Corowa, Howlong & Mulwala Flood Study

Federation Council is placing the draft Corowa, Howlong & Mulwala Flood Study report on public exhibition between the 14 August and the 11 September.

The Flood Study presents the results of detailed investigations into both Murray River and local runoff flooding conditions, focusing on flooding impacts to the townships of Corowa, Howlong and Mulwala.

The study has drawn on flood records for the Murray River dating back to 1867.  Of particular importance to the study has been data for floods which occurred in 1867, 1870, 1917, 1974, 1975, 1992, 1996, 2016 and 2022.

Computer modelling has been used to generate detailed flood mapping for a range of varying size floods.  This includes the 1% annual exceedance probability (AEP) flood, commonly referred to as the 1 in 100 event.  The 1% AEP flood has a probability of occurrence of 1 in 100 in any year.

Notable findings from the study for Howlong are that flooding from the Murray River does not impact on Howlong township in a 1% AEP flood.  Local runoff flooding including flooding from Majors Creek does however impact significantly on Howlong township, resulting in widespread inundation.

At Corowa, Murray River flooding impacts on low -lying developed areas, notably the four caravan parks and the lower terrace area occupied by the Civic Centre, Bowling Club, Aquatic Centre, Tennis Club, Cricket Club and John Foord Oval. These areas were most recently flooded in November 2022.

Local runoff flooding at Corowa also impacts significantly on some parts of the town as occurred during an extreme local runoff flood event in January 2022. Notable areas affected include the area surrounding two retarding basins located adjoining Sophia Close and Pinot Crescent, the Redlands Road industrial estate and other locations where water ponds.

At Mulwala, the study has found that Murray River flooding impacts significantly on much of the township in a 1% AEP flood.  A reoccurrence of Murray River flooding of the size which occurred in 1867, 1870 or 1917 would cause widespread inundation of Mulwala.  Mulwala is unaffected by smaller river floods including the recent November 2022 flood which was equivalent to a 10% AEP event (1 in 10 chance of occurring in any year).

Local runoff flooding at Mulwala also results in widespread inundation largely influenced by the town’s extremely flat terrain conditions.

Council will undertake a number of supporting community consultation activities during the public exhibition period, both online and in-person.  Details can be obtained from Council’s website.  Public submissions close on 29 September 2024.

Council’s General Manager, Adrian Butler, advised that Council has applied for a NSW Government grant to undertake a Floodplain Risk Management Study which would assess options for mitigating flooding impacts at each of the three towns.  If grant funding is secured, the mitigation study could take place as early as 2025.