- Wave energy dissipation by bottom muds is studied. A dissipation mechanism which contains explicit expressions of wavenumber modification due to a viscous bottom fluid is incorporated into a nonlinear wave shoaling model. This formulation allows a preliminary look at mud-induced energy decay without cumbersome root-finding numerics. Several cases of linear and nonlinear wave transformation over sloping and flat bottoms are run with the modified model. It is found that nonlinear energy exchange between spectral components, and a general trending toward spectral whiteness, is exacerbated in the presence of the mud layer. Strongest dissipation occurs only in the lower frequencies, contradicting field measurements of mud-induced decay which show dissipation over the entire frequency range. Thus, the need for a more comprehensive formulation of the interfacial dynamics between the water and the underlying mud layer is apparent.