Australia faces increased threats from extreme weather events, new research finds
A new study shows heavy but short rainstorms are intensifying more rapidly than expected, which could lead to increased instances of flash floods in urban and rural areas.
The study, produced by researchers at the University of Adelaide and published in Nature Climate Change, found that in Australia the amount of water falling during short, intense storms – such as thunderstorms – is increasing at rates higher than would be expected with climate change.
“This large increase has implications for the frequency and severity of flash floods, particularly if the rate stays the same into the future,” said Seth Westra, an associate professor from the University of Adelaide’s School of Civil, Environmental and Mining Engineering and co-author of the study.
Data from more than 100 Bureau of Meteorology weather stations across the country was analysed. The weather stations record rainfall information at five-minute intervals, and the researchers looked at data points stretching back to the 1960s.
The research team found that hourly rainfall extremes were double the expected strength in most areas, and triple in tropical areas like far north Queensland. These results contradict previously held thoughts about the upper limits of rainfall during extreme weather events.
Researchers also found that flash floods occurred more frequently in urban areas, as well as hilly rural areas where stormwater infrastructure can’t cope with high levels of rainwater.
“In urban areas, because they’re paved in concrete, the speed at which rainfall turns into runoff is accelerated,” Westra said.
“By the nature of these events, they tend to be very short lived and intense and severe. Emergency response is very important, but there are limits to how much you can address.”
Westra added that rising storm intensity and rainfall are linked to rises in temperature. While there is no clear indication of how strong thunderstorms can get in the future, he said that if temperatures continue to rise, there needs to be more planning for flash flooding events.
“It seems counterintuitive when large parts of Australia are now in drought, but we need to remember Australian droughts are often broken by severe floods. We have always been a country of weather extremes and it seems that climate change is causing both the dry and wet extremes to intensify,” he said.
“These changes are well above what engineers currently take into account when determining Australia’s flood planning levels or designing stormwater management and flood defence infrastructure. If we keep seeing this rate of change, we risk committing future generations to levels of flood risk that are unacceptable by today’s standards.
“If the rates of change continue into the future and we continue to have the warming that is anticipated, it will profoundly impact our stormwater infrastructure and our ability to cope with flash flooding events.”