Landslides are masses of rock, earth, or debris moving down a slope. They are activated by rainstorms, earthquakes, fires and by human-caused projects, such as road/building construction. Landslides can vary widely in size and can move at slow or very high speed depending on slope angle, water content, and type of earth and debris flow. Flows are generally initiated by heavy, usually sustained, periods of rainfall, but can sometimes happen as a result of shorts bursts of concentrated rainfall. Burned areas, such as from wildland fires, are also susceptible to debris flows.
Landslide/Rockslide Warning Signs
- Springs, seeps, or saturated ground in areas that not typically been wet before
- New cracks or unusual bulges in ground, street pavements or sidewalks
- Soil moving away from foundations or tree root systems
- Titling or cracking of concrete floors and foundations
- Structures such as decks and patios tilting and/or moving relative to the main house
- Broken water lines and other underground utilities
- Leaning telephone poles, trees, retaining walls or fences
- Offset fence lines
- Sunken or down-dropped road beds
- Rapid increase in creek water levels, possibly accompanied by increased water soil content
- Sudden decrease in creek water levels through rain is still falling or just recently stopped
- Sticking doors and windows, and suddenly appearing open spaces in frames or construction
- Faint rumbling sound that increases in volume as the landslide nears
- Unusual sounds, such as trees cracking or boulders knocking together
Areas generally prone to landslide hazards
- Existing old landslide paths
- On or at the base of slopes
- In or at the base of minor drainage hollows
- At the base or top of an old fill slope
- At the base or top of a steep cut slope
- Developed hillsides where leach field septic systems are used
Before a Landslide/Rockslide - House
- Do not build near steep slopes, close to mountain edges, near drainage ways or erosion valleys
- Get a ground assessment of your property
- Contact local officials, the Colorado Geological Survey (http://geosurvey.state.co.us/) or the Colorado Department of Natural Resources (http://dnr.state.co.us/)
- Watch the patterns of storm-water drainage near your home and note the convergence locations
- Learn about the emergency response and evacuation plans for your area. Check with your local emergency manager (http://dola.colorado.gov/dem/localem.htm) for emergency information specific to your area, including local preparedness information, warning systems and sources of information in the event of a disaster.
- Minimize hazards around your home by installing flexible pipe fittings, planting ground cover on slopes, building retaining walls, or channels to direct flow around buildings.
During a Landslide/Rockslide
- Stay alert when driving or around your house during storms. Debris-flow fatalities occer in the home when people are sleeping during storms and on the roadways when fast moving material impacts the road. When driving, remember to look around and up when in mountain areas.
- Be aware of weather conditions and remember that short burst of rain, particularly after longer periods of heavy rainfall and damp weather, can be especially dangerous conditions conducive to landslides/rockslides
- Stay out of the path of a landslide or rockslide, no matter how slow the ground appears to be moving
- 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, culverts overtopped and boulders may be dislodged. Embankments upon roadsides and the base of high-angle, steep terrain are 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. You neighbors, and particularly visitors to
unfamiliar with mountain terrain, my not be aware of potential hazards. Advising them of the threat may help save their lives. Colorado
- Evacuate any area you suspect of being involved in or imminently threatened by a landslide/rockslide
- If in 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 info
- Watch for flooding, which may occur after a landslide or debris flow. Floods are often tandem with landslides/rockslides since they may share a root cause
- 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 the 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.
- Replant damaged ground as soon as possible since erosion caused by loss of ground cover can lead to additional flooding, landslides/rockslides.
- Seek advice from experts to evaluate remaining or existing hazards or to design corrective techniques to reduce risk. Contact local emergency management officials, the the Colorado Geological Survey (http://geosurvey.state.co.us/) or the Colorado Department of Natural Resources (http://dnr.state.co.us/) for more.
And for much, much more on landslide/rockslide issues, history and safety, be sure to check out the source for most of the above safety tips, the United States Geological Survey's outstanding landslide information website at http://landslides.usgs.gov/learning/ls101.php