Flexible Roughness in Open Channels

by Nicholas Kouwen, (A.M.ASCE), Asst. Prof. of Civ. Engrg.; Univ. of Waterloo, Waterloo, ON, Canada,
Tharakkal Eroman Unny, (A.M.ASCE), Prof. of Civ. Engrg.; Univ. of Waterloo, Waterloo, ON, Canada,

Serial Information: Journal of the Hydraulics Division, 1973, Vol. 99, Issue 5, Pg. 713-728

Document Type: Journal Paper

Discussion: Gourlay Michael R. (See full record)


The logarithmic flow formula for open channels is valid for flow over a roughness cover made up of flexible plastic strips. The deflection of such roughness is an important parameter as the deflection directly influences the relative roughness. Dimensionless parameters which relate the amount of bending to the stiffness of the roughness and the boundary shear are defined. Three regimes of boundary behavior are observed for flexible plastic roughness, leading to two resistance functions. The flexible plastic roughness is produced by affixing thin plastic strips of various thickness to the bed of a flume. The flow of water over flexible plastic strips simulates flow over a vegetative channel lining.

Subject Headings: Hydraulic roughness | Plastics | Open channels | Flow simulation | Displacement (mechanics) | Parameters (statistics) | Open channel flow | Boundary shear

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