The council is preparing two climate change reports, but it is already warning residents to be ready to batten down the hatches.

Environmental planning manager Dr Tony Miskiewicz, studying rising water levels in estuaries - alongside a wider report - said the frequency and intensity of dangerous storms would increase.

Areas such as Windang could be flooded if water levels rose, he said.

"If one was applying to build a caravan park there now, I suspect they wouldn't be allowed," Dr Miskiewicz said.

He said storm surges combined with higher sea levels could have disastrous consequences for properties near oceans and lakes.

"The storm surge is the killer," Dr Miskiewicz warned.

"The sea-level rise might only be (small) but you have to combine that with a storm surge on top of that," he said.

The council's climate change studies will help to develop new planning guidelines aimed at reducing the risk to properties in the Illawarra.

Dr Miskiewicz said some properties could already be in danger as a result of rising water levels and the destabilisation of the region's sand dunes.

"Historically things have been allowed to happen that in hindsight should not have been, but we are now looking forward to the future and saying, with the best knowledge available, you shouldn't start these developments," he said.

"The biggest issue is the dunes, and structures like cycleways, bridges and stormwater pipes which could get undercut and fall away."

He believes the collapse of a cycleway in Bulli eight months ago was a sign of things to come.

The Department of Environment and Climate Change estimates the sea level rise on the NSW coast will be in the range of 0.18m to 0.91m before the end of the century.

Its flooding guidelines warn that houses may be put at risk.

"Annual average damage to a house built at the flood planning level in an area where flood levels are directly controlled by ocean levels could increase by more than 1000 per cent due to a high sea level rise scenario by 2090 to 2100," the department predicts.

"In addition, climate change impacts on flood producing rainfall events show a trend for larger scale storms."