Landslides

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Landslides occur in all U.S. states and territories. In a landslide, masses of rock, earth, or debris move down a slope. Landslides may be small or large and can be activated by storms, earthquakes, volcanic eruptions, fires, and human modification of land.

Debris and mud flows are like rivers of rock, earth, and other debris saturated with water. They develop when water rapidly accumulates in the ground during heavy rainfall or rapid snowmelt. They can flow quickly, strike with little or no warning at high speeds, and grow in size due to debris as they flow.

Before a Landslide or Debris Flow
  • Do not build near steep slopes, close to mountain edges, near drainage ways, or natural erosion valleys.
  • Get a ground assessment of your property.
  • Consult an appropriate professional expert for advice on corrective measures.
  • Minimize home hazards by having flexible pipe fittings installed to avoid gas or water leaks, as flexible fittings are more resistant to breakage (only the gas company or professionals should install gas fittings).
Landslide Warning Signs
  • Changes occur in your landscape such as patterns of storm-water drainage on slopes (especially the places where runoff water converges) land movement, small slides, flows, or progressively leaning trees.
  • 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 such as streets or driveways.
  • 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.
  • A faint rumbling sound that increases in volume is noticeable as the landslide nears.
  • The ground slopes downward in one direction and may begin shifting in that direction under your feet.
  • Unusual sounds, such as trees cracking or boulders knocking together, might indicate moving debris.
  • Collapsed pavement, mud, fallen rocks, and other indications of possible debris flow can be seen when driving (embankments along roadsides are particularly susceptible to landslides).
  • If you suspect imminent landslide danger:
  • Contact your local fire, police, or public works department. Local officials are the best persons able to assess potential danger.
  • Inform affected neighbors. Your neighbors may not be aware of potential hazards. Advising them of a potential threat may help save lives.
  • Help neighbors who may need assistance to evacuate.
  • Evacuate. Getting out of the path of a landslide or debris flow is your best protection.
During a Landslide or Debris Flow
  • Move away from the path of a landslide or debris flow as quickly as possible.
  • Curl into a tight ball and protect your head if escape is not possible.
After a Landslide or Debris Flow
  • Stay away from the slide area. There may be danger of additional slides.
  • Check for injured and trapped persons near the slide, without entering the direct slide area. Direct rescuers to their locations.
  • Watch for associated dangers such as broken electrical, water, gas, and sewage lines and damaged roadways and railways. Look for and report broken utility lines to appropriate authorities.
  • Replant damaged ground as soon as possible since erosion caused by loss of ground cover can lead to flash flooding and additional landslides in the near future.
  • Help a neighbor who may require special assistance--infants, elderly people, and people with disabilities. Elderly people and people with disabilities may require additional assistance. People who care for them or who have large families may need additional assistance in emergency situations.
  • Listen to local radio or television stations for the latest emergency information.
  • Watch for flooding, which may occur after a landslide or debris flow. Floods sometimes follow landslides and debris flows because they may both be started by the same event.
  • Check the building foundation, chimney, and surrounding land for damage. Damage to foundations, chimneys, or surrounding land may help you assess the safety of the area.
  • Seek advice from a geotechnical expert for evaluating landslide hazards or designing corrective techniques to reduce landslide risk.

 

 Publications:

A Homeowner's Guide to Landslides for Washington and Oregon

 

 

The Hazard-Specific Information section was created using information from the Federal Emergency Management Agency and American Red Cross.