Watershed Management Area Analysis (WMAA)

The Watershed Management Area Analysis (WMAA) is an optional element for inclusion in the Water Quality Improvement Plans (WQIPs) described in the 2013 MS4 Permit (Provision B.3.b.(4)). This analysis is intended to characterize important hydrologic processes and characteristics of each watershed through the creation of GIS layers that may be used to identify candidate projects that could potentially be used as offsite alternative compliance options in lieu of satisfying full onsite retention, biofiltration, and hydromodification runoff requirements, and to identify and/or prioritize areas where it is appropriate to allow certain exemptions from onsite hydromodification management BMPs.

In July 2013, the Copermittees elected to conduct the watershed characterization and hydromodification management exemption mapping on a regional scale to allow for uniform development of the WMAA elements for each of the 9 San Diego-area watershed management areas (WMAs) within the County of San Diego. The development of the WMAA provides the foundation to allow for implementation of the optional Offsite Alternative Compliance Program as described in Provision E.3.c.(3) of the permit.

For further information and questions regarding WMAA, please contact Sheri McPherson, County of San Diego, at Sheri.McPherson@sdcounty.ca.gov.


San Diego County Regional WMAA Report with Appendices  (October 2015)

Factor of Safety Memo  (June 2015)


WMAA Mapping Data from Attachment C (October 2018)

Comprehensive WMAA mapping files may be periodically updated to reflect revisions from WQIP Annual Reporting process. (Otay River HMP Exemption added on May 26, 2017; Critical Coarse Sediment layer now incorporated into Google Earth mapping, August 22, 2017; Escondido Creek HMP exemption added on October 18, 2018).

Disclaimer: Mapping data is provided to assist the public with permit compliance, but its use is not intended to guarantee or warrant compliance, which is the independent responsibility of the user. Mapping is intended to be used in conjunction with the process described in the Model Regional BMP Design Manual. In no event will the San Diego area municipal Copermittees be liable for any incidental, special or consequential damages of any kind (including, but not limited to, loss of information or other monetary loss) arising in any way in connection with the use or inability to use the mapping accessed from this website.