An experimental study on profile changes of sandy seabed under breaking waves

Sediment transport induced by wave breaking on the sandy sloping seabed leads to bed profile changes. Research on the mechanism of sandy seabed morphology change under the action of breaking waves is of great important to analyze the beach evolution. Experiments in this study are carried out in a wave flume on a 1:20 sloping artificial seabed, which is made of sands with median diameter of 0.47mm. The bed profile variations and the suspended sediment concentration on the top of the sandy bar are measured. By calculating the sediment transport rate in the surf zone as well as the dimensions and moving speed of the sandbar, the evolution of the seabed profile under breaking waves is analyzed. Experimental results show that the suspended sediment concentration in the surf zone on top of the sandbar is closely related to the local water depth and bed morphology. The concentration of the suspended sediment is larger when the sandbar forms and moves horizontally. There are both onshore and offshore movement of the sandbar and the back-and-forth movement of the sandbar on the slope have a random period. The dimensions of the sandbar tend to be stable and the net sediment transport tends to be zero under the action of wave trains. The result provides a reference for further study on the beach evolution.