Experimental study on the impact of bed forms on bed load transport in mountain streams

The flume experiments of bed load transport in the conditions of highslope shallow water flow were carried out in order to explore the impact of flow hydraulics and bed forms on bed load transport in gravel-cobble rivers in mountainous areas. A total of 19 runs were conducted with two groups of sediment mixtures. A data set of fluid hydraulics, sediment and 3D topographic field of riverbed in each run were obtained. The analysis of interrelationships among the flow resistance, bed form and bed load transport in different flow and sediment transport stages was made, by combining the flume experimental data and the observed data from natural rivers in the references. Experimental results demonstrate that the riverbed resistance coefficient increases with the increase of riverbed morphological strength parameter. The form drag is strongly correlated with riverbed morphological strength parameter. In the stage of sufficient sediment replenishment, the bed load transport rate is positively correlated with skin friction, form drag, and riverbed morphological strength parameter; in the current scour stage where sediment replenishment is insufficient, the bed load transport rate decreases with the increase of riverbed morphological strength parameter.