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
• alternate freezing or thawing
• steepening of slopes by erosion or human
modification.
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 flowing river of mud or “slurry.” They
can flow 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. In areas burned
by forest and brush fires, a lower threshold
of precipitation may initiate landslides.
Land-use zoning, professional inspections,
and proper design can minimize many landslide,
mudflow, and debris flow problems.
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.
Contact local officials, state geological
surveys or departments of natural resources,
and university
departments of geology. Landslides occur
where they have before, and in identifiable
hazard
locations. Ask for information on landslides
in your area, specific information on areas
vulnerable to landslides, and request a
professional
referral for a very detailed site analysis
of your property, and corrective measures
you can take, if necessary.
If you are
at risk from a landslide talk to your insurance
agent. Debris flow may
be covered
by flood insurance policies from the
National Flood Insurance Program (NFIP).
Minimize
home hazards:
Have
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).
Plant ground cover on slopes and build retaining
walls.
In mudflow areas, build channels
or deflection walls to direct the flow
around buildings.
Remember: If you build
walls to divert debris flow and the flow
lands on a neighbor's
property,
you may be liable for damages.
Recognize
Landslide Warning Signs
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).
