AN international expert in disaster response management has urged Lake Macquarie City Council to clear vegetation from floodways at Dora Creek to avert a potential tragedy in the town.
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Gavin Simpson is the former owner of the MCS Group, a specialist consulting firm which provided technical reports to insurers and government following natural disasters or major insurance claims.
"I have been in management on every Australian natural disaster event in the last 30-plus years and, yes, many floods included," Mr Simpson said.
"I know about flood damage, and I know how to avoid it."
Mr Simpson, who lives on Stingaree Point Drive, and other residents in the town have been frustrated by the council's refusal to clear vegetation from floodways on Dora Creek.
Floodways act as off-ramps for water racing down Dora Creek in times of flood.
Residents say two floodways, either side of the Eraring power station cooling canal, on Stingaree Point Drive, have become so clogged with shrubs and casaurina trees that their capacity to carry floodwaters has been seriously impeded.
They fear that unless the floodways are cleared water heights and velocities in the next flood could impact their homes.
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But the council said expert technical advice from hydrologists showed clearing the floodways would not achieve the results the residents wanted.
Council cites a hydrology report which used modelling to predict that clearing the floodways would provide just a 5cm reduction in flood levels upstream, and no difference to flood levels downstream, in the event of a 1-in-100-year flood.
Mr Simpson said a key point was the modelling was based on a 1-in-100-year flood event.
That is a major flood.
By comparison, the flood that Dora Creek experienced in 2007 - perhaps the largest Dora Creek flood in living memory - was rated a 1-in-20-year flood.
Mr Simpson said it stood to reason, then, that in a 1-in-100-year flood, the floodways would become inundated.
"A 1-in-100-year flood would be of such volume it would be impossible to cope with by conventional or reasonable mitigation methods," he said.
"Overspill of all areas would be inevitable. The height and depth of the water would take all in its path."
But it was during smaller, and more commonly occurring floods, that floodways produced the benefits they were designed to deliver - provided the floodways were free of blockages - he said.
Mr Simpson urged council to revisit the hydrology report and rethink its stance.
"In a flood, every centimetre counts."