Erosion and Deposition of Cohesive Soils

The effects of shear stress, suspended sediment concentration, and shear strength of bed on the erosion rates of a cohesive bed in an open channel with salt water have been investigated. The deposition rates of suspended cohesive sediment and the patterns of bed erosion have been studied to a lesser extent. For the experimental range the erosion rates were found to be independent of the shear strength of the bed and the concentration of suspended sediment. They depend strongly on the bed shear stress. The minimum shear stresses for initiation of erosion were also found to be independent of the shear strength of bed. There seems to exist a critical velocity for the clay part of suspended sediment, above which all such sediment remains in suspension, whereas even for velocities slightly below this critical limit, the suspended clay deposits rapidly. Scouring occurred predominantly within a well defined narrow and relatively straight zone near the center of the flume.