Energy Dissipation on a Rough Slope

by Ole Secher Madsen, (M.ASCE), Assoc. Prof.; Ralph M. Parsons Lab., Dept. of Civ. Engrg., MIT, Cambridge, Mass.,
Stanley M. White, (A.M.ASCE), Research Asst.; Ralph M. Parsons Lab., Dept. of Civ. Engrg., MIT, Cambridge, Mass.,

Serial Information: Journal of the Waterways, Harbors and Coastal Engineering Division, 1976, Vol. 102, Issue 1, Pg. 31-48

Document Type: Journal Paper


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.

Subject Headings: Friction | Energy dissipation | Slopes | Shear stress | Hydro power | Long waves | Linear functions | Shear waves

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