Spatial Variation in Sinusoidal Wave Energy on a Crescentic Nearshore Bar; Application to the Cap-Ferret Coast, France

Jean-Marie Froidefond, Jean-Marie Gallissaires, Robert Prud'Homme

Abstract


Simple sinusoidal wave refraction on a crescentic bar off the Aquitaine coast has been studied. In the case of parallel waves to the coast, this bar, composed of a cyclical repetition of troughs separated by ridges, induces a synchronous variation in wave height and energy flux along the shore. Energy flux is lower in the troughs than on the ridges. The longshore component of energy flux changes more rapidly than the total flux. The theoretical distribution of this energy is analyzed in comparison with the water depth changing in accordance with the tide. The results show a variation in the longshore component and thus a displacement of circulation cells and rip-currents during the course of the tide. In the case of oblique waves to the coast, the cyclic variation of energy flux decreases and the longshore component increases. The rip-currents are unwedged by comparison with the previous case. These results are compared with aerial photographs. A second crescentic bar and tidal channels complicate the refraction process.



Keywords


Crescentic bars; energy flux; parallel waves; refraction process; rip currents; tidal channel; French coast

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