Port Phillip and Westernport Region Flood Management and Drainage Strategy i “Ideallysocietywouldliketobefreeoftheriskofflooding, butthisisneitherpracticallynoreconomicallyfeasible. Whatconstitutesanacceptableleveloffloodriskhowever isavexedquestion.Theimmediateriskisbornebythe community,whichmusthaveasignificantinputintodefining theacceptablelevel.Tothisend,publicconsultationandrisk communicationisveryimportant.” Floodplain Management In Australia Best Practice Principles and Guidelines, (SCARM 2000) Development of this strategy has been guided by a steering committee headed by an independent chair, Rob Joy, with representatives from the following organisations: • Department of Sustainability and Environment • Office of the Emergency Services Commissioner • Shire of Macedon Ranges • Insurance industry • Department of Human Services • Municipal Association of Victoria • Stormwater Industry Association of Victoria • Institute of Public Works Engineers Victoria • Port Phillip and Westernport Catchment Management Authority • Melbourne Water. The strategy has been prepared following extensive consultation with flood management agencies and local government authorities in the Port Phillip and Westernport region. Stakeholder workshops were undertaken to identify issues of concern and submissions received in relation to a circulated discussion paper assisted in the formulation of future strategic actions. iii LollipopCreek,Werribee,February2005 iv FloodManagementandDrainageStrategy Contents 2 Introduction 6 Background 6 What is flooding? 8 Types of flooding in the region 12 History of flooding 14 Flood damage 20 Managing floods 22 Responsibilities for flood management across the region are shared 26 Flood management objectives Objective 1: Completing the knowledge base Objective 2: Potential long term future pressures on existing drainage systems Objective 3: An agreed approach to managing existing regional flood problems Objective 4: Enhanced community education, flood awareness and preparation Objective 5: Agreed responsibilities and improved collaboration between flood management agencies 44 Glossary Introduction Floods are a natural and inevitable event. We cannot always control them. Therefore, we must learn how we can live with them while minimising risks to public health and safety, property and infrastructure. The Port Phillip and Westernport Region faces significant Aside from the likely multi-billion dollar cost and extreme flood management and drainage challenges that require a disruption, the time frame to build such expensive coordinated and collaborative approach by flood managers infrastructure would exceed the lifespan of the properties and the community. they attempt to protect. There are currently more than 100,000 properties in the This strategy recognises that although it is not possible region that are known to be at risk from flooding of which to make the region completely free from flooding, there 82,000 properties are at risk of flooding from overland are some flooding risks that we may decide are intolerable flows. More than 40,000 of these properties contain and almost regardless of the cost, the consequence of buildings or dwellings that are at risk of flooding above flood should be reduced or eliminated. Consultation and floor level. On average, the annual damage caused by research will be undertaken to reach agreement on what flooding in the region has been estimated to be $245 constitutes intolerable flood risk. million. Our long term aim is to minimise all currently known The Flood Management and Drainage Strategy has been intolerable flooding risks to public health and safety, prepared following discussions between government property and infrastructure, and increase community departments, councils, emergency service organisations, understanding and preparedness for floods. and other agencies about how we can improve the This strategy proposes the development and management of flood risk in the Port Phillip and implementation of an accelerated program, in consultation Westernport Region. It complements other Melbourne with stakeholders, to identify and deal with intolerable Water programs that deal with river health, water flood risk across the region as quickly as possible. quality, floodplain environmental values, urban growth, stakeholder communications and cultural heritage. As part of this strategy, Melbourne Water will continue to map flood affected areas and will sponsor research into Melbourne Water and councils have traditionally used the intangible social and human health impacts of floods, engineering solutions to improve flood protection in to develop an improved flood risk assessment tool that identified high risk areas. takes these costs into account when determining flood risk Millions of dollars, funded primarily by council and priorities and responses. Melbourne Water drainage rates, are currently spent each Throughout this strategy there is broad recognition that no year on efforts to manage ongoing risks from overland single organisation and no single approach can deliver an flows and riverine flooding. effective response to flood management issues. While these efforts are effective at a local level they are While Melbourne Water and councils will continue to having little impact on the overall problem. deploy engineering solutions to mitigate flood risks, it is This is because it is not physically feasible to construct recognised that this approach must be accompanied by a required works to protect all properties in the region from range of non-structural responses. large events. 2 FloodManagementandDrainageStrategy Richmond,July1891 There are other tools that are equally effective and Objective1:Completingthe significantly less expensive, such as planning controls and public awareness programs that can be deployed knowledgebase immediately to assist in treating the residual and future flood risks. These tools will be developed in partnership Flood mapping with other flood managers. Actions In particular, the strategy recognises the importance and 1.1 Melbourne Water will undertake and maintain ongoing benefits of improved education in assisting the community local flood extent, rural waterway and tidal mapping to prepare, respond and recover from floods. for the Port Phillip and Westernport region, taking Part of this focus on existing flood risks will also involve into account the potential long term pressures of working with councils to develop detailed local flood climate change and urban consolidation. This will management plans, and working with the State Flood involve consultation with local government and the Policy Committee, Office of the Emergency Services Department of Sustainability and Environment. Commissioner and other stakeholders to develop an 1.2 Melbourne Water will update and maintain flood integrated flood management planning framework. information for municipal planning schemes to These plans will outline roles and responsibilities, set ensure appropriate standards of flood protection for priorities, aims and goals, and establish work programs new development in flood affected areas. This will and targets to address flood management objectives involve consultation with local government and the identified in the strategy. Department of Planning and Community Development. The strategy defines five flood management objectives and outlines actions that will be undertaken to achieve Understanding social impacts each objective and guide priorities and expenditure by Melbourne Water. Actions 1.3 Melbourne Water will support collaborative research into the social and economic impacts of flooding on the community. 3 We all have an important role to play – Melbourne Water, emergency service organisations, local councils, government departments, research organisations, developers and other businesses, and the community. Objective2:Potentiallong-termfuture 2.2 Melbourne Water will develop flood risk management measures in consultation with Department of Planning pressuresonexistingdrainagesystems and Community Development, Department of Sustainability and Environment and local government. Development in established areas Solutions may include upgrading infrastructure, planning and building controls to limit imperviousness, Actions and onsite measures such as water sensitive urban 2.1 Melbourne Water will work with Department of design and stormwater capture and reuse. Planning and Community Development and local government to understand the likely impact of urban Climate change consolidation on runoff volumes and flood risk in existing urban areas. Actions 2.3 Melbourne Water will continue to support research programs to better understand the impacts of climate change on flood and drainage management. 2.4 Melbourne Water will develop adaptable flood management programs to deal with changing rainfall patterns, rising sea levels, and storm surge. These programs will be developed in consultation with the Commonwealth Scientific and Industrial Research Organisation (CSIRO) and the Bureau of Meteorology. 4 FloodManagementandDrainageStrategy Objective3:Anagreedapproachto Objective4:Enhancedcommunity managingexistingregionalflooding education,floodawarenessand problems preparation Actions Actions 3.1 Melbourne Water will sponsor research and consult 4.1 A community flood education, awareness and with stakeholders to develop criteria to establish flood preparedness program, including flood warning, will risk tolerability thresholds which take into account be developed and