Sediment load calculations from point measurements in sand-bed rivers

Abstract

Point velocity and suspended sediment concentration measurements are used to calculate the total sediment discharge in sand-bed rivers. Calculations with the Series Expansion of the Modified Einstein Point Procedure (SEMEPP) depend on grain diameter ds and settling velocity ω, flow depth h shear velocity u*, and sampling depth hp. This procedure extends the applicability of the Modified Einstein Procedure (MEP) by using point sediment concentration and velocity measurements. This procedure is tested using the laboratory data from Coleman, and field measurements from the Enoree, Middle Rio Grande and Mississippi Rivers. Based on 801 point measurements over 124 verticals at flow depths ranging from 0.17 m to 33.5 m and sediment concentrations less than 0.1 kg L−1, the accuracy of the calculations depends on u*/ω and hp/ds. Point measurement techniques like SEMEPP are well-suited when u*/ω 5 where at least 60% of the total sediment load is measured when 90% of the flow depth is sampled. The determination of sediment discharge from point measurements is most accurate in deep rivers when hp/ds > 10,000, and u*/ω > 10. Point measurements are not well-suited for shallow rivers and laboratory flumes where h < 0.5 m and when u*/ω < 2.