BREAKER TYPE AND PHASE SHIFTS ON NATURAL BEACHES

Peter J. Cowell

Abstract


The kinematics of incipient breakers were measured on various complex natural beaches. Water velocities were found to consistently lag behind the wave crest. This phase shift appears to be partly inherent in shoaling waves and partly a result of partial wave reflection. Phase shifts vary from 5 degrees through to quadrature. This variation probably depends to a large extent upon beach reflectivity and distance of the break point from the shoreline. Phase shifting also varies vertically beneath the wave crests from uniform distributions to those in which maximum shifts occur near the bed. There is a strong relationship between the nature of phase shifting, the morphodynamic condition and the breaker type. Surging waves were associated with large, and vertically uniform phase shifts. Waves towards the plunging and spilling end of the breaker type continuum occurred where phase shifts were significantly larger at lower depths than near the surface.

Keywords


breaker type; phase shifts; natural beach; breaking waves

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