|Learn if landslides,
including debris flows, could occur in your area by contacting
local officials, your state geological survey or department of natural
resources, or the geology department of a state university. Get information on
specific locations that are vulnerable to landslides. Request a professional
referral for a detailed landslidevulnerability analysis of your property, and
take corrective measures if necessary.
Why talk about landslides?
a serious geologic hazard that occurs in almost all 50 states. Every year in the
United States, they cause significant damages and 25 to 50 deaths. Globally,
landslides cause billions of dollars in damages and thousands of deaths and
injuries each year.
Debris flows—“muddy” or “liquefied” landslides—are
most destructive when they are caused by volcanic eruptions. A spectacular
example of a massive debris flow resulted from the 1980 eruptions of Mount St.
Helens in Washington State. Areas near the bases of many volcanoes in the
Cascade Mountain Range of California, Oregon, and Washington are at risk from
the same type of flows during future volcanic eruptions.
Wildfires can also lead
to destructive debris flows. In July 1994, a severe wildfire swept Storm King
Mountain in Colorado, denuding the slopes of vegetation. Heavy rains on the
mountain in September resulted in numerous debris flows, one of which blocked
Interstate 70 and threatened to dam the Colorado River.
What are landslides, and
what causes them?
“landslide” describes many types of downhill earth movements ranging from
rapidly moving catastrophic rock avalanches and debris flows in mountainous
regions to more slowly moving earth slides. Some landslides move slowly and
cause damage gradually, whereas others move so rapidly that they can destroy
property and take lives suddenly and unexpectedly. Gravity is generally the
force driving landslide movement. Factors that trigger landslide movement
include heavy rainfall, erosion, poor construction practices, freezing and
thawing, earthquake shaking, and volcanic eruptions. Landslides are typically
associated with periods of heavy rainfall or rapid snowmelt and tend to worsen
the effects of flooding. Areas burned by forest and brush fires are particularly
susceptible to landslides.
Debris flows—sometimes referred to as
mudslides, mudflows, lahars, or debris avalanches—are common types of
fast-moving landslides. These flows generally occur during periods of heavy
rainfall or rapid snowmelt. They usually start on steep hillsides as shallow
landslides that liquefy and accelerate to speeds that are typically about 10
miles (16 kilometers) per hour, but can exceed 35 miles (56 kilometers) per
consistencies of debris flows range from watery mud to thick, rocky mud that can
carry such large items as boulders, trees, and cars. Debris flows from many
different sources can combine in channels, and, when this happens, their
destructive power can increase greatly as they flow downhill and through
channels, growing in volume with the addition of water, sand, mud, boulders,
trees, and other materials. When the flows reach flatter ground, the debris
spreads over a broad area, sometimes accumulating in thick deposits that can
wreak havoc in developed areas.
How do landslides affect
cause property damage, injury, and death and adversely affect a variety of
resources. For example, water supplies, fisheries, sewage disposal systems,
forests, dams, and roadways can be affected for years after a slide
The negative economic effects of landslides include the cost to
repair structures, loss of property value, disruption of transportation routes,
medical costs in the event of injury, and indirect costs, such as lost timber
and fish stocks. Water availability, quantity, and quality can be affected by
landslides. Geotechnical studies and engineering projects to assess and
stabilize potentially dangerous sites can be costly.
How can I protect myself
generally happen where they have occurred in the past, and in identifiable
hazard locations. Areas that are prone to landslides include existing old
landslides, the bases of steep slopes, the bases of drainage channels, and
developed hillsides where leach-field septic systems are used.
are typically considered safe from landslides include areas that have not moved
in the past; relatively flat areas away from sudden changes in slope; and areas
at the top of or along ridges, but set back from the edge of
People can reduce their personal risk by learning about potential
local landslide hazards and taking steps to reduce those
Landslides are usually isolated events occurring without public
warning. If you live in a landslide-prone area, be alert, particularly during
periods of heavy rainfall or snowmelt or after a wildfire. If you see signs of a
landslide or suspect a landslide may occur, you yourself must make the decision
What is the best source of
information in a landslide situation?
The best source
of information in a landslide situation is a local radio or television
Prepared for a Landslide
CORE ACTION MESSAGES
• Determine your risk.
Prepare members of your household.
• Consult an expert and correct potential
• Be alert to changes and patterns in the land.
preparedness, every household should create and practice a Family Disaster Plan
and assemble and maintain a Disaster Supplies Kit. In addition, every household
at risk from landslides should take landslide-specific precautions and plan for
and practice what to do if a landslide occurs.
If you are at
risk from landslides, you should:
• Develop an evacuation plan.
If your home
could be damaged in a landslide, you should know where to go if you have to
leave. Making plans at the last minute can be upsetting, create confusion, and
waste precious time. Contact local authorities to learn about the emergency
response and evacuation plans for your area and develop your own emergency plans
for your family and business.
• Familiarize yourself with
the land around you. Knowing the
land can help you assess your risk.
• Watch the patterns of storm
water drainage on slopes near your home and especially
the places where runoff water converges, increasing flow over soilcovered
slopes. Watch the hillsides around your home for any signs of land movement,
such as small landslides or debris flows, or progressively tilting trees.
Noticing small changes could alert you to an increased threat of a
• Discuss landslides and
debris flows with members of your household. Everyone should
know what to do to stay safe if one occurs.
• Be aware that, generally,
landslide insurance is not available; however, in
some cases, debris flow damage may be covered by flood insurance policies from
the National Flood Insurance Program (NFIP) (www.fema.gov/nfip).
What to Do During Severe Storms,
Which Can Trigger Landslides
| CORE ACTION MESSAGES
• Monitor local news.
• Look and listen for signs of landslide.
During a severe storm, if
you are in an area susceptible to landslides, you
• Stay alert and awake.
fatalities occur when people are sleeping.
• Listen to local stations on
a portable, battery-powered radio or television or to NOAA Weather Radio
for warnings of
heavy rainfall. Be aware that short bursts of heavy rain may be particularly
dangerous, especially after longer periods of heavy rain and damp
• Consider leaving if it is
safe to do so. Remember that
driving during a severe storm can be hazardous. If you remain at home, move to a
second story if possible. Staying out of the path of a landslide or debris flow
can save your life.
• Listen for any unusual
sounds that might indicate moving debris, such as trees cracking or boulders
knocking together. A trickle of
flowing or falling mud or debris may precede a large landslide. Moving debris
can flow quickly and sometimes without warning.
• If you are near a stream or
channel, be alert for any sudden increase or decrease in water flow and for a
change from clear to muddy water. Such changes
may indicate landslide activity upstream, so be prepared to move quickly. Act
quickly. Save yourself, not your belongings.
• Be especially alert when
along roadsides are particularly susceptible to landslides. Watch the road for
collapsed pavement, mud, fallen rocks, and other indications of a possible
• Bring your companion animals
indoors and maintain direct control of them. Be sure that
your pet disaster kit is ready to go, along with your family disaster kit,
should you need to evacuate.
• Consider a precautionary
evacuation of large or numerous animals. If you think an
evacuation might be advised or ordered and if you have large, unusual, or
numerous animals, start evacuating them as soon as you are aware of impending
danger. If you are using a horse or other trailer to evacuate your animals, move
early rather than wait until it may be too late to maneuver a trailer through
slow traffic. Road hazards may make this too dangerous for you and for
• If you are ordered to or
decide to evacuate, take your animals with you. If it is not
safe for you, it is not safe for your animals.
What to Do if You Suspect Imminent Landslide
| CORE ACTION MESSAGES
• Contact local officials.
• Inform your neighbors.
• Get out.
If you learn or suspect that
a landslide is occurring or about to occur in your area, you
• Contact your local fire,
police, or public works department. Local officials
are the people best able to assess the potential danger.
• Inform affected neighbors.
may not be aware of the potential hazard. Advising them of a threat may help
save lives. Help neighbors who may need assistance to
• Leave. Getting out of
the path of a landslide or debris flow is your best protection. Take your pets
with you when you leave, provided you can do so without endangering
What to Do During a Landslide
| CORE ACTION MESSAGE
• Get out of the landslide’s
If a landslide occurs, you
• Quickly move out of the path
of the landslide. Moving away
from the path to a stable area will reduce your risk.
What to Do After a
| CORE ACTION MESSAGES
• Stay away from the slide
• Help others.
• Report hazards.
After a landslide, you
• Stay away from the slide
area. There may be
danger of additional slides.
• Check for injured and
trapped persons and animals near the slide, without entering the slide area.
to their locations.
• Help people who require
elderly people, those without transportation, large families who may need
additional help in an emergency situation, people with disabilities, and the
people who care for them.
• Listen to local stations on
a portable, battery-powered radio or television for the latest
• Watch for flooding,
which may occur
after a landslide or debris flow. Floods sometimes follow landslides and debris
• Look for and report broken
utility lines to appropriate authorities. Reporting
potential hazards will get the utilities turned off as quickly as possible,
preventing further hazard and injury.
• Check your home’s
foundation, chimney, and surrounding land for
• Replant damaged ground as
soon as possible because erosion
caused by loss of ground cover can lead to flash flooding.
Media and Community Education
• If your area is
prone to landslides, ask your local newspaper or radio or television station
-Do a series on the dangers of landslides and debris
-Do a story featuring interviews with local officials about land
use management, zoning regulations, and building codes for landslide
-Highlight the importance of staying alert to land and rainfall
-Run public service ads about how to protect lives and
property in a landslide.
-Report on what city and county governments are
doing to reduce the possibility of landslides.
Help the reporters to
localize the information by providing them with the local emergency telephone
number for the fire, police, and emergency medical services departments (usually
9-1-1) and emergency numbers for the local utilities and hospitals. Also provide
the business telephone numbers for the local emergency management office, local
American Red Cross chapter, and state geological survey or department of natural
• Work with
officials of the local fire, police, and emergency medical services departments;
utilities; hospitals; emergency management office; and American Red Cross
chapter to prepare and disseminate guidelines for people with mobility
impairments about what to do if they have to evacuate.
• Support your
local government in efforts to develop and enforce land use and building
ordinances that regulate construction in areas susceptible to landslides and
debris flows. Buildings should be located away from steep slopes, streams and
rivers, intermittent-stream channels, and the mouths of mountain
Facts and Fiction
Fiction: Landslides are
caused by the earth collapsing into a hole or a void.
exhibit vertical and horizontal movement down a slope, and most are triggered by
heavy rain and snowmelt, earthquake shaking, volcanic eruptions, and
caused by human activities such as logging, road construction, and farming on
Facts: Although human
activities may cause landslides on unstable slopes, most landslides are caused
by natural forces or events, such as heavy rain and snowmelt, earthquake
shaking, volcanic eruptions, and gravity.
occur only on the West Coast.
Facts: California and
the Pacific Northwest experience numerous landslides; however, landslides
also occur in most states and territories in the United States. The Appalachian
Mountain region on the East Coast, Puerto Rico, and Hawaii are highly
susceptible to landslides.