ABSTRACT
The resuspension characteristics of cohesive bed sediment samples were assessed through
laboratory experiments using a device called the “shaker.” The samples were reconstructed in the laboratory from sediments obtained from ocean, estuarine, and riverine beds. Each sample was subjected to a series of increasing shear stresses, with each shear stress being maintained for a certain period. For each experiment, it was found that after a certain time into the resuspension process, the turbidity in the overlying water column reached a steady state indicating that net erosion at that time was equal to zero. The experimental observations affirm the theory that the bed armors after a finite amount of sediment has been resuspended into the water column due to the presence of underlying consolidated layers of greater shear strength. This prevents the underlying layers and particles from being exposed to the flow. At this point, the bed becomes armored. The steady state concentrations as well as the pre-steady state sediment concentrations in the overlying water column are influenced by the characteristics of the sediment bed and notably by the consolidation period of the sediment layers. For increasing bed shear stress, a longer time is required to attain steady-state concentrations in the water column. This is due to the variation in sediment strength with depth of the bed.
