The cost to the community of coastal flooding could more than double in some areas in the next fifty years due to global warming.

The effects of extreme weather events will be worsened by the increase in Australia's coastal population.

Dr Debbie Abbs and Dr Kathy McInnes, from CSIRO Atmospheric Research, assessed the likely costs of severe weather events on cities in a warmer world.

They found the combined influence of increasing sea-level rise and extreme weather will result in an increase in flood heights.

"This equates to flooding over an area much larger than has been historically affected," says Dr Abbs. "What isn't a flood prone area now may become one in the future."

For example, in Cairns floods due to storm surges would cover about twice the size of what would be expected today if a 1-in-100-year storm occurred, due to an increase in flood height from 2.6 to 3.0 metres.

The number of flood-causing storm surges is likely to increase due to higher sea level. On average, a storm that would normally be expected every 100 years would hit every 40 years if sea levels rise by 40cm.

"Floods already cause more damage in Australia than any other natural disaster in terms of cost to the community," says Dr Abbs. "In southern Queensland and northern NSW, our results suggest damage costs associated with flooding would increase by half if sea level rose by 20cm, and more than double if sea level were to rise by 40cm."

"Changes in the intensity and the frequency of rainfall will make these problems worse. We estimate that severe rainfall events may become up to 30% more intense and occur more frequently," says Dr Abbs.

Most scientists now agree that, by 2050, sea level will rise by 10 to 40cm, tropical cyclones will increase in intensity, and the frequency of extreme rainfall will increase.

The community will be more vulnerable to these changes as increasing numbers of people move to the coast. The population along most of Australia's coast is expected to increase, especially along the coastline from Bundaberg to Wollongong and coastal regions close to Perth and Melbourne.

Dr Abbs says Councils such as the Gold Coast are aware of climate change and are working with scientists to understand the risks. But she says more consideration of climate change is needed when planning building developments and infrastructure that will exist for the next 50 years.

"These likely impacts need to be taken into account when updating design rules and approving future developments," says Dr Abbs.

The scientists used a system of computer models that described rainfall runoff, coastal waves, tropical cyclones and other impacts on flooding to assess the risk to coastal towns. The research was done in collaboration with CSIRO Manufacturing and Infrastructure Technology, with funding from the Australian Greenhouse Office as part of the Australian Greenhouse Science Program.

Note:

Debbie Abbs will be available for interview on Thursday 5 June, World Environment Day. Depending on weather, television interviews can take place by the water's edge at nearby Aspendale (Vic.) beach.

An 8-page brochure detailing in plain English the impact of climate change on coastal communities is available at: www.dar.csiro.au/publications/CoastalBroch2002.pdf

More information from:

Dr Debbie Abbs, CSIRO Atmospheric Research,

Phone: 03 9239 4660, mobile: 0401 716 201

Email: deborah.abbs@csiro.au

Media assistance:

Simon Torok, CSIRO Atmospheric Research

Phone: 03 9239 4645, mobile: 0409 844 302

Email: simon.torok@csiro.au