NSW’s deadly one-in-100-years floods could have been slashed by two metres using dams, CSIRO finds
NSW’s One-in-100 Floods Could Have Been Reduced by Two Metres with Dams, CSIRO Study Reveals
NSW s deadly one in 100 years - A recent CSIRO study suggests that constructing ten additional water detention dams in NSW’s northern rivers could have cut flood levels during the 2022 one-in-100-years disaster by up to two metres. The research, published on Tuesday, highlights how strategic infrastructure might have mitigated the devastating impact of the floods that submerged Lismore and surrounding areas. While the Lismore CBD levee would still have been overtopped, the analysis offers hope for future flood resilience in the region, which has long struggled with extreme weather events.
2022 Floods: A Catastrophic One-in-100 Years Event
The 2022 floods in NSW’s northern rivers, classified as a one-in-100-years event, caused 13 deaths and damaged over 14,800 properties. More than 4,000 homes were rendered uninhabitable, with water levels peaking at 14.4 metres in Lismore—the city’s highest recorded flood. The economic toll of the disaster is estimated at $16 billion, underscoring the urgency for effective flood mitigation strategies. The study’s findings challenge the perception that such extreme floods are inevitable, showing how targeted infrastructure could significantly lower their impact.
CSIRO’s report outlines two key flood mitigation plans: Bundle 1 and Bundle 2. Bundle 1 proposes five new detention systems and upgrades, while Bundle 2 includes ten dams across the Richmond River catchment, Kyogle, Ballina, and Lismore LGAs. According to the research, Bundle 2 could have reduced flood levels by 2.1 metres during the February 2022 event, but the levee system in the central business district would still have faced challenges. This data reinforces the need for a combination of regional and localized flood defenses to address the one-in-100-years flood threat.
Community Responses to the CSIRO Findings
Residents of Lismore are divided over the proposed flood control measures. Marinda Hayward, a survivor of the 2022 floods, questioned the allocation of funds for a feasibility study, arguing that more resources should be directed toward immediate solutions like maintaining drainage systems. “A feasibility study is a lot of money for a small amount of progress,” she stated. Meanwhile, Irene Guymer, whose family farm was nearly submerged, advocated for relocating the CBD to Goonellabah, where many businesses have already moved post-disaster.
“We can reduce the impact of large floods with strategically located detention and other mitigation measures across the entire Richmond River catchment,” explained Dr Jai Vaze, the hydrologist leading the study. He noted that the proposed systems, which only activate when flood levels exceed a specific threshold, require a business case, architectural designs, and environmental approvals. Despite this, the report highlights progress made under $150 million in federal funding, offering a roadmap for future action.
Matthew Gooley, a local business owner in the Lismore CBD, acknowledged the cost of the dam project but emphasized its potential benefits. “Take two metres off [2022 levels] and it goes back to normal flood [heights], not getting in people’s top levels,” he argued. Paul Morgan, a computer solutions provider near the river, supported the study if it proved effective. However, some residents, like Jimmy Willing, a local artist, criticized the focus on long-term projects over urgent needs, calling it a misallocation of resources during a housing crisis.
Government Plans and the Path Forward
The NSW and federal governments have not yet confirmed implementation of the CSIRO recommendations as part of the $11.4 million Northern Rivers Resilience Initiative. A joint $3 million feasibility study was announced on Tuesday, aiming to evaluate the options for reducing the one-in-100-years flood risk. While this marks a step toward actionable solutions, critics argue that the investment should prioritize immediate measures like drainage maintenance and relocation plans, which could offer quicker relief to flood-prone communities.
Dr Vaze explained that the term “water detentions” was used to describe the proposed systems, as the gates only close when flood levels surpass a critical threshold. This distinction is important, as it clarifies that the dams are not a guaranteed solution but a part of a broader flood management strategy. The study’s results could influence future planning, ensuring that the one-in-100-years flood threat is addressed with both innovation and practicality. As the region recovers, the debate over flood resilience versus immediate needs continues, shaping the next phase of recovery and infrastructure investment.