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Which areas in a community have the greatest landslide
hazard? This is a very important question to consider
when creating a community development plan. In general,
landslides occur more frequently on steep slopes than
in level areas. In addition they also occur more frequently
where the surface soil has a low shear strength. The
areas with the greatest landslide hazard are generally
those where low shear strength soils are found on
steep slopes. Evidence of past landslide activity
will usually support this this approach for identifying
hazard areas.
Dr. Peter Lessing of the West Virginia Geological
and Economic Survey prepared some of the earliest
landslide hazard maps. A portion of his map for the
Clarksburg, West Virginia area is shown above. To
create this map, Dr. Lessing identified areas with
steep slopes which are underlain by shale bedrock
(shale bedrock typically yields clay-rich soils of
low shear strength). The areas on the map with the
red dot pattern are the landslide hazard areas (where
steep slopes are underlain by shale bedrock). Also
shown are recent and older landslides. Dr. Lessing's
maps have been used as models for may other landslide
hazard mapping projects.
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