Floods last week show NSW does not receive enough funding for mitigation, according to Floodplain Management Australia President Ian Dinham.

He says the state is a long way behind Queensland when it comes to flood prevention.

“There is massive underinvestment in mitigation works in NSW,” he told insuranceNEWS.com.au. “Not enough is being done.”

Mr Dinham says flood damage costs in NSW are higher than all other states when averaged over the long term.

Estimates from the federal Bureau of Resources, Energy and Economics put national flood damage costs at about $400 million a year, with NSW accounting for $240 million.

“So we are bearing the brunt of flood damage costs in Australia,” Mr Dinham said.

Last Wednesday more than 300 residents were evacuated in the Shoalhaven area, Sussex Inlet and St Georges Basin after days of heavy rain. The State Emergency Service received more than 1700 calls and performed 90 rescues after storms began on Monday.

Warragamba Dam, west of Sydney, began spilling on Thursday, raising fears of floods in Penrith, Windsor and Richmond. But river levels peaked below minor flood levels.

It is the first time in two years the dam has spilled, according to the Bureau of Meteorology.

In Queensland towns such as St George – where a levee has been built with government funding – insurance premiums have fallen as much as 70%.

Similar mitigation work and premium reductions should occur in NSW, Mr Dinham says.

The state grants committee of the NSW Floodplain Management Program last November allocated only $16.3 million to 51 mitigation projects, to help councils.

Mr Dinham says the committee met recently to consider about $200 million in funding applications, but only about $16 million will be granted, which includes federal funding.

Areas such as Hawkesbury-Nepean, which flooded last week, are of major concern.

Stage two of the Hawkesbury-Nepean Valley Flood Review – set up in 2013 after major floods – is due to report to the NSW Government in December.

“All eyes are on that report – it is a very difficult situation there,” Mr Dinham said.

Meanwhile, a Sydney academic has warned much of western Sydney could be devastated by floods if a major downpour occurs.

Stuart Khan, an associate professor at the School of Civil and Environmental Engineering at University of NSW, wants controlled releases of water from Warragamba Dam, so it never approaches full.

A 2011 report commissioned by the state’s planning department found up to 22,000 people would not have time to evacuate in some flood scenarios, due to inadequate exit roads.

Floodplain Management Australia has about 120 members including councils, catchment management authorities, businesses and professionals involved in floodplain risk management. It promotes appropriate development on floodplains and meets with state and federal governments regularly.