The Newcastle City-Wide Floodplain Risk Management Study and Plan
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A part of BMT in Energy and Environment NewcastleNEW CITY PLAN City-wide Floodplain Risk Management Study and Plan FLOOD HAZARD OVERLAY CODE Final Report June 2012 The Newcastle City-wide Floodplain Risk Management Study and Plan Offices Brisbane Denver Mackay Melbourne Prepared For: The City of Newcastle Newcastle Perth Sydney Prepared By: BMT WBM Pty Ltd (Member of the BMT group of companies) Vancouver K:\N2246_NEWCASTLE_FRMS_STAGE2\DOCS\R.N2246.001.03.DOCX DOCUMENT CONTROL SHEET BMT WBM Pty Ltd BMT WBM Pty Ltd R.N2246.001.03.docx 126 Belford Street Document : BROADMEADOW NSW 2292 Project Manager : Dr Philip Haines Australia PO Box 266 Broadmeadow NSW 2292 Tel: +61 2 4940 8882 Fax: +61 2 4940 8887 Client : The City of Newcastle (CofN) ABN 54 010 830 421 Client Contact: David Gibbins / Alastair Peddie www.bmtwbm.com.au Client Reference Title : The Newcastle City-wide Floodplain Risk Management Study and Plan Author : Dr Philip Haines (BMT WBM), David Gibbins (CofN), Rod Hardwick (CofN) Synopsis : This document is the complete Floodplain Risk Management Study and Plan for the Newcastle City-wide area. It is the culmination of many years of research and studies, including various Flood Studies for specific catchments, Floodplain Management Studies, and the previous Stage 1 Concept City-wide Flood Plan. The document provides a suite of actions, works and initiatives that when implemented will result in reductions to Risks to Life and Risks to Property across the City. This City-wide Floodplain Management Plan excludes the Wallsend Commercial Centre, as this area already has an adopted Flood Plan (2009). Apart from updating the mapping of floodplain categories, this document does not supersede or negate the Wallsend Plan in any way. Implementation of both the City-wide Flood Plan and the Wallsend Flood Plan should occur concurrently. REVISION/CHECKING HISTORY REVISION DATE OF ISSUE CHECKED BY ISSUED BY NUMBER 0 23 December 2011 PEH PEH 1 31 January 2012 PEH PEH 2 21 February 2012 PEH PEH 3 18 June 2012 PEH PEH DISTRIBUTION DESTINATION REVISION 0 1 2 3 CofN electronic electronic electronic electronic BMT WBM File BMT WBM Library K:\N2246_NEWCASTLE_FRMS_STAGE2\DOCS\R.N2246.001.03.DOCX Disclaimers Although great care has been taken in the preparation of these documents /maps, the City of Newcastle makes no representation or warranty as to the accuracy, adequacy, currency, reliability or completeness of any information contained in them. Assessing accuracy and reliability of information is the responsibility of the user. All documents /maps included in this are subject to change without notice and the City of Newcastle is under no obligation to update the information contained herein. The City of Newcastle accepts no responsibility for any misprints, errors, omissions or inaccuracies in these documents / maps or for loss or damages resulting from reliance on any information provided. The Newcastle City-wide Floodplain Risk Management Working Party has prepared this document with financial assistance from the NSW Government through the Office of Environment and Heritage. This document does not necessarily represent the opinions of the NSW Government or the Office of Environment and Heritage. K:\N2246_NEWCASTLE_FRMS_STAGE2\DOCS\R.N2246.001.03.DOCX EXECUTIVE SUMMARY I EXECUTIVE SUMMARY What is this Plan about and how has it been developed? The Newcastle City-wide Floodplain Risk Management Study and Plan (City-wide Flood Plan) has been developed to direct and co-ordinate the future management of flood prone lands across the City of Newcastle. It also aims to educate the community about flood risks across Newcastle, so that they can make more appropriate and informed decisions regarding their individual exposure and responses to flood risks. The City- wide Flood Plan sets out a strategy of short term and long term actions and initiatives that are to be pursued by agencies and the community in order to adequately address the risks posed by flooding. With the exception of updating the mapping of floodplain categories, the City-wide Flood Plan does not cover the Wallsend Commercial Centre, as this flooding hotspot already has a Flood Risk Management Plan that was adopted the City of Newcastle (CofN), in 2009. Concurrent with the City-wide Flood Plan, CofN is also pursuing opportunities for implementing management actions outlined in the Wallsend Flood Plan. This Flood Plan is the culmination of many years of studies and on-going research that have aimed to understand the nature and extent of flooding across the catchments of Newcastle. Development of the City- wide Flood Plan has been guided by the NSW Government’s Floodplain Development Manual (2005). Importantly, in following this Manual, CofN is managing its liability relating to flooding through provisions made under Section 733 of the Local Government Act 1993. Flooding affects about 1 in 3 properties within the City of Newcastle. The vast extent of flooding across the City necessitates that flooding is managed at a City-wide scale, rather than at a local catchment-scale. This Plan therefore is ground-breaking and it is hoped will assist the future of floodplain management across NSW. The structure of this City-wide Flood Plan is presented in Figure A1. In essence this Plan assessed the current management of floods in Newcastle against the principles for floodplain management as outlined in the Floodplain Development Manual (2005). Current flood management is a legacy of past works and actions, and also the unique flood environment of Newcastle – that is, flooding can occur as a result of: • flash flooding from the local catchments; • river flooding from the Hunter River; or even • ocean flooding from high water levels in the ocean and harbour. Based on the considered short-comings of current management, this Plan reviews potential alternative management options and then formulates a future flood management strategy. The strategy includes both short term works and actions as well as longer term initiatives. The short term works and actions have been chosen to give maximum priority Figure A1: Structure of the City-wide Floodplain Management Study & Plan K:\N2246_NEWCASTLE_FRMS_STAGE2\DOCS\R.N2246.001.03.DOCX EXECUTIVE SUMMARY II benefit while also being readily implementable within envisaged Quick Definitions affordable budgets. Implementation is still, however, subject to this albeit limited funding - customarily allocated year by year. Existing Risk: Flooding risks that affects existing development The longer term initiatives are still needed - to address the assessed gaps and deficiencies of current management. The definition of these Future Risk: Flooding risks that will affect future development, once built longer term initiatives is subject to future review before the short term works and actions are completed. Implementation of reviewed longer Continuing Risk: The risk remaining term flood management initiatives for the Newcastle LGA would be after all management works and subject to available future funding. It is important that these longer term initiatives have been implemented. initiatives are not excluded from Plan, since future communities and This is the risk that people just have Governments will then have opportunity to decide what level of funding to live with, and therefore it must be is appropriate for ongoing implementation – either accelerated or at an acceptable level deferred. These decisions would be made balancing whole of community and Government priorities against practical resourcing, Flash Flooding: Flooding from the spread across other needs such as health, education, transport and local catchments in Newcastle, social. Current legislation allows these necessary compromises and notably in Ironbark Creek, Dark protects Governments when they make these decisions. Creek, Throsby / Styx Creek and Cottage Creek, as well as flooding It is very important to acknowledge that it is impractical to eliminate all from direct rainfall flood risks from Newcastle. Instead, the aim of future flood management is to ensure that existing and future development is exposed to an River Flooding: Flooding from the ‘acceptable’ level of risk, consistent with other risks that people live with Hunter River. Only an issue for on a day to day basis. Most importantly, this Plan seeks to minimise areas around Hexham/Sandgate Risks to Life, as there can be no more serious loss during a flood event. and the fringes of Hexham Swamp What is a flood? Ocean Flooding: Flooding from very high ocean water levels, typically as In the context of this document, a flood is considered to be any a combination of big tides and storm significant flow within channel or waterway as well as concentrated surge overbank flow or temporary storage / ponding of water resulting from rainfall within local catchments, or backwater inundation from elevated Risk to Life: Flooding risks that downstream waters, such as the Hunter River. In the context of the threaten life. This is the worst type latter, high waters within the Hunter River can be the result of rainfall of flood risk. Managed for all floods further up the large Hunter catchment, or from high ocean water levels up to and including the PMF (see caused by storms and low pressure systems (e.g. East Coast Lows). below). Local street drainage is outside the scope of this City-wide Flood Plan. Risk to Property: Flooding risks that threaten to damage property. Typically only managed up to the 1% AEP flood (see below) 10% AEP flood: There is a 10% (1 in 10) chance that a flood of this size or bigger will occur in any year (sometimes called the 1 in 10 year flood) 1% AEP flood: There is a 1% (1 in 100) chance that a flood of this size or bigger will occur in any year (sometime called the 1 in 100 year flood). The June 2007 was about this big for many areas of Newcastle Looking north at flooding in Steel St, Newcastle West, 1908 PMF flood: This is an extreme flood that is many times larger than the 1% AEP.