Abstract

A depth integrated fluorescent tracer procedure was developed in order to study the movement of individual sand grains along the beach profile. The following pattern of littoral zone tidal-cycle sedimentation was derived from the collected data: During flood tide a small portion of the sediment eroded in the lower backwash scour zone is deposited just seaward of the upper swash limit. It consists mainly of the finer grain sizes of the beach sand. Most of the eroded sediment, including a large part of the coarse grains, is deposited in the building of the step under the breaker zone. There is a slight diffusion of fine grains seaward of the step to the shoaling wave zone. Sediment moved landward with the advance of the breaker zone is concentrated at the step. Ebb tide sedimentation is similar, but two slight differences can be discerned. The fine sediment eroded as the lower backwash scour zone is translated seaward is deposited seaward of the upper swash limit; however, as it is being deposited in a former scour zone it serves to restore the beach profile to its original form. Then too, there is little net diffusion of fine sediment to the shoaling wavezone when the breaker zone has returned to its original low-tide position. In upper swash deposition and step deposition there is a reversal of the sediment relative to the vertical position it held in the scour zone.

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