Senate Bill 5 (SB 5), which was enacted in 2007, authorized the California Department of Water Resources (DWR) to develop the Best Available Maps (BAM) displaying 100- and 200-year floodplains for areas located within the Sacramento-San Joaquin (SAC-SJ) Valley waterSenate Billshed. SB 5 requires that these maps contain the best available information on flood hazards and be provided to cities and counties in the SAC-SJ Valley watershed. This effort was completed by DWR in 2008.

DWR has expanded the BAM to cover all counties in the State and to include 500-year floodplains. The 100-, 200-, and 500-year floodplains are displayed on this web viewer. The web viewer allows users to view a particular area and identify their potential flood hazards. The following is a comprehensive list of the floodplains that are displayed on the web viewer and may be updated periodically.


The BAM does not replace existing FEMA regulatory floodplains shown on Flood Insurance Rate Maps (FIRM). For more information on the FEMA regulatory floodplains, please contact FEMA directly. The BAM floodplains identify potential flood risks that may warrant further studies or analyses for land use decision making. The floodplains shown delineate areas with potential exposure to flooding for three different storm events: one with storm flows that have a 1% chance of being equaled or exceeded in any year (100-year), one with storm flows that have a 0.5% chance of being equaled or exceeded in any year (200-year), and one with storms flows that have a 0.2% chance of being equaled or exceeded in any year (500-year). These flows and resulting flooded area are based on the best available floodplain information and may not identify all areas subject to flooding.

Accept and Continue Decline

In accordance with the requirements of Title II of the Americans with Disabilities Act of 1990 (ADA), the Department of Water Resources will not discriminate against individuals with disabilities on the basis of their disability in its programs, services, or activities.

The BAM web viewer requires a minimum Web browser of FireFox 69.0 or later, Microsoft Internet Explorer 11 or later, Chrome 77 or later, Microsoft EdgeHTML 16 or later, Safari 10 or later, or other Web browser compatible with these browsers. It also requires network connection at speed 768kbps or higher for downstream and resolution with 1024x768 (Recommend 1280x1024 or higher).

Designated Floodways and Regulated Streams

If your project is inside or 300 feet from the Designated Floodway or regulated streams you will need an encroachment permit from the Central Valley flood Protection Board.

View Floodway Data