Analyses of rock samples from the Circle Quadrangle, Alaska

Abstract

Suspendedsediment and reservoir sedimentation data have been analyzed to determine sediment yields and transport characteristics of Tennessee streams Data from 31 reservoirs plus suspendedsediment data from TVA sampling efforts in the 1930?s and 1960?s, and U.S. Geological Survey efforts from 1975-82 have been used. Results of the analyses show that the measured suspended-sediment is mostly silt and clay-size material even in the sand bed channels of western Tennessee. Samples of suspended sediment rarely exceed 25 percent sand. Computed unmeasured load is less than 10 percent of the total sediment load in western Tennessee. Unmeasured load has not been computed for middle and eastern Tennessee streams because the bed material is generally coarse and quite variable. However, unmeasured load in these streams is believed to be less than 5 percent of total load. Transport curves show that when flow is less than about 1 cubic foot per second per square mile, western Tennessee streams have higher concentrations than middle or eastern streams. When flow exceeds about 10 cubic feet per second per square mile, however, concentrations in middle and eastern streams can equal or exceed those in western streams. The more efficient sediment-delivery processes operating in middle and eastern Tennessee basins are responsible for the rapid increases in suspended sediment concentrations with increasing flow. Sediment yields for middle and eastern Tennessee basins generally are less than 800 tons per square mile per year, however, heavily strip-mined basins can have yields from 1,000 to 3,000 tons per square mile per year. Yields for the heavily agricultural and channelized basins of western Tennessee generally range from 700 to 1,000 tons per square mile per year.