TRAPPED AND FREE-WAVE PROPAGATION IN CHANNELS AND HARBOURS

Joao A. Santos, D.H. Peregrine

Abstract

Most of the literature on edge waves is only concerned with edge-wave propagation over a bottom that is uniform in the propagation direction.  There is still little knowledge of what happens when the bottom topography changes suddenly, as in the presence ofa cape, submarine valley or harbour.  This paper presents some results of our study on the wave motion in such places, where edge waves may be transmitted, reflected or radiated as free waves and thus may have an important role in determining the wave conditions in otherwise sheltered regions.  We send an edge wave along a coast with an alongshore uniform bottom profile and, at a given section change suddenly for another bottom profile.  This study is carried out with a very simple model.  The linearised shallow water equations are used in a wide channel with the simplest bottom profile that enables the existence of edge waves: a ledge close to the coast and a uniform depth offshore.