Landslide Risk in the US: How FEMA Scores It and How to Prepare

Landslides are the National Risk Index’s most underestimated hazard — they occur in all 50 states, cause an estimated $1–2 billion in annual damage nationally, and kill 25–50 Americans in a typical year, yet they carry no dedicated insurance market and often no warning system. The 2014 Oso, Washington slide killed 43 people in a valley mapped as hazardous decades earlier; the 2018 Montecito debris flows killed 23 in the first big rain after a wildfire. In the NRI, landslides (hazard code LNDS) account for roughly $250 million in national expected annual loss, with measurable risk in all 3,143 counties.

What counts as landslide risk

The NRI’s landslide hazard covers the downhill movement of rock, soil, and debris — from slow-creeping slumps that crack foundations over years to debris flows, the fast, deadly variety: slurries of mud, boulders, and trees moving at 30+ mph down channels. The recipe is almost always the same three ingredients: steep slopes, weak or saturated material, and a trigger — usually intense or prolonged rain, sometimes earthquakes, snowmelt, or human earthwork (undercut slopes, leaking pipes, added fill).

The most predictable subtype is the post-wildfire debris flow: burned soil sheds water like pavement, so for 2–5 years after a fire, even a modest downpour on a burn scar can launch a flow. This is now a routine, forecastable emergency in the West — Montecito was exactly this.

How the NRI measures it

FEMA combines each county’s exposure in landslide-susceptible terrain (buildings and population), annualized landslide frequency, and historic loss ratios into an Expected Annual Loss scored 0–100 against all counties. Note that the underlying loss records are widely considered incomplete — landslide damage is often filed under the triggering storm — so the NRI’s totals here are conservative.

Where the risk concentrates

The top of the ranking is the Pacific coast: Santa Barbara County, CA leads (score 100, ~$51M expected annual loss — Montecito’s county, logging ~60 slide events/year), with Snohomish County, WA (Oso’s county, ~$25M), San Bernardino County, CA, Monterey County, CA (Big Sur’s perpetually sliding coastline, ~130 events/year in the data), and Island County, WA (Puget Sound’s collapsing coastal bluffs). Beyond the top five, high ratings follow the Appalachians — eastern Kentucky, West Virginia, western North Carolina (where Helene’s 2024 rains triggered thousands of slides) — plus Colorado’s canyons and Alaska.

How to read your county’s score

Landslide risk is the most parcel-specific hazard in the index after wildfire: county scores flag regions, but your risk lives in your slope, your soil, and what’s uphill of you. The questions that matter: Are you on, above, or below a steep slope or in a canyon mouth? Has the area burned recently? Do your state or county publish landslide-susceptibility maps (Washington, Oregon, California, and North Carolina do)? And know the insurance reality: standard homeowners policies exclude earth movement — coverage requires a separate “difference in conditions” policy, and few homeowners have one.

What actually reduces the risk

• Learn the warning signs on your property: new cracks in foundations, driveways, or soil; doors and windows sticking; tilting trees, poles, or fences; new springs or seeps on a slope; bulging ground at a slope’s base. These are how slow failures announce themselves — get a geotechnical engineer promptly.
• Control the water. Most residential slides are water-triggered: keep gutters, downspouts, and drains discharging away from slopes, fix leaking irrigation and pipes, and never let runoff concentrate onto a hillside.
• Respect burn scars. If you live below one, treat every NWS debris-flow warning as an evacuation order for the 2–5 years after the fire — flows arrive too fast to outrun.
• During intense rain in steep terrain, stay alert to the sounds of a flow (cracking, rumbling, boulders knocking) and move up-slope or to upper floors; canyon bottoms and channel mouths are the kill zones.
• Before buying in hill country: check susceptibility maps, look for repaired cracks and retaining walls on the property, and ask about slide history in disclosures — mitigation after purchase (retaining structures, dewatering) costs tens to hundreds of thousands.

Sources

• USGS Landslide Hazards Program — national susceptibility maps
• FEMA NRI landslide methodology
• NWS/USGS post-fire debris flow warnings
• Ready.gov landslide safety