Researchers from the ARC Centre of Excellence for Climate Extremes found rain bursts, which occur over a period of 10 minutes, have intensified in Sydney by 40 per cent over the past 20 years.
The rapid rain bursts bring a large amount of water which falls rapidly over a small region, increasing the likelihood and severity of flash-flooding.
Dr Hooman Ayat, a climate data scientist at the University of Melbourne, said researchers couldn't identify the climate processes that drove the change.
"Climate change may be a factor in this shocking result," he said.
The discovery means city planners must re-evaluate how they design their infrastructure in order to withstand the wetter conditions, UNSW climate researcher Jason Evans said.
"The potential for very localised flash flooding is much higher now than it used to be," Professor Evans said.
"Instead of failing once every 20 years, now (the structures) are failing all the time."
While the flooding won't result in disasters like Lismore, it can result in things like roof leaks or gutter overflow, UNSW climate researcher Professor Steven Sherwood said.
"If you're dumping a lot of rain in a very short period of time, there's only so much that structures can get rid of."
The researchers discovered the trend after examining weather radar data rather than looking at rain gauges, satellite data and climate models which failed to detect small-scale storms.
Professor Sherwood said the new technique and research will have global implications.
"If what we saw over Sydney is occurring in other cities around the world, governments, councils, city planners and communities need to prepare for the possibility that rapid rain bursts will get more and more extreme," he said.
"This is a concerning new phenomenon that needs more research."
23°C