WA beaches, parks, to 'disappear' by 2100
Perth's waterfront areas face a perilous future if sea-level rise forecasts come true.
The Kwinana Freeway and Perth's riverside roads will flood every two weeks and parks and beaches including Cottesloe will disappear by 2100, according to sea-level rise predictions released by the federal government's Climate Commissioner yesterday.
The commission's report The Critical Decade has found sea levels around Australia's west and far north have risen the most, with an eight millimetre rise recorded since the early 1990s.
We're predicting that it will start having an effect in the next 30-40 years. We have to do something about it.
The figure is much higher than the United Nations' 2007 forecast of 59 centimetres but below the 0.9-1.6 metres predicted by the Arctic Monitoring and Assessment Program earlier this month.
Professor Chari Pattiaratchi from the University of Western Australia's Oceans Institute said a sea level rise of one metre by 2100 was now the accepted measurement among climate change scientists.
Such a rise would have profound impacts on the tidal range along the West Australian coast. Each centimetre of sea-level rise causes approximately one metre of beach erosion, meaning that the coastline can be expected to move 100 metres inland.
"Our tidal range in the South-West is about 0.6 metres, so one metre is quite large compared to our tidal range. It's quite a significant [change]," Professor Pattiaratchi said.
The highest tide recorded in WA was 1.98 metres in 2003, he said.
Professor Pattiaratchi said if the sea rose one metre, the present record level would be recorded almost every two weeks, causing estuaries to flood and beaches to erode.
"Rivers which already experience a lot of erosion and cause problems would get much, much worse," he said.
In particular, Cockburn Sound off Rockingham, coastlines in northern Mandurah and along the Busselton region and the Swan River in Perth would "flood every couple of weeks".
Limestone reefs at Cottesloe Beach would be the only thing preventing seaside homes from flooding as the beach disappeared.
Professor Pattiaratchi said Kwinana Freeway and Riverside Drive also would regularly flood, similar to flash flooding last Friday when 20 millimetres of rain fell in just 40 minutes during peak-hour, and parks throughout the city would be consumed by water.
"We're predicting that it will start having an effect in the next 30-40 years," he said.
"We have to do something about it."
WA climate scientists have claimed adaption was the only way to avoid sea-level rise impacts because natural increases in greenhouse gas emissions were comparable to the level emitted by humans, meaning a reduction in practices such as the burning of fossil fuels was too late.
As an example, Director of the Centre for Water Research at UWA, Professor Jorg Imberger, said a barge at Fremantle could save the suburb.
"The water level rise within the city is manageable without too much money," he said.
"But the thing that won't be is the big impact on the lifestyle of Perth - beaches would be gone. We've built roads next to the beaches so the sand dunes can't migrate.
"There will be increased humidity, that means dengue fever and malaria would be coming down to Perth. So it's not good.
"And there's no action that can be taken [to prevent the sea level rise] ... people just aren't able to respond [quick enough]. The only thing is adaption."
Professor Imberger said on a positive note, WA was well positioned to make long-term impacts on rainfall and potentially become carbon neutral.
"We could revegetate some of the South-West to give the farmers back some rain," he said.
"We could better manage Lake Argyle [in the Kimberley] and stock it with fish and aquaculture. That would increase the net primary production in the lake, which potentially could sequent 30 per cent of emissions.
"Third, we could take a really hard look at the resources industry and the money that's being made from that is predominantly going overseas. We could use those earnings to really get ahead in a very positive way.
"With a bit of will WA could lead the world in sustainable living."
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