Author(s): M. Nouh
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Keywords: No Keywords
Abstract: Laboratory experiments were conducted to investigate the effect of original size distribution of sediment and unsteady flow characteristics on the composition of armoring layer in straight open flume. Bed sediments of different size distribution were subjected to f1iow hydrographs that vary in depth (D) and duration (T). Size distribution of the armoring layer was more sensitive to the variation of hydrograph duration than that of hydrograph depth. Such sensitivity increased as the geometric mean diameter of theoriginal sediment decreased and as the geometric standard deviation of the sediment increased. The gradation of armor coat developed under unsteady flow condition was larger than that developed under equivalent steady flow condition (i. e. having the same mean discharge and friction slope), and was found to depend on the value of the parameter P= (D/T) (1/u_*) up to the limit of P=0.01, where ug is the shear velocity. A model is proposed to predict the final compositions of armoring layer developed under the effects of unsteady flow conditions.
Year: 1989