hazard identification and vulnerability analysis - Mason County

locks of rock moving slowly down slope are sometimes called block
glides.
• Deep-seated landslides are slides in which the sliding surface is mostly
deeply located below the maximum rooting depth of trees. Deep-seated
landslides usually involve loose dust, soil, broken / weathered rock, and/or
bedrock and include large slope failure associated with translational,
rotational, or complex movement.
CONCLUSIONS
Washington is one of seven states listed by the Federal Emergency Management
Agency as being especially vulnerable to severe land stability problems.
Earthquakes combined with heavy precipitation may increase risk for those
previously thought to be on stable ground.
With population increasing and demanding “view” property and tree removal to
be able to “see the view” there is increasing risk of landslides in residential areas.
Those buildings on steep slopes and bluffs are at risk in seasons of heavy rains
or prolonged wet spell. The property below the landslide is also at risk.
Landslide, mudflow and debris flow problems are often complicated by problems
of land management. By studying the effects of landslides in slide-prone regions,
plans for the future can be made and the public may be educated to prevent
development in vulnerable areas. Applying established ordinances where
geological hazards have been identified will prevent some landslide losses.
However, Mason County already has many areas above or below unstable
slopes that have established houses and businesses. Careful maintenance of
vegetation on slopes, prevention of erosion, and engineered drainage of slopes
and mitigation using qualified expertise is necessary to protect these areas.
RESOURCES
Federal Emergency Management Agency
National Weather Service
United States Army Corps of Engineers
Washington State Department of Natural Resources
Washington State Department of Ecology
ATTACHMENTS
Highway 101 Major Slide Areas
Major Slide Areas Along North Shore Road
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