toAppendix I for a discussion of Stormwater Management Systems). Given the time andfunding constraints for this plan’s preparation, it is likely that the plan will not be ascomprehensive as may be desired. The critical issue is that it represents the start of theprocess, and raises awareness of the need for improving current stormwater managementpractices. It may not provide all of the long-term solutions, but provides a framework fordeveloping these solutions.

A stormwater management plan prepared to comply with the EPA’s notice is to address“environmental protection” as a minimum requirement. Additional issues can, however,be included in the plan, including stormwater management for flood protection,stormwater management of rural-residential and rural areas and management of existingstormwater assets

3 THE NEED FOR STORMWATER MANAGEMENT PLANS

Stormwater management plans are needed to:• minimise future impacts on the stormwater environment• provide a framework for mitigating existing impacts on the stormwater environment.

Changes to the water environment that can occur due to urbanisation include:• increased runoff volumes and peak flow rates• elevated pollutant concentrations and loadings• increased channel erosion and sedimentation• removal of riparian and foreshore vegetation (and possible replacement with exotic

species)• degradation of aquatic habitats• installation of barriers (eg culverts, weirs)


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The resulting impacts of urbanisation on the water environment include:

Water quality:• Elevated suspended solids levels can reduce light penetration, inhibiting primary

productivity and predator visibility, and deposited sediment can eliminate habitats foraquatic insects.

• Elevated nutrient levels can increase primary productivity, including algal andmacrophyte growth.

• Toxicants may be lethal to fish and other aquatic fauna.• Herbicides may reduce the abundance of algae and macrophytes.• Increased temperatures can alter the life cycles of aquatic fauna and stimulate primary

productivity.

Streamflow:• increased frequency and magnitude of flows and associated disturbance to terrestrial

(eg urban bushland gullies) and aquatic ecosystems• altered tidal excursion and salinity in estuaries• increased channel erosion

Riparian vegetation:• increased water temperature• increased primary productivity and weed growth• altered organic matter inputs, altering aquatic fauna communities

Habitats• loss of refuge, habitat and spawning areas for fauna• reduction in variability in velocity and flow distribution characteristics• reduced diversity and abundance of aquatic fauna and flora

Barriers• impact on the colonisation and dispersal of aquatic fauna• culverts/bridges over estuaries can reduce upstream tidal flushing and increase tidal

velocities

In summary, whilst it is difficult to make generalisations about the impacts of urbanisationon aquatic ecosystem health, it is expected that the diversity of aquatic flora and faunawill be reduced and community composition altered, although the relative abundance ofspecies tolerant to the altered conditions may increase.

The magnitude of these impacts will be catchment-specific and also depend on the pre-development land uses. These impacts are discussed further in Appendix B.

4 STORMWATER MANAGEMENT PRINCIPLES

The stormwater management plan is to be based on ecologically sustainable development(ESD) principles (refer to Appendix D for a discussion of ESD in legislation). The resultingmanagement principles also need to be tailored to each catchment’s climatic, ecological,social, land use and administrative characteristics.

There are however, three broad management principles that can be followed, with thehierarchy of these principles noted in Table 4.1.This hierarchy is compatible with ESD. It preserves valuable features of the waterenvironment and promotes cost-effective stormwater management by controlling


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stormwater at the source and only proposing “end of pipe” techniques for the residualimpacts that cannot be cost-effectively mitigated by source control.

Broad management practices that are compatible with this hierarchy are noted in Table5.1. Further details of these management practices are contained in Section 8.

A ‘river health’ approach to stormwater management is encouraged. This involvesconsideration of water quality, streamflow, riparian vegetation and aquatic habitatmanagement issues, which are discussed in detail in Appendices B and C. There isincreasing evidence that solely managing stormwater quality using a “best managementpractice” approach is insufficient to mitigate the impacts of urbanisation (eg Maxted andShaver 1996; Shaver et al 1996).

*if degradedTable 4.1 – Stormwater Management Hierarchy

5 UNCERTAINTY

There is a degree of uncertainty associated with many aspects of stormwatermanagement, including:• pollutant generation from different land uses• the response of waterways to pollutant loadings• aquatic ecosystem responses to changed water quality, flow and other conditions• the response of channel morphology to changed flow regimes• the effectiveness of stormwater treatment measures and other management practices• water quality and hydrological modelling

Despite this uncertainty, there is ample evidence that urbanisation results in negativeimpacts on the stormwater environment. The current difficulties in quantifying theseimpacts should not prevent actions being implemented to minimise these impactsfollowing the precautionary principle of ESD.

Uncertainty in stormwater management needs to be acknowledged and accepted.

Retain (and restore)*valuable features of the

water environment

Source control(water quality & quantity)

“End of pipe”management practices


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Table 5.1 – Potential Stormwater Management Techniques

Issue Retention and RestorationTechniques

Source Control Techniques ‘End of pipe’ Techniques

Flow management Retain (and restore if degraded)existing watercourses and wetlands(flow attenuation)

• Minimise impervious areas(water sensitive urbandesign)

• Stormwater reuse• Stormwater infiltration• Limit development on

floodplains• On-site detention

• Retarding basins

Channel morphologymanagement

Retain (and restore) existingwatercourses

• Minimise changes tostreamflows

• Channel stabilisation• “Natural” channel design

Water quality management Retain (and restore) existingwatercourses and wetlands (in-streamwater treatment)

• Urban capability assessment• Community education• Improved operations and

maintenance practices• Small (on-site) stormwater

treatment measures.

• Erosion and sediment control• Large (off-site) stormwater

treatment measures

Riparian vegetationmanagement

Retain (and restore) existing riparianand foreshore vegetation

• Urban capability assessment• Water sensitive urban design

Aquatic habitatmanagement

Retain (and restore) existingwatercourses and wetlands

• Urban capability assessment• Water sensitive urban design• Route selection for roads

• Stream/habitat restoration


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PART B – THE STORMWATER MANAGEMENTPLANNING PROCESS


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6 FRAMEWORK FOR PREPARING STORMWATERMANAGEMENT PLANS

6.1 Legal Framework

The notice to prepare a stormwater management plan will be issued by the EPA undersection 12 of the Protection of the Environment Administration Act 1991. The EPA has issuedthis notice as it considers that the preparation of the plan will contribute to environmentalprotection. Relevant details of the Act are contained in Appendix D.

There are a number of additional Acts that provide powers related to stormwatermanagement, and which need to be considered when preparing stormwater managementplans. These Acts and their primary role relevant to stormwater management include:

• Clean Waters Act – controlling water pollution.• Pollution Control Act - licensing pollution discharges and approving pollution controls• Environmental Planning and Assessment Act - land use planning, environmental impact

assessment, and development and subdivision approvals• Local Government Act - building and other activity approvals, orders, and water,

sewerage and drainage works (refer also to section 6.6)• Soil Conservation Act - soil conservation and erosion• Water Act - riparian water usage• Rivers and Foreshore Improvement Act - works adjacent to watercourses• Catchment Management Act - establishing Catchment Management Committees and

Trusts• Fisheries Management Act - management of aquatic fauna habitats.

Further details of these Acts are provided in Appendix D.

The Clean Waters Act and the Pollution Control Act will be superseded by the Protection ofthe Environment Operations Act, which is currently in Bill form. The draft Bill retains theoffence to pollute waters. Appendix D contains further details of the Bill.

6.2 Relationship with other Plans

It is important that the stormwater management plan preparation considers the findingsor recommendations of other plans or reports that may affect stormwater management ina catchment. These may include:• Catchment management plans• River management plans• Floodplain management plans• Estuary management plans• Healthy Rivers Commission report• Council management plans

6.3 Cooperation between stormwater managers

In many catchments, there will be more than one organisation responsible for stormwatermanagement. These organisations may include a number of councils, the Roads andTraffic Authority, the Sydney or Hunter Water Corporations and a CatchmentManagement Committee or Trust. To integrate management objectives, a SteeringCommittee or Task Force can be formed with representatives for each stormwatermanagement organisation and possibly community representatives. The effectiveness of


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the Committee will be enhanced if a coordinator is appointed from one of the memberorganisations.

The Committee would be responsible for the preparation of the stormwater managementplan and broad identification of management tasks to be undertaken by each memberorganisations. This arrangement avoids a ‘pyramid’ management structure that mayresult in one organisation dictating requirements to other organisations. This is illustratedin Figure 6.1.

Figure 6.1 – Possible Stormwater Management Structure(after Throsby Creek SMS)

6.4 Consultation

Consultation with the public and other stakeholders is to be undertaken during thepreparation of the plan and a consultation strategy should be developed early in the planpreparation process. Stakeholders can provide information that will be useful in thepreparation of the plan. Further, it is important that the community be encouraged toaccept a degree of ‘ownership’ of the resulting Management Plan . The Plan should not be“imposed” on the community without consultation, as the community is responsible formany of the stormwater problems within a catchment. This is discussed further in Section7.

6.5 Council Activities Affecting Stormwater

There are a wide range of Council activities that have a direct or indirect influence on

Council A, Council BWater Corporation

Catchment Management CommitteeRoads and Traffic AuthorityCommunity representatives

CoordinatorSteering

Committee

Prepare stormwatermanagement plan

Implementactions

Council A Council B

Water Corporation Roads and Traffic Authority


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stormwater management, which are noted in Table 6.1. It is therefore important thatplans be prepared in consultation with all sections of a Council that have a direct orindirect involvement in stormwater management. If this consultation is not undertaken,there is a risk that the implementation of actions may be less effective.

Table 6.1 – Potential Influence of Council Activities on Stormwater

Council Activities Potential Influence on StormwaterEnvironmental planning – strategicplanning

Urban capability assessmentSection 94 plans for stormwater management

Environmental planning –development control

Stormwater management practices for newdevelopments

Building approvals and inspections Soils and water management of building sites.Environmental health Trade waste, discharges to stormwater,

educationParks and gardens Maintenance activities (eg tree planting, fertiliser

application, grass cutting)Road maintenance Various maintenance activitiesDrainage system maintenance Various maintenance activitiesWaste collection Litter managementRoad and drainage design Road route selection, drainage system designFinance Budgets for stormwater managementLibrary Community educationHuman Resources And skills development

6.6 Stormwater Management under the Local Government Act

The Local Government Act requires a council to prepare a management plan with respect tothe council’s activities for at least the next three years and the council’s revenue policy forthe next year. Relevant sections of the Act which relate to the framework for council’sresponsibilities stormwater management planning are contained in Appendix D. ACouncil’s implementation program within a stormwater management plan is to becompatible with the provisions of a council management plan.

7 STAKEHOLDER INVOLVEMENT IN THE PLANNING PROCESS

There are likely to be three broad groups of stakeholders who may be involved in thepreparation and implementation of urban stormwater management plans:

• Stormwater managers - including council(s), Sydney or Hunter Water Corporations, Roads and Traffic Authority

• Community - including residents, local industry, operators of commercial premises,conservation groups.

• Coordination groups – such as Catchment Management Committees and Trusts,Estuary Management Committees etc.

• State Government agencies - including the Environment Protection Authority,Department of Land and Water Conservation, Department of Urban Affairs and


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Planning, NSW Fisheries, NSW Waterways Authority, National Parks and WildlifeService.

Coordination of stormwater managers within a catchment, which can be achieved by theestablishment of a steering committee or a task force, has been discussed in Section 6.3.

Community representatives could be included on the Steering Committee/Task Force. If acatchment has large areas of industrial or commercial land use, inclusion of industrygroups (eg the local Chamber of Commerce) could be beneficial. Alternatively, acommunity advisory committee could be established to provide a single point of contactfor the steering committee/task force.

Structured community input could be obtained at the following stages in preparing orimplementing the plan:• when values and issues are being identified, possibly through review of an issues

report• following preparation of a draft stormwater management plan• during monitoring programs• revision of the plan.

Potential techniques for obtaining public input include (after OMEE & OMNR 1993):• brochures, highlighting the plan-preparation process and requesting community input

(a tear-off postage-paid questionnaire can be very effective)• articles or advertisements in local newspapers• displays at local shopping centres, council chambers, libraries and any parks adjacent

to the stormwater system• field trips, where cause-effect relationships can be demonstrated and proposals

presented• public meetings, to discuss issues and proposals.

As noted in section 1.2, State Government agencies with stormwater and/or landmanagement responsibilities are to cooperate with local councils in the preparation ofcatchment-based stormwater management plans. The extent and nature of an agency’sinvolvement is expected to be catchment specific, depending largely on the managementresponsibilities within the catchment.

If an agency has a significant responsibility within the catchment, it could be invited tojoin the steering committee/task force. Alternatively, if the responsibilities are lesssignificant, the agency could be consulted at an early stage in the plan preparation processto identify any issues of specific interest to the agency. Following preparation of a draftmanagement plan, the agency could again be consulted to obtain their comments on thedraft plan.

8 PREPARING STORMWATER MANAGEMENT PLANS

The stormwater planning process is relatively flexible and should be responsive to thecatchment’s characteristics. The important issue is the resulting content of the plan andwhether the plan has complied with the requirements of the EPA’s notice.

There are a number of tasks that can be undertaken when preparing stormwatermanagement plans, which are illustrated in Figure 8.1. These tasks should be consideredas an example process, rather than being a prescriptive requirement.


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An effective catchment-based approach to stormwater management will be enhanced ifthe following tasks are undertaken in an integrated and complementary manner. However, the allocation of resources to stormwater management is clearly a matter forindividual Councils and other stormwater managers. It is therefore important that Plansare consistent with Councils ability to resource the actions identified in the Plan. Thisapproach therefore provides for a single integrated, catchment-based plan whichincorporates separate, but complementary implementation strategies developed by eachseparate Council.

Figure 8.2 illustrates the links in the Plan preparation process, from catchment valuesthrough to separate implementation strategies for each Council or stormwater manager.

Figure 8.1 – Tasks for Preparing Stormwater Management Plans

Task 1 – Establish Framework

Task 6 – Identify issues and causes

Task 2 – Collect Existing Data

Task 3 – Describe Existing Conditions

Task 4 – Identify Values

Task 5 – Identify Objectives

Task 7 – Prepare Issues Report

Task 8 – Identify Potential Options

Task 9 – Evaluate Options

Task 11 – Prepare Draft Plan

Task 12 – Prepare Final Plan

Stakeholder Review

Stakeholder Review

Task 10 – Implementation Strategy


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CATCHMENTVALUES

STORMWATERMANAGEMENT

OBJECTIVES

ISSUES &CAUSES

MANAGEMENTOPTIONS

RANK IMPLEMENTATIONSTRATEGIES

Mgt. Option ‘A’ 1Mgt. Option ‘B’ 9Mgt. Option ‘C’ 7

ValuableCharacteristics

AssessmentCriteria

ObjectiveIssue:Ø CauseØ Cause

Mgt. Option ‘D’ 3Implementation Strategy(Council 1)

Time

Mgt. Option ‘A’ 1998Mgt. Option ‘D’ 1999

Mgt. Option ‘E’ 2 Mgt. Option ‘E’ 2000Mgt. Option ‘F’ 6Mgt. Option ‘G’ 4

Objective Mgt. Option ‘B’ 9Mgt. Option ‘H’ 5

Implementation Strategy(Council 2)

TimeValuableCharacteristics

Long-TermObjectiveAssessment Objective

Issue:Ø Cause

Mgt. Option ‘I’ 6 Mgt. Option ‘E’ 2000Mgt. Option ‘J’ 9 Mgt. Option ‘G’ 1999Mgt. Option ‘D’ 8 Mgt. Option ‘H’ 1998

Figure 8.2 – Linkages between catchment values, stormwater management objectives, issues, causes and management options.


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Task 1: Establish Framework

The first task in the process can involve establishing the overall framework for the planand the plan preparation process. This can involve establishing:• the purpose of the plan (eg compliance with the EPA’s notice)• the scope of the plan (eg first plan, revised/second plan)• responsibilities for stormwater management within the catchment• the boundaries for the plan (eg catchment/sub-catchment, individual township)• public and other stakeholder consultation processes.• relevance of the findings or recommendations of any other relevant plan.

Task 2: Collect Existing Data

The collection of existing data describing the characteristics of a catchment and itswaterways is useful for a number of purposes, including:

• describing the existing conditions within the catchment• enabling the values of the catchment to be determined, from which management

objectives can be derived• assisting with catchment audits, by prioritising areas for investigation• identifying constraints and opportunities for improved stormwater management

practices, both structural and non-structural.

The data collected in this task should be related to one of these purposes, to avoidcollecting unnecessary data. For many catchments, a proportion of the potential dataneeds noted below may not be readily available or cannot be quantified. It is difficult toprovide a ‘priority list’ for identifying these characteristics, as their importance will varybetween catchments. Items that may have a lower importance are italicised.

Further, for a first stormwater management plan, a preliminary assessment could beundertaken using existing or readily available data. Any requirements for furtherinformation that arise during the plan preparation process could be identified in the planas an action to be implemented.

Physical characteristics:

• soils, including permeability, erodability and dispersivity• bedrock geology, including geochemical characteristics• topography, including slope characteristics• climate, including rainfall, evaporation and temperature distributions• major services that may influence stormwater management practices (eg major

telecommunications cables, major gas mains)• bridge and culvert crossings• point sources of pollution (eg sewage treatment plants)• major sewer overflows• existing structural stormwater management practices (eg retarding basins, constructed

wetlands).


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Social characteristics:

• regulating tools• population characteristics, including demographics and language characteristics• recreational areas, including water related (eg riverside parks) and water based (eg

swimming, boating, fishing) activities• land use zoning• land use (eg commercial, residential, industrial, recreation) and land ownership

categories (eg private, local government, State Government).• Revenue from stormwater levy vs cost of

Waterway characteristics:

• physical characteristics of the stormwater ‘transport’ system (eg piped, lined or naturalchannels)

• physical characteristics of receiving water bodies (eg lakes, reservoirs, wetlands andestuaries), including bathometry, flushing rates and tidal conditions for estuaries

• fluvial geomorphology processes for natural (or modified natural) stormwater systemsand receiving waters, including erosion and sedimentation patterns

• surface hydrology, including flooding and baseflow characteristics• groundwater characteristics• water quality in stormwater ‘transport’ systems and receiving water bodies, under wet

and dry weather conditions.• Costs, depreciation and upgrading costs.

Ecological characteristics:

• aquatic fauna and flora characteristics, including habitat value (this applied to both thestormwater ‘transport’ system and receiving water bodies)

• riparian zone fauna and flora characteristics, including habitat value.• areas of urban bushland.

Task 3: Describe Existing Conditions

Using the available data, a description of existing catchment conditions can beundertaken. These conditions can include:• topography, land use, soils• hydrology (eg flooding and low flow characteristics)• water quality (eg wet and dry weather, receiving water quality, major pollution

sources)• watercourse and water body physical characteristics, and fluvial geomorphology (eg

channel erosion, sediment transport)• aquatic habitat characteristics• riparian and foreshore vegetation.• aquatic ecosystems• urban bushland, and existing stormwater-related impacts on urban bushland

A comprehensive assessment of these characteristics could be an extensive exercise. Following the precautionary principle, the lack of detailed knowledge on thesecharacteristics should not prevent the development of a plan to improve currentmanagement practices and prevent serious environmental degradation. Options forovercoming any serious data needs include:


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• undertaking a preliminary assessment based on the existing or readily availableinformation and one of the actions specified in the plan could be further detailedinvestigations. Existing information could be supplemented by the use of scientific orengineering judgement.

• modifying the Expert Panel Assessment Method that has been used to estimateenvironmental flows (Swale and Harris 1995, Snowy Genoa CMC 1996). This couldinvolve a site visit by a series of experts in fields such as water quality, hydrology,ecology, and geomorphology, who would use their knowledge of other stormwatersystems to provide a preliminary assessment of these characteristics in a short report.

• undertake additional studies before proceeding further. This may be appropriatewhere there is limited knowledge on significant characteristics that may have a majorinfluence on the management plan. This approach may not be warranted for a firststormwater management plan.

Where an existing information Expert Panel is used to assess existing conditions, thisshould be noted in the plan.

Where this information is already reported by Council in a State of the Environment Report,the Stormwater Management Plan may simply refer to that Report.

Task 4: Identify Management Values

There are a number of techniques available for assessing catchment and water bodyvalues that relate to stormwater management. In general, these values will not bequantitative, but qualitative or relative (ie related to high, medium or low values). Apreliminary assessment of these values could be undertaken, which may be refinedfollowing receipt of additional information. It may be useful to establish these values byholding a stakeholder workshop to obtain community input into the identification of thevalues. These values may also be mapped over the catchment area.

Ecological values

The ecological values of a stormwater system relate primarily to the physical habitatcharacteristics, streamflow and water quality conditions. A measure of the ecologicalvalue of a stormwater system can be the extent to which a healthy and diverse ecosystemexists. Values for the following categories can be assessed:

• Aquatic fauna: important habitats in freshwater systems include substrate (bed materialand geometry), woody debris and aquatic plants. For estuarine and coastal systems,seagrass beds, mangroves and saltmarshes are valuable habitats. Details of habitatrequirements can be found in publications including Koehn and O=Connor (1990),Newbury and Gaboury (1993), McDowall (1996), Underwood and Chapman (1995). It should be noted that the requirements for Australian aquatic fauna may differ fromthose for Northern Hemisphere fauna.

• Terrestrial fauna: habitats for terrestrial fauna including reptiles, mammals andamphibians are extremely variable. From a stormwater management perspective,these habitats relate principally to riparian zone vegetation. Publications describingthese habitats include Cogger (1992) and similar references.

• Aquatic flora: the principal habitat for freshwater aquatic flora such as macrophytes is


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a substrate with appropriate attachment sites such as sediment. Streamflowcharacteristics and water quality also influence the value of a watercourse tomacrophytes, particularly floating species. A sandy substrate is also required forseagrass beds in estuaries and coastal waters, with flow characteristics, depth andwater quality are also relevant. Refer to Sainty and Jacobs (1990), Hutchings andSaenger (1987), Adam (1990) and Underwood and Chapman (1995) for further detail.

• Terrestrial flora: the habitat value of a stormwater system to terrestrial flora is related tothe morphology of the banks and floodplain, and the prevailing streamflow andgroundwater conditions. These are discussed in Harden (1993) and similarpublications.

• Avifauna: the riparian zone, the stormwater >transport= system and receiving waterbodies can all provide habitats for land based and water birds. Details of thesehabitats can be found in a range of publications including Frith (1977), Frith (1982)and Marchant and Higgins (1991).

Social Values

• Public health and safety: a value of a stormwater system is that it conveys stormwaterrunoff degree of risk to public health and safety. This also applies to water quality,particularly for bacterial pollution (and other pathogens).

• Recreation: stormwater systems can provide valuable water based or water relatedrecreational opportunities, for both passive and active recreation. Recreational valuesare discussed in DoP (1992).

• Visual amenity: stormwater systems and the riparian zone can provide aestheticallypleasing landscapes. DoP (1992) and DoP (1993) describe the aesthetics of stormwatersystems.

Economic Values

• Water use: surface or groundwaters can be used to provide a water source fordomestic, irrigation, stock and industrial purposes.

• Aquaculture and other commercial fishing activities.

• Stormwater reuse: stormwater can be reused for potable or non-potable purposes tominimise the demand for reticulated water, potentially reducing the costs of majorheadworks projects and reticulation for conventional water supply systems.

• Property values: visually attractive stormwater systems can enhance adjacent propertyvalues, particularly for properties adjacent to constructed wetlands and naturalchannels.

Task 5: Identify Management Objectives

Following identification of the values of a stormwater system and its catchment,management objectives can be developed to protect these values. These objectives may beinterim until further data is collected.

It is likely that two sets of objectives will be appropriate. The first may be long-termobjectives (effectively a ‘vision’ for the catchment) and the second being more short term,


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quantifiable objectives. These short term objectives can be the basis for evaluating theperformance of the plan at the end of a certain period (eg 3 years).

The actual objectives (particularly the short-term objectives) will depend on the adoptedcatchment values but may be similar to the following:

Ecologically Sustainable Development:

• Stormwater management shall be based on the principles of ecologically sustainabledevelopment. These include the requirement to integrate environmental and economicconsiderations in decision making. Key principles include:- the precautionary principle Χ namely that if there are threats of serious or

irreversible environmental damage, lack of full scientific certainty should not beused as a reason for postponing measures to prevent environmental degradation

- inter-generational equity Χ namely that the present generation should ensure thatthe health, diversity and productivity of the environment is maintained orenhanced for the benefit of future generations

- conservation of biological diversity and ecological integrity- improved valuation and pricing of environmental resources.

Long-term objectives:

• water quality in the catchment is to meet ambient water quality objectives.• flows within the catchment are to meet the river flow objectives.• the impact of urban stormwater on weed propagation and growth in bushland should

be minimised.• the value of indigenous riparian, floodplain and foreshore vegetation is to be optimised• the watercourses within the catchment are to be in a state of dynamic equilibrium

from a fluvial geomorphology perspective.• the value of physical habitats for aquatic fauna within the stormwater system is to be

optimised• the impact of stormwater on public health and safety should be optimised.• the visual amenity of the stormwater system should be optimised.• opportunities for the multiple use of stormwater facilities are to be optimised, to the

degree that they are compatible with other management objectives.• the impact of new urban developments on these objectives is to be minimised.

Short-term objectives

• the ambient concentrations of nutrients within the catchment are to be reduced by [aspecified amount]

• litter is to be trapped from high litter generation areas, including [name of majorshopping centres, streets with strip shopping, major active recreation areas]

• the annual average flow from the catchment is to be reduced by [a specified amount]• the majority of the urban stormwater entering the [name of a bushland reserve] is to

be treated to minimise weed propagation and growth.• the riparian vegetation along [name of watercourse] is to be restored with indigenous

species• the erosion in [name of watercourse] is to be addressed, to create a watercourse in a

state of dynamic equilibrium• the physical habitats for aquatic fauna in [name of watercourse] are to be restored.• improved recreational access adjacent to the [name of watercourse].• the impact of new urban developments on these objectives is to be minimised.


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Stormwater treatment objectives that could be adopted are noted in Table 8.1. Theseobjectives are also presented in two levels, namely a long-term vision and an ESDobjective. The ESD objective is based on what is currently considered to be a cost-effectivelevel of stormwater treatment. This is similar to the “Best Management Practice”approach adopted in the United States, which is based on achieving the “point ofdiminishing returns” in the performance of treatment techniques. This ESD objective isexpected to increase over time with advances in stormwater treatment techniques, movingtowards the long-term objective. For existing urban areas, compromises on the level oftreatment may be required.

A discussion on assessing the potential impacts of new urban developments on pollutantloadings in presented in Appendix H.

Task 6: Identify Issues and Causes

This step of the plan preparation process involves identifying the factors that currentlyprevent, or may prevent, the adopted management objectives from being satisfied. Theseproblems or issues may be environmental, social and managerial, and may include:

Environmental issues:• poor water quality in waterways, under both dry and wet weather conditions• inappropriate streamflow regime, both flooding and baseflows• degraded aquatic habitats• degraded riparian vegetation• channel erosion and sedimentation• weed growth in urban bushland• degradation of ecologically sensitive water bodies (eg coastal wetlands identified under

State Environmental Planning Policy No.14)

Social issues:• health risks associated with recreational use of polluted waters• insufficient integration of stormwater systems and recreational facilities• low visual amenity and landscape value of the stormwater system• inadequate public involvement in stormwater management.

Managerial Issues• inconsistency between environmental planning instruments and stormwater

management objectives• inadequate funding allocated to stormwater management or management practices

are not cost-effective• inadequate coordination of council operations affecting stormwater management

These issues can be identified by a combination of:• a desk-top study, involving a review of existing information contained in reports,

studies and monitoring programs. This is particularly appropriate for identifyingenvironmental issues;

• field work, involving an inspection of the catchment, possibly by a catchment audit, asdescribed in Appendix E. This approach is also appropriate for identifyingenvironmental issues, although some social and management issues may also be


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Table 8.1 – Potential Stormwater Treatment Objectives

Pollutant: Goal/Vision: ESD Treatment Objective:

Post construction phase:Suspended solids (SS) Suspended solids loads equal to that which would have been

exported from the equivalent forested catchment80% retention of the average annual load**

Total phosphorus (TP) The load of phosphorus from the catchment that results in theattainment of the ambient water quality concentration objective

45% retention of the average annual load**

Total nitrogen (TN) The load of nitrogen from the catchment that results in theattainment of the ambient water quality concentration objective

45% retention of the average annual load**

Litter No anthropogenic litter in waterbodies. Input of organic litterequal to that which would have occurred from the equivalentforested catchment

Retention of litter greater than 50 mm for flowsup to 25% of the 1 year ARI peak flow

Coarse sediment Coarse sediment loads equal to those which would have beenexported from the equivalent forested catchment

Retention of sediment coarser than 0.125 mm*for flows up to 25% of the 1 year ARI peakflow

Oil and grease(hydrocarbons)

No visible oil and grease (anthropogenic hydrocarbons) inwaterbodies

In areas with concentrated hydrocarbondeposition, no visible oils for flows up to 25%of the 1 year ARI peak flow

Construction phase:Suspended solids Suspended solids loads equal to those which would have been

exported from the equivalent forested catchmentMaximum SS concentration of 50 mg/L for all5 day rainfalls up to the 75th percentile depth.All practical measures to reduce pollution areto be taken beyond this event.

Other pollutants No export of toxicants (eg pesticides, petroleum products,construction chemicals) from the site

Limit the application, generation andmigration of toxic substances to the maximumextent practicable

* based on idealised settling characteristics** a design storm of 25% of the 1 year ARI flow is to be adopted for the design of certain elements of some stormwater treatment measureswhich can be used to meet this objective


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identified• discussions, involving council staff and staff from relevant State Government Agencies,

which can obtain information on a range of issues.• Community consultation of Council client surveys

Involvement of the community and other stakeholders in identifying management issuesmay encourage greater community ‘ownership’ of the resulting management decisions. This is discussed further in Section 7.

Management issues and their causes can be generally identified to a qualitative level usingexisting information and the use of scientific or engineering judgement. The exact scopeand causes of the issues may, however, not be quantifiable with existing data. Followingthe precautionary principle, this lack of quantifiable data should not prevent thepreparation of a plan to address the issues.

Further studies or monitoring may need to be undertaken in the longer term. If necessary,this can be undertaken during the plan preparation process, which is likely to beapplicable for significant issues. Alternatively, this information can be collected as arecommendation of the management plan and interim decisions made based on theexisting information.

Following identification of these problems, the causes can be identified and their relativecontribution to the problem assessed (quantitatively or qualitatively). This can enable thedevelopment of cost-effective management strategies and assist with allocating prioritiesfor action.

A range of management issues which may exist in a catchment and their possible causesare noted in Table 8.2

Task 7: Prepare Issues Report

The results of the above investigations can be presented in a Stormwater ManagementIssues Report, which can be directly incorporated into the final Management Plan. Theaim of this report would be to summarise the management issues to enable stakeholderreview before investigating potential management options. This may result in useful inputfrom stakeholders on the importance of management issues, the values and objectivesused to derive the issues, and potentially highlight additional issues.

The contents of the report may include:• an introduction, outlining the purpose of the report• a description of the catchment• a description of existing conditions within the catchment• the identified catchment values• the stormwater management objectives• the identified stormwater management issues

Task 8: Identify Potential Options

A broad range of structural and non-structural practices is available to address identifiedstormwater management issues. Error! Reference source not found. provides a list ofpotential practices, and notes where further information can be located about eachpractice in the Managing Urban Stormwater documents and other sources.


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Table 8.2 – Possible Management Issues and Causes

Category Issue Possible Cause

Elevated nutrient concentrations • excess fertiliser application in residential areas• excess fertiliser application in parks and gardens• washing of cars in streets• sewer overflows• atmospheric deposition

Elevated suspended solids concentrations • poor erosion and sediment control of construction activities• channel erosion• sewer overflows• washing of cars in streets

Elevated bacterial concentrations • faecal contamination from domestic animal droppings• sewer overflows

Litter in watercourses • insufficient number of rubbish bins• insufficient emptying of rubbish bins• littering in retail, commercial and industrial areas

Erosion of watercourses • removal of riparian vegetation• increased flood-flows following urbanisation• deposition of sediment from upstream sources

Weed growth in urban bushland • nutrients from stormwater• weed propogules from residential gardens• removal of canopy vegetation

Degraded aquatic habitats • physical alteration to habitats• increased flood-flows• increased sediment deposition• removal of riparian vegetation

Environmental

Degraded riparian vegetation • physical removal of vegetation• introduction of exotic species


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Table 8.2 – Possible Management Issues and Causes

Category Issue Possible Cause

Inappropriate streamflow regime • increased runoff due to impervious areas• increased flow rates due to hydraulic efficiency of stormwater systems• insufficient stormwater reuse• reduced baseflow due to decreased infiltration• increased baseflow due to leaking water services

Environmental(Cont’d)

Barriers to aquatic fauna migration • culvert over watercourse• weir in watercourse• narrow bridge over estuary

Insufficient integration of stormwatersystems and recreational facilities

• no walking paths adjacent to watercourses• no fishing areas• no swimming areas

Low visual amenity and landscape valueof the stormwater system

• concrete lined channels• degraded ‘natural’ channels• litter along watercourses

Social

Inadequate public involvement instormwater management

• no catchment management committee

Inconsistency between environmentalplanning instruments and stormwatermanagement objectives

• environmental planning instruments (eg LEPs, DCPs) do not reflectstormwater management objectives

Inadequate funding for stormwatermanagement

• insufficient allocation of rate income

Inadequate coordination between councildepartments

• poor communications between divisions• poor integration of responsibilities across divisions

Managerial

Inadequate coordination betweenstormwater managers within a catchment

• poor communications between managers• absence of a catchment-based stormwater management plan


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Table 8.3 – Potential Management Practices

Applicable for:Issue Category Management Practice

existing proposed

Further information

Educational material y y Source Control : .

Planning controls (land capability assessment) Χ Y Source Control : .

Water-sensitive urban design Χ Y Source Control :

Control sewer overflows y Χ

Label stormwater pits y y Source Control :.

Erect signs along creeks, lakes, estuaries, etc. y y Source Control :

Provide facilities for disposal of oils and harmful chemicals y y Source Control :

Conduct regular catchment audits, concentrating on commercial/industrial areas y Χ Source Control :

Undertake regular maintenance of stormwater treatment measures y y Source Control :

Eliminate illegal sewer connections to stormwater systems y Χ

Waterquality

Non-structural

Assessment of the water quality impacts of new urban developments at the landuse planning stage (eg preparation of local environmental plans)

- y Source Control :

Erosion and sediment control Χ construction activities y y Soils and Construction:

Litter baskets y y Treatment Techniques:

Litter racks y y Treatment Techniques:

Litter booms y y Treatment Techniques:

Sediment traps y y Treatment Techniques:

Gross pollutant traps y y Treatment Techniques:

Waterquality

Structural

Catch basins y y Treatment Techniques:

WaterQuality(Cont’d)

Structural

Cont’d)

Water quality inlets y y Treatment Techniques:


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existing proposed

Further information

Buffer strips y y Treatment Techniques:

Grass swales (y) y Treatment Techniques:

Extended detention basins y y Treatment Techniques:

Constructed wetlands y y Treatment Techniques:

Triple Interceptors y y Treatment Techniques:

Coalescing plate interceptors y y

Infiltration basins y y Treatment Techniques:

Infiltration trenches y y Treatment Techniques:

Porous pavements y y Treatment Techniques:

Sand filters Treatment Techniques:

Further informationFurther information

Proprietary products y y

Planning controls (delineate floodplains) (y) y Source Control:

Purchase flood prone properties y n

Non-structural

Rainwater tanks y y

Infiltration basins y y Treatment Techniques: s.

Infiltration trenches y y Treatment Techniques: s.

Infiltrate roof runoff y y

Streamflow

Structural

Porous pavements y y Treatment Techniques:

Grass swales (y) y Treatment Techniques:

Retarding basins y y

Streamflow

(Cont’d)

Structural

(Cont’d)

Extended detention basins y y


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existing proposed

Further informationFurther informationFurther information

Retain urban watercourses (flow attenuation) (y) y

Preserve existing habitats y yNon-structural

Planning controls (delineate riparian buffers) (y) y Source Control

Aquatichabitats

Structural Reconstruct habitats y y Appendix C

Preserve existing vegetation y yNon-structural

Planning controls (delineate riparian buffers) (y) y Source Control

Riparianvegetation

Structural Replanting y y Appendix C

Streamflow management y y Appendix C

Bank stabilisation and protection y y Appendix C

Channelerosion

Structural

Riparian vegetation planting y y Appendix C

Stormwater quality management y y Treatment TechniquesWeedgrowth inbushland

Structural

Plant indigenous vegetation y y Appendix C


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Task 9: Evaluate Options

The evaluation of these management options can be undertaken by assessing:• estimated capital cost (including any associated costs such as service relocation)• estimated operations and maintenance costs• effectiveness in addressing the issue, including the ability to address multiple issues• ability to complement other potential management practices• land take requirements• proportion of the problem/issue addressed by the option• environmental impacts• technical and administrative viability• whether legal requirements are satisfied• consistency with policies on other related issues (eg public health)• expected community acceptance.

A ranking system can be a valuable technique for allocating a priority to managementoptions. Scores can be allocated to the costs and benefits of identified options to determinea priority. Although this is a relatively simplistic and subjective process, it is ‘transparent’and avoids unstated assumptions. While this is a potentially valuable management tool,judgement will need to be applied when interpreting the results.

A potential ranking methodology derived for stormwater quality management is describedbelow, with the general description of the methodology being:• each option is assessed in terms of its costs and benefits• all factors are assigned a score from 1 to 10• the cost index is comprised of 2 and the benefit index of 6 individual factors• the cost factors are averaged and benefit factors are averaged to provide the cost and

benefit indices• the cost index is divided by the benefit index and multiplied by 10, to avoid decimals,

to provide the cost benefit ratio• the options are ranked (1 being the most desirable)

The limitations of this methodology include:• some options may not readily lend themselves to this process• although an attempt has been made to identify the most important factors, no attempt

has been made to include every possible factor• the scores assigned to the benefit factors will be relatively subjective• the scores assigned to the cost factors will probably be estimates only• no attempt has been made to place weightings on the individual cost or benefit factors

or the ratio between them (eg: higher cost recommendations may be made morecompetitive by dividing the cost index by 2 or some other factor consideredappropriate)

• the scheme may need to be tailored for the characteristics of a particular catchment.

The costs for each option can be allocated a score in accordance with Error! Referencesource not found.. When a stormwater treatment measure requires pre-treatment (eg agross pollutant trap upstream of a constructed wetland), the combined costs can be usedin the analysis.


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Table 8.4 – Cost scores for Option Ranking Scheme

Capital Costs Operation and maintenance cost (annual)

Estimated cost ($) Score Estimated cost ($) Score

< 5,000 1 < 5,000 15,000 – 10,000 2 5,000 – 10,000 210,000 – 15,000 3 10,000 – 15,000 315,000 – 20,000 4 15,000 – 20,000 420,000 – 30,000 5 20,000 – 30,000 530,000 – 40,000 6 30,000 – 40,000 640,000 – 50,000 7 40,000 – 50,000 750,000 – 70,000 8 50,000 – 70,000 870,000 – 100,000 9 70,000 – 100,000 9>100,000 10 >100,000 10

For water quality management options, the potential benefits can be allocated a score forthe estimated relative harm of the pollutant, number of pollutants targeted by the optionand proportion of the catchment addressed, in accordance with Error! Reference sourcenot found..

The relative harm of pollutants category addresses the pollutants considered to be themost significant in urban stormwater and the corresponding scores are based on EPAexperience in a number of urban catchments. If the recommendation deals with a numberof pollutants, the highest score could be used.

The catchment proportion factor could be weighted in accordance with the relativeproportion of the pollutant sources in the catchment targeted by the option, not just thephysical area of the catchment.

Table 8.5 – Benefit Scores for Ranking Options Scheme

Relative harm of pollutants No of Pollutants Proportion of catchment

Pollutant Score Number Score Area (%) Score

Litter 2 1 1 < 10 1Nutrients 4 2 2 11 – 20 2Sediments 4 3 3 21 – 30 3Bacteria 5 4 4 31 – 40 4Oil & grease 6 5 5 41 – 50 5Organic matter 7 6 6 51 – 60 6Heavy metals 7 7 7 61 – 70 7Toxins 8 8 8 71 – 80 8

81 – 90 991 – 100 10


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Other factors that can be included in a water quality ranking include:

• relative level of the major pollutants to be targeted by each recommendation comparedwith other pollutants. Each option could be provided with a score from 1 to 10;

• relative effectiveness of the option in dealing with the target pollutants. Each optioncould be provided with a score from 1 (low) to 10 (high). A guide could be obtainedfrom Managing Urban Stormwater: Treatment Techniques.

• relative community education score of the recommendation. Options which will resultin increased community awareness and consequently enhance source control couldreceive a higher ranking than structural solutions with low education capacity. Eachoption could be provided with a score from 1 (low) to 10 (high).

A ranking sheet, similar to Table 8.6, could be used to evaluate the options.

An alternative ranking methodology is described in CDM (1993).

For structural water quality management practices, computer modelling can beundertaken to assess the effectiveness of a range of options. A discussion on water qualitymodelling is contained in Appendix F.

Task 10: Develop an Implementation Strategy

Following the evaluation and ranking of a series of stormwater management actions forthe catchment, it is advisable to review this ranking from a practical viewpoint beforeprogressing further. This may be particularly necessary if a simplistic evaluation andranking procedure, such as that outlined in Task 9, has been employed. It is importantthat this ‘reality check’ be undertaken on an entire catchment basis to identify potentialoverlaps or synergies between different management practices.

Following this review, a separate Implementation Strategy can be developed for eachstormwater manager within the catchment. Each Strategy should include prioritisation ofspecific management actions to be implemented by each stormwater manager in thecatchment, and a tentative timeframe for their implementation. The broad prioritisationof actions is aimed at facilitating the incorporation of proposed measures into councils’development of Management Plans under the Local Government Act.

The Implementation Strategy will be crucial to the success of the plan. The failure toadequately address financial and institutional considerations has been found tocompromise the efficiency of a number of early management plans prepared in the UnitedStates (US EPA 1983). There is also the potential for loss of community support if therecommendations of the plan are not implemented.


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Table 8.6 –Example Options Ranking Sheet

RANKING THE OPTIONS

OPTION COSTS BENEFITS RANK

No Description

Installation Operating CostIndex

Relative Harmof Pollutants

No ofPollutants

RelativeLevel ofPollutants

% ofCatchment Targeted

Effectiveness ofRecommendation

CommunityEducationValue

BenefitIndex

Cost/Benefit Ratio

Rank


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Task 11: Prepare Draft Plan

The draft stormwater management plan should include:• the contents of the Issues Report (refer to Task 7)• a discussion on the identified management options• the evaluation of the management options• the Implementation Strategy developed for each stormwater manager in the

catchment• a monitoring program, which includes mechanisms for incorporating the results of the

program into revisions of the plan (discussed in Appendix G)• a program for the revision of the plan and linking its implementation to councils (and

other stormwater managers’) management planning processes.• a mechanism for the dissemination of information on the implementation of the plan

and the results of any monitoring programs (this information could also be included inthe Council’s State of the Environment Reports)

Following the preparation of the draft stormwater management plan, stakeholders couldbe invited to review the document.

Task 12: Prepare Final Plan

Following receipt of comments from stakeholders on the draft plan, a final stormwatermanagement plan can be prepared.

9 IMPLEMENTATION

There are a number of institutional requirements that may need to be satisfied for thesuccessful implementation of a stormwater management plan. These requirements from alocal government perspective are described in WSROC(1996), and can include:

• Structure and responsibility: a senior management representative can be nominated totake responsibility for ensuring that the plan is implemented and reporting to council. The staff and sections responsible for implementing the plan can be clearly identified. The council can also take responsibility for developing a coordinated approach withother stakeholders to achieve the plan’s objectives.

• Resourcing: council should take responsibility for ensuring adequate resources areavailable to appropriate sections of the organisation. These resource requirements mayinclude staff, information, expertise, equipment and funding. Councils can investigateall possible sources of funding.

• Training, awareness and competence: council should ensure that all staff whoseactivities may have an impact on stormwater are aware of the causes of the impacts,the benefits of good stormwater management and their specific responsibilities forimplementing the plan. Training of staff and other stakeholders may also be required.

• Communication: councils can establish procedures for effective communicationbetween stakeholders regarding stormwater management. Internal communicationbetween sections and staff may need to be defined by specific procedures. Councilscan also establish procedures for reporting on the implementation of the plan and the


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results of any monitoring. This can be addressed in Council’s State of the EnvironmentReports, Annual Reports and Plans of Management.

• Operational control: for areas of council operations that can have an impact on urbanstormwater (listed in Table 6.1), councils can define operating procedures to give effectto the recommendations of the plan and monitor the implementation and effectivenessof these procedures.

• Emergency preparedness and response: councils can establish procedures foridentifying and responding to stormwater related emergencies such as floods andpollutant spills.

The implementation of the stormwater management plan will be reliant upon effectiveintegration of Implementation Strategy into Council’s management planning processrequired under the Local Government Act 1993. Figure 9.1 illustrates this important link.

Preparation of stormwatermanagement plan:

Preparation of Councilmanagement plan:

Council managementplans:

Year 1 Year 2 Year 3 Year 4 Year 5

Figure 9.1 – Linkages between a catchment-based Stormwater Management Plan andCouncil Management Plans

10 MONITORING

There are two broad types of monitoring that can be undertaken for stormwatermanagement:• water quality and biological monitoring• observation monitoring.

This is in addition to monitoring the performance of a management plan, by comparingplanned actions against their achievement, and deriving strategies for addressing anyproblems (refer to Appendix I).

Stormwater monitoring can be undertaken for the following purposes:• assessing the prevailing conditions within a stormwater system or receiving waters• obtaining water quality data for use in designing new stormwater management

practices• determining the performance of existing stormwater management practices.


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The conventional approach to monitoring relies solely on technical monitoring programs. There is, however, considerable benefit in primarily non-technical monitoring undertakenby the community. If the community is involved in monitoring the success of a plan, itcan be expected that they will be more likely to modify their behaviour if the objectives ofa plan are not being met. Conversely, a sense of pride in their achievements can begenerated if the monitoring indicates that the plan is succeeding.

Making the results of technical monitoring programs readily available to the community,including both the detailed results of the program and a more widely circulated non-technical summary, can assist this. Catchment Management Committees can be a usefulforum for both undertaking and reporting on monitoring programs.

Information on stormwater quality monitoring techniques is contained in Appendix G. Where possible, stormwater quality modelling should be undertaken at sites that havebeen used in the past for water quality monitoring, to enable a comparison betweenresults.

Observation-based monitoring can provide a general indication of the conditions existingwithin a stormwater system and potentially highlight the need for more scientificmonitoring. This monitoring can be undertaken by council staff or interested members ofthe public. The value of the monitoring may be enhanced if a pro-forma is developed,which indicates the date, time of day, weather conditions, flow conditions, and possiblyflow depth. This approach will improve the consistency of the observations.

Items that can be identified by this technique include:• litter• foam• surface scum• surface oil• algae Χ surface or attached• odour• water clarity Χ turbidity, visibility depth• aquatic plants (macrophytes) Χ emergent, submerged, floating• organic matter (leaves etc.)• fish• condition of riparian vegetation• bank erosion• sedimentation.

Further details can be found in Chapman (1996) for water quality monitoring and Raineand Gardiner (1995) for riparian vegetation assessment.

11 REVISING THE PLAN

A timetable should be developed for revising the plan. A revision to the plan may beappropriate:• when significant additional monitoring data is available;• if significant additional funding for stormwater management becomes available;• following completion of significant additional investigations;• if the monitoring data indicates that the plan will not achieve its objectives.

A revision to a plan does not necessarily need to involve the preparation of a


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comprehensive new plan. The revision could involve the preparation of a supplementaryplan or an addendum.

As each catchment will differ in the need for a plan’s revision, it is difficult to provide firmguidance on when a plan should be revised. In metropolitan and large regional centres,the plan could be revised every 3-5 years, with a longer period possibly being appropriatefor small rural towns.


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PART C – EXAMPLE STORMWATER MANAGEMENTPLAN


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1 INTRODUCTION

Please note: Some Figures and Appendices referred to in this Plan are not provided. This Plan isprovided for guidance only.

1.1 Purpose of this Plan

This document is the Stormwater Management Plan (SMP) for the Example Creekcatchment. This catchment is located within the catchment of the Model Estuary, and islocated approximately 50 km east of the Sydney CBD.

This Plan has been developed cooperatively by Alpha and Beta Councils. Alpha Council,being responsible for the largest portion of the catchment coordinated the preparation ofthe Plan.

The aim of this plan is to improve the management of stormwater within the ExampleCreek catchment. The plan:• Describes the catchment• Identifies existing catchment conditions• Establishes the values of the catchment• States appropriate management objectives• Identifies management issues• Evaluates potential management practices• Contains Plan implementation strategies for Alpha and Beta Councils• Presents a performance monitoring program• Establishes stormwater management objectives for new developments• Describes a mechanism for reporting on the implementation of the plan

1.2 Framework for Preparing this Plan

This plan has been prepared to comply with the requirements of a Notice issued to Alphaand Beta Councils by the Environment Protection Authority (EPA) under Section 12 of theProtection of the Environment Administration Act. This notice is contained in Appendix 1.

This is the first stormwater management plan prepared for the Example Creek catchment. There are currently no other plans or reports that provide a framework for this plan.

The EPA (1997) has, however, released for public comment a series of proposed interimwater quality and river flow objectives for the catchment. Water quality objectives(WQOs), at this stage in the State Government’s Water Reform Package, are onlyexpressed in terms of environmental values, while a series of river flow managementprinciples has also been released for comment. Excerpts from the EPA’s Discussion Paperrelating to the Example Creek catchment are attached in Appendix 2.

1.3 Stakeholder Consultation

This plan has been prepared in consultation with a number of stakeholders groups,namely:

• The Example Creek Catchment Management Committee (CMC);• The Model Estuary Management Committee (EMC);• The Alpha and Beta Regional Conservation Society ;• The Omega Chamber of Commerce;


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• Environment Protection Authority ;• Department of Land and Water Conservation (DLWC);• National Parks and Wildlife Service (NPWS); and• Department of Urban Affairs and Planning (DUAP)

These stakeholders were invited to raise issues that should be addressed in the preparationof this plan. Responses to this invitation are presented in Appendix 2.

In addition, the stakeholders were invited to two public meetings that were held duringthe preparation of this plan. These meetings discussed management issues and the draftmanagement plan. Notes of discussions from these meetings are also included inAppendix 2.

2. CATCHMENT DESCRIPTION

2.1 Waterways

There are two major tributaries of Example Creek, namely Eastern and Western Creeks, asindicated in the catchment map shown in Figure 1. Example Creek upstream of itsconfluence with Eastern Creek is locally known as Upper Example Creek. The catchmentarea of Example Creek is 5.2 km2, with Eastern and Western Creek’s having catchmentareas of 1.7 and 2.2 km2 respectively. These subcatchments are also shown in Figure 2.

There are also a number of unnamed tributaries of Example Creek.

Example Creek upstream of Omega is in a largely natural condition, although the ruralland uses have impacted water quality, and probably also stream flows. Through Omega,the Creek has been largely concrete lined, as have many of the smaller urban tributaries. The lower reaches of Eastern Creek have been locally modified, and realigned in sections. The lower reach of Western Creek has been brick lined through Omega, althoughupstream of Omega, the creek is in relatively natural condition. These channel conditionsare mapped in Figure 2. Numerous bridges cross these Creeks, which are also indicatedon Figure 3.

The Example Creek catchment drains to the Model Estuary. This is a relatively shallowestuary, with a surface area of 75 ha, an average depth of 1.8 m and a volume of 1,350ML. The mouth of the estuary opens intermittently to the Tasman Sea.

2.2 Land Use

Land use within the Example Creek catchment is mixed. The broad scale land use acrossthe catchment is mapped in Figure 5 and summarised in Table 1. A more detailed landuse map for the Omega urban area is presented in Figure 6.

Table 1 – Land Use in the Example Creek Catchment (ha)

Sub-catchment Urban(residential)

Industrial Rural Forest/NationalPark

Example Creek 120 12 188 55Eastern Creek 25 2 88Western Creek 28 0 22Total 173 14 298 55


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Figure 1 – Example Creek Catchment Plan

ModelEstuary

EpsilonNational Park

OmegaUrban Area

Alpha CouncilArea

BetaCouncilArea

EasternCreek

WesternCreek

ExampleCreek

N

CatchmentBoundary

Councilboundary

OmegaUrban Area


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As shown in Figure 6, the urban residential areas have a medium to high density in thevicinity of the Sigma highway and the Main Railway. This density decreases to standardresidential on the outskirts of Omega. Premises located within the industrial area includemotor repair and sheet metal workshops, small warehouses, building and landscapingsupplies and a petroleum depot.

A broad land use zoning map, also showing the local government area boundaries for thecatchment, is provided in Appendix 3.

2.3 Topography

The topography of the Example Creek catchment is gently undulating. Example Creekhas an average longitudinal grade of 1.5%, with Eastern and Western Creeks havingmarginally steeper gradients of 1.5 and 1.8% respectively. Valley side slopes generallyrange between 5% and 10%. In the northern portion of the catchment, slopes increase to25%. Figure 7 indicates the coarse contours of the catchment.

2.4 Geology and Soils

The Example Creek catchment lies predominantly on shales and mudstones. The steepernorthern (forested) portion of the catchment is located on sandstone.

The catchment’s soil landscapes are indicated on Figure 4, which were obtained fromDLWC soils mapping. There are four main soil landscapes within the catchment, withtheir characteristics summarised in Table 2. The majority of the catchment is located onthe Theta soil landscape, which predominates on the slopes of the valleys. The Kappalandscape dominates on the crests of the ridges, with Epsilon being the dominantlandscape in the valley floors. The Lambda soil landscape occurs on the steeper slopes ofthe sandstone hills in the northern area of the catchment.

Table 2 – Soil Landscape Characteristics

Erosion hazardSoillandscape

Soil depthConcentratedflows

Non-concentratedflows

Fertility

Theta 50-150 cm Moderate Slight Moderate-lowKappa 50-100 cm Moderate Slight LowEpsilon > 150 cm Extreme High Moderate-highLambda 10-100 cm Extreme Moderate LowSource: DLWC soil landscapes

2.5 Climate

Long term rainfall data was obtained from the Bureau of Meteorology for the Omegarainfall station (station number 998877), which has records since 1889. Pan evaporationdata was also obtained from the Bureau of Meteorology from the nearest recordingstation, being the Seagull Airport (station number 998899), where records commenced in1954. The average monthly rainfall and evaporation data is presented in Table 3.

It can be seen from this data that the rainfall is distributed relatively evenly throughoutthe year. Pan evaporation, however, shows a distinct summer peak and winter low. During summer, the average evaporation rate is considerably higher than the averagerainfall.


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Table 3 – Average Rainfall and Evaporation

Month Average Rainfall (mm) Average Pan Evaporation (mm)

January 85 151February 72 148March 70 85April 65 40May 55 38June 52 35July 50 30August 56 34September 63 37October 75 42November 75 75December 92 122Total 810 837

3 EXISTING CATCHMENT CONDITIONS

3.1 Hydrology

The DLWC have operated a stream gauging station at the Sigma Highway crossing ofExample Creek since 1967 (location shown on Figure 2). The average monthly flow ispresented in Table 4.

Table 4 – Average Streamflow at DLWC Monitoring Station

Month Average Flow (m3/s) Average Monthly Runoff (mm)

January 8 8February 5 5March 8 8April 10 10May 15 15June 18 18July 18 18August 18 18September 17 17October 16 16November 15 15December 12 12Total 160 160

This table indicates that the monthly runoff peaks in spring, with a low in autumn. Dueto the high evaporation rates in summer, rainfall tends to be relatively ineffective ingenerating runoff over this period. This may be significant in the design of stormwatercontrol measures, particularly constructed wetlands (eg species planted).


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A flow duration curve for the DLWC monitoring station is presented in Figure 7. Thisshows the percentage of time that any given rate of stream flow is equalled or exceeded atthat point in the catchment.

To estimate flows at other locations within the catchment, a computer model wasestablished (described in Appendix 4). Estimated flows for Example Creek at the ModelEstuary are presented in Table 4 for a range of average recurrence intervals (ARIs).

Table 5 – Estimated Flow Rates

Location Estimated flow for nominate ARI (m3/s)

1 year 2 year 5 year 50 year 100 yearModelEstuary

2 4 6 8 9

There have been numerous occurrences of flooding in the low-lying areas of Omega,particularly in the vicinity of the Example and Eastern Creek’s confluence. Theinvestigation of flooding is beyond the scope of this Plan, and Beta Council is currentlyundertaking a drainage study in this area. It is envisaged that the recommendations ofthe Drainage Study will be integrated into the next version of this StormwaterManagement Plan.

3.2 Fluvial Geomorphology

The fluvial geomorphology of the Example Creek catchment is summarised in Figure 2. The upper reaches of Example Creek are steep and deeply incised through the sandstonebedrock, with no floodplain development. Sinuosity is low and these reaches act as asediment source zone. The middle reaches of this Creek have moderate sinuosity and themain channel is moderately incised. These reaches are a sediment transport zone, withtemporary sediment deposition occurring in sand and gravel bars. Localised bank erosionoccurs on the outside of bends, particularly where riparian vegetation has been removed. The lower reaches of Example Creek are a distinct sediment deposition zone. The mainchannel is wide and shallow, with extensive floodplains and sediment deposition in themain channel. Bank erosion occurs along the majority of this reach, with the most severeerosion occurring on the outside of bends where riparian vegetation has been removed.

Model Estuary can be classified as a barrier estuary, using the classification schemedeveloped by Roy (1984). Sand dunes occur across the estuary, with the estuary entranceopen to the sea during the autumn to spring period, with occasional entrance closuresoccurring during summer. The entrance channel is relatively shallow. A sediment deltaoccurs at the upstream end of the estuary due to the deposition of sediment from theExample Creek catchment.

3.3 Water Quality

3.3.1 Ambient Water Quality

Ambient water quality monitoring has been undertaken at monthly intervals in ExampleCreek at the Railway Bridge for the last 3 years. Monitoring over the same period has alsobeen undertaken in the Model Estuary. The results of the monitoring for total phosphorus(TP), orthophosphate (PO4), total nitrogen (TN), nitrate (NOx) chlorophyll a (Chl a) and


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faecal coliforms (FC) are presented in Table 6. The ambient water quality objectives(WQO) for Example Creek and Model Estuary are also noted in Table 6.

More detailed ‘whisker’ plots of water quality at these two sites are provided in Appendix5.

Table 6 – Ambient water quality data

Location 90th

Percentile Ambient Concentrations (mg/L)

TP PO4 TN NO3 Chl a FC*ExampleCreek

0.08 0.8 690

WQO 0.05 0.5 150

Model Estuary 0.03 0.09 0.028 190WQO 0.01 0.05 0.01 150* cfu/100 mL

It can be seen that the water quality of Example Creek and Model Estuary fails to meet theadopted WQOs.

3.3.2 Estimated Pollutant Loads

An estimate of the average annual pollutant loads from the Example Creek catchment tothe Model Estuary has been undertaken and is detailed in Appendix 7. Estimates of loadshave been made for TP, TN and suspended solids (SS) for both existing and pre-development (ie forested) catchment conditions. The latter modelling was undertaken toprovide a frame of reference for the existing loads. There has been no continuous wet-weather water quality monitoring undertaken in the catchment, and the modelparameters were derived from other catchments with similar land uses, as detailed inAppendix 7. The estimated loads for the entire catchment are presented in Table 7.

Table 7 – Estimated Average Annual Pollutant Loads

Condition Pollutant loads (t/yr)Total Phosphorus Total Nitrogen Suspended Solids

Existing 12 50 8,000Pre-development 6 30 5,000

It can be seen from this table that the existing loads are considerably higher than the pre-development loads.

3.4 Aquatic Habitat

The aquatic habitats in the upper reaches of Example Creek are a diverse mixture of poolsand riffles zones, containing extensive large organic matter. The substrate ranges fromcoarse sand to cobbles. Through the middle reaches of the creek, the habitat becomesmore uniform, with moderately shallow pools and bars. The substrate is predominantlycoarse sand, with some large organic matter. In the lower reaches, the habitat is relativelyuniform, comprising shallow pools and sand bars. The substrate is sand and organic


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matter is limited.

Within the Model Estuary, seagrass covers an area of 25 hectares.

3.5 Riparian and Foreshore Vegetation

Indigenous riparian vegetation occurs adjacent to the upper reaches of Example Creek. Inthe middle reaches, riparian vegetation is not extensive and is composed of bothindigenous and exotic species. The lower reaches of this Creek also have limited riparianand floodplain vegetation. This majority of this vegetation is exotic.

Mangroves in the vicinity of the Example Creek delta dominate the foreshore vegetation ofModel Estuary. Some mangroves also occur along the northern shore of the Estuary in theEpsilon National Park, and isolated areas of the southern shore. Salt marshes are presentup-slope of the National Park’s mangroves.

4 CATCHMENT VALUES

A workshop was held on 1 October attended by representatives from all stakeholdersidentified in section 1.3. The aim of the workshop was to identify and prioritise thedesired values that stakeholders placed on the waterways of the Example Creekcatchment. The notes from this workshop are contained in Appendix 8. These values aresummarised in Table 8.

5 STORMWATER MANAGEMENT OBJECTIVES

5.1 Ecologically Sustainable Development

Stormwater management in the Example Creek catchment is to be based on ecologicallysustainable development (ESD) principles. ESD requires the effective integration ofeconomic and environmental considerations in decision-making processes. ESD can beachieved through the implementation of the following principles and programs:

(a) The precautionary principle – namely, that if there are threats of serious orirreversible environmental damage, lack of full scientific certainty should not beused as a reason for postponing measures to prevent environmental degradation.

(b) Inter-generational equity – namely, that the present generation should ensure thatthe health, diversity and productivity of the environment is maintained orenhanced for the benefit of future generations.

(c) Conservation of biological diversity and ecological integrity.

(d) Improved valuation and pricing of environmental resources.


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Table 8 – Desired Catchment Values

Catchment Value Value

Ecological:• Maintenance and restoration of aquatic ecosystem of Model

Estuary.High

• Diversity of indigenous aquatic fauna and flora in the upperreaches of Example Creek

High

• Diversity of indigenous aquatic fauna and flora in the middle andlower reaches of Example Creek

Medium

• Diverse of indigenous aquatic fauna and flora in the middle andlower reaches of Western Creek

Low

• Retention of indigenous riparian vegetation along the upperreaches of Example Creek

High

• Retention and restoration of indigenous riparian vegetation alongthe middle and lower reaches of Example Creek

Medium

• Maintenance and restoration of indigenous foreshore vegetationaround Model Estuary

High

• Protection of bushland in the Coastal National Park High

Social Values:• Swimming and sailing on Model Estuary High• Swimming in lower reaches of Example Creek Medium• Swimming in middle and upper reaches of Example Creek Low• Fishing in Model Estuary and lower reaches of Example Creek High• Visual amenity of Model Estuary High• Visual amenity of Example Creek High

Economic values:• commercial prawn fishing in Model Estuary High• commercial oyster farming in Model Estuary High• property values adjacent to Model Estuary and Example Creek Medium• withdrawals from Example Creek for watering of Omega Golf

CourseMedium

5.2 Management Objectives

Management objectives have been developed to protect the ‘high priority’ catchmentvalues of the stormwater system and its catchment. These include both ‘long-term’commitments to principle (a ‘vision’ for the catchment) and ‘short-term’, quantifiableobjectives help form the basis of actions to be incorporated into this Plan.

The manner in which the stormwater management objectives have been derived from thehigh-priority values is illustrated in Figure 8.

It is envisaged that the short term management objectives may evolve as new informationand understanding of the catchment and its processes is achieved.

Figure 8 Linking Stormwater Management Objectives to Catchment Values


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Catchment Values Stormwater Management Objectives

Ecological values Long - Term Short - Term

Water Quality Model Estuarymeets requirements forprotection of aquaticecosystem

Ambient concentration ofnitrogen and phosphorus withinand downstream of urban areas,including Example Creek andModel Estuary, reduced by 30 %

Maintenance andrestoration of Modelestuary aquaticecosystem

Catchment watercourses in astate of dynamic equilibriumfrom fluvial geomorphologicalperspective

Bank erosion in Example Creekwill be addressed in a mannerwhich restores a state of dynamicequilibrium to the system.

Physical habitats for aquaticfauna within catchmentwaterways are to be protectedand restored as appropriate

The physical habitat value ofExample Creek for aquatic faunais to be restored.

Diversity of indigenousaquatic fauna and flora inthe upper reaches ofExample Creek.

Indigenous riparian, foreshoreand floodplain vegetationprotected and restored asappropriate

The riparian vegetation along thatreach of Example Creek withinthe urban area is to be restoredwith indigenous species

Maintenance andrestoration of indigenousforeshore vegetationaround Model Estuary

Protection of bushland inthe Epsilon NationalPark

Impact of urban stormwateron weed propagation andgrowth in bland, particularlyEpsilon National Park, to beminimised

Urban stormwater enteringEpsilon National Park will bemanaged in a manner whichminimises weed propagation andgrowth

Social ValuesAny negative impacts ofstormwater on public healthor safety are to be minimised

Public safety to be considered inthe design of all structuralstormwater management works

Stormwater channelsand structures are to besafe

Water quality meets therequirements for primary andsecondary contact recreation

The waters of Model estuary areto be safe for primary contactrecreation at least 90 % of time

Fishing in Model Estuaryand lower reaches ofExample Creek.

Impact of new devts on waterquality is to be controlled, at leastto the levels listed in Table 9..

Impact of new urbandevelopments on catchmentvalues, and the achievement ofthe management objectives isto be minimised

Frequency of 1.5 Year ARI Flowevents not increased due to devt

Swimming in and sailingon Model Estuary

Visual amenity of ModelEstuary

Visual amenity ofExample Creek

Visual amenity of waterwaysis to be maximised

No significant litter will be visiblein streams within / downstreamof urban area following storms upto 0.25 of 1 year ARI

Economic values

Commercial oysterfarming and prawnfishing in Model Estuary

Water quality meetsrequirements for safeconsumption of fish,crustaceans and shellfish.

Ambient concentration of faecalcoliforms in Model Estuaryreduced by 30 %.

Table 9 – Stormwater Treatment Objectives for New Urban Areas


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Pollutant: ESD Treatment Objective:

Post construction phase:Suspended solids (SS) 80% retention of the average annual loadTotal phosphorus (TP) 45% retention of the average annual loadTotal nitrogen (TN) 45% retention of the average annual loadLitter Retention of litter greater than 50 mm for flows up to

25% of the 1 year ARI peak flowCoarse sediment Retention of sediment coarser than 0.125 mm* for

flows up to 25% of the 1 year ARI peak flowOil and grease(hydrocarbons)

In areas with concentrated hydrocarbon deposition,no visible oils for flows up to 25% of the 1 year ARIpeak flow

Construction phase:Suspended solids Effective treatment of 90% of daily runoff events (eg

<4 months ARI). Effective treatment equates to a50%ile SS concentration of 50 mg/L.

Other pollutants Limit the application, generation and migration oftoxic substances to the maximum extent practicable

* based on idealised settling characteristics

6 STORMWATER MANAGEMENT ISSUES

This step of the plan preparation process involved identifying the factors that currentlyprevent, or may prevent, the adopted management objectives from being satisfied. Theseproblems or issues were environmental, social and managerial.

These issues have been identified by a combination of:• desk-top study, involving a review of existing information contained in reports, studies

and monitoring programs.• field work, involving an inspection of the catchment and the undertaking of a ‘first-

order’ (approximate) a catchment audit; and• discussions, involving interviewing community representatives, council staff and staff

from relevant State Government Agencies, which can obtain information on all typesof issues.

Table 10 identifies a series of stormwater management issues, and nominates possiblecauses of these problems.

7. IDENTIFICATION OF POTENTIAL MANAGEMENT OPTIONS

A broad range of structural and non-structural practices is available to address identifiedstormwater management issues. Table 10 provides a list of potential practices which havebeen identified for as potential options to address the identified stormwater managementissues for the Example Creek catchment (which have, as previously noted, been derivedfrom the stormwater management objectives and catchment values.


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Table 10(a). Stormwater Management Issues & Options, and Potential ManagementOptions

Issue / Cause1 Potential Management Option Ranking2

• Residents’ education campaign in relation tofertiliser use and car washing

12

• Review fertiliser use by Councils on public parks,sporting ovals etc.

4

• Encourage low-maintenance garden plants 21Site 1 10Site 2 5Site 3 30Site 4 31Site 5 38

A. Elevated nutrient levels, andconsequent algal blooms inExample Creek and ModelEstuary, possibly due to:-

• Excessive fertiliserapplication

• Car washing in streets• Impact of toxicants on algal

grazers

• Install constructed wetland totreat urban runoff atfollowing potential sites (asshown in Figure *)

Site 6 40

• Educational and regulatory campaign aimed aterosion and sediment control at building sites

1

• Require Erosion and Sediment Control Plans fornew developments, and compliance therewith as aBA / DA condition of consent

8

• Education campaign on washing cars in streets 14

Site 1 As aboveSite 2 As aboveSite 3 As aboveSite 4 As aboveSite 5 As above

B. Elevated suspended solids andturbidity levels in ExampleCreek, possible due to:-

• Poor erosion and sedimentcontrols at devt. Sites

• Channel erosion• Car washing in streets • Install constructed wetland to

treat urban runoff atfollowing potential sites (asshown in Figure *)

Site 6 As above

• Install more rubbish bins in problem areas 15• Increase frequency of emptying of bins in problem

areas32

High risk 7Medium risk 29

• Install litter baskets instormwater pits servicingareas marked in Figure # as: Low Risk 34

• Undertake local education program on littering 33

Site 7 16

C. Litter in watercourses,possibly due to :-

• Insufficient rubbish bins• Rubbish bins not emptied

regularly• Littering in commercial,

retail areas• Littering from motor

vehicles• Install litter racks at

Locations marked in Figure& as:-

Site 8 35

• Encourage installation of rainwater tanks at newand existing developments

18

Site 3 3• Install retarding basins atSites marked on Figure $ as: Site 5 17

Eastern Reach 1 23Western Reach 1 13Example Reach 1 19Example Reach 2 20

D. Erosion of ExampleCreek downstream of andwithin Omega urban area,probably due to:-

• Removal of riparianvegetation

• Increased flood flows fromurban areas

• Replanting of riparianvegetation, progressivelyalong reaches of ExampleCreek and tributariesmarked on Figure % as: Example Reach 3 36

1. Issues linked to catchment values and stormwater management objectives, listed in Table 5.2. Rankings derived used methodology and calculations contained in Appendix D.

Table 10(b) . Stormwater Management Issues and Options, and Potential Management


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Options.

Issue / Cause Potential Management Option Ranking

• Preserve existing habitats 6

Example Reach 1 25

Example Reach 2 26

Eastern Reach 1 37

• Reconstruct in-streamphysical habitats suitablefor aquatic fauna withinthose stream reachesmarked on Figure % as:

Western Reach 1 34• See also Issue A (previous page)

E. Degraded aquatic habitatswithin Example Creek, possiblydue to:-• Physical alteration to

habitats• Increased flood flows from

urban areas• Increased sediment

deposition• Removal of riparian

vegetation

• See also Issue D (previous page)

• Develop ‘exhibition reach’ of drainage system wherewater sensitive urban design principles can beadopted.

22

• Construct access / bicycle paths along drainageelements

24

• Construct signs and other public informationeducating the public in relation to potential values ofstormwater drainage system.

27

F. Low public value placed inurban stormwater system,probably due to:-

• Poor current condition ofsystem.

• Public not aware ofpotential benefits ofproperly designed andmaintained system

• See also Options listed under Issues A, B, C, D and E. As above

• Treat runoff before it flows into Epsilon National Park 2

• Divert urban stormwater flows entering EpsilonNational Park to ‘established’ flow paths rather thandry gullies

28

G. Weed growth along gullies inEpsilon National Park whichreceive runoff from urban areas,due to:• Elevated nutrient levels in

runoff and soils• Drainage now enters sites

which did not receiveconcentrated flows prior to urban development

• Increased frequency offlows

• Remove existing weeds and plant indigenous speciesonce upstream treatments in place

32

• Public education campaign on collection of dog faeces 9

• Undertake monitoring program to identify andsource and high bacterial levels

11

Site 1 As above

Site 2 As above

Site 3 As above

Site 4 As above

H. Intermittently high levels offaecal bacteria within ExampleCreek and Model Estuary,particularly (but not always)following storm events, possiblydue to:• Contaminated runoff from

urban area (dog faeces etc.)• Sewer overflows• Illegal discharge of septic

waste

• Install constructed wetland totreat urban runoff at followingpotential sites (as shown inFigure *)

Site 5 As above

1. Issues linked to catchment values and stormwater management objectives, listed in Table 5.2. Rankings derived used methodology and calculations contained in Appendix D.

8. EVALUATION OF POTENTIAL MANAGEMENT OPTIONS

8.1 Methodology


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The methodology outlined in the EPA’s Managing Urban Stormwater: Council Handbook hasbeen adopted for the assessment and evaluation of the various management options listedin Table 10.

8.2 Evaluation and Ranking of Potential Management Options

Table 10 lists the ranking of potential management options derived by the EPA’s suggestedmethodology for the Example Creek catchment.

9. IMPLEMENTATION STRATEGIES

Implementation strategies for the implementation of the higher priority managementoptions is outlined in Tables 11 and 12 for Alpha and Beta Councils respectively. TheseTables prioritise specific management actions to be implemented by each stormwatermanager in the catchment, and provides a tentative timeframe for their implementation.Programs which are proposed to be undertaken jointly by the two Councils (eg publiceducation programs) are italicised in Tables 11 and 12.

10. MONITORING

Alpha and Beta Councils are committed to continuing the existing routine water qualitymonitoring programs are Example Creek and Model Estuary respectively. Theseprograms are generally designed and undertaken in accordance with the principlesoutlined in the EPA’s Managing Urban Stormwater: Council Handbook document. Inaddition, Beta Council will undertake an assessment of sediment quality, and associatedtoxicity impacts in the Model estuary.

11. REPORTING

The results of these environmental monitoring programs will be reported in Councils’State of the Environment Reports. In addition, this information will be a valuable inputinto the refinement of this Stormwater Management Plan in future years.

12. REVISION

This plan will be reviewed in 3 years. This review will involve assessing whether the shortterm management objectives have been satisfied and if additional management optionsneed to be developed. The tentative implementation strategy will provide an input intothe management planning process of both councils in future years.

12. CONCLUSIONS

The stormwater management plan for the Example Creek catchment provides an intergradedscheme for the ecologically sustainable and cost-effective management of stormwater within thecatchment.


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Table 11. Stormwater Management Implementation Strategy – Alpha Council

Financial Year & Expenditure

1998-99 1999-00 2000-01Action Rank

Capital Maint. Capital Maint. Capital Maint.Undertake educational and regulatory campaign aimed at erosion andsediment control at building sites

1 5,000 - 5,000 - 5,000 -

Review fertiliser use by Councils on public parks, sporting ovals. 4 5,000 - - - - -

Construct stormwater treatment wetland at Site 2 5 - - 10,000 - 115,000 5,000

Install litter baskets in stormwater pits servicing ‘high risk’ areas 7 50,000 10,000 - 10,000 - 10,000

Require Erosion and Sediment Control Plans for new devts 8 10,000 - 2,000 - 2,000 -

Undertake public education campaign on cleaning up after dogs 9 - - 8,000 - - -

Undertake education campaign re. fertiliser use and car washing 12 12,500 - - - - -

Replant riparian vegetation along Reach 1 of Western Ck. 13 - - 20,000 - - 5,000

Install additional rubbish bins in problem commercial areas 15 10,000 2,000 10,000 3,000

Install litter rack at Site 7 16 45,000 - - 4,000 - 4,000

Encourage installation of rainwater tanks at new & existing devts 18 4,000 - - - - -

Reconstruct aquatic fauna habitat along Reach 1 of Example Ck. 19 - - 5,000 - 30,000 -

Total Cost 142,500 12,000 60,000 17,000 152,000 24,000

Actions which may be undertaken jointly by Alpha and Beta Councils are italicised


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Table 12. Stormwater Management Implementation Strategy – Beta Council

Financial Year & Expenditure

1998-99 1999-00 2000-01Action Rank

Capital Maint. Capital Maint. Capital Maint.Undertake educational and regulatory campaign aimed at erosion andsediment control at building sites

1 5,000 - 5,000 - 5,000 -

Treat urban stormwater before it flows into Epsilon National Park 2 15,000 - 15,000 5,000 15,000 5,000

Install flow retarding basin at Site 3 3 10,000 - 110,000 - 20,000 5,000

Review fertiliser use by Councils on public parks, sporting ovals. 4 5,000 - - - - -

Preserve existing habitats when considering new devt proposals 6 10,000 - - - - -

Install litter baskets in stormwater pits servicing ‘high risk’ areas 7 50,000 10,000 - 10,000 - 10,000

Require Erosion and Sediment Control Plans for new devts 8 10,000 - 2,000 - 2,000 -

Undertake public education campaign on cleaning up after dogs 9 - - 8,000 - - -

Construct stormwater treatment wetland at Site 1 10 15,000 - 120.000 - - 5,000

Undertake education campaign re. fertiliser use and car washing 12 12,500 - - - - -

Install additional rubbish bins in problem commercial areas 15 10,000 2,000 10,000 3,000

Install flow retarding basin at Site 5 17 - - 20,000 - 119,000 4,000

Encourage installation of rainwater tanks at new & existing devts 18 4,000 - - - - -

Reconstruct aquatic fauna habitat along Reach 2 of Example Ck. 20 - - 5,000 - 30,000 -

Total Cost 146,500 12,000 295,000 18,000 191,000 29,000

Actions which may be undertaken jointly by Alpha and Beta Councils are italicised


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REFERENCES


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REFERENCES

Adam P, 1990. Saltmarsh Ecology, Cambridge University Press, Cambridge

Agriculture and Resource Management Council of Australia and New Zealand andAustralian and New Zealand Environment and Conservation Council, 1996. DraftGuidelines for Urban Stormwater Management.

Allan JD, 1995. Stream Ecology - Structure and Function of Running Waters, Chapman andHall, London.

Allen M and Argue J, 1995. Disposal of Stormwater by Infiltration: The Pro∋s and Con∋s,proceedings of an Institution of Engineers Australian and Stormwater IndustryAssociation seminar Stormwater Towards the Year 2000.

American Public Health Association, American Water Works Association, WaterEnvironment Federation, 1995. Standard Methods for the Examination of Water andWastewater, 19th edition.

American Society of Civil Engineers and Water Environment Federation, 1993. Design andConstruction of Urban Stormwater Management Systems, ASCE Manuals and Reports ofEngineering Practice N1 77, WEF Manual of Practice, FFD-20.

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