Landslides and Debris Flow

  • Landslides, also known as debris or mud flow can occur in all U.S. states and territories. 
  • They are often caused by storms, earthquakes, fires, and volcanoes.  However, they can also occur due to seasonal rainfall or erosion.  Debris and mud flows are 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, changing the earth into a flowing river of mud or “slurry.”
  • They can flow rapidly, striking with little or no warning at avalanche speeds.
  • They also can travel several miles from their source, growing in size as they pick up trees, boulders, cars, and other materials.

Learn more about landslide preparedness here.

During a landslide or debris flow....

  • Listen to a NOAA Weather Radio, or portable, battery-powered radio or television for warnings of intense rainfall. Be aware that intense, short bursts of rain may be particularly dangerous, especially after longer periods of heavy rainfall and damp weather.
  • Have an Emergency Supply Kit and Household Disaster Plan in place.
  • Stay alert and awake. Many debris-flow fatalities occur when people are sleeping.
  • If you are in areas susceptible to landslides and debris flows, consider leaving if it is safe to do so. Remember that driving during an intense storm can be hazardous. If you remain at home, move to a second story if possible. Staying out of the path of a landslide or debris flow saves lives.
  • Listen for any unusual sounds that might indicate moving debris, such as trees cracking or boulders knocking together. A trickle of flowing or falling mud or debris may precede larger landslides. Moving debris can flow quickly and sometimes without warning.
  • If you are near a stream or channel, be alert for any sudden increase or decrease in water flow and for a change from clear to muddy water. Such changes may indicate landslide activity upstream, so be prepared to move quickly. Don't delay! Save yourself, not your belongings.
  • Be especially alert when driving. Embankments along roadsides are particularly susceptible to landslides. Watch the road for collapsed pavement, mud, fallen rocks, and other indications of possible debris flows.

If you suspect imminent lanslide 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.
  • Curl into a tight ball and protect your head if escape is not possible.

Terms

Familiarize yourself with these terms to help identify a landslide.

  • mudflow - a general term for a mass-movement landform and process characterized by a flowing mass of fine-grained earth material with a high degree of fluidity. The water content may range up to 60%; also spelled mudflow
  • mudslide - an imprecise but popular term coined in California, USA, frequently used by laymen and the news media to describe a wide scope of events, ranging from debris-laden floods to landslides. Not technically correct.