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Flood Management

Floodplain Evaluation & Delineation

California has a wide range of climatic, topographic, and geologic features, all of which result in varied and challenging floodplain issues. A report prepared by the Information Center for the Environment at the University of California, Davis has identified 172,000 miles of rivers in California with 70,000 miles of rivers downstream from dams. While not insurmountable, delineation of all of these systems would be a very formidable task.

Adding to existing floodplain management issues, over the next 25 years California is expected to have an increase in population of about 14 million. The demand for development will put a heavy load on the remaining floodplains that are not mapped. It is currently estimated that up to one-third of California's stream reaches are or will be experiencing development pressures during this period.

All areas of the State are subject to flooding and resultant losses. The Central Valley specifically is subject to large and devastating floods that would impact millions of people currently located in flood hazard areas or dependent upon support from facilities in identified or unidentified floodplain areas. Disruption of the State's critical water supply is a prime example. Major flooding from stream systems and/or levee failures would result in many billions of dollars in losses to individuals and the State's economy.

Floodplain information is essential for community planning needs, and for floodplain management programs aimed at reducing flood damages for existing and future development as well as increasing public safety. There are eight fundamental and related floodplain evaluation projects underway in the Central Valley as well as in the rest of California.

For more information, please see below or contact the floodplain evaluation team at