A group of business leaders in northern NSW has backed engineering work to reduce flooding following a landmark study.
The CSIRO report found strategically placed water retention basins could significantly reduce flooding and protect homes and businesses in the Richmond River catchment.
The devastating Lismore floods in 2022 were estimated to cost close to $1 billion to rebuild the community, including more than $350 million in damage to council assets.
Lismore Alliance, which represents 6,000 members, said at a press conference on Thursday the measures could be "the difference between a region with an economic future and one without".
"Flood risk is not just a community safety issue — it is the single biggest constraint on the economic future of this region," said alliance chair and head of the Casino Food Co-op, Simon Stahl.
"It would just give so much confidence to this region, knowing there is something being done about the height of the floods."
"The first thing you look at when investing [in a region] is the risk to property, assets and workforce."
Lismore Alliance chair Simon Stahl says the feasibility of the CSIRO modelling needs to be explored (ABC North Coast: Hannah Ross)
He said a lot of important considerations had become "lost in the noise" of the public meetings, including the question of compensation for landholders whose properties could be inundated by detention basins.
"If the feasibility does go that far, we are fully supportive of that because people's lives are going to be affected," he said.
Heated debate
More than a thousand people attended a series of information sessions hosted by the CSIRO last week to explain the science behind its flood mitigation modelling.
The meetings became heated at times, with many people frustrated that issues like property inundation and nature-based solutions were not addressed.
Meetings across the Northern Rivers became heated. (ABC North Coast: Hannah Ross)
The national science agency has tested how flooding could be reduced across the catchment if engineering solutions were built, including up to 10 detention basins and a secondary outlet for the river to flow out to sea.
Under February 2022 flood conditions, these measures would reduce flooding in Lismore by 2.07 metres.
That record-breaking flood saw water overtop the Lismore levee at 10.2 metres and reach a height in the CBD of 14.37 metres.
The NSW and federal governments have committed $3 million to now assess the technical, environmental, economic and social feasibility of the mitigation measures.
Business confidence
Lismore business owner Felicity Hyde had to cease trading for three months after flooding inundated her shop in 2022, and lay off four employees.
She said so many businesses had rebuilt after the floods, trusting that no level of government had made a decision to relocate the city's central business district.
Lismore ice cream shop owner Felicity Hyde has rebuilt her business since the 2022 floods. (ABC North Coast: Hannah Ross)
"If the government had the idea that Lismore needs to move, they would have suggested that early on, or at some stage," she said.
Former Summerland Bank chief executive John Williams said the bank's repair bill after the 2022 floods was $4 million, which was only partially covered by insurance, and it can no longer get coverage for its branch in the Lismore CBD.
Mr Williams said he saw first-hand the social impact of the disaster on people trying to pay mortgages on houses destroyed or damaged by flooding.
John Williams says mitigation will attract insurers and investment. (ABC North Coast: Hannah Ross)
He said reducing flood heights by 2 metres would help businesses get insurance.
"What we need to do is reduce the risk to bring insurers back to the market,"
he said.
"It will still be expensive but it will definitely be worthwhile to encourage investment back into Lismore."
The National Emergency Management Agency is expected to release maps in early August showing which properties around the detention basins would be inundated in times of flood.
Farmers are demanding information about how much of their pasture would be underwater, and for how long.
The largest detention basin would hold 94 gigalitres. (Supplied: CSIRO)
Communities in the upper catchment have also raised concerns about how the detention basins could affect road access and other services.
The NSW Reconstruction Authority will be co-ordinating feasibility assessments of the CSIRO modelling.
