Discontinuity in equilibrium wave–current ripple dimensions on mixed clay-sand substrates

Xuxu Wu - University of Hull

We conducted a large-scale flume experiment to investigate combined-flow ripple development on mixed sand-clay beds. The experiment results reveal a threshold bed clay content controlling the generation of two distinct types of equilibrium ripples: large ripples are comparable with clean-sand counterparts and relatively small and flat ripples reflect strong bed cohesion preventing ripple growth. Additionally, we find clay loss at relatively deeper layer below the large equilibrium ripples due to strong clay winnowing under combined flow. This possibly reduces rippled bed stability.