Transcript Summary presentation from Community

LT Creek Floodplain Risk Management Study &
Plan
Community Consultation Meeting No 1
30th November 2016
Presented by: Richard Dewar, WMAwater Pty Ltd
Overview – NSW Floodplain Management
Process
We are here
LT Creek Catchment 7km2
Floodplain Risk Management Study
• Identify the magnitude of the flood problem
– House floor levels v flood levels
• How often are house floors inundated and what damages
occur?
Levee
• Measures to reduce the flood problem?
1) Flood Modification
2) Property Modification
3) Response Modification
• Evaluate the Value of each Measure
Raising
– Reduction in flood level
– Cost
Warning
– Environmental impact
– Social impact
Raised floors
Community survey
• Mail-out and online version (Survey Monkey)
• 200 letters sent to residents and 20 to key stakeholders
•
Responses via post /Survey Monkey
Survey response summary
Survey response summary
Survey response summary
Survey outcomes
•
•
•
•
1 flood photo
1 person has flood debris marks
No above floor inundation
Concerns
– Silt
– Bluewater Avenue overflow & Croft Oval overflow
• Suggestions
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–
–
–
Dredging
Bluewater Avenue
Decrease insurance – individual inspections
Wetland containment area to limit sedimentation
Building Floors Inundated
• Catchment Flood = rain over LT Creek catchment
– 1% AEP (100 year)
– PMF
nil
52
• Lake Flooding = rain over Lake Macquarie catchment
raising lake levels
– 1% AEP (100 year)
– PMF
7
108
• CONCLUSIONS
– Very small tangible($) damages to buildings
– Minor intangible damages – inconvenience, worry, risk to life
– Hard to justify expenditure on flood mitigation measures
Flood Mitigation Measures
• Flood Modification
–
–
–
–
Vegetation clearing – environmental impact
Levees – visual impact, cost
Dams, retarding basins – cost, no available space
Dredging – next page
• Property Modification
– House raising – little interest, cost
– Flood proofing – only for commercial
– New buildings – Development Controls
• Response Modification
– Flood warning – too quick response
– Evacuation planning – infrequently used
Issues considered in the study report
Water Quality
• Outside our Scope
• Will be mentioned but cannot recommend measures
Dams in Newstan Colliery
 Many there already
 Will reduce peak flows and levels downstream
 Risk of failure – subject to Dams Safety regulations
 Will address in report
Mining Activities in Newstan Colliery
 Unable to advise if affect flooding
 Water quality outside our scope
Dredging
•
•
•
•
•
•
Suggested for water quality purposes
Nil benefit for flooding as no floors inundated
Environmental impact on flora and fauna
Not sustainable – must dredge forever
High cost – where to place spoil?
Dredging not permitted for flood mitigation in NSW
Sea Level Rise & Lake Macquarie Flooding
 Addressed in separate FRMS
 Council has initiated sea level rise adaptation plans
 Flood warning for lake flooding being updated