Interpretation of grain-size distributions from measured sediment data, Platte River, Nebraska

Authors

  • THOMAS R. ESCHNER,

    1. U.S. Geological Survey, Water Resources Division, Box 25046, MS 415, Denver Federal Center, Denver, Colorado 80225, U.S.A.
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    • *

      ARCO Exploration Company, P.O. Box 51408, Lafayette, LA 70505, U.S.A.

  • JAMES E. KIRCHER

    1. U.S. Geological Survey, Water Resources Division, Box 25046, MS 415, Denver Federal Center, Denver, Colorado 80225, U.S.A.
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ABSTRACT

Breaks in the slope of log-probability plots of cumulative grain-size distributions of bed material are compared with frequency distributions of bedload and suspended sediment over a range of discharges at two stations on the Platte River in south-central Nebraska. The break between suspension and intermittent suspension as determined from the bed-material curve coincides with the upper limit of the grain-size overlap between bedload particles and suspended-sediment particles, whereas the break between intermittent suspension and traction corresponds to the grain size at the lower limit of overlap of bedload particles and suspended-sediment particles. Although grain-size distributions of bedload change little with discharge, the size of the coarsest grains in suspension increases with increasing discharge. Thus, the length of overlap of bedload and suspended-sediment distributions increases with increasing discharge. The limits of grain-size overlap of bedload and suspended-sediment distribution curves associated with near-flood discharges most closely approximate the breaks in the bed material grain-size distribution.

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