Reducing Road-Related Sediment Delivery to Stream Systems in the Wing Canyon Subwatershed: Napa River

completed

With grant funds from State Water Resources Control Board (SWRCB), California Department of Fish and Wildlife (CDFW) and financial contributions from the landowner, the RCD hydrologically disconnected approximately 1.8 miles of unpaved road in the Wing Canyon subwatershed of the Napa River watershed through road grading and shaping. The RCD also implemented sediment reduction treatments at 22 discrete sites, including 12 stream crossings and 10 road-related discharge points (i.e. off road gullies). RCD estimates that treating the 22 sites and 1.8 mi of road reaches substantially diminished the delivery of coarse and fine sediment to the stream system. The work prevented approximately 2,647 yd3 of sediment from episodic erosion (erosion due to large storm event or some other trigger) at individual sites and approximately 2,089 yd3 of sediment from chronic erosion (annually erosion from unpaved surfaces, ditches and cutbanks), over the next two decades, from being delivered to the stream network. Project design was reviewed by a Licensed California Professional Geologist and carried out by a licensed and experienced contractor, with oversight from experienced RCD staff. Pre- and post-project photo monitoring was conducted, and post-project review was completed by a Licensed California Professional Geologist. Environmental review and permitting was conducted through the California Department of Fish and Wildlife’s Fisheries Restoration Grant Program.

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