Bedload Transport In A Model Gravel Stream

Abstract

The presence of a natural pavement consisting of coarse materials in gravel streams is of great interest with regard to fluvial hydraulics and stream ecology. Very little information is available on the mechanics of pavement formation and its characteristics. In this study, insight into the characteristics of sediment transport and pavement evolution in gravel streams was gained by means of a physical model of a gravel stream in the Pacific Northwest. The results from the geometrically undistorted Froude model (scale 1:8) agreed well with the field data. The agreement was further improved when laboratory data and field data were compared in terms of dimensionless bedload W* and relative Shields shear stress ¢. The W* - ¢ plots allow for the quantification of differences in Reynolds number and roughness which were not or could not be scaled by means of Froude similarity. The study leads to the conclusions that bedload transport in natural gravel streams can be simulated in the laboratory and that prototype behavior can be predicted from laboratory data, The experiments also illustrate that pavement can form under conditions of continuous equilibrium transport of all available sizes of interest. This report was submitted in fulfillment of grant No. EPA R 806632-01. The report covers a project period from July 5, 1979 to January 4, 1980. A first draft of this report was submitted in April, 1980.