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.