A storm of heavy rain, snow, and strong winds brought dangerous conditions to the Pacific Northwest this week. By Friday, up to 16 inches of rain could inundate Northern California.
The storm is what’s known as an atmospheric river, a long narrow strip heavy with moisture that slam into the mountains of the West Coast and dumps out prodigious amounts of rain.
While scientists haven’t concluded whether atmospheric rivers are increasing because of climate change, a warmer atmosphere, driven by the burning of fossil fuels, can hold more moisture, which can lead to increased extreme rain events. That increase in extreme rain events has likely caused more landslides, according to experts.
Fast-moving landslides called debris flows, which are mud and rock-laden torrents, are more common on land that has recently, and severely, burned, like wildfire-scarred regions. July’s Park Fire, the fourth largest fire in California history, happened in a region that could see up to 12 inches of rain and remains under a flood watch until Saturday morning, according to the National Weather Service.
So far, about a dozen small landslides, including one that resulted in a car wreck, have been reported in Northern California.
What makes a landslide happen?
Landslides occur when a big slip of soil — including all the trees, rocks, and vegetation atop it — dislodges from a slope and tumbles downward. Landslides can have a variety of natural triggers like earthquakes, melting permafrost, rapid snow melt or retreating glaciers. They can also be triggered by human activity like deforestation and development. But scientists agree that the main catalyst is rain.
The study of landslides and climate change is younger, and therefore less conclusive, than the science connecting climate change to events like wildfires or hurricanes. But scientists like Dave Petley, a landslide expert who collects global landslide data for the American Geophysical Union, say climate change is undoubtedly making landslides more common.
So far, 2024 has broken all records for landslide occurrence, according to Dr. Petley. By the end of October, 679 landslides had claimed 4,460 lives across the globe.
New data from the United States Geological Survey shows that 44 percent of the United States is at risk of landslides, a risk that increases in mountainous areas with steep slopes and narrow valleys, especially in the Appalachian Mountains, Rocky Mountains, the Pacific Coast, and in parts of Alaska, Hawaii and Puerto Rico.
Extreme rain events in recent years have highlighted the risks. After the 2022 floods in Eastern Kentucky, more than 1,000 landslides and debris flows were documented. After Hurricane Helene, more than 2,000 landslides were triggered by the storm and at least half of those landslides caused damage to rivers, roads and structures like homes and businesses. In Southeast Alaska, four landslides have killed a dozen people over the last decade.
How can I protect myself?
Landslides are particularly tricky hazards. While some can move slowly over days or weeks, others occur suddenly with almost no warning and move faster than a person can run, according to the United States Geological Survey.
The U.S.G.S. highlights signs you can watch for.
Unusual sounds like cracking trees or groaning ground. Some people have described the sound as the roaring of a train or the screech of an engine.
Ground vibrations like those an earthquake might generate. One landslide survivor described the sensation as a giant mole tunneling up under her home.
Sudden changes in stream levels during or after a storm, or water flowing down a hill. Watch for changes to water color. If clear water typically flows down the side of a hill along your drive home, but suddenly becomes brown, muddy or choked with debris, that could be a sign of a landslide. You can also look for new cracks or deformations in the ground, on roads or along the side of houses.
If you’re in a region susceptible to landslides, it’s best to prepare like you would for an earthquake, wildfire or flood. Have a fully charged phone and a go-bag ready with essentials like medication, water and emergency supplies.
If you’re in a building that’s hit by a landslide, don’t evacuate until the movement subsides, and instead move to a higher floor or a countertop.
Will insurance cover landslide damage?
Standard homeowner’s insurance does not cover earth movement like landslides or earthquakes, and unlike flood insurance, separate landslide insurance is not available through the federal government.
One way to find coverage is through a separate line item called difference-in-conditions. Such insurance could cost up to $15,000 a year, according to a report by RAND Corporation, and the quotes are notoriously difficult to find, especially after a community has already faced a landslide.
Experts say the dearth in insurance is largely because the risk is so difficult to predict and the marketplace of people requesting the insurance is so small.
The lack of insurance access has led some communities at a higher risk for landslides to push back against hazard maps that could better protect them because they don’t want to lower the value of their homes or prevent development. People who’ve lost homes, cars or other property to landslides can suffer a total loss, and some can still be on the hook to pay back the mortgage for a house that no longer exists.
What is the federal government doing to address the problem?
In 2021, Senator Lisa Murkowski of Alaska, a Republican, along with Senator Maria Cantwell of Washington, a Democrat, introduced the National Landslide Preparedness Act. It provided more funding for the United States Geological Survey to map the hazards, improve forecasting and set up landslide hazard offices in states across the country.
In November, as the Pacific Northwest faced its first atmospheric river of the season, Sen. Murkowski, along with California Senator Alex Padilla, introduced a bill to improve forecasting of atmospheric rivers that could help reduce flood risks and bolster emergency preparedness. The announcement came a year after a landslide in Wrangell, Alaska, linked to an atmospheric river, caused the death of six people, including three children.
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