Localisation of coastal trapped waves by longshore variations in bottom topography

Variations in shelf geometry mean that a coastal trapped wave mode can propagate within some finite length of shelf but be evanescent outside this region. This paper constructs such geographically localised coastal trapped waves using a WKBJ approximation. Comparison with full numerical solutions of the non-linear differential eigenvalue problem demonstrates that the approximation is extremely accurate. The asymptotic and full numerical models are then used to examine the parameters and geometries that govern the existence of these modes.