ABSTRACT

It is essential in river dynamics to predict sediment movement and its impact on processes in the water column in unsteady sediment-laden water flows. The relationship between the dynamics of turbulent unsteady (accelerating and decelerating) depth-varying open-channel flow over a movable (but not moving) coarse gravel bed and fine sediment resuspension has been investigated. The thickness of the fine sediment (mean particle size about 160 µm) layer on the bed was stepwise increased. Using acoustic Doppler and imaging methods, quasi-instantaneous profiles of velocity and sediment concentration were taken simultaneously and collocated with spatial and temporal resolution of turbulence scales. A high-speed camera allowed for fine sediment resuspension visualization during the unsteady range. The event structure of resuspension is made evident.