Landslides occur when slopes become unstable and masses of rock, earth, or debris move downhill. They can be triggered by rainfall, earthquakes, volcanic activity, or human modifications to slopes. While some landslides move slowly over days, others strike suddenly without warning, traveling at high speeds.
Areas with steep slopes, previous slide activity, or certain soil types face higher risk. Heavy rainfall is the most common trigger. Understanding your local risk and knowing warning signs provides the best protection in landslide-prone areas.
Understanding Your Risk
High-risk locations: Steep slopes, canyon areas, areas below slopes, near stream channels, areas with previous landslide activity, and areas where slopes have been modified by construction or road cuts.
Triggers: Heavy or prolonged rainfall (most common), rapid snowmelt, earthquakes, volcanic activity, and changes to drainage patterns. Risk increases significantly during and after heavy rain events.
Know your area: Contact local emergency management or geological surveys for landslide hazard maps. Previous landslide activity strongly indicates future risk. Examine your property for signs of past movement.
Warning Signs
Landslides often provide warning signs before failure. Recognizing these can provide time to evacuate.
Ground changes: New cracks in ground, walls, or pavement. Tilting trees, fences, or utility poles. Bulging ground at base of slopes. Ground settling or dropping.
Water signs: New springs or seeps. Changes in water flow in streams. Sudden decrease in stream water level despite rain (may indicate blockage uphill).
Structural signs: Doors or windows sticking for first time. Visible gaps where structures meet ground. Cracks in foundations.
Sounds: Unusual sounds of cracking, snapping trees, or boulders knocking together may indicate moving debris.
Preparation
Assess your property: Identify potential slide areas. Consider professional geotechnical evaluation if you have concerns. Understand drainage patterns.
Manage drainage: Direct surface water away from slopes. Maintain drainage systems. Do not increase water flow onto unstable slopes.
Vegetation: Maintain ground cover. Plant roots help stabilize soil. Avoid removing vegetation from slopes without professional guidance.
Emergency planning: Know evacuation routes that do not cross slide-prone areas. Have go-bag ready. Know how to receive emergency alerts.
During Landslide Threat
Evacuate if ordered or if you observe warning signs. Do not wait for official orders if you believe a slide is imminent.
If evacuating: Leave immediately. Take the route least likely to cross potential slide paths. Do not attempt to cross flowing debris.
If trapped: Move to upper floor or highest ground. Curl into tight ball and protect your head if debris approaches.
After heavy rain: Stay alert even after rain stops. Landslides can occur hours or days after heavy rainfall as water percolates through soil.
After a Landslide
Stay away from slide area. Additional slides may occur. The area remains unstable.
Report damage to authorities. Downed utility lines, blocked roads, and structural damage should be reported.
Do not enter damaged buildings until inspected. Structural integrity may be compromised even if damage is not obvious.
Watch for flooding. Landslides can block streams creating temporary dams that may burst.
Landslide Preparedness Checklist
- Local landslide risk assessed
- Property evaluated for slope stability
- Drainage properly directed away from slopes
- Warning signs known
- Evacuation route planned avoiding slide zones
- Emergency kit ready
- Alert systems enabled
- Insurance coverage reviewed
Frequently Asked Questions
How fast do landslides move?
Varies enormously. Some creep inches per year. Debris flows can move over 35 mph. Assume any slide is fast enough to be dangerous.
Will my insurance cover landslide damage?
Standard homeowner's policies often exclude landslides. Separate coverage may be needed. Review your policy and discuss with your agent.
Can I prevent landslides on my property?
You can reduce risk through proper drainage, vegetation, and avoiding slope modifications. Major stabilization requires professional engineering.
When is landslide risk highest?
During and after heavy or prolonged rainfall. Also during rapid snowmelt, after earthquakes, and following wildfires (which remove stabilizing vegetation).
Should I evacuate during heavy rain if I live on a hill?
If you observe warning signs or authorities issue evacuation orders, yes. If you have previously identified high risk on your property, consider precautionary evacuation during extreme rain events.
Disclaimer: This guide provides general educational information. For property-specific concerns, consult geotechnical professionals. Follow local emergency guidance.