The annual bill for councils to fix or protect eroding beachside property or infrastructure often exceeds $1 million each year, and may hit $54 million in some areas as worsening extreme weather takes its toll, a new report from the Climate Council and the Cities Power Partnership says.

The report coincides with new modelling from Coastal Risk Australia, which shows in graphic detail the parts of the Illawarra which will be worst hit by rising sea levels by the year 2100.

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Some residential areas in Windang, Primbee, Lake Illawarra, several nature reserves, and many of the region's ocean pools would be inundated by high tides under predicted sea level rises, the modelling found.

The modelling, developed in partnership with FrontierSI and NGIS Australia, uses the latest Intergovernmental Panel on Climate Change data on ice sheet melting rates.

If current trends continue the modelling indicates global sea levels could have increased by 0.84m by 2100.

Climate Council report author Professor Lesley Hughes said climate impacts cut across all areas of local government responsibility, from critical assets to service delivery.

"As the closest tier of government to the community, councils are often at the forefront of disaster response," Professor Hughes said.

"State and federal assistance is falling short of what's required to help councils prepare for and respond to extreme weather.

"Councils are being asked to do more, with less. Without increased funding, guidance and support, I can't imagine how they will continue to protect and provide for their communities."

Wollongong Lord Mayor Gordon Bradbery said with other levels of governments in debt, councils will be forced to handle the costs.

"It's not only mitigating the chances of damage in terms of sea level rises and extreme weather events, which we've experienced over the last decade or so," he said.

"When you have significant East Coast lows and those kinds of events, it's exacerbated by higher sea levels.

"Putting in that infrastructure is extremely expensive - we've got a lot of assets such as our ocean pools, and they're getting pummelled.

"There's a lot of cost-shifting going on as well - there's a massive amount of debt state and federal governments will have to handle post-COVID and there's only one way of doing that, and it's make the ratepayers pay. It will be a cost that will have to be met at the local level."

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