Sand Transport on Steeply Sloping Plane and Rippled Beds

Experiments on sand transport have been carried out in the Sloping Sediment Duct at HR Wallingford. The aim of the experiments was to investigate sediment transport mechanisms, for sand of varying degree of grading, on sloping beds. The Sloping Sediment Duct is a steady flow, recirculating duct, capable of generating mean flow speeds of up to 1 m/s and tilting to +/–30°. Twenty-two tests with two different sediments were conducted. Both sediments had a median grain size of about 0.23 mm but different standard deviations. Bed slopes up to +/–20° were used in the experiments. The results show that bedforms have a significant effect on the transport rate. Since the bedforms, in turn, are affected significantly by the slope, the relation between transport rate and slope is not a monotonic function. Maximum suspended transport rates were attained for downslope flows at angles of about 10°. The transport rate for widely graded sediment was significantly larger than that for well-sorted sediment for almost all flows and slopes.