Estimating cohesive sediment erosion and deposition rates in wide rivers

Abstract

Sediment erosion and deposition rates are two of the most important factors that influence fluvial geomorphology. Several experimental devices have been constructed to estimate cohesive sediment erosion rate. However, estimated erosion rates may not be reliable for large rivers due to limited soil sampling and a high dependency of cohesive sediment behaviour on several physical, mechanical, and electrochemical properties of the sediment and eroding fluid. A new methodology has been developed to estimate the erosion and deposition rate of wide rivers using in situ measurements. To test this methodology, an acoustic Doppler current profiler was used to collect bathymetry and velocity profiles over a study area along the Red River in Winnipeg, Canada. Sediment concentration profiles along an 8.5 km reach of the river were measured several times under different flow conditions. Finally, an advection–dispersion equation was numerically solved using measured and calculated streamwise dispersion coefficients, flow and channel characteristics to calculate net erosion and deposition over the study area. Moreover, an exponential relationship was obtained between the river discharge and longitudinal dispersion coefficient for the Red River.