by LOS ANGELES – A wave of intense rainstorms has accelerated landslides and helped damage coastal erosion in California, leaving multimillion-dollar homes on the edge of cliffs, sending hundred-foot palm trees into the surf and forcing the closure of a historic church.
The state is drying up now, but impacts from the second season of heavy rains could be felt in the coming years. Climate change, which is boosting rainfall rates, fueling sea-level rise and making droughts more severe, is contributing to some of the forces reshaping California’s landscape.
This season’s storms have offered California a dramatic exposure and a preview of the consequences of a warming world, with slow-moving processes that scientists have warned are accelerating in clear light. Mike Phipps, a geologist with the geotechnical engineering firm Cotton, Shires and Associates, said landslide risk and sea level rise are converging to reshape California’s coastline.
“The coast is in great danger,” he said. “As those cliffs try to recede, the buildings are going to be threatened and there are cases up and down California where buildings are destroyed and buildings are falling into the ocean.”
Two years ago, 100% of the state was in drought and much needed rain, according to the National Drought Monitor. Now, only tiny pockets of the state – 7% of the total – are considered “very dry” and residents are pleading for mercy from heavy rains.
The transition began last winter when more than a dozen atmospheric rivers bombarded the state with precipitation, reducing drought and soaking the state’s hills with moisture.
This year, the extremes only continued.
This month, downtown Los Angeles has recorded more than 12.5 inches of rain — four times the typical monthly average and nearly twice as much as fell in all of 2022, according to National Weather Service data.
The rain has pushed some slopes to the brink, making landslides more likely.
During the most recent storm, the city of Los Angeles said it received 63 reports of debris flows or mudslides. After a heavier storm earlier this month, the city said it received calls for service for 592 mudslides. At least 16 buildings are “red tagged”, meaning people have been denied entry due to the danger.
“When you have this continuous storm surge, you’re more likely to get water on the slopes and that increases your chances of landslides,” said Nate Onderdonk, a professor and geomorphologist at California State University Long Beach.
In the community of Rancho Palos Verdes, a landslide-prone coastal city in Los Angeles County, recent rain has accelerated ground movement and caused changes in previously unmapped areas of slides, according to a city news release.
Onderdonk said layers of sedimentary rock in the area are tilted towards the sea. When weak clay layers become saturated with water, they often expand and slide because they have little friction.
The severe rainy season has become more and more frequent and is a cause for concern. Twenty years ago, geologists drew up a plan to dewater slopes in the Abalone Cove landslide area, which greatly slowed movement, Onderdonk said.
But about a week ago, an accelerating movement forced the closing of the Wayfarers Chapel, a national historic landmark designed by Frank Lloyd Wright Jr. in Abalone Cove.
“That got my attention,” Onderdonk said. “This area appears to have stabilized.”
With homes and roads at risk, the city of Rancho Palos Verdes asked Gov. Gavin Newsom to pursue a state and federal emergency declaration, which could speed emergency arrangements through the approval process.
Many coastal cities along the California coast are exposed to landslide risk.
Homes in Dana Point made headlines this week after the Los Angeles Times and other media organizations published drone footage showing several large oceanfront homes atop landslide debris.
Scientists are still investigating how climate change will alter the frequency and severity of landslides. A 2022 study published in the peer-reviewed journal Geophysical Research Letters found that landslides are sensitive to changes in climate and move much faster in wet years than in dry years.
A study published in 2019 in the Bulletin of the American Meteorological Society found that landslides coincided with atmospheric river storms about 76% of the time in the San Francisco Bay area.
Scientists say atmospheric river storms are becoming more frequent and intense on the West Coast, because a warmer atmosphere can absorb and transport more water vapor.
The bluffs of California are fighting more than gravity.
Rising seas and more intense storms are chewing up the state’s beaches and coastlines, something climate scientists have warned about for years. A report from the United States Geological Survey found that, with sea levels rising due to climate change, Southern California could lose up to two-thirds of its beaches by 2100.
Global warming – driven by human use of fossil fuels – is the main cause of sea level rise. Melting glaciers and polar ice sheets are raising sea levels. The volume of ocean water is also increasing as it gets warmer.
It’s a dynamic that has left many watching their beaches shrink.
Homeowners Edward and Debbie Winston-Levin, who live in Dana Point, California, in a home that overlooks Capistrano Beach, said they’ve watched the sea clear over time.
“There used to be a volleyball court and a basketball court there that were all corroded,” said 77-year-old Edward Winston-Levin. “And on a surf day, it covers the car park.”
They worry that their property, which is on a steep slope, could one day slide into the sea.
“If one slide starts, it’s going to keep going, we’re going to lose our houses with beautiful views, you know,” he said.
Many coastal cities are making major changes to try to adapt.
In San Diego, plans are underway in the beach town of Del Mar to move train tracks that are now considered too close to the coast. And in San Clemente, the state is planning to build a $7.2 million wall to reinforce a landslide area in an effort to contain a landslide that shut down train service through Orange County.
In Isla Vista near UC Santa Barbara, a cliff collapse recently forced students to evacuate their homes and now some of those buildings are being rebuilt farther from shore.
Experts say overtime this changing landscape could lead to a dilemma: save the state’s iconic beaches or wall them in to protect the cliffside homes.
“That’s a very complicated question,” Phipps said. “Obviously, Californians love their beaches and everyone will want to keep their beaches, and there will be places where that can be done, but in many places, beaches are receding and being lost.”
This article was originally published on NBCNews.com
