Characterization of discharge, turbidity and suspended sediment, upper Salmon Creek watershed, Humboldt County, California
Graduation Date
2013
Document Type
Thesis
Program
Other
Program
Thesis (M.S.)--Humboldt State University, Environmental Systems: Environmental Resources Engineering, 2013
Committee Chair Name
Eileen Cashman
Committee Chair Affiliation
HSU Faculty or Staff
Keywords
Turbidity, Headwaters Forest Reserve, Salmon Creek, Humboldt State University -- Theses -- Environmental Resources Engineering, Total suspended solids, Turbidity threshold sampling, Watershed monitoring
Abstract
Salmon Creek lies in the Headwaters Forest Reserve in northern California, an area of high biodiversity and sensitive habitat for endangered species. The watershed is primarily managed by the Bureau of Land Management (BLM). The history of the reserve includes extensive timber harvesting and road construction. Salmon Creek is listed as an impaired waterway under the Clean Water Act for turbidity and contains populations of Coho salmon, Chinook salmon, and Steelhead, which are listed as threatened species under the Endangered Species Act. One of the primary management goals for the Headwaters Forest Reserve is the protection and recovery of threatened species and their habitats. These goals are dependent on a long term reduction in sediment yield to Salmon Creek. Part of the watershed restoration process is monitoring the effectiveness of road removal and other activities in order to determine if water quality objectives are being met. This project established a stream gaging station on Upper Salmon Creek and implemented Turbidity Threshold Sampling (TTS). The stream data collected were used to determine the stage-discharge and turbidity-suspended sediment relationships for the watershed, and to develop an estimate of the annual sediment yield for Hydrologic Year (HY) 2012. Both individual storm regression and annual regression (before and after a significant landslide in March 2012), were used to estimate the annual sediment yield. Two discharge rating curves were developed, owing to the lack of discharge measurements at high flows. The annual sediment yield estimates using rating curve A were 185 tons/mi2 and 150 tons/mi2, respectively. The annual sediment yield estimates using rating curve B were 65 tons/mi2 and 59 tons/mi2. While overall turbidity in the watershed was low, with a median of 4.9 NTU, the 10% exceedence level of 34.4 NTU is elevated with respect to unharvested watersheds. However, the 10% exceedence level was consistent with other legacy harvest and low intensity harvest watersheds. The Upper Salmon Creek watershed is within the 10-15 year post-harvest period when root mass may be reaching a minimum and sediment inputs can be expected to be elevated. This data is a first step in allowing the BLM to assess the effectiveness of watershed restoration activities within the reserve with respect to sediment yields to the creek, and to inform management and policy decisions in the future.
Recommended Citation
Bailey, Kathleen, "Characterization of discharge, turbidity and suspended sediment, upper Salmon Creek watershed, Humboldt County, California" (2013). Cal Poly Humboldt theses and projects. 1016.
https://digitalcommons.humboldt.edu/etd/1016
https://scholarworks.calstate.edu/concern/theses/7s75df859