Development of Watershed Management Modeling System: The Los Angeles County Flood Control District's Watershed Based Approach for Urban Runoff and Stormwater Quality

Improving the quality of urban runoff and stormwater in the Los Angeles County's coastal watersheds is challenging. Thousands of separately permitted discharges with multiple Total Maximum daily Loads flow into the same receiving water bodies simultaneously. This makes it necessary and economical to address many different pollutant sources concurrently. In order to help overcome such challenges, the Los Angeles County Flood Control District is developing a watershed modeling system (WMMS) that would ultimately identify cost-effective projects through an integrated, watershed based approach. Using WMMS, collective impact of a variety of pollutant sources from point to non-point is evaluated and thereby comprehensive, long-term strategies for overall water quality improvement of the entire watershed will be planned. In addition, the WMMS will be used as an integrated watershed management tool for future planning of projects that achieve multiple benefits besides water quality such as water conservation, flood control, and open space development. This would eventually allow for an effective stormwater resource management.