Scientists have identified 6.5 million Americans living on terrain highly susceptible to potentially deadly landslides, according to the first nationwide building-level assessment of its kind. The study, which analyzed 128 million U.S. buildings, found that 3.8 million properties valued at an estimated $1.2 trillion are situated in the country's most landslide-prone areas.
Nearly four in five of these exposed residents are concentrated in two regions: Appalachia and along the West Coast, impacting communities near major cities such as Seattle, San Francisco, and Los Angeles. West Virginia emerged as the most vulnerable state, with approximately one in five residents living on terrain susceptible to landslides.
Rural Vulnerability and Urban Risk
Researchers highlighted a stark contrast in the risks faced by rural and urban populations. Rural Americans in landslide-prone areas are often more vulnerable due to living on steep slopes farther from emergency services and possessing fewer resources for disaster recovery. Approximately 62 percent of buildings in these susceptible areas are in rural locations. The study identified roughly 732,000 exposed people living in poverty, primarily in the central and southern Appalachians.
In contrast, at-risk properties in urban settings are more likely to be expensive hillside homes occupied by residents with greater financial means, often valued for their scenic views. However, dense development in these areas means a single landslide can affect numerous properties, and damage to emergency facilities like fire stations could disrupt rescue and recovery efforts.
Regional Hotspots
The Appalachian Highlands alone contain 3.6 million people living in highly susceptible areas, representing 55 percent of the national total. Exposure is concentrated from eastern Kentucky through western North Carolina, with additional high-risk zones in Pennsylvania's Ridge and Valley region. States like Pennsylvania, New York, Tennessee, North Carolina, and Virginia also have large exposed populations where the Appalachian terrain meets established communities.
Along the West Coast, Washington and Oregon show above-average exposure, particularly in areas along the Cascadia corridor. California recorded the largest absolute number of residents living in landslide-prone areas.
Understanding Landslide Triggers and Future Threats
Landslides already cause an estimated $3 billion to $6 billion in damage and multiple fatalities annually across the U.S. The primary triggers are intense rainfall and earthquakes, but human activities such as road construction and excavation can further destabilize vulnerable slopes. The threat is projected to increase as housing development expands onto unstable slopes and climate change intensifies rainfall patterns.
The study's findings were derived from a new database created by researchers at the University of Washington. They combined high-resolution U.S. Geological Survey susceptibility maps with building footprints, occupancy records, and Census data on factors like income and vehicle access. The database classified the terrain surrounding 128 million structures nationwide based on landslide susceptibility. Testing against verified landslides in Seattle and those associated with Hurricane Helene indicated the database's accuracy in identifying at-risk buildings, though it noted that debris can travel significant distances beyond the initial failure point.