Landslides and Mudslides

Landslides and mudslides are mass downhill movements of rock, earth or debris. Landslides are caused by disturbances in the natural stability of a slope. They can be caused by heavy rains, earthquakes or volcanic eruptions. Mudslides, also called Debris Flows are a common type of fast moving landslide that tends to flow in channels. Mudslides develop when water rapidly accumulates in the ground (heavy rainfall or thaw) and results in a surge of water-saturated rock, earth and debris. Remember landslides can occur weeks after an intense storm.

Areas that are prone to landslides:

  • Areas where wildfires or human modification of the land have destroyed vegetation
  • Areas where landslides have occurred before
  • Steep slopes and areas at the bottom of slopes or canyons
  • Channels along a stream or river
  • Areas where surface runoff is directed
  • Slopes that have been altered for construction of building and roads

Landslide warning signs:

  • Sudden increase and decreases in water level on a stream or creek
  • Look for tilted trees, poles, walls and fences and for new holes or bare spots on hillsides
  • If driving watch the road for collapsed pavement, sunken ground, mud, fallen rocks and other indications of possible debris flows.
  • Listen for unusual sounds (rumbling, trees cracking, boulders knocking together)

What to do:

  • Move quickly! Getting out of the path of a landslide is your best protection.
  • Head for a safer area – flat-lying area away from slopes and steep river banks or at the top or along the nose of ridges, set back from the tops of slopes.
  • If escape is not possible look for the nearest shelter and take cover. Curl into a tight ball and protect your head. This position will provide the best protection for your body.

After a landslide:

  • Stay away from the slide area. There may be danger of additional slides
  • Watch for flooding. Floods sometimes follow landslides and mudslides because they may both be started by the same event.