After a wildfire, a Pacific Palisades home was split by a landslide. Is there risk of more?

After a massive wildfire tore through the Pacific Palisades, a home on a hillside was left split in half. While it was survived the flames, a landslide left part of the home slumped over — a clear break through its roof visible from above.

Now, thousands of homes in the area could be compromised and geologists are being brought in to assess the potential for future landslides, according to the Los Angeles Fire Department. So how do these landslides happen after fires? And what raises the risk of them occurring?

When a landslide follows fire: The deadly Montecito mudslides

Geology and wildfire experts say landslides and mudslides, usually a concern following heavy rainfall, can be triggered by fires that destabilize the ground below. In January 2018, a month after the 280,000-acre Thomas Fire ripped through Ventura and Santa Barbara counties, heavy rain loosened mud and debris in parts of the Santa Ynez Mountains that had been left burn-scarred.

With the landscape scorched barren by the Thomas Fire weeks before, the rain sent mud and debris flowing from the mountains down south to the community of Montecito. In the town of just 8,600, 23 people were killed and more than 100 homes destroyed.

"It had to have been terrifying for those people in those homes that night, to hear these boulders getting closer and closer and hearing all those trees snapping as they were getting closer," Mike Eliason, a former Santa Barbara County Fire Department spokesperson, said in an account of the natural disaster from the California Governor's Office of Emergency Services. 

"I can't imagine the fear in those people as they knew what was coming and they had no escape," Eliason said.

Mudslides like those in Montecito can happen with very little warning, potentially leading to more loss of life and destruction than other natural disasters which may be more easily predicted, as the U.S. Geological Survey notes.  

Can a post-fire landslide happen without rainfall?

In Los Angeles County, rainfall hasn't followed the devastating wildfires which burned tens of thousands of acres this past week, leaving at least 25 people dead and thousands of buildings damaged or destroyed. But mudslides and landslides in post-fire areas do not necessarily always follow rain, particularly in places with steep slopes and hillsides like the Pacific Palisades.

"Wildfire increases the susceptibility of steep slopes to landslides and debris flows," the U.S. Geological Survey states, explaining that fires can lead to the destabilization of pre-existing, deep-seated landslides.

The home split by a landslide this week along Castellammare Drive overlooks the Pacific Coast Highway and the stretch of ocean along it, situated on a small hillside with the ground around the outer perimeter of the home sloping downward. It mirrors how many of California's most scenic, affluent neighborhoods look — positioned high up on hillsides with picturesque views from above.

But the topography of such locations can make them especially vulnerable to land movement, experts say. 

Los Angeles firefighters are now on the lookout for other properties in Pacific Palisades and Malibu damaged by landslides, taking note of any as part of their ongoing assessments into the widespread damage and destruction, LAFD Captain Erik Scott said.

"This certainly caught a lot peoples' eyes and that's why we're here. But there could be other similar homes," Scott said of the home in the Palisades. "It's safe to say that the infrastructure under thousands of homes have been compromised. And with that, can come challenges like this — if it's on a steep hillside."

The forecast for rainfall and fires in Southern California

This year, the greater Los Angeles area has faced an especially dry winter. While Northern California and parts of Central California received a fair amount of rainfall, Southern California has seen "near record dry conditions" this past fall and winter, according to an assessment by the Geographic Area Coordinating Group (GACG), a government agency made up of federal and state officials.

Southern California is expected to see below-normal levels of precipitation through the first week of February while a few parts of the region could see more normal levels of rainfall between February through April, according to the National Weather Service. 

GACG details its predictions for weather patterns in the region, and how they may lead to or affect natural disasters, in an assessment issued Dec. 31. While noting weather conditions bringing wildfire risks in January, the report says there is a "moderate tilt in the odds" for higher-than-normal temperatures and "below normal precipitation" for January through April.

However, the risk of wildfires in the region is not expected to lower until "significant" rainfall arrives, the report says.

"Until widespread rains occur, this risk will continue," the report says. "Outside of the South Coast and adjacent foothills, fire potential will be minimal through April, with the growing cycle beginning to get underway."

For this coming year, the government report goes on to note that desert areas of Southern California may begin to see fire activity as soon as April, but "it is too early to speculate on the upcoming season's fire potential for the deserts." 

"Should conditions remain very dry over Southern California, it would support an earlier than normal start to mid and high elevation fire activity in 2025, but that would still be beyond this outlook period," the report says.

Ironically, rainfall may increase the risks of landslides in burn-scarred areas — but no rain could also mean a higher risk of wildfires. 

It's important to note that landslides triggered by wildfires can happen even years after a blaze breaks out. The U.S. Geological Survey reports that some landslides happen over longer periods of time, sometimes years, moving slowly as root decay and loss of soil strength contribute to the ground's movement. This is what's been happening in recent months in Rancho Palos Verdes. In the coastal LA community, 30 miles south of Pacific Palisades, at least 650 homes have been impacted by a slow-moving landslide.

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