Landslides and Mudslides
What are landslides and debris flows?
when masses of rock,
earth, or debris move down a slope. Debris flows, also known as mudslides, are a
common type of fast-moving landslide that tends to flow in channels.
What causes landslides and debris flows?
are caused by disturbances in the natural stability of a slope. They can
accompany heavy rains or follow droughts, earthquakes, or volcanic eruptions.
Mudslides develop when water
rapidly accumulates in the ground and results in a surge of water-saturated
rock, earth, and debris. Mudslides usually start on steep slopes and can be
activated by natural disasters. Areas where wildfires or human modification of
the land have destroyed vegetation on slopes are particularly vulnerable to
landslides during and after heavy rains.
What are the health threats from landslides and debris flows?
In the United States,
landslides and debris flows result in 25 to 50 deaths each year. The health
hazards associated with landslides and mudflows 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; and
- 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 mudflows, including:
- 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
- Slopes that have been altered for construction of
buildings and roads;
- Channels along a stream or river; and Areas
where surface runoff is directed.
What you can do to protect yourself?
Before intense storms and rainfall:
- Assume that steep slopes and areas burned by
wildfires are vulnerable to landslides and debris flows.
- Learn whether landslides or debris flows 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
- Develop emergency and evacuation plans for your family and business.
- Develop an emergency communication plan in case
family members are separated.
you live in an area vulnerable to landslides, consider leaving it.
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 mudflow.
- Be alert when driving. Roads may become blocked or
closed due to collapsed pavement or debris.
- If landslide or debris flow danger is imminent,
quickly move away from the path of the slide. Getting out of the path of a
debris flow 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 (if possible, under a desk, table, or other piece of sturdy furniture).
After a landslide or debris
- Stay away from the site. Flooding or additional
slides may occur after a landslide or mudflow.
- 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
- Listen to the radio or TV for emergency information.
- Report broken utility lines to the appropriate
- 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.
Where you can get
additional information on landslide and mudflow hazards:
The Federal Emergency
Management Agency (FEMA) has a fact sheet containing information on landslides
and mudflows in the United States, as well as recommendations on how to prepare
and behave during and after a landslide.
The American Red Cross (ARC)
has a Web site containing information on
landslides and mudslides.
The United States Geological Survey (USGS) landslide news Web site
up-to-date information on recent and past landslide events.
For more emergency preparedness
please visit the MedicineNet.com
First Aid Channel.
Source: Centers for Disease Control
Last Editorial Review: 1/12/2005