SMART NEWS

California Hammered by Heavy Rains, Mudslides in Devastating Atmospheric River Storms

Some areas received as much as 13 to 15 inches of rain over a five-day period as storms felled trees, destroyed homes and killed nine people

Will Sullivan

Daily Correspondent

Mud covers land where a house used to be. The house is pushed over and flattened by the mud.
A house in the Beverly Crest neighborhood of Los Angeles was pushed off its foundation by a mudslide on Monday morning. No one was in the house when the mudslide occurred. Recent storms caused at least 475 mudslides in the Los Angeles area. Allen J. Schaben / Los Angeles Times via Getty Images

Heavy storms hit California over the weekend and continued into the middle of this week, dumping historic amounts of rain in some places and leading to flooding, mudslides, damaged homes, evacuations and the deaths of nine people.

In the Los Angeles area, the storms produced at least 475 mudslides, felled 390 trees and created 441 potholes, per ABC News’ Marilyn Heck. More than 200,000 Californians lost power.

The nine deaths included four people killed by fallen trees in Northern California and two killed in car crashes in Southern California.

“In my 35 years of being in this canyon, this is the scariest it’s ever gotten,” Dennis Hacela, a resident of a hard-hit Beverly Drive neighborhood, tells the Los Angeles Times’ Rong-Gong Lin II.

Thunderstorms led to winds of up to 82 miles per hour in Ventura County and 75 miles per hour in Los Angeles County. By Thursday morning, several locations in Los Angeles County had been drenched with between 13 and 15 inches of rain over five days, according to the National Weather Service. Parts of San Diego received similar amounts of precipitation, with the Middle Fork Lytle Creek area getting almost 15.5 inches.

Over Sunday and Monday, some parts of Southern California received almost half the amount of precipitation typical for an entire season. And from Sunday to Tuesday in downtown Los Angeles, 8.51 inches of rain landed—the second highest amount for a three-day period since records began in 1877, report Grace Toohey and Hannah Fry of the Los Angeles Times.

Los Angeles, Long Beach and Pomona remained under a flash flood warning from late Wednesday night into early Thursday. While the rain was expected to be lighter, all the precipitation that had already landed made the region vulnerable to more damage.

“Our hillsides are already saturated. So even not-very-heavy rains could still lead to additional mudslides,” Los Angeles Mayor Karen Bass said at a Tuesday evening news conference, per Stefanie Dazio and Julie Watson of the Associated Press (AP). “Even when the rain stops, the ground may continue to shift.”

A cliffside collapsed in Santa Barbara on Tuesday morning, according to NPR’s Alejandra Borunda and Vanessa Romo. Mudslides and rockslides will continue to be a threat in Southern California in the coming days. But after Wednesday night’s rain, the area is expected to dry out, Tyler Kranz, a meteorologist with the National Weather Service, tells the AP.

The inundation of rain originated from an atmospheric river—a long, narrow band of water vapor in the atmosphere. These plumes of moisture form over oceans, and when they reach land, they release the water vapor as rain or snow. Exceptionally strong atmospheric rivers can carry up to 15 times the average flow of water at the mouth of the Mississippi River, per the National Oceanic and Atmospheric Administration.

An additional atmospheric river hit California last week. The state was also pummeled by the storms last winter—nine consecutive atmospheric rivers hit the state over the course of three weeks between December 2022 and January 2023, Qian Cao, a hydrologist at the University of California, San Diego, writes in the Conversation.

Climate change and this year’s El Niño, a climate pattern that pushes warm water toward the Pacific Coast, are exacerbating the effects of atmospheric rivers, per NPR. Both contribute to warmer oceans, and the extra heat evaporates water, forming vapor that contributes to the storms. Since warmer air can also hold more moisture, increasing air temperatures also allow for more intense atmospheric rivers, according to the Conversation.

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Will Sullivan

Will Sullivan is a science writer based in Washington, D.C. His work has appeared in Inside Science and NOVA Next.