L.A. River Watershed Study Identifies Where Stormwater Projects Can Make Most Difference

Often the trickiest part of planning a project is placing it where it can do the most good. A series of studies hopes to bring a little science to this task.

The State Coastal Conservancy and Santa Monica Mountains Conservancy has just awarded a total of $550,000 to Community Conservation Solutions (CCS) to fund the fourth phase of a water sustainability study in the upper Los Angeles River watershed.

"This would allow us to advance our understanding of the energy consumption and reduction in greenhouse gases implementing stormwater projects would have in the upper Los Angeles River watershed," says Esther Feldman, President of CCS.

According to Feldman, CCS's system involves weaving together land use, hydrologic, storm drain, pollutant loading, community and conservation data, and the use of geographic information systems (GIS). "It's really getting a lot of data to talk to each other."

The grant builds on previous studies undertaken by CCS. The initial Green Solutions project in 2008 identified nearly 20,000 acres of public lands in Los Angeles County that could be converted to these "smart" green spaces. At the time, nearly all of the county's waters were in violation of federal and state water quality standards. Green Solutions presented alternatives that included removing concrete and retrofitting green areas to naturally filter and clean urban runoff. If implemented, CCS projects that up to 40 percent of the county's water quality improvement requirements could be met.

The most recently completed report focuses on the Upper Los Angeles River watershed. The report, which was released December 2013, provided public agencies with 268 prioritized sites on public vacant, school, and college lands. "The report told us where to do stormwater projects, but also in what order," says Feldman.

The suggested conversion project sites would create 1,000 acres of new parks and green spaces in park-poor areas, and over 600 million gallons of water. Runoff from 20-square miles of the Upper Los Angeles River watershed could be captured and cleaned.

Bell Creek Conceptual Site Design

It further developed suggestions for four high priority sites. At Bell Creek, a 16-acre site in West Hills at the intersection of Sherman Way and Woodlake Avenue, the study suggests developing $5-million open space project with a wetland and a permanent pond area that could treat more than 1.2 million gallons of water and create 6.5 acres of greenery. At John F. Kennedy High School in Granada Hills, incorporating vegetated swales, vegetated stormwater curb extensions and retention galleries would treat at least 2.9 million gallons of runoff a year and create 9.5 acres of green space. At Pierce College, a 374-acre site in Woodland Hills, developing a $15-million project with vegetated swales and a retention gallery would treat more than 2.8 million gallons of runoff and add 63.5 acres of green space.

This recently-funded study adds an environmental layer to the research, helping agencies quantify just how much stormwater capture projects can add to water supplies and by how much these projects could reduce greenhouse gas emissions. The report would also expand the list to 400 projects for implementation.

"Even in dry weather, there is 25 million gallons of water flowing through the Upper Los Angeles river watershed," says Feldman. "If we capture even a portion of that, we could be less reliant on the Eastern Sierra Nevada and the Colorado rivers for our water supply."

Though the report doesn't guarantee anything would actually be built or retrofitted, according to Feldman, CCS continues to work with the Santa Monica Mountains Conservancy to help realize some of the projects they had outlined. Results of this latest study are expected by September 2015.

Images courtesy of Community Conservation Solutions