Wednesday evening, the Sonoma County Water Agency and its partners presented to a full room of concerned citizens a multi-benefit project to mitigate flooding in two area creeks and to revitalize groundwater in the Valley.
The Jan. 29 meeting, hosted in the Community Meeting Room, outlined the City Watersheds of Sonoma Valley project, which was awarded a highly competitive $1.89 million grant by the California Department of Water Resources through Proposition 1E funding. To receive the grant, the group had to demonstrate a strong partnership of agencies working on a multiple-use project with an education component.
The project, which is still in preliminary and test phases, will be located on the Montini Preserve and along Fryer Creek.
Sonoma County 1st District Supervisor Susan Gorin, who serves on the water agency and Agricultural Preservation and Open Space District boards, as well as on the county’s Water Advisory Committee, said, “It’s strange to talk about flooding during a dry period, but the reality is what’s part of climate change is unpredictable weather, so we have to look at the long term.”
After numerous scoping studies to identify an area ideal for a multi-benefit project, the water agency’s Principal Engineer, Kent Gylfe, explained that the Fryer Creek and Nathanson Creek areas, along with the Schell Creek area in Kenwood, were prime locations to both mitigate flooding in high-risk urban areas and increase groundwater supplies that are on the decline throughout the county. While the first part of the project, Gylfe explained, will look specifically at Fryer and Nathanson creeks, eventually the group plans to implement similar projects throughout the Valley.
The multi-benefit wetland enhancement project includes a detention basin in the existing pasture, off Fifth Street West, at Montini Open Space Preserve, to reduce flood risks during large storms and to recharge the groundwater supply.
It also includes an education component for public awareness and a restoration and re-vegetation of the basin to make it compatible with the surrounding landscape. The raised culvert on Fryer Creek at MacArthur Street that bisects the creek and creates a water and fish blockage will also be replaced or modified.
The collaborative effort includes the water agency, the City of Sonoma, Sonoma County Agricultural Preservation and Open Space District and the Sonoma Ecology Center. It also includes private contractors who specialize in hydrogeology and water projects.
Betty Andrews, a contractor on the project and a principal engineer focusing on environmental hydrology at Environmental Science Associates, Phillip Williams and Associates (ESA PWA), explained how humans modify watersheds by building homes and businesses, and adding things like storm drains.
“Undisturbed water moves more slowly, but humans come in and create these slick, flat surfaces that don’t absorb water,” she said. “So, when we have more water in a storm, water moves more quickly and can up the chance of flooding.” The project, she added, will “chip away” at this flooding path and the changes humans have created in the watershed.
Within the Sonoma Valley watershed, Gylfe said, the Nathanson and Fryer creeks sub-watershed covers 80 percent of the City of Sonoma and has the potential to cause serious damage to the highly developed area.