Earl E. Brabb

Real-Time Landslide Warning During Heavy Rainfall

A real-time system for issuing warnings of landslides during major storms is being developed for the San Francisco Bay region, California. The system is based on empirical and theoretical relations between rainfall and landslide initiation, geologic determination of areas susceptible to landslides, real-time monitoring of a regional network of telemetering rain gages, and National Weather Service precipitation forecasts. This system was used to issue warnings during the storms of 12 to 21 February 1986, which produced 800 millimeters of rainfall in the region. Although analysis after the storms suggests that modifications and additional development are needed, the system successfully predicted the times of major landslide events. It could be used as a prototype for systems in other landslide-prone regions.

The San Mateo County California Gis Project for Predicting the Consequences of Hazardous Geologic Processes

San Mateo County, California adjoining San Francisco has several hazardous geologic processes, including movement of the San Andreas fault and associated ground failures, landsliding, flooding, and coastal erosion. In the early 1970’s, county planners requested help from the U.S. Geological Survey in determining the location and severity of the most hazardous processes, and in preparing maps that would help them deal with the problems. Maps were prepared showing the location of fault zones and the most recently active fault traces, areas subject to flooding, and an inventory of past and recently active landslides. Geographic Information Systems (GIS) techniques were used to make a map of landslide susceptibility, but the analysis was done by hand.

HOW USEFUL IS LANDSLIDE HAZARD INFORMATION? LESSONS LEARNED IN THE SAN FRANCISCO BAY REGION

Landslides, worldwide and in the United States, are arguably the most costly natural hazard. Substantial landslide information is available, but much of it remains underutilized, as a disconnect exists among geologists, decision makers, and the public. The lack of a national landslide insurance policy exacerbates this situation and promotes litigation as the principal recourse for recouping landslide-damage losses. The U.S. Geological Surveys landslide investigation in the San Francisco Bay region of California provides a context for making suggestions on how Earth science information could be used more effectively.

The Development and Application of a Historical Bibliography to Assess Landslide Hazard in the United States

A project supported by the U. S. Geological Survey was initiated in 1980 to determine the extent and economic significance of landsliding in the United States, and to prepare recommendations to management about the kind of work needed to investigate and mitigate the problem. At the time of this project, no comprehensive bibliography or database had previously been compiled for landslides. A bibliography was initiated in 1981 using commercially available library database services, combined with systematic library study, and reference collections from individual researchers in the United States. About 6,500 landslide references were obtained, including those from other U.S. government agencies such as the U.S. Forest Service, U.S. Bureau of Reclamation, and the U.S. Army Corps of Engineers Waterways Experiment Station. Development of the bibliography essentially ended with information published through 1983, although a few references published in 1984 and 1985 were included. Data on landslides contained in the published and unpublished reports cited in the bibliography have been used primarily for reconnaissance-level research, although they remain a useful tool for further studies. For example, many of the published and unpublished reports gathered for the bibliography were used by Brabb et al. (1999) to prepare a map to show where debris flows have been observed or mapped in the United States and help identify where they may occur in the future. The bibliography is still the largest compilation on landslides for all states, territories and possessions of the United States.

The landslide hazard in the San Francisco Bay region

Development in hilly or mountainous terrain has resulted in much landslide damage. Areas susceptible to landsliding can be recognized. Practices for minimizing landslides are presented.