Measurement of shear velocity and bed load discharge

Abstract

Most of bed load formulas employ shear velocity to predict bed load discharge. However, it is very difficult to measure local shear velocity over the bed with sand waves because flow resistance over sand waves is composed of grain roughness and form roughness and have been evaluated in one wavelength. A new method is introduced to determine the local shear velocity for evaluating bed load discharge. The bed load discharge predicted by the new method is compared with results obtained from an experiment using aDcps and a multibeam echo sounder in an experimental flume nearly as large as an actual river. We also found that bed load discharge estimated using the local shear velocity can successfully reproduce bed load calculated based on a longitudinal riverbed elevation profile observed by a multibeam echo sounder.