Water wave propagation over uneven bottoms

In Part I of this report, a time dependent form of the reduced wave equation of Berkhoff is developed for the case of water waves propagating over a bed consisting of ripples superimposed on an otherwise slowly varying mean depth which satisfies the mild slope assumption. The ripples are assumed to have wavelengths on the order of the surface wave length but amplitudes which scale as a small parameter along with the bottom slope. The theory is verified by showing that it reduces to the case of plane waves propagating over a non-dimensional, infinite patch of sinusoidal ripples, studied recently by Davis and Heathershaw and Mei. We then study two cases of interest--formulation and use of the coupled parabolic equations for propagation over patches of arbitrary form in order to study wave reflection, and propagation of trapped waves along an infinite ripple patch. In the second part, we use the results of Part 1 to extend the results for weakly-nonlinear wave propagation to the case of partial reflection from bottoms with mild-sloping mean depth with superposed small amplitude undulations.