Counties in Idaho where landslides pose the greatest threat
IrinaK // Shutterstock
Counties in Idaho where landslides pose the greatest threat
Hurricane Helene wrought devastation across the Southeast. The storm’s high winds and flooding killed more than 230 people, and the damage to property, infrastructure, and other economic impacts is estimated to be worth tens of billions of dollars.
But heavy rains and destructive winds weren’t the only natural disasters out in force: The hurricane also activated nearly 2,000 landslides, of which over half have impacted roads, rivers, and structures, according to early estimates.
Even on their own, landslides are a deadly and costly natural disaster. There were 310 fatal landslides globally in the first half of 2024 alone, which killed 2,315 people—unusually high numbers compared to previous years. In the U.S., 25 to 50 people on average are killed by landslides each year, according to the Department of Interior.
Landslides from Hurricane Helene alone killed 20 people in North Carolina, which endured the worst of the storm’s landslides. A combination of fast-moving mud and water destroyed roads, rail links, water access, homes, and businesses across the state.
As climate change strengthens hurricanes and increases the frequency and severity of extreme weather events, the risk of landslides is also rising. To get a clearer picture of where the risk is greatest, Truck Parking Club mapped county-level data from the Department of the Interior Geological Survey, then ranked Idaho counties by the share of their land that is susceptible to landslides as part of a larger national analysis. Data was published in September 2024. Counties are displayed by the share of their land area that is susceptible to landslides.
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Counties within mountain ranges have high landslide susceptibility
In Idaho, over half of the land is susceptible to landslides in 28 counties. In 5 counties, over 90% of land is susceptible.
A landslide occurs when rock, debris, or earth moves down a slope. Inclines like hills and bluffs are a critical element of slides, meaning mountainous regions are at higher risk. Typically, landslides are triggered by forces like heavy rainfall, snowmelt, earthquakes, volcanic activity, human activities, or some combination of factors. Often, they’re impossible to predict.
According to the Geological Survey, places where weak or fractured earth sit on steep slopes are likely to experience landslides—for example, areas with a history of strip mining. In Appalachia, about 1,400 square miles of land are scarred by strip mining within the Ohio River basin, according to an Inside Climate News analysis of satellite imagery. Together, the “waste rock” left behind, increasing stream flows, and heavy rainfalls brought on by climate change create a deadly recipe for landslides. This part of Appalachia is also near the Gulf of Mexico, where fast-warming waters stir up exceptionally fast-growing storms, as was the case with Hurricane Helene.
Combined, these elements create the highest vulnerability to landslides in the region. Much of West Virginia, in particular, is at risk: In 47 of the state’s 55 counties, more than 90% of the land is susceptible to slides. Parts of Virginia, Kentucky, Ohio, Tennessee, and North Carolina are also exceedingly vulnerable.
Parts of California’s coastline have also been plagued by major landslides. Earlier this year, a rockslide destroyed a part of Highway 1 along the state’s famed Big Sur. The earth below the highway isn’t sturdy, and wetter storms are further weakening it, contributing to more frequent and severe landslides. The majestic Big Sur stretch is an iconic road trip and tourism destination, where the highway winds along cliffs above the Pacific Ocean. However, it was forced to close to most traffic, and still offers just one lane at some points.
Other landslide risk factors include population growth, rapid land use changes, urbanization, heavy logging and deforestation, and inappropriate use of lands—slopes in particular. Wildfires also generate landslide hazards, leaving behind excess debris that can be dragged down during floods, as was the case in Big Sur.
The heightened frequency and severity of landslides are a direct consequence of logging, mining, and climate change, with massive repercussions for safety and critical infrastructure in the U.S. and around the world.
Hazard maps like those from the Geological Survey are a tool that federal, state, and local governments can use to identify landslide vulnerabilities and prepare for them. Preparation and mitigation efforts might include landslide drills, evacuation plans, improved drainage systems, and slope stabilization. Governments in susceptible areas can adopt disaster-resilient building codes and standards, as well as restrictions on mining and logging.
In some cases, such as Highway 1, there are no obvious solutions to fully protect against landslides. Still, with increased awareness and response plans, people can make more informed decisions on where to live (or safely visit) and can prepare themselves for landslides and their aftermath.
Read on to see where in Idaho is most vulnerable to the growing landslide threat.
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#44. Jefferson County
– Percent susceptible area: 6.0%
– Total susceptible area: 66 square miles
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#43. Minidoka County
– Percent susceptible area: 6.9%
– Total susceptible area: 53 square miles
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#42. Jerome County
– Percent susceptible area: 8.8%
– Total susceptible area: 53 square miles
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#41. Canyon County
– Percent susceptible area: 11.8%
– Total susceptible area: 70 square miles
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#40. Lincoln County
– Percent susceptible area: 18.4%
– Total susceptible area: 222 square miles
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#39. Gooding County
– Percent susceptible area: 19.7%
– Total susceptible area: 145 square miles
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#38. Ada County
– Percent susceptible area: 21.3%
– Total susceptible area: 226 square miles
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#37. Twin Falls County
– Percent susceptible area: 23.8%
– Total susceptible area: 457 square miles
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#36. Bingham County
– Percent susceptible area: 27.6%
– Total susceptible area: 579 square miles
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#35. Owyhee County
– Percent susceptible area: 35.8%
– Total susceptible area: 2,753 square miles
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#34. Madison County
– Percent susceptible area: 36.5%
– Total susceptible area: 173 square miles
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#33. Butte County
– Percent susceptible area: 37.3%
– Total susceptible area: 833 square miles
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#32. Fremont County
– Percent susceptible area: 37.8%
– Total susceptible area: 709 square miles
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#31. Cassia County
– Percent susceptible area: 44.4%
– Total susceptible area: 1,141 square miles
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#30. Power County
– Percent susceptible area: 47.6%
– Total susceptible area: 671 square miles
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#29. Clark County
– Percent susceptible area: 47.7%
– Total susceptible area: 843 square miles
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#28. Teton County
– Percent susceptible area: 50.9%
– Total susceptible area: 217 square miles
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#27. Lewis County
– Percent susceptible area: 54.3%
– Total susceptible area: 260 square miles
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#26. Payette County
– Percent susceptible area: 57.1%
– Total susceptible area: 234 square miles
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#25. Blaine County
– Percent susceptible area: 58.3%
– Total susceptible area: 1,542 square miles
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#24. Oneida County
– Percent susceptible area: 61.4%
– Total susceptible area: 738 square miles
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#23. Elmore County
– Percent susceptible area: 61.4%
– Total susceptible area: 1,896 square miles
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#22. Bonneville County
– Percent susceptible area: 62.1%
– Total susceptible area: 1,147 square miles
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#21. Caribou County
– Percent susceptible area: 65.9%
– Total susceptible area: 1,160 square miles
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#20. Camas County
– Percent susceptible area: 67.8%
– Total susceptible area: 729 square miles
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#19. Bannock County
– Percent susceptible area: 71.9%
– Total susceptible area: 801 square miles
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#18. Franklin County
– Percent susceptible area: 72.4%
– Total susceptible area: 480 square miles
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#17. Bear Lake County
– Percent susceptible area: 73.1%
– Total susceptible area: 703 square miles
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#16. Kootenai County
– Percent susceptible area: 73.5%
– Total susceptible area: 915 square miles
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#15. Gem County
– Percent susceptible area: 74.1%
– Total susceptible area: 419 square miles
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#14. Benewah County
– Percent susceptible area: 76.7%
– Total susceptible area: 597 square miles
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#13. Bonner County
– Percent susceptible area: 76.7%
– Total susceptible area: 1,338 square miles
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#12. Washington County
– Percent susceptible area: 77.3%
– Total susceptible area: 1,128 square miles
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#11. Nez Perce County
– Percent susceptible area: 78.4%
– Total susceptible area: 671 square miles
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#10. Boundary County
– Percent susceptible area: 84.3%
– Total susceptible area: 1,077 square miles
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#9. Latah County
– Percent susceptible area: 84.4%
– Total susceptible area: 908 square miles
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#8. Custer County
– Percent susceptible area: 85.4%
– Total susceptible area: 4,213 square miles
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#7. Lemhi County
– Percent susceptible area: 86.3%
– Total susceptible area: 3,944 square miles
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#6. Adams County
– Percent susceptible area: 86.5%
– Total susceptible area: 1,183 square miles
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#5. Valley County
– Percent susceptible area: 90.9%
– Total susceptible area: 3,340 square miles
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#4. Idaho County
– Percent susceptible area: 93.0%
– Total susceptible area: 7,912 square miles
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#3. Clearwater County
– Percent susceptible area: 94.6%
– Total susceptible area: 2,332 square miles
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#2. Boise County
– Percent susceptible area: 97.4%
– Total susceptible area: 1,855 square miles
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#1. Shoshone County
– Percent susceptible area: 98.0%
– Total susceptible area: 2,582 square miles
This story features data reporting and writing by Paxtyn Merten and is part of a series utilizing data automation across 50 states.
This story originally appeared on Truck Parking Club and was produced and
distributed in partnership with Stacker Studio.
