Physical and Numerical Modeling of Submerged Vegetation Roughness in Rivers and Flood Plains
Publication: Journal of Hydrologic Engineering
Volume 16, Issue 11
Abstract
The Manning’s -value, a fundamental resistance coefficient to balance driving forces of a river stream, is known to depend on the flow condition (depth and velocity) as well as vegetation condition (type and density). In this study, flume experiments were conducted to investigate the variation of -value with flow and vegetation conditions for submerged vegetation in river beds, banks, and flood plains. Artificial plastic plants, for a length of 8 cm, were laid on the floor of a 4-m-long section of a variable slope flume. The Manning’s -values were estimated for different slopes, discharges, flow depths, and vegetation densities. The results reveal that the Manning roughness coefficient () increases as vegetation density increases, whereas it decreases when the flow depth and velocity increase. The proposed physical model in this study was customized as a subroutine in a numerical model (FASTER) for a large river reach. The estimated water levels and discharges by the model were much closer to the field records than those calculated by FASTER using a constant value for Manning’s . The advantage of the developed model is its capability to estimate the -value in subsections across the main channel and flood plains where cross-section geometry is known. The significant response of the proposed model to flow and vegetation states supports its application in practice.
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Acknowledgments
The writers acknowledge Professor Nicholas Kouwen at the Department of Civil Engineering of the University of Waterloo, Waterloo, Canada, for his invaluable comments on this research. Acknowledgement is also extended to the Chamran University of Ahwaz, the Center of Excellence on Operation Management of Irrigation and Drainage Networks, and the Khuzistan Water and Power Authority (KWPA) for financial support and facilitation of the experiments.
References
Baptist, M. J., Babovic, V., Uthurburu, J. R., Keijzer, M., Uittenbogaard, R. E., and Verwey, A. (2007). “On inducing equations for vegetation resistance.” J. Hydraul. Res., 45(4), 435–450.
Cui, J., and Neary, V. S. (2008). “LES study of turbulent flows with submerged vegetation.” J. Hydraul. Res., 46(3), 307–316.
Ebrahimi, N. G., Fathi-Moghadam, M., Kashefipour, M., Saneie, M., and Ebrahimi, K. (2008). “Effects of flow and vegetation states on river roughness coefficients.” J. Appl. Sci., 8(11), 2118–2123.
Einstein, H. A., and Banks, R. B. (1950). “Fluid resistance of composite roughness.” Trans., Am. Geophys. Union, 31(4), 603–610.
Fathi-Moghadam, M. (2007). “Characteristics and mechanics of tall vegetation for resistance to flow.” Afr. J. Biotechnol., 6(4), 475–480.
Fathi Moghadam, M., and Kouwen, N. (1997). “Nonrigid, nonsubmerged vegetative roughness on floodplains.” J. Hydraul. Eng., 123(1), 51–57.
Fischer-Antze, T., Stoesser, T., and Bates, P. (2001). “3D numerical modeling of open-channel flow with submerged vegetation.” J. Hydraul. Res., 39(3), 303–310.
Fisher, K., and Dawson, H. (2003). “Reducing uncertainty in river flood conveyance: Roughness review.” Project No. W5A-057Dept. for Environment, Food, and Rural Affairs/Environment Agency, London, UK.
Järvelä, J. (2002). “Flow resistance of flexible and stiff vegetation: A flume study with natural plants.” J. Hydrol. (Amsterdam), 269(1–2), 44–54.
Järvelä, J. (2003). “Influence of vegetation on flow structure in flood plains and wetlands.” Proc., 3rd IAHR Symp. on River, Coastal, and Estuarine Morphodynamics (RCEM 2003), International Association for Hydraulic Research, Madrid, Spain, 845–856.
Kashefipour, M., Lin, B., Harris, E. L., and Falconer, R. A. (2002). “Hydro-environmental modeling for bathing water compliance of an estuarine basin.” Water Res., 36(7), 1854–1868.
Keulegan, G. H. (1938). “Laws of turbulent flow in open channels.” J. Res. Natl. Bur. Stand. (U. S.), 21(6), 707–741.
Kothyari, U. C., Hashimoto, H., and Hayashi, K. (2009a). “Effect of tall vegetation on sediment transport by channel flows.” J. Hydraul. Res., 47(6), 700–710.
Kothyari, U. C., Hayashi, K., and Hashimoto, H. (2009a). “Drag coefficient of unsubmerged rigid vegetation stems in open channel flows.” J. Hydraul. Res., 47(6), 691–699.
Kouwen, N. (1992). “Modern approach to design of grassed channels.” J. Irrig. Drain Eng., 118(5), 733–743.
Kouwen, N., and Fathi-Moghadam, M. (2000). “Friction factors for coniferous trees along rivers.” J. Hydraul. Eng., 126(10), 732–740.
Nikora, V., Goring, D., McEwan, I., and Griffiths, G. (2001). “Spatially averaged open-channel flow over rough bed.” J. Hydraul. Eng., 127(2), 123–133.
Rameshwaran, P., and Shiono, K. (2007). “Quasi two-dimensional model for straight overbank flows through emergent vegetation on floodplains.” J. Hydraul. Res., 45(3), 302–315.
Righetti, M., and Armanini, A. (2002). “Flow resistance in open channel flows with sparsely distributed bushes.” J. Hydrol. (Amsterdam), 269(1–2), 55–64.
Stephan, U., and Gutknecht, D. (2002). “Hydraulic resistance of submerged flexible vegetation.” J. Hydrol. (Amsterdam), 269(1–2), 27–43.
Velasco, D., and Bateman, A. (2008). “A new integrated, hydro-mechanical model applied to flexible vegetation in riverbeds.” J. Hydraul. Res., 46(5), 579–597.
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Published In
Journal of Hydrologic Engineering
Volume 16 • Issue 11 • November 2011
Pages: 858 - 864
Copyright
© 2011 American Society of Civil Engineers.
History
Received: Jun 26, 2010
Accepted: Jan 12, 2011
Published online: Oct 14, 2011
Published in print: Nov 1, 2011
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