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Local Flood Hazards

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Seven principal watersheds originate or traverse through the County of San Diego.  They are the Santa Margarita, San Luis Rey, San Dieguito, San Diego, Sweetwater, Otay, and Tijuana Rivers. The County of San Diego has suffered from numerous major flood events brought on by intense or prolonged rainfall and resulting in loss of life and millions of dollars in property damages. Over the past decade, major floods have occurred in Mission Valley, El Cajon, Ramona, and Borrego Springs.  In addition to these major flood events, flooding has been known to occur in localized areas of the County during average seasonal rainstorms.

The central and eastern portions of the County of San Diego are most susceptible to flash floods where mountain canyons, dry creek beds, and high deserts are the prevailing terrain. Alluvial fans are found in the Borrego Valley and require special construction methods to protect buildings.

In August 2007, the County of San Diego completed a Floodplain Management Plan (FMP) that assesses the flooding hazards within the unincorporated areas of the County, summarizes current County programs, describes potential mitigation strategies, and presents a plan for future action.  It was prepared with input from County residents, responsible officials, and consultants, and with the support of the State of California Office of Emergency Services and Security and the Federal Emergency Management Agency.

The FMP discusses a series of flood hazard issues and presents follow-up actions and recommendations for risk reduction.  Based on the findings and recommendations in each of these areas, the County developed a Mitigation Action Plan (MAP).  The County’s Hazard MAP identifies mitigation activities, the priority assigned to implementing each activity, a responsible lead Department or staff position, and deadline.

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If you have questions or would like additional information, 
call the County Stormwater hotline at 1(888) 846-0800
or e-mail us at

Report a Stormwater Violation On-Line
Department of Public Works
Flood Control
5510 Overland Ave., Suite 410, MS O326
San Diego,  CA  92123,  USA
(858) 495-5318           Fax: (858) 495-5263