Post on 14-Jan-2022
transcript
Broughton Creek Floodplain Risk Management Study and Plan
Committee Meeting – 12 April 2012
• Study Objectives • Study Area • Study Approach • Existing Flood Behaviour • Summary of Community Feedback • Flood Management Options • Forthcoming Activities
Overview
Study Objectives
Form a Floodplain Risk Management Committee
Data Collection
Flood Study
Floodplain Risk Management Study
Floodplain Risk Management Plan
Adoption and Implementation of the Plan
Monitor and R
eview
NSW Floodplain Management
Process
• 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 Objectives
Study Area
Berry
Broughton Village
Back Forest
Far Meadow Meroo
Meadow
Jaspers Brush
Bundewallah Broughton Vale
Bundewallah
Broughton Vale
Jaspers Brush
David Berry
Hospital
• 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
Study Approach
Existing Flood Behavior
Figure: 1% AEP Flood Event Extent
Major Flowpaths
• Major Waterways
– Broughton Mill Creek – Bundewallah Creek
• Flowpaths
– Town Creek – North St Overland Flowpath – Hitchcocks Lane Creek
Broughton 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
– Bundewallah Creek
• Flowpaths
– Town Creek – North St Overland Flowpath – Hitchcocks Lane Creek
Broughton Mill 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
• Flowpaths
– Town Creek – North St Overland Flowpath – Hitchcocks Lane Creek
Bundewallah 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
– North St Overland Flowpath – Hitchcocks Lane Creek
Town 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
– Hitchcocks Lane Creek
North St Overland Flowpath • 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
• Options Development: – Results of flood modelling, – Community consultation outcomes, – Engineering judgement.
• Options Assessment: – Economic
• Cost of implementation vs. likely reduction in flood damages – Environmental
• Potential positive or negative impacts on the environment – Social
• Likely positive or negative social impacts.
Triple Bottom Line
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
Flood Management Options
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 / Southern By-Pass • Implementation $2,729,000 • Recurrent $17,200
• Northern By-Pass • Implementation $482,200 • Recurrent $12,200
• 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
EM1 Information transfer to the
SES High
EM4 Public awareness and
education High
DC1 Data collection following
a flood event High
P2 Building and
Development Controls High
P1 LEP Update High
P8 Flood Proofing Guidelines High
FM
1.2
Town Creek Vegetation
Clearing High
ID Description Priority
EM2 Preparation of Local Flood
Plans and update of DISPLAN Medium
EM5 Flood warning signs Medium
FM
1.7 Town Creek Diversion Medium
FM
4.1 Stock Mounds Medium
EM3 Flood warning system Low
FM
1.6 North St Diversion Swale Low
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?