Addressing the Sediment Problem in Sonoma Creek Watershed Rebecca Lawton1, Deanne DiPietro1, Laurel Collins2, Arthur Dawson1 1Sonoma Ecology Center, P.O. Box 1486, Eldridge, CA 95476 2Watershed Sciences, 1128 Fresno Avenue, Berkeley, CA 94707

1996—Section 303(d) Listing Sediment Production, Natural Processes Sonoma Creek Watershed Sonoma Creek is listed as impaired for sediment, nutrients, and 54,500 tons/year Channel pathogens under the Clean Water Act. Sediment listing is and Incision, Surface 25,400 based on evidence of watershed erosion and fisheries decline. Erosion, tons/yr, 47% 8,400 Sonoma Creek and tributaries watershed, about 100 square tons/yr, 15% miles in size above current tidal limit, receives up to 50 inches of Soil Creep, rainfall per year. 16,600 Landslides, tons/yr, 30% 4,100 tons/yr, 8% 2006—Sonoma Creek Watershed Limiting Factors Analysis Study identifies sediment among several factors limiting health SedimentSediment Production, Production, Human Human Processes Processes and survival of diverse assemblage of aquatic species that SonomaSonoma Creek Creek Watershed Watershed 57,25057,250 tons/year tons/year include steelhead/rainbow , , and Roads and Sediment Source Analysis shows that over 70 Crossings, freshwater shrimp. Surface percent of human-caused sediment in Sonoma’s 5,600 Erosion, Channel tons/yr, 10% creeks comes from erosion of channels (as they 7,500 Erosion and tons/yr, 13% Incision, produce and 43,250 adjust to altered stream network with added tons/yr, 76% ditches, storm drains, and impervious surfaces). carry sediment during Landslides, 900 tons/yr, storms such as 100+ 2% year flow in Sonoma 2006—Sonoma Creek Watershed Sediment Source Analysis Creek, which peaked Study identifies sediment sources in watershed and estimates rates of at 20,300 cubic feet per sediment supply for each source—channels, roads, and surfaces— Sediment Production, Natural + Human Processes second on December between years 1800 and 2005. Hydromodification is found to be Sonoma Creek Watershed 111,750 tons/year 31, 2005 (at Agua chief reason for sediment problem in Sonoma Creek. Caliente Road, catching drainage area HUMAN 2007—Stream Stewardship Program 49% of 58 square mi). Hydromodification NATURAL Program involves, teaches, and 51% coordinates landowners in Land use changes over , encouraging 150 years have restoration along stream reaches. intensified stream and surface flows, increasing erosion and resulting in pervasive channel Channel 2008—Adoption of Basin Plan Amendment incision. During floods, connections and California Regional Control Board incised streams erode straightening were adopts Sonoma Creek TMDL Implementation beds and banks at largely completed Plan (later approved by EPA). higher-than-natural by 1877. Increased rates, increasing ditching, piping, human-caused and hardening of 2010—Restoration Site Prioritization Pilot Study sediment supply. surfaces followed. Study integrates data from Sediment Source Analysis into digital formats and includes pilot GIS analysis to inform prioritization of reaches needing restoration.

2002 to present—Suspended sediment monitoring is conducted at continuous 2011—Restoration Site Prioritization Study automated station and grab-sampling Study launches in May 2011 to expand 2010 pilot locations, as empirical check on source study to entire watershed, refining sediment estimates. source estimates (including effects of 2005 flood) and developing channel modeling capabilities. Acknowledgements go to Sonoma Creek landowners, TMDL Steering Committee, Bay Regional Water Quality Control Board (RWQCB), Watershed Sciences, Martin Trso, P.G., Talon Associates LLC, For Technical Reports and Data: Search our Tessera Consulting, Southern Sonoma County Sonoma Valley Knowledge Base at Resource Conservation District, and Sonoma County Water Agency. Funding for this work has been http://knowledge.sonomacreek.net provided by USEPA, San Francisco Foundation Bay Restoration focuses on increasing protective vegetation Fund, California Department of Conservation, and on highly erodible stream banks to reduce sediment Sonoma County Water Agency. supply and increase channel stability.