Cross‐shore sediment transport partitioning in the nearshore during a storm event

Vertical profiles of fluid velocity and sediment concentration have been collected across the surf‐zone during the SandyDuck '97 field experiment. Analysis from data collected during a 3‐day storm event shows that, in agreement with preceding observations, the mean component of cross‐shore sediment transport throughout the water column and across the surf‐zone is almost uniformly in the offshore direction. Similarly, the wave coherent component is generally onshore directed but does on rare occasions exhibit offshore transport. The infragravity component in these conditions, while exhibiting a definite offshore bias, is generally a negligible component. Thus net cross‐shore transport is predominately a balance between the wave coherent component and the mean component. In observations that stress the importance of the near bed region to cross‐shore sediment transport, it is shown that this balance is a function of elevation above the bed. The increasing importance of the wave coherent component as the bed is approached can lead to situations where the net transport direction shifts from being directed offshore higher in the water column to onshore directed near the bed.