Measuring Sediment in Jack London's Streams: Sonoma Creek Watershed, Sonoma County

Used In: 
Watershed Plan
Used In: 
Watershed Scorecard
Lawton, R.; Camacho, K.
Publication Date: 
Sonoma Ecology Center
Publication Place: 
Sonoma, CA

The Sonoma Ecology Center is studying turbidity and suspended sediment concentration (SSC) in Sonoma Creek and tributaries. In the Sonoma Creek watershed, salmonids of concern are chinook salmon (Oncorhynchus tshawytscha) and steelhead trout (Oncorhynchus mykiss), both listed as threatened species under the Endangered Species Act.

This poster describes a study to observe the effects of an old complex of roads in Jack London State Park on
sedimentation to salmonid-bearing headwaters of Sonoma Creek, an important tributary to San Pablo Bay, due to wet-season runoff from roads with poor alignment, infrequent maintenance, undersized culverts, and uncontrolled drainage.

Research has connected elevated turbidity and SSC with observed effects on sampled salmonid populations, such as reduced feeding and growth rates, avoidance of turbid waters, or death. Newcombe and Jensen (1996) developed a severity index for ranking and analyzing the effects of excess turbidity or SSC on salmonids. Rankings in the index ranged from 0 (no effect) to 14 (80 to 100 percent mortality). Using this severity index, Trush (2001) proposed that long-term reduction of feeding rates and feeding success (severity index ranking of 8 or greater) directly results in smaller salmonids with higher mortality rates; therefore, a severity ranking of 8 has been demonstrated to be harmful to salmonids through compromise of the cold water fishery (Trush, 2001).

From the SSC values, we used the Newcombe and Jensen (1996) index to calculate severity for sixteen storms in HY 2002, nine storms in HY 2003, and twelve storms in HY 2004. Maximum indices observed were 8.35 in HY 2002, 9.04 in HY 2003, and 8.20 in HY 2004. At SSC values above 27 mg/L (50 NTU-a), or in “turbid” water:

-Severity indices were often above 4 during storms, corresponding to short-term reduction in salmonid feeding rates.
-Severity indices were frequently above 5, associated with minor physiological stress, increased coughing rates, and increased respiration rates.
-Severity indices for “first flush” events rose above 6, associated with moderate physiological stress; 7, associated with moderate habitat degradation and/or impaired homing; and 8, associated with major physiological stress.

SEC filepath: 
W:\Publications_Presentations/Posters/Sediment-Turb/2005JackLondonSed-TurbPoster.ppt and W:\Publications_Presentations/Posters/Sediment-Turb/pdfs/2005JackLondonSed-TurbPoster.pdf
water quality, sediment, fish habitat
Date Period: 
01/01/2002 - 01/01/2004
Becca Lawton
Sonoma Ecology Center

Measuring Sediment in Jack London's Streams: Sonoma Creek Watershed, Sonoma County data, by Station

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