By Alison Fox
February 11, 2020

As torrential rains in Australia are a welcomed reprieve from the wildfires that have devastated large swaths of the country for months, they could bring another unintended consequence: mudslides.

Beach erosion is seen at Collaroy on the Northern Beaches on February 10, 2020 in Sydney, Australia. Homes were evacuated after a landslip at Bayview. The Sydney area experienced its wettest weekend in more than 20 years, with strong winds and torrential rain causing flash flooding across the city. Evacuation orders remain in place for some parts of Sydney, while thousands of homes remain without power. The Bureau of Meteorology has forecast severe weather conditions again today with heavy rains, strong winds and damaging surf expected along NSW's entire coast.
Brook Mitchell/Getty Images

More than 12 inches of rain fell over 48 hours this weekend in some parts of New South Wales, NPR reported. Fires have burned many of the trees that once covered the landscape, the station reported, and without the leaves, the water falls directly on hard earth. That, in turn, causes the water to pool and then gather and, eventually, could turn into a mudslide.

“Essentially it's a flash flood that's full of rocks and logs," Charlie Showers, a groundwater geologist for the Department of Environment, Land, Water and Planning in the Australian state of Victoria, told NPR.

Last week, rains in New South Wales put out 20 of the 60 fires that had been burning. 

According to NBC News, these storms have been the heaviest and most constant rainfall in Sydney and the surrounding areas in 30 years. And if these rains continue, experts told the network that the remaining fires in New South Wales could be extinguished by the end of the week.

While the rain continues to fall, experts tell NPR it’s very difficult to determine where a potential landslide may hit. To help narrow it down, the radio station reported that experts have been looking to lessons learned during California’s wildfire seasons.

Gary Sheridan, a soil scientist at the University of Melbourne, told NPR that debris flows after rainstorms are fairly common.

"In the U.S., you guys have been doing [research] for decades and decades, and we had just a handful of little studies," Sheridan said, adding: “You know people would talk about 'freak mud-flows' and 'freak landslides' after a fire, and it was always the idea that these things were extraordinary events… But the kind of rainfall that triggers them off, although it's intense and very short, it's actually quite a common rainfall event. It's the sort of rainfall event you could expect once every two years, or once every five years."

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