Research by engineers at the University of New South Wales claims that flash flooding from events such as the storms which hit south eastern Australia in recent days is more likely as a result of climate change.
Professor Ashish Sharma and doctoral student Conrad Wasko, of UNSW’s School of Civil and Environmental Engineering analysed data from 1,300 rain gauges and 1,700 temperature stations across Australia to see how air temperature affected the intensity and spatial organisation of storms.
They found that atmospheric moisture was more concentrated near the storm’s centre in warm storms than in cooler ones, resulting in more intense peak rainfalls in those areas. The storms were clearly shrinking in space, irrespective of the amount of rain that fell.
Sharma said most urban centres have older stormwater infrastructure designed to handle rainfall patterns of the past, which are no longer sufficient.
“The increase is especially noticeable in urban centres, where there is less soil, unlike rural areas, to act as a dampener,” he said.
“So there is often nowhere else for the water to go, and the drainage capacity is overwhelmed. So the incidence of flooding is going to rise as temperatures go higher.”
He said this problem is not restricted to Australia.
“Look at the incidents of flooding in Mumbai or in Bangkok last year – you see urban streets full of water,” Sharma said.
“You see it now in Jakarta and Rome and many parts of Canada. That’s because the stormwater infrastructure cannot handle the rain, and part of the reason there’s more rain is the increase in global temperatures.”
Sharma said the Australian Rainfall and Runoff national guidelines, maintained by Engineers Australia, were updated for the first time since 1987, a process that took three years. He believes they will need further adjustment, as the safety and sustainability of Australian infrastructure adapts to a warming climate. And he notes there are still many unknowns to contend with.
“When we say that the storms are shrinking in space and shrinking in time, and we say floods will increase, we are making an assumption that the volume of water coming down is not changing,” said Sharma.
“That assumption is very conservative, because you would expect the air to hold more moisture. If you factor that in as well, there’ll be even more rainfall, and more floods.”
[Photo: FreeImages.com/Igor Kasalovic]
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