Landslides are destroying multimillion-dollar homes in California, and they’re getting worse | CNN (2024)

CNN

The deep landslides beneath the multimillion-dollar homes in Rancho Palos Verdes moved at an almost glacial pace, until they didn’t.

This affluent coastal city in Southern California, around 30 miles south of Los Angeles, has long enticed people with its Pacific Ocean views and lush greenery. But it sits atop a complex of slow-moving landslides that have been active since the 1950s, causing the land to shift by roughly a few feet a year. Recently, after intense winter rain, the pace and scale of movement hasincreased.

Last weekend, a drastic acceleration brought devastating consequences.

Homes now lie sprawled unevenly across distorted ground, roads have buckled and power has been shut off to more than 200 households. On Tuesday, Gov. Gavin Newsom declared a state of emergency in the city.

The sight of luxurious, ocean-front houses teetering precariously over cliff tops or part-swallowed by the ground is not unfamiliar in this part of the US. Landslides destroy homes, take lives and leave communities fearing for their future.

But scientists warn they are set to become more frequent as the climate crisis fuels heavier rainfall and more powerful storms, reshaping landscapes.

Landslides depend on three factors: the slope, the rock type and the climate, said Alexander Handwerger, a landslide scientist at NASA’s Jet Propulsion Laboratory.

Rancho Palos Verdes sits on top of a volcanic ash bed, laid down about 10 to 15 million years ago, that slopes down to the Pacific shoreline.

“It has weathered to a type of clay mineral that can expand and get slippery when it gets wet,” said Gary Griggs, distinguished professor of earth and planetary sciences at the University of California Santa Cruz.

A variety of factors can trigger landslides, including earthquakes and human activities. But rainfall is one of the most common.

As it rains, water seeps into the ground, percolating into the layers below. There, it can reduce the suction and friction holding together grains of soil or rock, causing the ground to weaken and shift.

Slopes are always trying to reach a stable angle, which depends on what kind of climate they are in, said Dave Petley, an earth scientist at the University of Hull in England. If the climate changes, and rainfall becomes heavier, the slope “might now be too steep to be stable, so it will suffer a landslide or a series of landslides to find a new, stable angle,” he told CNN.

In California the changing climate is forcing the landscape to respond.

For the past two years, atmospheric rivers — long plumes of water in the sky that sweep in from the tropics — have lashed the state with rain.

This February, an atmospheric river dumped record amounts of rain across southern California, triggering hundreds of mudslides and leaving at least nine people dead.

Rain ate away at cliffs; one stark image shows a small cluster of mansions in Dana Point perilously close to tumbling onto the rubble-strewn beach below.

Landslides are destroying multimillion-dollar homes in California, and they’re getting worse | CNN (2)

Luxury homes in danger of falling due to a landslide following heavy rainfall, in Dana Point, California, on February 15 2024.

Scientists have found clear links between the climate crisis and heavier rain. A warmer atmosphere can hold more moisture, meaning more intense rain or snow when it falls, and hotter oceans fuel more powerful storms.

In California, climate projections suggest the state will experience less frequent but more intense rainfall in the future, especially from atmospheric rivers, which are expected to become more potent as the world warms.

The risk for landslides is clear, said Handwerger, who published a study on the topic in 2022. “We’ve looked all across the state, and we see that in years that are wetter than average, the landslides speed up.”

The climate crisis raises other landslide risks too. Sea level rise and storm surge are eating away at cliffs. Hotter, drier summers are increasing the frequency and severity of wildfires, leaving the landscape vulnerable to mudslides, Griggs said.

The 2018 mudflows that tore through Montecito, killing 23 people, followed the Thomas Fire, at the time the largest wildfire in California’s history, which incinerated trees and plants.

Landslides are destroying multimillion-dollar homes in California, and they’re getting worse | CNN (3)

A firefighter stands on the roof of a house submerged in mud and rocks after a landslide in Montecito, California, in 2018.

Landslides are of course a global phenomenon, and scientists are identifying climate change-fueled landslide risks across the world.

Cyclone Gabriel in New Zealand triggered more than 140,000 mapped landslides — and possibly more than 800,000 in total, researchers believe.

In July, a landslide triggered by heavy monsoon rains in India’s southern state of Kerala killed at least 150 people. The rainfall was made at least 10% heavier by the climate crisis, according to a scientific analysis.

Climate changeis not the only factor increasing the likelihood of landslides; human behavior has an impact too.

Cutting into slopes to flatten areas for houses or roads can weaken them and mountain-sides, making both unstable, said Ugur Öztürk, a landslide scientist at the University of Potsdam and the GFZ German Research Centre for Geosciences.

As can adding too much water to the ground, Griggs said. In Southern California, “people wanted to pretend they lived in the tropics,” he said, “and planted a lot of landscaping that required lots of watering.”

Deforestation is another factor. Tree and plant roots hold the soil together and ripping them out can destabilize the ground, the University of Hull’s Petley said.

But, he added, “climate change is key.”

For those living in Rancho Palos Verdes, where the ground is now moving up to 12 inches a week, the future of their community hangs in the balance. It’s not clear when the movement will slow, or whether they can save their homes from being torn apart.

Landslides are destroying multimillion-dollar homes in California, and they’re getting worse | CNN (2024)

FAQs

Which area in California has the greatest likelihood of landslides? ›

Landslides are common in Southern California, the San Francisco Bay Area and other parts of Northern California, and the Sierra Nevada.

What is causing the landslide in Rancho Palos Verdes? ›

The ground in the affluent neighbourhood has been shifting for decades, usually about a manageable foot a year. Now it's moving that amount a week in some areas, as two years of heavy rains accelerated the shift, causing irreparable damage to some homes and prompting California to declare a state of emergency.

Why is Rancho Palos Verdes moving? ›

This affluent coastal city in Southern California, around 30 miles south of Los Angeles, has long enticed people with its Pacific Ocean views and lush greenery. But it sits atop a complex of slow-moving landslides that have been active since the 1950s, causing the land to shift by roughly a few feet a year.

Why does California have a greater risk of landslides in the winter? ›

Landslide Risk

Landslides typically occur during periods of higher-than-average rainfall, like El Niño winter seasons, and are more likely to occur: On steep slopes; On slopes made top-heavy by construction debris (e.g. road grading);

What U.S. state has the most landslides? ›

Washington state is one of the most landslide-prone states in the U.S., according to the state Department of Natural Resources. In fact, the entire west coast is much more likely to experience a landslide than other parts of the country.

Where would you expect landslide potential to be the highest in the United States? ›

Landslides affect all 50 states and U.S. territories, though mountainous regions such as the Pacific Coast range, the Rockies, the Appalachians, Alaska, and Hawaii bear the most severe risk.

What town in California was buried by a landslide? ›

On March 4, 1995, the hill behind La Conchita failed, moving tens of meters in minutes, and buried nine homes with no loss of life. The County of Ventura immediately declared the whole community a Geological Hazard Area, imposing building restrictions on the community to restrict new construction.

What was the worst landslide ever recorded? ›

The eastern half of the Koʻolau Volcano collapsed into the Pacific Ocean, leaving behind its remnant western rim on Oahu as the Koʻolau Range The landslide had a run-out of more than 140 miles (225 km), climbing about 1,000 feet (305 m) over the last 85 miles (137 km) and leaving a massive debris field north of Oahu ...

What was the primary cause of the landslide? ›

A landslide occurs because the force of gravity becomes greater than either friction or the internal strength of the rock, soil, or sediment. The amount of friction between a deposit of rock or soil and the slope that it rests on plays a large role in when landslides happen.

Do any famous people live in Palos Verdes? ›

Christen Press, a forward for the United States women's national soccer team and two-time World Cup champion, grew up there. Professional poker player Barry Greenstein and artist John Van Hamersveld have resided in Rancho Palos Verdes. Chester Bennington of rock band Linkin Park was a longtime resident of Palos Verdes.

Is Rancho Palos Verdes a rich area? ›

America's richest retirement town: Ranchos Palos Verdes, California. Ranchos Palos Verdes, Calif. ranked as the richest retirement town, with a median household income of $166,747.

What kind of people live in Rancho Palos Verdes? ›

Rancho Palos Verdes Demographics

White: 50.17% Asian: 32.41% Two or more races: 10.54% Other race: 4.72%

What is the biggest danger to California from climate change? ›

Sea level rise, coastal flooding and coastal erosion.

The sea level along California's coasts has risen nearly 8 inches in the past century and is projected to rise by as much as 20 to 55 inches by the end of the century.

Why is it raining so much in California in 2024? ›

Wondering why it's been so rainy in Southern California in early 2024? The answer may lie in a program that uses man-made weather modification to increase precipitation. Last year, Southern California water officials announced a four-year pilot program aimed at increasing precipitation by 5-15% for the year.

Where is the greatest landslide hazard in the United States? ›

Landslides generally strike where there is a presence of unstable geologic materials (rock and soil). Landslides occur in every state and U.S. territory. The Appalachian Mountains, the Rocky Mountains, and the Pacific Coastal Ranges and some parts of Alaska and Hawaii have severe landslide problems.

Which areas have the highest landslide potential? ›

Slides can occur in all 50 states, but regions like the Appalachian Mountains, the Rocky Mountains and the Pacific Coastal Ranges have “severe landslide problems,” according to the USGS.

What areas are most at risk for landslides? ›

Landslides occur in every state and U.S. territory including the Appalachian Mountains, the Rocky Mountains, the Pacific Coastal Ranges, and some parts of Alaska and Hawaii. Any area composed of very weak or fractured materials resting on a steep slope can and will likely experience landslides.

Which is the most landslide prone area in? ›

The two areas in India that are most prone to landslides are the Himalayas and the Western Ghats. The Himalayan region, due to its high seismic activity and heavy rainfall, frequently witnesses landslides.

In which location would you expect to have the most landslides? ›

Explanation: Among the four options given, we would expect to have the most landslides in Option 2: A forested mountain slope. Landslides require a certain slope of land for the downward force of gravity to overpower the strength of the earth holding it in place.

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