Landslides in the San Francisco Bay area (SFBA) of California
Dates
Start Date
2009
Summary
Landslides in the San Francisco Bay area (SFBA) of California impact people, infrastructure, and the environment, and are commonly induced by intense or prolonged rainfall associated with strong winter storms. Both shallow (<3 meter) and deep (≥3 meter) landslides can occur. Typically, shallow landslides occur as a result of high-intensity precipitation when the ground is already nearly saturated with water from previous storms. These types of events typically occur during the height of the rainy season, from December through February. Deep-seated landslides can also initiate or renew movement during these times but are also often triggered during the spring months (March through May), when water from rainfall has had a chance to make [...]
Summary
Landslides in the San Francisco Bay area (SFBA) of California impact people, infrastructure, and the environment, and are commonly induced by intense or prolonged rainfall associated with strong winter storms. Both shallow (<3 meter) and deep (≥3 meter) landslides can occur. Typically, shallow landslides occur as a result of high-intensity precipitation when the ground is already nearly saturated with water from previous storms. These types of events typically occur during the height of the rainy season, from December through February. Deep-seated landslides can also initiate or renew movement during these times but are also often triggered during the spring months (March through May), when water from rainfall has had a chance to make its way to deeper soil and bedrock.
The U.S. Geological Survey (USGS) conducts active monitoring of cumulative rainfall, rainfall intensity, soil water content (soil moisture), groundwater pressure, air temperature, and relative humidity in several locations throughout the San Francisco Bay area:
East Bay (BALT1) near Castro Valley, CA
Marin County (BALT2) Site near San Rafael, CA
SF Peninsula (BALT3) Site near Brisbane, CA
SF Peninsula (BALT4) Site near Pacifica, CA
Monitoring data have been collected since 2009 and soil moisture data provide an indication of the “soil wetness” (that is, the antecedent soil moisiture conditions) that may lead to widespread shallow landsliding and potential for debris flows if a storm of sufficient intensity impacts the region. If the soil moisture is low, even high rainfall intensity may not lead to landslides. On the other hand, high soil moisture and high rainfall intensity are more likely to cause widespread landsliding with consequences such as road closures, property damage, and potential fatalities.
This project landing page provides links to ScienceBase data releases and publications related to the SFBA project.
A regime shift in sediment export from a coastal watershed during a record wet winter, California—implications for landscape response to hydroclimatic extremes
The U.S. Geological Survey, in cooperation with local and state government organizations, operates several shallow landslide monitoring sites in the SFBA for research purposes. The goal of this research is to identify thresholds for widespread shallow landsliding and related high-mobility debris flows based on in-situ soil moisture conditions. This information is being used to develop landslide warning criteria with the National Weather Service.
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2023 landslide source area for long-runout debris flow on San Bruno Mountain