Need for Swan River flood barrier: UWA study

Swan River.
Swan River.

A UNIVERSITY of WA study wants all levels of government to think about a flood barrier to protect Swan River foreshores and homes from flooding from the sea within 30 years.

“What we are saying is that by 2050 under normal conditions a barrier would be raised four times a year, but under the tidal and weather conditions we are predicting it could be used 10 to 14 times a year,” Oceans Institute professor of coastal oceanography Charitha Pattiaratchi said.

The institute’s Flood Mitigation Strategies for the Swan River in Response to Sea Level Rise study, conducted by 17 final-year Masters students and released earlier this year, said doing nothing would create “significantly higher damage costs” compared to protecting specific sites along the foreshore.

The researchers want to know how flooding from the sea will affect all the rivers’ edges.

Prof Pattiaratchi said Perth’s 18-year “high stand” tidal cycle, which will peak about 2022, was crucial to understand how tides, storms and global mean sea level rise could combine by about 2050 to create a river tide 2.7m above its current mean highest level.

A 2.7m rise could result in flooding at sites including North Fremantle, Peppermint Grove and Nedlands foreshores, send water over the Mitchell Freeway, and undermine Mounts Bay Road and Perth CBD river walls.

Prof Pattiaratchi said decision-makers needed a joint approach to the threat to Perth, including the potential Fremantle traffic bridge site for a barrier and money should not be wasted on “over-engineered” projects such a new 100m, $1 million river wall in Dalkeith.

A Department of Conservation, Biodiversity and Attractions spokesman said a storm surge barrier was one of many strategies that would be considered, and the study would be reviewed by the department.

The spokesman said that despite some consideration of cost, the study did not assess environmental or social impacts of a barrier, and it had not been peer reviewed.

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