2015-2016 El Niño Landslide Information

The USGS conducts landslide research in the San Francisco Bay area for the purpose of understanding the physical process of landslide initation. Some of this research investigates what types of conditions it takes to cause landslides. This is one way that the USGS is helping reduce the long-term losses from landslide hazards in the United States.


Landslide Folio

The San Francisco Bay Region Landslide Folio comprises six separate but related reports. These were originally prepared in anticipation of damaging Bay area storms during the 1997-1998 El Niño, but are relavent for current and future storm seasons (whether during or outside of an El Niño season) as well; the reports are keyed by letter to Open-File Report 97-745. These reports contain digital maps of topography, locations of existing and possible future landslides, and rainfall amounts needed to trigger shallow landsliding. The data contained within these reports covers the entire region, as well as each county individually. This information is useful for responding to possible slope failure within the San Francisco Bay Area, California.

  1. Introduction to the San Francisco Bay Region, California, Landslide Folio
  2. Shaded Relief Map of the San Francisco Bay Region, California
  3. Summary of Distribution of Landslide and Earth Flows in the San Francisco Bay Region, California
  4. Index to Detailed Maps of Landslides in the San Francisco Bay Region, California
  5. Map Showing Principal Debris-Flow Source Areas in the San Francisco Bay Region, California
  6. Map of Rainfall Thresholds for Debris Flows in the San Francisco Bay Region, California

Landslide Inventory by County

Ever wanted to see what a geologist sees? Below is a link to the online Digital Landslide Distribution Database. There are landslide inventories for a number of regions within the San Francisco Bay Area, California, two of which are available on-line.

What happened during the last strong El Niño in 1997-1998?

Heavy rainfall associated with a strong El Niño caused over $150 million in landslide damage in the 10-county San Francisco Bay region during the winter and spring of 1998. Scientists from the USGS Landslide Hazards Program based in Reston, Virginia; Golden, Colorado; and Menlo Park, California; and from the USGS Geologic Mapping Program's San Francisco Bay Mapping Team based in Menlo Park, California, cooperated in the landslide-damage assessments. Click here to see the results.

The 1998 El Nino storm triggered several thousand small shallow landslides, known as debris flows, in hilly terrain east of San Francisco Bay south of the city of Oakland. These potentially dangerous landslides were mapped in detail from aerial photographs and studied in order to better understand the hazard.

Was the February 1998 El Niño storm a unique event?

Severely destructive winter rainstorms in Central California are infrequent, but can be counted on to reoccur.

For example, a catastrophic 32-hour storm triggered landslides and floods throughout the San Francisco Bay area in Januray 1982. More than 18,000 debris flows damaged over 100 homes and killed 14 residents; one large landslide caused 10 additional fatalities. Direct costs from damage by slope failure alone exceeded $66 million. An event of similar magnitude occurred in the winter of 1955.

Landslide hazard in the Oakland - Berkeley Area

As part of the Federal Emergency Management Agency's Project Impact, an initiative to develop more disaster-resistant cities, USGS scientists made analyses of susceptibility to various kinds of landslides in and around Oakland and Berkeley.