During a 6-month period from December 1980 through May 1981, samples were collected from Cow Creek near Azalea, Oreg., and analyzed for suspended sediment, particle-size distribution, and turbidity. Of the estimated suspended-sediment discharge of 4,270 tons for the 1981 water year, 95 percent (4,050 tons) was transported during a major storm event, December 2-4, 1980. The 1981 water year suspended-sediment discharge of 4,270 tons is well below the average annual suspended-sediment discharge of 22,000 tons reported earlier by Curtiss (1974).
A clay-sediment transport curve was used in conjunction with the flow-duration curve to estimate average annual clay discharge of 3,700 tons for Cow Creek near Azalea.
Turbidity in Cow Creek near Azalea is estimated to be equal to or less than 15 NTU (nephelometric turbidity units) 90 percent of the time.
A method for predicting turbidity values in a hypothetical impoundment is presented in this report. This method utilizes a suspended-sediment transport curve of the fine (<0.002 mm) material and measures residual-turbidity values. This method probably could be used to assess the impact of proposed reservoirs on stream turbidities in basins similar to that of Cow Creek basin.
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USGS Numbered Series
An evaluation of suspended sediments and turbidity in Cow Creek, Oregon