Energy Dissipation on a Rough Slope

Assuming long normally incident waves, described by linear theory, the energy dissipation on a rough slope is accounted for by introducing a term expressing the bottom shear stress. The theoretical development leads to a determination of the reflection coefficient as a function of the horizontal extent of the slope relative to the wave length in front of the slope and an equivalent slope friction factor. A method for the accurate determination of the reflection coefficient from experimental data is developed and used to establish an empirical relationship for the frictional characteristics of a rough slope. The resulting semi-empirical procedure for estimating the reflection coefficient of rough slopes is shown to yield fairly accurate results. The results show that bottom friction may account for the dissipation of 80% of the incident wave energy on a slope as large as 1:3 where the incident waves show no sign of breaking.