Commenced in 2020, delayed to include the 2022 flood event along the Murray River, Federation Council’s draft Corowa, Howlong and Mulwala Flood study has now been adopted.
Prepared by WMA Water, financed by the NSW Government Floodplain grant funding program in 2019, the plan was unanimously adopted at council’s latest monthly meeting, on November 26.
The study was undertaken in accordance with the 2023 NSW Flood Risk Management Manual and overseen by the Corowa, Howlong and Mulwala Floodplain Risk Management Committee.
Following Council's resolution from the July 2024 council meeting the study was publicly exhibited from August 11 to September 18, 2024.
Following the exhibition process some minor amendments were made to the report and the report was presented back to the Corowa, Howlong and Mulwala Floodplain Risk Management Committee for review.
At its meeting on November 11, 2024 the committee resolved that the Corowa, Howlong and Mulwala Flood Study be recommended for adoption by Federation Council.
Three submissions were received at the completion of the public exhibition period, summarised as follows:
A submission posed a number of questions specific to Mulwala including queries regarding future flood mitigation options and a future solar farm development proposal.
“Mitigation options will be assessed as part of the next phase of the project (Floodplain
Risk Management Study and Plan) which pending funding being available will commence in 2025,” the council staff response stated.
“Any future development proposals including the referenced solar farm proposal will be considered by council taking into account what impact, if any, the development proposal is expected to have on flooding conditions.”
Another submission posed a number of questions specific to Corowa including a request that Bridge Road be raised to its previous height and a comment that any flood mitigation measures should be cost effective.
“Bridge Road at its existing height will be subject to infrequent inundation as occurred most recently in November 2022.
“It would be uneconomic for council to raise Bridge Road to its previous height, given that alternative flood-free access across the floodplain is available via Federation Way.
“The Floodplain Risk Management Study and Plan will assess potential mitigation measures with respect to their cost effectiveness,” was council’s response.
The third submission queried whether the flood study utilised sufficiently reliable in-stream terrain data, referring to past river bank erosion over the previous 60 years.
“The flood study was undertaken using the best available data, including cross section data for the Murray River channel and bathymetry data for Lake Mulwala.
“The aerial survey data utilised for the broader out of channel floodplain is extremely accurate and pinpoints the river channel bank locations precisely,” the council response stated.“
Federation Council’s planning director Susan Appleyard said the flood study includes a damages assessment and the estimated annual cost for damages in certain events.
“Further work will be required in future projects to define the costs of flooding on the communities and what flood mitigation protection measures can be utilised to reduce the risks and damages from future events,” she said.
“The flood study identifies the council assets that will be impacted by various flood events and will allow council to better program maintenance and renewal pre and post flood.
“Possible protection measures will be identified and assessed as part of the next stage of the flood risk management process, the flood risk management study and plan.”
The study requires council to consider the impact of flooding on operations in a number of areas. For example, council’s planning and development department will have to assess Development Applications against the 1% AEP event and the defined hydraulic and hazard categories in the study.
Emergency management will have to assess the current flood response practices against the study outputs.
Ms Appleyard emphasised the significance of the participation by John Skinner of Howlong, Corowa’s Geoff Lewis and Robert Pearce, and Ross McHenry from Mulwala.
Mayor Cheryl Cook said: “It’s been a long journey. The floods in 2022 confirmed what we were doing was right.”