Nonrigid, Nonsubmerged, Vegetative Roughness on Floodplains
Publication: Journal of Hydraulic Engineering
Volume 123, Issue 1
Abstract
Individual pine and cedar tree saplings and branches were used to model the resistance to flow in a water flume for nonsubmerged and nonrigid vegetation to determine the amount that streamlining decreases the drag coefficient and reduces the momentum absorbing area. Currently, vegetation on floodplains is commonly assumed to behave as rigid roughness that can lead to large errors in the relationships between velocity and drag force. This presents a basic fluid mechanics problem. An extreme variation of roughness with depth of flow can result due to a large increase in the momentum absorbing area in nonsubmerged vegetation as depth is increased. This deems all the available roughness equations (which generally are based on relative roughness approach) useless for this application. In this paper a dimensional analysis, supported by experimental results, is developed to obtain a relationship between roughness conditions (i.e., density and flexural rigidity) and flow conditions (i.e., velocity and depth) for floodplains and vegetative zones of natural waterways.
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Published In
Journal of Hydraulic Engineering
Volume 123 • Issue 1 • January 1997
Pages: 51 - 57
Copyright
Copyright © 1997 American Society of Civil Engineers.
History
Published online: Jan 1, 1997
Published in print: Jan 1997
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