MEAN CURRENTS AND SEDIMENT TRANSPORT IN A RIP CHANNEL

Measurements of hydrodynamics and suspended sediment transport were ca rried out along a cross-shore transect in a rip channel. A tidally ind uced threshold for rip flow initiation was found; this threshold depen ded upon the degree of wave energy dissipation and could be identified through a critical value of the ratio of significant wave height to w ater depth (gamma(s)) in the rip neck. With normally incident waves, r ip current velocities were well correlated with velocities predicted f rom a simple model involving the onshore mass transport in asymmetric breaking waves crossing the bar. Hydrodynamics and sediment transport were tidally modulated with strong offshore directed rip currents and associated offshore sediment transport due to the mean flow at low tid e. At high tide when the rip was inactive, the tendency was for weak o nshore directed mean flows and/or oscillatory incident waves transport ing smaller amounts of sediment landward. The net result was a gradual lowering of the topographic relief along the rip channel with net dep osition seaward of the rip. Outside the surf zone, transport was mainl y landward due to oscillatory incident waves. (C) 1997 Elsevier Scienc e B.V.