Broughton Creek Floodplain Risk Management Study and Plan
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Broughton Creek Floodplain Risk Management Study and Plan Committee Meeting – 12 April 2012 Overview • Study Objectives • Study Area • Study Approach • Existing Flood Behaviour • Summary of Community Feedback • Flood Management Options • Forthcoming Activities Study Objectives Form a Floodplain Risk Management Committee Data Collection Monitor and Review NSW Floodplain Flood Study Management Process Floodplain Risk Management Study Floodplain Risk Management Plan Adoption and Implementation of the Plan Study Objectives • Review the flood study. • Update flood modelling to improve understanding of flood behaviour. • Consider the available flood management options. • Compare the management options and identify preferred options. Study Area Bundewallah Broughton Vale Broughton Village David Berry Bundewallah Broughton Hospital Vale Berry Jaspers Brush Far Jaspers Meroo Meadow Brush Meadow Back Forest Study Approach • Update flood modelling • Stakeholder consultation – Council, SES, RMS (RTA), Utilities. • Community consultation – Survey, information day, public exhibition • Develop & assess management options • Identify preferred management options • Develop Floodplain Risk Management Plan Existing Flood Behavior Figure: 1% AEP Flood Event Extent Major Flowpaths • Major Waterways Broughton Creek – Broughton Mill Creek – Bundewallah Creek • Flowpaths – Town Creek – North St Overland Flowpath – Hitchcocks Lane Creek • Passes through south east corner of model area • Primarily affects rural land • Affects access to David Berry Hospital Major Flowpaths • Major Waterways – Broughton Creek Broughton Mill Creek – Bundewallah Creek • Flowpaths – Town Creek – North St Overland Flowpath – Hitchcocks Lane Creek • Runs past east side of Berry • Overbank flooding affects eastern Berry • A high hazard floodway • Affects access along Woodhill Mountain Rd and the Princes Highway Major Flowpaths • Major Waterways – Broughton Creek – Broughton Mill Creek Bundewallah Creek • Flowpaths – Town Creek – North St Overland Flowpath – Hitchcocks Lane Creek • Runs north of Berry • Affects rural land and some properties near the confluence with Broughton Mill Creek • Affects access along Woodhill Mountain Rd Major Flowpaths • Major Waterways – Broughton Creek – Broughton Mill Creek – Bundewallah Creek • Flowpaths Town Creek – North St Overland Flowpath – Hitchcocks Lane Creek • Flows through Berry • Responsible for the majority of flood damages in the study area • Channel flows are high hazard, overbank flows generally low hazard Major Flowpaths • Major Waterways – Broughton Creek – Broughton Mill Creek – Bundewallah Creek • Flowpaths – Town Creek North St Overland Flowpath – Hitchcocks Lane Creek • Affects properties along North St, Alexander St and Albert St • Conveys relatively little water • A low hazard flowpath Major Flowpaths • Major Waterways – Broughton Creek – Broughton Mill Creek – Bundewallah Creek • Flowpaths – Town Creek – North Street Overland Flowpath Hitchcocks Lane Creek • Affects access along the Princes Highway • A high hazard region, low velocity but depths up to 1.6m through the floodway Flood Management Options • Options Development: – Results of flood modelling, – Community consultation outcomes, – Engineering judgement. • Options Assessment: – Economic • Cost of implementation vs. likely reduction in flood damages – Environmental Triple Bottom • Potential positive or negative impacts on the environment Line – Social • Likely positive or negative social impacts. Flood Management Options • Three option categories – Structural options – Property Modification Options – Response Modification Options • Different options will suit different regions of the study area • Broadly speaking, the study area can be divided up into three broad regions – Berry Township – affected by Town Creek flooding – Berry Township – affected by Broughton Mill Creek flooding – Rural properties – affected by Shoalhaven River flooding Structural Management Options • Physical changes to alter the flood behaviour • Drainage upgrades • Channel improvements • Levees • Detention Basins • Aimed at removing or reducing the flood risks / damages • These options would be best suited to managing Town Creek flooding, where the volume of flood waters is small enough to be effectively managed Modelled Structural Options Property Modification Options • Changes to structures to make them more flood compatible • Planning controls • Flood proofing • House raising • Voluntary purchase • Stock mounds • Aimed at making structures better able to cope with flooding, and thus reducing the flood damage Emergency Response Modification Options • Changes to how emergency services, Council and residents respond to flood events • Preparation of a local flood plan • Flood warning systems • Public awareness campaigns • Flood warning signs • Aimed at improving the response to flood events to reduce the risk to life and property • They would be suitable to be applied across the study area The Princes Highway Upgrade • The RTA is proposing to upgrade the Princess Highway which incorporates a by-pass around Berry • At present, two options are being investigated – a northern option and a southern option • The northern option has the opportunity to help alleviate flooding – Inclusion of storage north of the highway to reduce downstream flooding – The diversion of Town Creek – The use of excess cut to create stock mounds to provide flood safe regions for animals • The southern options does not offer any flood alleviation opportunities • As such, two Plans have been prepared, taking into account each scenario Proposed FRM Plan – Summary • Existing Conditions / • Northern By-Pass Southern By-Pass • Implementation $482,200 • Implementation $2,729,000 • Recurrent $12,200 • Recurrent $17,200 • Key differences in the Plans is that the northern by-pass allows for the removal of the Town Creek detention and diversion options from the Plan. • An effort has been made to have the first stages the same for both options, to allow time for the Princes Highway diversion option to be determined Existing / Southern By-Pass Plan ID Description Priority ID Description Priority Information transfer to the Preparation of Local Flood EM1 High EM2 Medium SES Plans and update of DISPLAN Public awareness and EM4 High EM5 Flood warning signs Medium education FM Data collection following Town Creek Diversion Medium DC1 High 1.7 a flood event FM Building and Stock Mounds Medium P2 High 4.1 Development Controls EM3 Flood warning system Low P1 LEP Update High P8 Flood Proofing Guidelines High FM North St Diversion Swale Low FM Town Creek Vegetation 1.6 High 1.2 Clearing Next Steps • Council Review of the draft FRM Study & Plan • Public exhibition of the draft FRM Study & Plan, and gathering of community comments • Update of the FRM Study & Plan based on Council and community feedback • Finalisation of the FRM Study & Plan Questions? .