SWASH ON A NATURAL BEACH

Masaur Mizuguchi

Abstract


A field measurement was conducted in order to clarify the swash motion on a natural beach. It is found on this particular beach, which had a rather steep foreshore slope, that cross spectra calculated between the surface elevations, onshore velocities and the swash agree very well with those given by linear long two-dimensional standing wave theory in the lower frequency region than a certain value. This finding together with the observed f~ (f; frequency) high frequency saturation in swash spectra encourages a partial reflection model to describe the fluid motion in the inner surf zone, including the swash. The model developed shows a good agreement with the observed results, in which being employed an analogy to regular waves for the criticality of wave reflection. This model makes it possible to predict the swash spectrum for a given incident wave spectra and a given beach profile, as far as wave breaking takes place on a foreshore slope.

Keywords


swash; natural beach; beach swash; field measurement

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