Changes in Sediment Transport and Bed Topography in Response to Step-Up Flows in Laboratory Flume

摘要

It can be difficult to predict sediment transport in sand-bedded ephemeral streams because of rapidly changing conditions that may not be sustained long enough to reach equilibrium. This situation often leads to the inheritance of bed topography from previous flows, which may result in under- or overpredictions of transport rate due to bed forms and flow resistance that are not in equilibrium with the flow conditions. To address this difficulty, a series of lab experiments was used to examine changes in sediment transport rate and bed topography after rapid increases in flow depth and discharge. It was found that sand transport rates reached equilibrium conditions in as little as 1-15 min after the step-up in flow rate and depth. Transport rate equilibrium was likely reached in advance of centerline bed-form amplitude, although bed forms also responded quickly to step-up flows, and the response was much more rapid than in previous experiments that examined the effects of decreases in flow rate and depth. (C) 2021 Published by American Society of Civil Engineers.