Historical and present day watershed management practices have decreased the volume of sediment that was once naturally delivered to the Bay. Creeks and streams have been dammed, diverted, or altered, sometimes causing sediment buildup in the lower parts of the channel. Sediment removed from flood control channels and soil excavated in construction projects is often taken to landfill as a waste product. In this component of the project, SFEI will 1) develop watershed sediment reuse strategies, and 2) support pilot sediment reuse implementation projects for the North Bay (partnering with Sonoma Water) and the South Bay (partnering with Santa Clara Valley Water (Valley Water)).
The primary focus of the watershed sediment reuse strategies will be beneficial reuse of sediment removed from flood control channels within tidal marsh restoration and shoreline adaptation projects. The strategies will build from recommendations from a past EPA-funded SFEI report, Towards a Regional Coarse Sediment Strategy for the Bay Area, developing a “playbook” that details specific management actions for increasing sediment reuse within each area. The strategies will be built from a quantitative analysis of the historical flood control channel sediment volumes that have gone to landfill, and specific challenges regarding beneficial reuse to date. These results will be used as the starting point for identifying watershed-specific opportunities for increasing sediment reuse. SFEI and San Francisco Estuary Partnership (SFEP) will facilitate workshops with the flood control agency partners, watershed and bayland restoration practitioners, and regulatory agency representatives to identify these opportunities, which may include logistical changes to current operations (e.g. connecting watershed sediment supply with bayland sediment demand over space and time) and a review of thresholds that determine sediment reuse suitability. From these opportunities will come the suite of near- and longer-term management actions that make up the strategy.
The first step towards implementation of the watershed sediment reuse strategies will be pilot projects to increase the reuse of flood control channel sediment. Each pilot project will be focused on Sonoma Water or Valley Water implementing deliberate choices within a sediment removal project that will lead to more beneficial uses compared to the current fates, and assessing environmental impacts. Each pilot implementation project will be documented with a factsheet for outreach to aid with future projects and to provide lessons to and encourage other agencies around the region.