Australian cities are at an increased risk of experiencing flash flooding as temperatures warm, researchers from the University of New South Wales (UNSW) have found.

Conclusions published in the journal Nature Geoscience suggest peak downpours during storms are intensifying at warmer temperatures, leading to greater risk of flash flooding in urban centres.

The study’s authors have pointed to recent extreme weather events in Sydney and Queensland as examples of what they have documented.

They are urging local councils to redesign sewerage and road infrastructure as a result.

“Unless you fix the sewers and the storm drainage network you will have problems,” study co-author Ashish Sharma said.

“If you’re having bigger floods coming along in the future, the existing infrastructure cannot handle it. It will spill over.”

Civil engineers from the UNSW analysed 30 years of weather records from 79 locations across Australia.

They looked at the 500 largest storms by rainfall volume from each of these locations and measured the corresponding near-surface temperature at the time of the storm.

The research found that the most intense downpours of rain are getting more extreme at warmer temperatures, dumping larger volumes of water over less time, leading to more flash floods.

“This is the first study in the world, to our knowledge at least, that looks at what will happen within an individual storm,” Professor Sharma said.

“While it uses data from Australia it is actually very global in its reach because what we have gone about doing is we have just picked data from a lot of high quality rainfall stations in Australia.

“This holds across Australia so you can expect that this change is universal. And it’s a mechanism nobody has really looked at until now.

“We certainly didn’t expect it to be universal across Australia, which was a big surprise, and which basically says that you should see some other types of patterns in other climate zones around the world.”

CSIRO scientist Kevin Hennessy said if greenhouse gases increased at their current rate, Australia would experience warming of about 2.5 to 5 degrees Celsius by the end of the century.

“We know the world is warming. We know that there have been changes in sea level rises and extreme weather events. And we expect more of the same in the future.”

Professor Sharma said an increase of 5 degrees would cause flood peaks to rise by an average of 5 to 20 per cent for a typical medium-sized catchment.

He said the results showed how important it was for councils to think about redesigning sewerage and road infrastructure and even updating guidelines about where it is safe to build homes.

Engineers Australia said it would consider all the research in its upcoming National Rainfall and Runoff Report.

That report will be released later this year and will provide the most up-to-date information on flood flows across Australia.

– Weatherzone/ABC