FloodsFlooding, rainfall extremes in cities to rise as climate changes
Cities face harsher, more concentrated rainfall as climate change not only intensifies storms, but draws them into narrower bands of more intense downpours, engineers have found. This has major implications for existing stormwater infrastructure, particularly in large cities, which face higher risks of flash flooding.
Cities face harsher, more concentrated rainfall as climate change not only intensifies storms, but draws them into narrower bands of more intense downpours, University of New South Wales (UNSW) engineers have found. This has major implications for existing stormwater infrastructure, particularly in large cities, which face higher risks of flash flooding.
UNSW notes that in the latest issue of Geophysical Research Letters, doctoral student Conrad Wasko and Professor Ashish Sharma of School of Civil and Environmental Engineering at the University of New South Wales show the first evidence of storm intensification triggering more destructive storm patterns.
“As warming proceeds, storms are shrinking in space and in time,” said Wasko, lead author of the paper. “They are becoming more concentrated over a smaller area, and the rainfall is coming down more plentifully and with more intensity over a shorter period of time. When the storm shrinks to that extent, you have a huge amount of rain coming down over a smaller area.”
Wasko and Sharma, working with collaborators at the University of Adelaide, analyzed data from 1,300 rain gauges and 1,700 temperature stations across Australia to see how air temperature affected the intensity and spatial organization of storms.
They found that atmospheric moisture was more concentrated near the storm’s center 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.
Although the data is sourced from Australia, this has global implications, said Sharma. “Australia is a continent that spans almost all the climate zones in the world - Mediterranean, tropical, temperate, subtropical - everything except the Arctic or Antarctic. So the results hold a lot of value - we are finding the pattern repeating itself over and over, happening around Australia and around the world.
“Look at the incidents of flooding in Mumbai or in Bangkok last year - you see urban streets full of water,” he added. “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.”
