Effects of Vegetation Canopy Density and Bank Angle on Near-Bank Patterns of Turbulence and Reynolds Stresses
Publication: Journal of Hydraulic Engineering
Volume 138, Issue 11
Abstract
Vegetation growing on the surface of a streambank has been shown to alter the shear stresses applied to the boundary, but basic questions remain regarding the influence of vegetation and streambank configurations on near-bank hydraulics. In the present study, Froude-scaled flume experiments were used to investigate how changes in vegetation density (ratio of frontal area to channel area, including both stems and leaves) and bank surface angle influence near-bank turbulence intensities () and Reynolds stresses ( and ) estimated using velocities obtained with an acoustic Doppler velocimeter positioned beneath the canopy. Results illustrate how, with increasing vegetation density, turbulence intensities and Reynolds stresses decreased along the sloped bank surface but increased at the base of the slope and within the main channel. The steeper bank angle resulted in greater vertical stresses on the bank surface than the shallower angle, but lateral momentum exchange was larger than vertical exchange along the base of the slope, regardless of bank angle. Leaves were an important influence on near-bank turbulence intensities and Reynolds stresses, whereas the influence of bank slope was small relative to the influence of vegetation density.
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Acknowledgments
Support for this research was provided by an NSF IGERT graduate fellowship (NSF award 0333257) in the Ecosystem Informatics IGERT program at Oregon State University and the USDA-ARS National Sedimentation Laboratory at Oxford, Mississippi. Cross-sections at the Goodwin Creek bendway site were surveyed by staff of the Watershed Physical Processes Research Unit of the USDA-ARS-NSL. The authors appreciate advice provided by Vincent Neary. The authors are also grateful for technical advice and review provided by Daniel Wren and technical assistance provided by Lee Patterson. This manuscript was greatly improved by the comments of four anonymous reviewers, the associate editor, and the editor.
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Information & Authors
Information
Published In
Journal of Hydraulic Engineering
Volume 138 • Issue 11 • November 2012
Pages: 974 - 978
Copyright
© 2012 American Society of Civil Engineers.
History
Received: Feb 19, 2011
Accepted: May 11, 2012
Published online: May 14, 2012
Published in print: Nov 1, 2012
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