It covers varying size events from a 20% Annual exceedance probability (AEP) or 4.5 year event through to the legislatively required 1% AEP (100 year event) and the PMF - Probable Maximum Flood.
The study covers both riverine flooding from the Murray River and local runoff generated overland flow flooding. The study identifies the flood impacts on the three towns. The study has been reviewed by the Department of Climate Change, Energy, the Environment and Water (DCCEEW).
WMA Water undertook the study which was on public exhibition for a period of 28 days, with a closing date of September 11 and a submission period of 42 days.
The technical nature of the report has resulted in a large amount of map/plan output information.
Flood mapping produced included: Riverine flooding maps and local runoff flooding maps, flood depth, height and extent, velocity of floodwaters, hydraulic hazard, hydraulic categorisation, flood planning area, flood planning constraint categories and flood emergency response classification.
Federation Council successfully applied for NSW Government floodplain management grant funding in 2019.
A grant amount of $154,000 was subsequently awarded on the basis that council would contribute $1 for every $6 of grant funding.
Tenders were called in June 2021. Council received five tenders. The project was awarded to WMA Water in August 2021.
The project was undertaken in accordance with the 2023 NSW Flood Risk Management Manual, overseen by the Corowa, Howlong and Mulwala Floodplain Risk Management (FRM) Committee.
The project was delayed in 2022 after significant flood events in the three towns. Given the scale of flooding, a variation to the project was sought and granted to include the modelling of the November 2022 Murray River flood event.
The draft report was reviewed by the FRM Committee at its meeting on the 4 July 2024 with the committee agreeing to the exhibition of the draft study report.
The flood map outputs/plans were included in the appendices to the report, notably: Appendix F - Murray River flood maps – all three towns, Appendix G - Local runoff flood maps – Howlong township, Appendix H - Local runoff flood maps- Corowa township, Appendix I - Local runoff maps – Mulwala township, Appendix K - Design flood result graphs.
Federation Council will consider the study’s findings at a future council meeting. Council’s planning director Susan Appleyard also advised, at council’s latest monthly meeting on August 27, that a report on council’s Local Environmental Plan will be prepared for council’s October meeting.
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