Flow Velocity Measurements in Vegetated Channels
Publication: Journal of Hydraulic Engineering
Volume 128, Issue 7
Abstract
Understanding of the hydraulics of flow over vegetation is very important to support the management of fluvial processes. In this paper the flow over flexible bottom vegetation is experimentally studied. A two-dimensional-acoustic doppler velocimeter is used to measure the local flow velocities for different vegetation concentrations, discharges, and flume slopes. The influence of vegetation concentration and the depth/vegetation height ratio on the measured velocity profiles is analyzed. All measured velocity distributions are S-shaped and exhibit a three-zone profile. The relationship between the velocity distribution and the turbulence intensity distribution is also analyzed. The characteristics (inflection point, maximum value, asymptotes) of the measured velocity distributions and the results of the previous investigators are used to select an analytical expression for the shape of the velocity profile. A theoretical velocity profile is deduced using the classical Prandtl’s mixing length approach with a new expression for the mixing length. The deduced four-coefficient profile allows description of the flow both inside and above the vegetation. The physical and geometrical meaning of the four coefficients are also shown.
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Published In
Journal of Hydraulic Engineering
Volume 128 • Issue 7 • July 2002
Pages: 664 - 673
Copyright
Copyright © 2002 American Society of Civil Engineers.
History
Received: Feb 6, 2001
Accepted: Nov 28, 2001
Published online: Jun 14, 2002
Published in print: Jul 2002
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