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. This was reported by Qazaqyia.kz citing The Guardian.

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.

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.

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."

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.

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.