Nonrigid, Nonsubmerged, Vegetative Roughness on Floodplains

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 floodpla...

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Bibliographic Details
Published in:Journal of hydraulic engineering (New York, N.Y.) N.Y.), 1997-01, Vol.123 (1), p.51-57
Main Authors: Fathi-Maghadam, M, Kouwen, N
Format: Article
Language:English
Subjects:
Absorbing
Coefficients
Density
Dimensions
Drag (hindrance)
Earth sciences
Earth, ocean, space
Errors
Exact sciences and technology
Extreme values
Fluid mechanics
Flumes
Hydraulic engineering
Hydraulic structures
Hydrology
Hydrology. Hydrogeology
Mathematical models
Momentum
Rigidity
Roughness
Roughness measurement
Sediments
TECHNICAL PAPERS
Trees
Variations
Vegetation
Velocity
Waterways
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Summary: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.
ISSN:0733-9429
1943-7900
DOI:10.1061/(ASCE)0733-9429(1997)123:1(51)