Lagunitas Creek Watershed Sediment TMDL

New: The Basin Plan amendment adopting the TMDL was approved by the State Board on November 18, 2014 and by the Office of Administrative Law on March 17, 2015.


June 11, 2014 Water Board Hearing Documents


STAFF SUMMARY REPORT

APPENDICES:

State Water Board Hearing Documents

Background

fisherwoman high flows
sand in bed juvenile steelhead
Clockwise from top left: Fisherwoman on Lagunitas Creek in 1922 (Courtesy: Anne T. Kent California Room, Marin County Free Library); Today, there are few places where fish can find refuge during high flows; A large juvenile coho salmon and a juvenile steelhead measured on their way to the ocean (photo credit: Eric Ettlinger, MMWD); and Lots of sand in the streambed in 2010 (photo credit: Matt Cover, Stanislaus State University).

Lagunitas Creek, from its headwaters on Mount Tamalpais to its mouth in Tomales Bay, is the largest watershed in Marin County.  It provides critical habitat for coho salmon, steelhead, and California freshwater shrimp, all of which are listed under the federal Endangered Species Act. 

Habitat simplification and changes in sediment delivery, transport, and storage have contributed to the decline of the salmonid runs.  There has been a two-fold or greater increase in sediment supply to Lagunitas creek and its tributaries (Stillwater Sciences, 2010).  Channel incision, or down-cutting into its bed, is the primary source of increase in sediment supply, and also a primary agent of channel habitat simplification, and disconnection from its floodplain[*].  Dam construction, development, and management actions have interacted to cause incision/ habitat simplification, and to fundamentally alter channel sediment delivery, transport, and storage.  The concentration of sand and fine gravel in the streambed is elevated significantly above the natural background and the streambed is much more mobile during high flows (Cover, 2012).  Fine sediment control, channel habitat enhancement, and floodplain restoration projects are needed in concert to restore properly functioning habitat conditions. 

[*]Also there are fewer large fallen trees in channels as a result of nineteenth century logging, intensive removal of debris from channels, and as a consequence of channel incision (e.g., incised channels are narrow and deep and many fallen trees remain perched above the channel).  The lack of large fallen trees in channels is a problem for fish because large trees force pools and bars to form, cause sediment to be sorted into discrete patches (that vary in grain size), and create side channels, islands, and floodplains.


Studies and Reference Materials

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Mike Napolitano
Engineering Geologist
San Francisco Bay Regional Water Quality Control Board
1515 Clay St., Suite 1400
Phone: (510) 622-2397
Fax: (510) 622-2460
E-mail: MNapolitano@waterboards.ca.gov