Rising seas are threatening to encroach on low-lying parts of Melbourne within 20 years, causing flooding and erosion in suburbs including St Kilda, Point Cook, Mordialloc, Seaford and Frankston.

Other places at risk include areas around Queenscliff and Barwon Heads on the Bellarine Peninsula; the south-west Victorian towns of Port Fairy and Portland; and Tooradin, Lang Lang and Seaspray in the state's south-east.

A report tabled in Victoria's Parliament last week examines the myriad threats to the state’s fragile coastline, painting an alarming picture of damage to the environment and suburban Melbourne if no action is taken.

The Victorian Environmental Assessment Council report cites a 20-centimetre sea-level rise by 2040 and between 40 centimetres and one metre by century’s end.

“Sea-level rise will lead to more frequent inundation of low-lying areas, loss of coastal habitat, cliff, beach and foreshore erosion,” the report says.

“Climate change will also put pressure on ageing coastal infrastructure and ultimately impact on feasibility of living in or developing some coastal locations.”

Locals Dave Sutton (left) and Phillip Heath on the remaining strip separating the surf beach from the road at Inverloch, where erosion has caused major problems.

Locals Dave Sutton (left) and Phillip Heath on the remaining strip separating the surf beach from the road at Inverloch, where erosion has caused major problems.CREDIT:JUSTIN MCMANUS

Increasing storm intensity, coupled with rising seas, will cause extensive erosion of the Victorian coastline by 2040, the report says.

“The most extensive area vulnerable to erosion by 2040 is the Gippsland coast,” it says. “Other coasts at risk include west of Portland, beaches in Port Phillip Bay between Mordialloc and Frankston, and the coast between Cape Paterson and Cape Liptrap in South Gippsland.”

Coastal erosion has already had a dramatic impact on the foreshore at Inverloch, which has receded 33 metres since 2012.

Erosion has also caused major problems in Port Fairy, where the local council has stepped up research and planning to tackle the problem.

The report also considers the impact of other coastal threats, including tourism and development. It outlines how a growing population may increase water pollution, with higher levels of treated sewage effluent and industrial wastewater expected to be discharged into the sea.

School students protesting for greater action on climate change.

School students protesting for greater action on climate change. CREDIT:JUSTIN MCMANUS

The report is intended as a planning tool for the state government, which is developing a policy for coastal protection.

A government spokeswoman said action was being taken to protect the coastline in the face of climate change.

"We’re preparing the Victorian coast for the climate change challenges ahead through research, policy change and on-ground action – investing more than $60 million into marine and coastal projects since 2014," she said.

The spokeswoman said the government was working with communities and councils on a range of projects, including a beach "renourishment program" to mitigate erosion.

It has also spent $10 million on its Port Phillip Bay Fund, which provides grants for community projects that protect and preserve the health of the bay.

Victorian Environmental Assessment Council member Geoff Wescott said the modelling and predictions contained in the report laid out the consequences of failing to take action.

“When you see those maps of St Kilda or the Elwood Canal flooding, that is what happens if nothing is done,” he said.

The government has also commissioned the CSIRO to begin a fresh assessment of the likely coastal hazards that rising seas and bigger storm surges will create along the shores of Port Phillip Bay.

The swollen Elster Creek flooded the Elwood Canal in 2016.

The swollen Elster Creek flooded the Elwood Canal in 2016. CREDIT:PENNY STEPHENS

That work by Australia’s national science agency is due to be finished by the middle of next year.

Melbourne University senior property lecturer Georgia Warren-Myers said even small sea-level rises coupled with storm surges could have a major impact on some densely populated parts of Melbourne.

A report Dr Warren-Myers co-wrote found that 33 per cent of properties in the City of Port Phillip would be affected by a sea-level rise of half a metre when combined with storm surges.

But she warned property taxes, a key revenue source for state and federal governments, would also be impacted if buyers began rejecting particular areas due to their vulnerability to flooding.

“There are future economic implications that haven’t been really thought out,” she said.

Dr Warren-Myers called for local governments to include more information about sea-level rise and potential flood risk in planning overlays, so they had to be included in Section 32 legal documents that sellers are required to provide to potential buyers.

Port Phillip Baykeeper Neil Blake said erosion and sea-level rises posed huge challenges and may eventually force some Victorians to move from currently populated areas. “There will have to be a major adaptation required to address that,” he said.

Mr Blake said it was beyond time to be discussing climate change in theoretical terms as its consequences were now having a tangible impact on the community and environment.

But he said plastic litter was one of the biggest threats to the health of Victoria’s coastline.