Effective Hydraulic Roughness for Channels Having Bed Roughness Different from Bank Roughness: A State of the Art Report.
ARMY ENGINEER WATERWAYS EXPERIMENT STATION VICKSBURG MISS
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The report summarizes two numerical studies, one laboratory experimental study, and one analytical study of flow resistance in rectangular channels having one type or degree of boundary roughness on the bed and a second type or degree of roughness on the sidewalls. The numerical study showed that usual procedures for estimating resistance coefficients for channels of this type are not adequate. The laboratory study indicated that the relations between the effective Mannings n , the sidewall Mannings n , the bed Mannings n , and the channel geometry could be established empirically by extensive laboratory testing. The analytical study proved that laboratory studies using a smooth surface for one of its boundaries had little application to practical design problems. It also showed that the best solution to the problem probably would result by use of hydraulic roughness values to describe the boundary surfaces. The study showed that relatively large errors in estimating the hydraulic roughness effect only minor errors in capacity design. Author
- Hydrology, Limnology and Potamology
- Civil Engineering