Author(s): Albert Molinas; Baosheng Wu
Keywords: Large river; Sediment transport; Alluvial river; Stream power; Universal stream power; Amazon river; Mississippi river; Deep river; Bed material load; Sediment transport capacity
Abstract: A sediment transport equation based on universal stream power is presented for the prediction of bed-material concentrations in large sand-bed rivers. The universal stream power, which is derived from the energy concept, has the advantage of eliminating the energy slope as a parameter. The energy slope, which is in the order of 10-5 for large rivers, is a major source of uncertainty in measurements. The analysis shows that relationships derived from flume experiments with shallow flows cannot be universally applied to large rivers with deep flows. Also the use of dimensionless homogeneous parameters in an equation is not sufficient to ensure its applicability to flow conditions where flow depths are several orders of magnitude larger. The comparisons between computed and measured sediment concentrations indicate that the commonly used Engelund and Hansen, Ackers and White, and Yang equations which were developed using mainly flume experiments are not applicable for large rivers with flow depths and Reynolds numbers up to 100 times larger than those found in flumes. The Toffaleti's method which was developed mainly from field data gives reasonable predictions of sediment transport rates for large rivers. Using the proposed equation, the computed sediment transport rates are in much closer agreement with the actual measured values in large and medium rivers.