Key points
- The CSIRO team behind the Northern Rivers Resilience Initiative has delivered its final report.
- It brings together years of extensive community engagement, robust flood mitigation options, high-resolution hydrodynamic modelling and analysis of historical flood events.
- Lessons learnt through this project could be applied in other flood-prone areas of Australia.
CSIRO hydrologist Dr Jai Vaze has lost count of how many times over the past four years he has been asked if he can flood-proof the Northern Rivers region of New South Wales.
He first started working in the region with his team following the terrible loss of lives and homes due to unprecedented flood events in February-March 2022.
His answer is still ‘no’.
However, his optimism about reducing the region’s vulnerability to future floods has only grown.
“No one can stop a flood from happening,” he said.
“While we might not be able to prevent a flood like 2022, with a coordinated approach we can reduce flood heights and impacts, which can help lessen damage and support future resilience for the community.”
Dr Vaze leads the CSIRO team behind the Northern Rivers Resilience Initiative (NRRI) which is funded by the National Emergency Management Agency (NEMA) and aims to identify flood mitigation options for areas such as Lismore, Ballina, Casino and Kyogle.
The final report outlines the project’s welcome and significant results, bringing together years of extensive community engagement, robust flood mitigation options, high-resolution hydrodynamic modelling and analysis of historical flood events.
A final report with lots of hope
Often referred to as the flood capital of Australia, Lismore has always been an area of focus in media reports and recognised as one of the worst hit areas in the region in 2022.
The final report not only shows promising results for Lismore but also for the entire Richmond River catchment. CSIRO used the hydrodynamic model to test how flood mitigation measures could perform across the whole Richmond River Catchment.
It found that strategically located water detentions and other infrastructure upgrades could reduce flood peaks, inundation extent and flood depth across the catchment. The larger or more comprehensive bundle of measures, known as Bundle 2, delivered the greatest benefits.
The modelling shows how water could have been held below levee banks during the 31 March 2022 flood in Lismore and significantly reduced for the February 28 event that occurred just a month earlier.
By applying Bundle 2 measures, these flood peaks at Lismore could have been reduced by up to 1.71 metres for the March event and by as much as 2.07 metres in the February flood.
“The model has surpassed my expectations, I was actually expecting smaller reductions,” said Dr Vaze.
“To be able to show how the water level could be reduced by up to 2.07 metres for such a major flood is substantial and goes a long way towards helping the region as well as governments.”
The results provide a scientific basis for informed decision-making and future flood resilience investments in the Northern Rivers region.
It wouldn’t have been possible without the significant input of the Northern Rivers community.
Community was key during consultation
Engagement with residents in flood-affected areas started from the beginning of the project in July 2022 and their knowledge and views on priorities for investment have been key to the project. Once the hydrodynamic model was completed, residents also provided input on the flood mitigation interventions through consultation sessions.
NEMA and CSIRO will return to the region in July to discuss the final report findings with the community at drop-in sessions.
“Community consultations have been critical in this project,” Dr Vaze said.
“We developed the scenarios with the community and the councils. CSIRO was providing the technical inputs, but they were all discussed and agreed with the community and council across multiple rounds of stakeholder engagements.”
Dr Vaze relays stories of individuals sharing field data of flood levels during the 2017 and 2022 flood events, farmers providing water levels from their farms over time and even a local floodplain engineer telling him where a series of underground pipes were that CSIRO’s high-resolution LiDAR imagery could not detect.
“They have been very generous in helping where they can and I need to thank the community, especially given the community has been suffering from floods for decades.”
Next steps
NEMA is working with the New South Wales Government, councils and communities to consider how the report’s findings can inform future hazard risk reduction work, including the Northern Rivers Disaster Adaptation Plan.
Further work is required to better understand the feasibility of such mitigations, including detailed cost-benefit analysis, environmental analysis, geotechnical investigations and detailed design, subject to future funding decisions.
What is certain is that lessons learnt through the NRRI project could be applied in other flood-prone areas of Australia.
Disasters such as floods are becoming more frequent and intense due to climate change impacts.
“If you can reduce a flood by two metres in an area as complex as Lismore with very steep terrain and fast-moving water then of course there’s potential for other catchments too,” Dr Vaze said.
His optimism remains.