Landslide / Rockslide

Banner image of a pile of rocks

Did you know that after fire flooding can cause debris flow and landslides?

Landslides are masses of rock, earth or debris moving down a slope. They are activated by rainstorms, earthquakes, fires and human-caused projects, such as construction. Landslides can vary widely in size and can move at slow or very high speeds depending on slope angle, water content and geologic characteristics of the ground both at the surface and at depth.  Flows are often initiated by heavy periods of rainfall, but can sometimes happen as a result of concentrated rainfall.  Land movement related to landslides, mud and debris flows, and rockfalls occur naturally across Colorado on an ongoing basis.  It is estimated that there are thousands of landslides in Colorado each year although the number, frequency, and severity fluctuate. Landslides constitute a major geologic hazard because they are widespread, occur in all 50 states and U.S. territories, cause $1-2 billion in damages and result in 25 to 50 fatalities on average each year. Expansion of urban and recreational developments into hillside areas leads to more people being exposed to the threat of landslides each year.

Note: Generally, landslide insurance is not available, but debris flow damage, in some cases may be covered by flood insurance policies from the National Flood Insurance Program (NFIP) at  Despite the risk, everyone can take steps to prepare for landslides and rockslides.  Explore the information below to learn more about landslide preparedness.

Before A Landslide / Rockslide
  • Do not build near steep slopes, close to mountain edges or near drainage ways or erosion valleys.
  • Get a ground assessment of your property.
  • Learn about the emergency response and evacuation plans for your area.
  • Minimize hazards around your home by installing flexible pipe fittings, building retaining walls or building channels to direct flow around buildings.
During a Landslide / Rockslide
  • Stay alert when driving during storms.
  • Be aware of weather conditions and remember that short bursts of rain,  particularly after longer periods of heavy rainfall and damp weather, can provide especially dangerous conditions.
  • Stay out of the path of a landslide or rockslide, no matter how slow the ground appears to be moving.  Debris flows can move quickly and it is best to treat them like floods and move to higher ground, if possible. 
  • Listen for any unusual sounds that might indicate moving debris, such as trees cracking or boulders knocking together. A trickle flow may precede the much larger event and many slides can onset rapidly.
  • If you are near a stream or channel, be alert for sudden changes in water levels or if the water changes from clear to muddy. Such changes indicate activity upstream and you should be prepared to move quickly.
  • Be especially alert when driving. Bridges may be washed out and boulders may be dislodged. Embankments upon roadsides and the base of high-angle, steep terrain is particularly susceptible to landslides and rockslides.
  • Contact your local fire, police or public works department immediately if you suspect or have witnessed a landslide.
  • Inform affected neighbors. Your neighbors, and particularly visitors to Colorado unfamiliar with mountain terrain, may not be aware of potential hazards. Advising them of the threat may help save their lives.
  • Evacuate any area you suspect of being involved in or imminently threatened by a landslide/rockslide.
  • If you are caught in a landslide/rockslide with no option to evacuate, curl in to a tight ball and protect your head.
After A Landslide / Rockslide
  • Stay away from the slide area. There may be danger of additional slides.
  • Contact local officials to provide information on the slide location and any injuries/conditions.
  • Listen to local radio or television stations or emergency management warning systems for information.
  • Watch for flooding, which may occur after a landslide or debris flow.
  • Check for injured and trapped persons near the slide, without entering the slide area. Stay on-site to direct rescuers to their locations.
  • Help anyone who may require special assistance. Elderly, families with young children and people with disabilities my benefit from additional help.
  • Look for and report any broken utility lines and damaged roadways and railways to appropriate authorities. Reporting potential hazards will help direct efforts to mitigate any additional hazards and injury.
  • Check building foundations, chimneys and surrounding land for damage.
  • Seek advice from experts to evaluate remaining or existing hazards or to design corrective techniques to reduce risk.
More Landslide / Rockslide Information

References, Resources and More Information:

Rockslide: It Happened Here

On March 8, 2010, a large rockfall in the Glenwood Canyon shut down Interstate 70. Twenty boulders, ranging from three feet to 10 feet in diameter, fell on the interstate. As they fell, these heavy rocks punched several holes through the roadway, including one that was 20 feet by 10 feet. The largest boulder weighed 66 tons! Crews were able to restore one lane in each direction within four days, eliminating the two-hour detour and preventing any long-term disruptions to tourism and the transportation industry.  Between maintenance, traffic control and repairs, the total cost of the incident was $2,180,000.

Cover photo courtesy of the Colorado Department of Transportation