Another storm is heading to Southern California, and while it isn’t projected to be as bad as the last, it could bring the possibility of even more mudslides and landslides.
Matt Thomas, research hydrologist with the U.S. Geological Survey, told KNX News’ Margaret Carrero that the amount of rainfall we’ve already gotten this season increases the risk of landslides in the future.
“We know antecedent conditions are really important, meaning there is kind of a carryover effect from storm to storm in terms of what you can expect in landslide activity,” he said. “The kind of published guidance right now for Southern California for landslides says that you need about 10 inches of rainfall for your season, and after that, rainfall intensities on the order of about a quarter inch an hour can get things moving.”
Much of Los Angeles County has received more than 10 inches of rainfall just in the past two weeks, meaning any additional high-intensity storm could trigger landslides. Areas that were affected during the previous storm are more susceptible to further problems.
“In landslide science, we have an axiom that the best place to look for a landslide is where one has already occurred,” Thomas said. “Landslides can remove material, but they actually can also overstep and potentially weaken the surrounding hillslope materials more so than they were prior to that landslide. And so in this sense, we do consider areas that had had previous landslides to be susceptible in the future.”
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Thomas said homeowners can protect themselves by checking on how water drains off their property. If there are places where surface water concentrates, those areas “end up being erosional hotspots,” he said.
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