NSW’s deadly one-in-100-years floods could have been slashed by two metres using dams, CSIRO finds

North Lismore artist and musician Jimmy Willing stands on the site of his studio, destroyed in the 2022 floods. Photograph: Christine Tontorf View image in fullscreen North Lismore artist and musician Jimmy Willing stands on the site of his studio, destroyed in the 2022 floods. Photograph: Christine Tontorf NSW’s deadly one-in-100-years floods could have been slashed by two metres using dams, CSIRO finds Governments have not committed to measures modelled in the report on Lismore’s 2022 floods, which led to the deaths of 13 people Get our breaking news email, free app or daily news podcast Building 10 new dams in New South Wales’s northern rivers could have reduced flood levels by up to two metres during devastating floods in 2022, but not enough to prevent a key levee overspilling, a report has found. The CSIRO report was released on Tuesday, four years after it was commissioned by the Morrison government following NSW’s one-in-100-years floods. The extensive flooding in the northern rivers between late February and early April 2022 led to the deaths of 13 people. More than 4,000 properties were left uninhabitable and another 10,849 were damaged. The total socioeconomic and structural damage is estimated at $16bn. The report found additional water detention dams would have reduced flooding by 2.1 metres, but would not have prevented the 3.8 metre over-topping of the Lismore CBD levee in February 2022. The state and federal governments have not committed to delivering the measures modelled in the report as part of the $11.4m Northern Rivers Resilience Initiative. On Tuesday, they announced a joint $3m feasibility study. While the report involved community engagement over several years, some Lismore residents have called for alternative measures, including relocating or establishing a second CBD above the flood level. CSIRO hydrologist Dr Jai Vaze, who led the report, said while implementing the measures in the report would probably be dependent on a business case, detailed architectural proposals and environmental approvals, as well as other flood resilience measures had already been implemented under $150m in federal funding. “We can reduce the impact of large floods with strategically located detention and other flood mitigation measures across the entire Richmond River catchment,” he said of Tuesday’s findings. View image in fullscreen Matthew Gooley, who operates a menswear business in the Lismore CBD, said the measures in the CSIRO report would be ‘amazing for Lismore’. Photograph: Christine Tondorf ‘Businesses have gone’ On Tuesday, Lismore residents had mixed reactions to the reports’ findings. Matthew Gooley, the operator of a family-run menswear business that has been in the Lismore CBD since 1957 and which lost an estimated “millions in stock” in the floods, said the measures considered in the report would cost a “lot of money” but would be “amazing for Lismore”. “Take two metres off [2022 levels] and it goes back to normal flood [heights], not getting in people’s top levels”. Paul Morgan, the operator of Lismore Computer Solutions, which sits next to the river in the CBD, said he was “all for it if it works”. “There have been a few interesting ideas over the years,” he said. View image in fullscreen Paul Morgan, the owner of Lismore Computer Solutions. Photograph: Christine Tonforf Marinda Hayward, who was left homeless by the 2022 floods, said $3m was “a lot of money for a feasibility study” and wanted more spent on practical measures like keeping Lismore’s drains clean. Irene Guymer, whose daughter’s farm flooded to “nearly the second floor of the house” in 2022, said the measures would be a “waste of money”. “I really do they think would be better off … shift[ing] the CBD up to Goonellabah where a lot of people … and businesses have gone.” View image in fullscreen Lismore residents Marinda Hayward (left) and Irene Guymer. Photograph: Christine Tondorf North Lismore artist and musician Jimmy Willing criticised the spending on the report and feasibility study while Lismore was experiencing a housing crisis. “It’s a bit like putting men on the moon while people are starving”. CSIRO used hydrodynamic modelling and analysis of historical events to investigate the impact of two flood mitigation proposals: “Bundle 1”, which includes five new water detention systems as well as other upgrades, and “Bundle 2”, which includes 10 water detentions across the Richmond Valley, Kyogle, Ballina and Lismore LGAs. Vaze said he preferred the use of “water detentions” rather than “dams” to describe the proposed systems, as gates only close when flood waters rise beyond a certain level. “A dam holds water forever. These are only temporary,” he said. The report found Bundle 2 delivered the greatest mitigation, including potential reduction of water levels up to 2.1 metres during February 2022 floods, when the flood level in Lismore reached 14.4 metres, the highest on record. It would not have prevented the city’s CBD levee from overtopping. The modelling showed water levels could have been reduced by up to 1.7 metres during a flood which followed on 31 March 2022, as well as 1.4 metres during 2017 floods, both holding below levee banks. View image in fullscreen State member for Lismore Janelle Saffin, pictured here in 2022, has welcomed the report’s findings. Photograph: Dan Himbrechts/AAP The federal minister for emergency management, Kristy McBain, and her NSW counterpart, Janelle Saffin, welcomed the findings, which they said would inform future flood resilience measures. Saffin, who is the state MP for Lismore, appeared to indicate her support for the 10 new water detention measures. “My reading of this report gives us real hope because it shows technically that flood levels can be lowered across all four local government areas in the Richmond River catchment,” she said. But the NSW Greens upper house member Sue Higginson, a Lismore local, said the report showed that “billions of dollars in new dams for the Richmond River will not prevent severe flooding”. “This is not renewed hope to think that we can engineer our way out of climate change”. Higginson called for a “planned retreat and nature-based solutions”, including replanting forests higher in the river basin, and revegetating and repairing river. She has proposed transforming the Lismore CBD into a “wetland cultural market hub”, which would involve the removal of buildings. The federal Nationals MP for Page, Kevin Hogan, who has led the call for engineering works to improve flood resilience since 2022, on Tuesday said the report “details how flood mitigation could make our communities safer”. “It’s not if we have another flood in our region, it’s when. The CSIRO have provided a solution to keep us safe. The state and federal Labor governments must act on this,” he said in a statement. Both Higginson and Hogan have been critical of the rollout of the $100m Resilient Lands Program (RLP), set up to provide land for flood-affected residents to relocate their homes, and $880m Resilient Homes Program (RHP), a scheme to buy back homes and fund flood-resilient measures. Together they are the costliest disaster recovery program in Australian history. The state government has defended the RHP, under which 813 properties have been bought back as of this month, and which has seen controversial demolitions and evictions. Seventy resilient measures have been completed. Last month a NSW auditor general’s report found that after three and a half years, the RLP had yet to deliver a single home or lot. Explore more on these topics New South Wales CSIRO Flooding Extreme weather news Share Reuse this content