Operation of a landslide warning system during the California storm sequence of January and February 1993
Raymond C. Wilson, 1997. "Operation of a landslide warning system during the California storm sequence of January and February 1993", Storm-Induced Geologic Hazards, Robert A. Larson, James E. Slosson
Download citation file:
From 1986 to late December 1995, the U.S. Geological Survey and the National Weather Service operated a landslide warning system for debris flows triggered by intense rainstorms in the San Francisco Bay region. The Landslide Warning System tracked storm systems as they approached the region, determined actual rainfall with a network of radio-telemetered rain gauges, compared the rainfall to thresholds for initi-ation of debris flows, and issued the appropriate public advisories.
A series of intense rainstorms during January 1993 created hazards from landslid-ing and flooding over much of California. In the San Francisco Bay region, January rainfall was over 200% of normal, triggering debris flows on natural hillslopes and road cuts across Marin, San Mateo, Alameda, Santa Clara, and Santa Cruz Counties. The warning system issued Flash Flood/Debris Flow Watches during the most intense storms on January 13 and 15,1993. Most debris flows in this area were small and widely scattered, so damage was largely limited to several blocked roadways in mountainous areas. Storm damage was much heavier in southern California, where rainfall amounts were over 350% of normal for January, triggering flash floods and many landslides. This damage prompted inquiries about developing a landslide warning system for southern California.
A number of elements for a landslide warning system already exist in southern Cal-ifornia, including quantitative rainfall forecasting and a network of radio-telemetered rain gauges. Regional rainfall thresholds for debris flow initiation, consistent with the climate, topography, and geology of the region, remain to be developed. Such thresholds could probably be developed with a modest investment of research effort and resources.
Figures & Tables
A multidisciplinary volume of case histories presenting the work of professionals who investigated catastrophic damage caused by the 1992—1993 winter storms in southern California and Arizona. Papers in this volume discuss topics such as: why severe winter storms occur and how the resulting floods fit into the context of the geological record; flood-damaged infrastructure development and mining operations in river channels; storm damage to four counties in southern California; ground settlement intensified by rising ground water caused by infiltrating rain, and the subsequent litigation; warning the public of imminent debris-flow hazards and how to set the moisture and rainfall thresholds that must be reached to issue a warning; and major infiltrating-rainfall-activated landslides that damaged homes in southern California. The release of this volume marks the 50th anniversary year of the Engineering Geology Division.
- Alameda County California
- debris flows
- geologic hazards
- Marin County California
- mass movements
- Orange County California
- San Francisco Bay region
- San Mateo County California
- Santa Clara County California
- Santa Cruz County California
- slope stability
- Southern California
- United States
- landslide warning system
N33°25'00" - N33°53'60", W118°07'60" - W117°25'60"
N36°51'00" - N37°16'00", W122°17'60" - W121°35'60"
N36°52'00" - N37°30'00", W122°12'00" - W121°12'00"
N37°30'00" - N37°49'60", W122°25'00" - W121°30'00"
N37°06'00" - N37°42'00", W122°34'60" - W122°10'00"
N37°47'60" - N38°19'60", W123°00'00" - W122°30'00"