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Landslides occur in all U.S. states and
territories. In a landslide, masses of
rock, earth, or debris move down a slope.
Landslides may be small or large, slow
or rapid. They are activated by storms,
earthquakes, volcanic eruptions, fires,
and human modification of land.
Debris and mud flows are rivers of rock,
earth, and other debris saturated with
water. They develop when water rapidly
accumulates in the ground, during heavy
rainfall or rapid snowmelt, changing the
earth into a fl owing river of mud or “slurry.” They
flow can rapidly, striking with little
or no warning at avalanche speeds. They
also can travel several miles from their
source, growing in size as they pick up
trees, boulders, cars, and other materials.
Landslide problems can be caused by land
mismanagement, particularly in mountain,
canyon, and coastal regions. Land-use zoning,
professional inspections, and proper design
can minimize many landslide, mudflow, and
debris flow problems.
Before a Landslide or Debris Flow
The following are steps you can take
to protect yourself from the effects
of a landslide or debris flow:
- Do not build near steep slopes,
close to mountain edges, near drainage
ways, or natural erosion valleys.
- Get a ground assessment of your
property.
- Consult an appropriate professional
expert for advice on corrective measures.
- Minimize home hazards by having
flexible pipe fittings installed
to avoid gas or water leaks, as flexible fittings
are more resistant to breakage (only
the gas company or professionals should install
gas fittings).
- Changes occur in your landscape
such as patterns of storm-water drainage
on slopes (especially the places
where runoff water converges) land movement,
small slides, flows, or progressively
leaning trees.
- Doors or windows stick or jam for
the first time.
- New cracks appear in plaster, tile,
brick, or foundations.
- Outside walls, walks, or stairs
begin pulling away from the building.
- Slowly developing, widening cracks
appear on the ground or on paved
areas such as streets or driveways.
- Underground utility lines break.
- Bulging ground appears at the base
of a slope.
- Water breaks through the ground
surface in new locations.
- Fences, retaining walls, utility
poles, or trees tilt or move.
- A faint rumbling sound that increases
in volume is noticeable as the landslide
nears.
- The ground slopes downward in one
direction and may begin shifting
in that direction under your feet.
- Unusual sounds, such as trees cracking
or boulders knocking together, might
indicate moving debris.
- Collapsed pavement, mud, fallen
rocks, and other indications of possible
debris flow can be seen when driving
(embankments along roadsides are particularly susceptible
to landslides).
During a Landslide or Debris Flow
The following are guidelines for what you
should do if a landslide or debris flow
occurs:
- Move away from the path of a
landslide or debris flow as quickly as
possible.
- Curl into a tight ball and protect
your head if escape is not possible.
After a Landslide or Debris Flow
The following are guidelines for the period
following a landslide:
- Stay away from the slide area.
There may be danger of additional slides.
- Check for injured and trapped persons
near the slide, without entering the
direct slide area. Direct rescuers to their locations.
- Watch for associated dangers such
as broken electrical, water, gas, and
sewage lines and damaged roadways and railways.
- Replant damaged ground as soon as
possible since erosion caused by loss
of ground cover can lead to fl ash flooding
and additional landslides in the near
future.
- Seek advice from a geotechnical expert
for evaluating landslide hazards or
designing corrective techniques to reduce landslide
risk
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