I recently visited one of the California regions that were identified and mapped for inventory by the CGS (California Geological Survey) as the landslide hazardous areas, San Francisco. San Francisco had a great photogenic view of the golden bridge, a historical structure of Alcatraz in the middle of the ocean, and inspiring culture throughout the city. Although it was a beautiful place, I don’t think I could live there. In the city, the houses sit on a slope. For over 50 years, CGS has mapped landslide areas based on a broad range of categories such as previous landslide disasters, recency of activity, classification of landslides (fall, topple, spread, slide, flow), characteristic of landforms (scarps, cracks, erosion), type of material failures (rocks, soil), slope stability, and earth movement (plate tectonics). Due to the complexity in landslides, CGS had to provide technical reports, disaster responses, highway landslide hazardous mapping zones, specification of land usage, and etc. Considering that San Francisco is one of the cities that is subject to landslide hazardous and slope failure, I can only imagine the number of programs and insurances needed to reside there.
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| Type of landslide activities. Source: California Department of Conservation |
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Image of an earth flow. Source: Diagram by J. Appleby, R. Kilbourne, and C. Wills after Varnes, 1978; California Dept. of Conservation
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| Image of a debris slide. Source: Diagram by J. Appleby, R. Kilbourne, and C. Wills after Varnes, 1978; California Dept. of Conservation |
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