LONGSHORE CURRENT AND LATERAL MIXING IN THE SURF ZONE

Ichiro Deguchi, Toru Sawagi, Masanobu Ono

Abstract


We investigated the occurrence of FIG waves generated by a shear instability of steady longshore current on a uniformly sloping beach so that we can discuss the characteristic of Fig waves with respect to a wave breaking. We also carried out experiment to investigate cross-shore distribution of lateral mixing coefficient that determines the cross-shore profile of longshore current. It is found that the occurrence and characteristic of FIG waves depend on a crossshore profile of steady longshore current on the uniformly sloping beach as well as those on a beach of a constant depth analyzed by Bowen et al.(1989). The bottom slope affects FIG waves indirectly through the cross-shore profile of longshore current. The measured lateral mixing coefficient, which also gives influence on longshore currents, becomes maximum within the surf zone and decreases rapidly toward offshore. The locus where the maximum longshore current occurs, that plays an important role in the generation of FIG waves, depends on the surf similarity parameter of the incident wave.

Keywords


lateral mixing; surf zone; longshore current; current

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