1. Preliminary maps showing rainfall thresholds for debris-flow activity, San Francisco Bay Region, California [electronic resource] Yale Public content 1997. 2006-07-18T19:20:08Z. 2006-07-18T19:20:08Z. Geological Survey (U.S.). The Survey ; USGS Information Services (Open-File Report Sales). English. Public. California, San Francisco Bay Area, and San Francisco Bay Area (Calif.).