Analysis of sediment transport in an ephemeral stream

Abstract

Ephemeral stream channels may be modified considerably by aggradation, degradation or lateral migration. Computer programs utilizing a variety of sediment-discharge equations have been developed to predict these changes. The equation of Laursen was examined in this study. Suspended and bed load samples were collected from the Santa Cruz River during 12 flow events. Sediment compositions from the dry wash were used in the Laursen equation to predict that data. Sampled suspended load plotted as a scatter band, but the variation could be explained by slight changes in the bed material composition during flow. Predicted values correlated well with observed data during moderate discharges, but not at high or low flows, possibly because fine material was either re-suspended or supplied from upstream in those ranges. Removing the wash load from consideration did not improve the correlation significantly. Bed load seemed to be adequately predicted by the Laursen equation.