This monograph presents selected analytical and direct simulation techniques for the problem of nonlinear wave interaction in a two-layer density stratified fluid. These techniques are specifically used to solve nonlinear wave-bottom and wave-wave interaction problems. In the first part of this book, a detailed analysis of the interaction of surface and interfacial waves with bottom topography, the so called Bragg resonance, is discussed. Second and third order resonances (triad and quartet) ar ...