ABSTRACT
Physical model tests were carried out in a closed-circuit flume to investigate the overall erosion stability of wide-graded bed material in estuarine and coastal conditions by means of simulating tidal flow conditions with reversing currents. As a result of the reversing flow conditions, previously protected sediment eventually becomes exposed again, leading to bidirectional displacement processes in dependency of the flow direction. Furthermore, sediment fractions are slightly coarser under the following reversed flow than under the initial flow. This indicates higher critical shear stresses and thus erosion stability for the initial flow direction. In comparison to unidirectional current, this study finds a higher erosion stability for sediment fractions smaller than the median d 50 diameter of the initial bed material under reversed current conditions.
