Landslides and debris flows are among the most geographically widespread natural hazards in the United States, occurring in all 50 states and causing billions of dollars in damage and dozens of deaths each year. While California, the Pacific Northwest, and Appalachia are particularly vulnerable, landslide risk exists wherever steep slopes, unstable soils, and water combine — which, given enough rainfall, can include almost anywhere with terrain. Ready.gov’s Landslide Hazard Information Sheet outlines the risk factors, warning signs, and protective actions that can save lives.
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What Causes Landslides?
A landslide is any rapid movement of earth, rock, or debris down a slope. Debris flows — sometimes called mudslides or mudflows — are landslides in which water-saturated soil and rock move very rapidly, often following drainage channels and valley floors at speeds that can reach 35 mph. Triggers include heavy or prolonged rainfall (the most common cause, particularly after wildfire removes vegetation), rapid snowmelt, earthquakes, volcanic eruptions, and human activities such as deforestation, construction, and mining that destabilize slopes.
Warning Signs of an Impending Landslide
Ready.gov identifies these warning signs to watch for during or after heavy rain or earthquakes:
- Doors or windows stick or jam for the first time
- New cracks appear in plaster, tile, brick, or foundations
- Outside walls, walks, or stairs begin pulling away from the building
- Slowly developing, widening cracks appear on the ground or on paved areas
- Underground utility lines break
- Bulging ground appears at the base of a slope
- Water breaks through the ground surface in new locations
- Fences, retaining walls, utility poles, or trees tilt or move
- You hear a rumbling sound that increases in volume (debris flows sound like freight trains)
Landslide Preparedness: Before an Event
- Know your risk. Contact your local planning or geologic survey office to find out if your property is in a landslide hazard zone. USGS publishes landslide hazard information at landslides.usgs.gov.
- Have contingency plans. Know multiple evacuation routes and identify high ground locations to move to if you cannot evacuate.
- Consult a professional. If you suspect your property is on an unstable slope, consult a licensed geotechnical engineer. Retaining walls and proper drainage systems can reduce risk.
- Plant ground cover. Vegetation is nature’s slope stabilizer. Plant erosion-resistant ground cover and trees on slopes around your property.
- Listen to local warnings. Sign up for emergency alerts and monitor local emergency broadcasts for landslide watches and warnings during intense rainfall events.
During a Landslide
- Move away quickly if you detect a landslide or debris flow approaching
- If evacuation is not possible, move to an upper floor of your building
- If outdoors, run to the nearest high ground away from the slide path — do not try to outrun a debris flow down a valley or drainage channel
- Curl into a tight ball and protect your head if caught in a debris flow
After a Landslide
- Stay away from the slide area — additional slides are common
- Check for injured and trapped people but do not enter the slide area yourself
- Report broken utility lines, blocked roads, and other hazards to authorities
- Allow professionals to assess structural damage before returning to buildings
How PubSafe Supports Landslide Response
Landslides often happen in areas where roads become impassable and traditional communication is disrupted. PubSafe enables communities to report slide locations and blocked roads in real time, helping neighbors and emergency responders navigate around hazards. PubSafe also supports coordination of search and rescue for missing or trapped community members, sharing of verified information about evacuation routes and open shelters, and safety status signaling so family members and responders know who is accounted for.
After the 2014 Oso, Washington mudslide — which killed 43 people — communities emphasized how critical real-time communication was in the chaotic hours after the disaster. PubSafe is designed to be that communication lifeline. Connect your community on PubSafe before landslide season arrives.
Resources
- Ready.gov Landslides page
- USGS Landslide Hazards: landslides.usgs.gov
Download the Ready.gov Landslide Hazard Information Sheet and assess your slope risk today. Then connect your community on PubSafe.
Landslide Risk Assessment and Land Use Planning
Preventing landslide disasters requires thoughtful land use planning that takes geologic hazards into account when approving new development. In the United States, land use decisions are primarily made at the local and state level, with significant variation in how rigorously geologic hazards are considered. Some states — particularly California and Washington — have robust regulatory frameworks requiring geologic hazard assessments before development in landslide-prone areas. Other states have minimal requirements, allowing development in high-risk zones with inadequate mitigation.
The USGS National Landslide Hazards Program provides science support for landslide risk assessment, including the development of national-scale landslide hazard maps and the operation of debris flow early warning systems in areas of elevated risk. In partnership with the National Weather Service, USGS operates a debris flow early warning system in burn areas (areas recently burned by wildfires), where the risk of post-fire debris flows is dramatically elevated during the first several years after a fire. These post-fire debris flow warnings are issued when rainfall intensities exceed thresholds determined through field measurements of burn scar hydrology.
If you own property in a landslide-prone area, consulting with a licensed geotechnical engineer before making significant investments in the property or planning major construction is strongly advised. A site-specific geotechnical investigation can identify specific risk factors on your property and recommend cost-effective mitigation measures. Many homeowners are surprised to find that relatively modest investments in drainage improvements and slope stabilization can significantly reduce their landslide risk.
Post-Wildfire Landslide Risk
The relationship between wildfires and landslides is one of the most important — and underappreciated — compound hazard relationships in the western United States. When a wildfire burns through a forested or shrub-covered slope, it removes the vegetation whose root systems help bind the soil and whose canopy reduces the intensity of rainfall at the soil surface. The result is dramatically increased susceptibility to debris flows during subsequent rain events. This elevated risk can persist for 3–5 years after a fire, until vegetation recovers sufficiently to re-stabilize slopes.
The 2018 Montecito, California debris flow — which killed 23 people just weeks after the Thomas Fire burned the slopes above the community — is a sobering example of the devastating potential of post-fire debris flows. Community members received evacuation orders, but many chose to shelter in place, unaware of how fast and how far debris flows can travel. The event underscored the importance of heeding evacuation orders in burn areas, even when rainfall seems modest by normal standards — because burned slopes respond to rainfall very differently than healthy vegetated slopes.
If you live downstream or downslope from a recent burn area, sign up for local emergency alerts, follow NWS debris flow watches and warnings during rain events, and have a rapid evacuation plan ready. And connect your community on PubSafe to ensure that warning information and evacuation updates reach every household in your community promptly — including those without traditional media access.
Taking the Next Step in Your Preparedness Journey
Preparedness is not a single action — it is an ongoing practice. Every time you review your emergency plan, check your supply kit, or connect a neighbor to a preparedness resource, you are building community resilience. The cumulative effect of thousands of individuals and families taking preparedness seriously is a community that absorbs shocks, recovers faster, and takes care of its most vulnerable members during the worst days.
Bookmark the relevant Ready.gov hazard page, download the Hazard Information Sheet, and share this article with your family, coworkers, and neighbors. Join the PubSafe network to stay connected with your community before, during, and after any emergency. Check your local emergency management agency’s website for preparedness resources specific to your region. And consider volunteering with local emergency response teams — CERT (Community Emergency Response Team), volunteer fire departments, and local emergency management councils all welcome community members who want to contribute to a more resilient community.
Emergency preparedness does not require perfection. Start where you are, with what you have. Each small step builds on the last, and the journey from being unprepared to being genuinely ready is shorter than most people think. Take one step today — for yourself, for your family, and for your community.
