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As catastrophic as the 2022 floods in the Northern Rivers were, we now know it could have been much worse.
If the flood that inundated Lismore in February 2022 had occurred six hours earlier, it would have coincided with a king tide at Ballina, CSIRO modelling shows.
CSIRO senior principal research scientist Dr Jai Vaze, an experienced hydrologist, said if the floodwaters had combined with the higher sea level it would have resulted in even more devastation and destruction, mostly in Ballina.
“Looking at the timings, if the flood peak was at the same time as the king tide or high tide, then you will get larger flooding in the Ballina area because then the ocean is actually a higher level,” Vaze said. “The higher up[stream] you come, the tidal impact becomes smaller and smaller, so by Casino there is no tidal impact at all.”
On Monday CSIRO delivered a hydrodynamic model to the National Emergency Management Agency that has accurately recreated several floods in the Richmond River catchment from 2008-2022, including the changing landscape and development. Vaze said the 2017 recreation was important because it was a large flood that was a much more common scenario than 2022.
“In 100 years [a flood similar to 2017] might happen about five times, whereas the 2022 flood was outside the range of anything observed, so we can’t even put a number on it,” Vaze said.
Vaze’s model will now be used by CSIRO to test and investigate further flood mitigation options for the Northern Rivers region.
The 2022 flood in Lismore was the worst recorded in the town’s history.Credit: Getty
Vaze said the project proposals from seven councils and community consultations had generated about 330 suggestions for flood mitigation, such as engineering projects or tree planting, and a few dozen had already been funded. His model would help assess the community’s preferred mitigation projects, with each scenario taking a few months to run.
In an earlier paper for Nature, looking at the 2022 floods in the entire Northern Rivers and South-East Queensland region, Vaze found that some areas had downstream areas peak earlier than upstream areas. He said this unusual occurrence was because of local runoff driven by intense rainfall and soil that was already too waterlogged to absorb more liquid.
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Flood risk is one of the key reasons for rising home insurance premiums. This masthead has previously reported on industry data showing the higher insurance premiums paid in different parts of Sydney and Melbourne based on flood risk.
Insurance and actuarial consultancy Finity has also found the average residential building insurance premium in the Mid North Coast, Hunter-Newcastle and Central Coast regions is $4268. This is more than 30 per cent higher than Sydney’s average of $3220. The rate of increase is also higher.
NRMA says insurance claims for wild weather in the first five months of this year have already surpassed 2024.
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