Landslides and Mudslides
Landslides occur when masses of rock, earth or
debris move down a slope. Mudslides, also known as debris flows or mudflows, are
a common type of fast-moving landslide that tends to flow in channels.
For more information, visit Mudslide Infographic.
What Causes Landslides
and Mudslides?
Landslides are caused by disturbances in the
natural stability of a slope. They can happen after heavy rains, droughts,
earthquakes or volcanic eruptions. Mudslides develop when water rapidly collects
in the ground and results in a surge of water-soaked rock, earth and debris.
Mudslides usually begin on steep slopes and can be triggered by natural
disasters. Areas where wildfires or construction have destroyed vegetation on
slopes are at high-risk landslides during and after heavy rains.
Health Threats from
Landslides and Mudslides
In the United States, landslides and mudslides
result in 25 to 50 deaths each year. The health hazards associated with
landslides and mudslides include:
Rapidly moving water and debris that can lead to
trauma.
Broken electrical, water, gas and sewage lines that can
result in injury or illness.
Disrupted roadways and railways that can endanger motorists
and disrupt transport and access to health care.
What Areas Are at
Risk?
Some areas are more likely to experience
landslides or mudslides, including:
Areas where wildfires or construction have destroyed
vegetation.
Areas where landslides have occurred before.
Steep slopes and areas at the bottom of slopes or
canyons.
Slopes that have been altered for construction of buildings
and roads.
Channels along a stream or river.
Areas where surface runoff is directed.
Protect
Yourself
Before Intense Storms and
Rainfall
Assume that steep slopes and areas burned by wildfires are
vulnerable to landslides and mudslides.
Learn whether landslides or mudslides have occurred
previously in your area by contacting local authorities, a county geologist or
the county planning department, state geological surveys or departments of
natural resources or university departments of geology.
Contact local authorities about emergency and evacuation
plans.
Develop emergency and evacuation plans for your family and
business.
Develop an emergency communication plan in case family
members are separated.
If you live in an area vulnerable to landslides, consider
leaving it.
During Intense Storms and
Rainfall
Listen to the radio or watch TV for warnings about intense
rainfall or for information and instructions from local officials.
Be aware of any sudden increase or decrease in water level
on a stream or creek that might indicate debris flow upstream. A trickle of
flowing mud may precede a larger flow.
Look for tilted trees, telephone poles, fences or walls,
and for new holes or bare spots on hillsides.
Listen for rumbling sounds that might indicate an
approaching landslide or mudslide.
Be alert when driving. Roads may become blocked or closed
due to collapsed pavement or debris.
If you see a landslide or mudslide starting, quickly move
away from the path of the slide. Getting out of the path of a mudslide is your
best protection. Move to the nearest high ground in a direction away from the
path. If rocks and debris are approaching, run for the nearest shelter and take
cover (under a desk, table or other piece of sturdy furniture).
After a Landslide or
Mudslide
Stay away from the site. Flooding or additional slides may
occur after a landslide or mudslide.
Check for injured or trapped people near the affected area,
if it is possible to do so without entering the path of the landslide or
mudslide.
Listen to the radio or TV for emergency information.
Report broken utility lines to the appropriate
authorities.
Consult a geotechnical expert (a registered professional
engineer with soils engineering expertise) for advice on reducing additional
landslide problems and risks. Local authorities should be able to tell you how
to contact a geotechnical expert.
For more information visit:
CDC Fact Sheet on Mudslides
American Red Cross Fact Sheet
US Geological Survey (PDF)