MORE than 80,000 coastal buildings in Victoria are at risk and large parts of Western Port are likely to be swamped as climate change triggers rising seas, floods and erosion, a report to Federal Parliament has warned.
An 18-month investigation by a House of Representatives committee, backed by members of both major parties, warns the Government that the ''time to act is now'' to prepare thousands of kilometres of Australian coastline for the threat of sea-level rise and extreme weather.
Proposals include improving evacuation routes for coastal communities and introducing early warning systems for coastal areas.
In Victoria, the most consistent threat is at Western Port, with nearly one-fifth of the region south-east of Melbourne likely to be inundated, damaging the environment and infrastructure.
About 18,000 Western Port properties valued at nearly $2 billion are considered vulnerable to flood.
Nationwide, more than 700,000 coastal properties with a combined worth of about $150 billion are potentially at risk, the report finds.
In parts of northern Australia, it warns, coastal communities will also become more vulnerable to insect-borne disease, and the celebrated Kakadu National Park's freshwater wetlands faces being flooded with saltwater.
The report by the Standing Committee on Climate Change, Water, Environment and the Arts, calls on Canberra to boost its role in preparing coastal communities for the threats, working with states and local governments. Its recommendations include:
* Increasing biosecurity to protect Australians from dengue fever and chikungunya virus.
*Asking the Productivity Commission to look at the impact of climate change on the insurance industry, including recommending a clear definition of when an insurance claim would be payable after an event triggered by climate change.
*Considering bans on occupation or rebuilding on properties deemed at risk.
*Classifying more coastal wetlands as sites of international significance under the Ramsar convention.
*Expanding research into the impact of climate change on Australian lives, ecosystems and property.
The report calls for the Australian Emergency Management Committee to be charged with improving access and evacuation routes for coastal communities. It compares the potential risks they face to those experienced by people fleeing this year's Black Saturday bushfires in Victoria.
''Evacuation routes were a significant contributing factor to the extent of the tragedy,'' the report says. ''A reliable evacuation route is vital in a disaster management strategy.
''It is therefore imperative that evacuation routes and methods be examined when developing community emergency responses.''
On insect-borne disease, the report says immediate action is needed to get better early warning of threats. ''The significant outbreak, in early 2009, of dengue fever in Cairns, Queensland, with over 1000 cases marks a cause for concern,'' it says.
The emergency committee would also be asked to devise improved early warning systems for coastal areas hit by storm surges, erosion and floods.
The climate change committee cites the advice of the United Nations Intergovernmental Panel on Climate Change that sea levels are likely to rise about 80 centimetres by 2100.
But the increased potential for storm surges under climate change means properties even further above current sea levels are expected to be at risk.
Climate scientists warn that even a 50-centimetre sea-level rise is expected to increase the number of extreme tidal events by a factor of 300.
The area at risk of storm surges is expected to grow by up to 15 per cent by 2030 and up to 63 per cent by 2070, when what would now be called a ''1-in-100 year storm'' is tipped to hit Victoria at least once in four years.
Western Port is considered particularly environmentally sensitive, with its tidal nature creating valuable mangrove and mudflat ecosystems. It has several marine national parks and is internationally recognised under Ramsar as a wetland of significance for migratory birds.
Greg Hunt, an environmental consultant who works with six local councils around Western Port on climate change issues, said coastal villages in the City of Casey, such as Tooradin, were among the most susceptible to rising sea levels.
He said consideration should also be given to industries supported by the bay, including fishing and agriculture.
''It's not a sexy bay like Port Phillip Bay, with sandy beaches, but it's a very productive area and climate change has the potential to alter that productivity,'' he said.
''If we get inundation of coastal lands by salt water, then that changes and we can no longer grow pastures or at least the same pastures.
''We produce a lot of food from that area, so if their data is correct then our food production is going to have impacts.''
Bittern resident Brian Cuming, who has long campaigned to protect Western Port from what he sees as inappropriate development, said the projections further challenged those wishing to develop the region.
''There will be many sociological concerns about planning, but this reinforces and adds to our concerns about the lack of wisdom in planning an expanded port,'' he said.
Climate Change Minister Penny Wong is expected to deliver the first major assessment of the vulnerability of Australia's coast to sea level rise next month.