Effects of Vegetation Arrangement and Floodplain-main Channel Interaction on the Longitudinal Dispersion Coefficient in Compound Channels

Document Type : Research Paper

Authors

1 Water Engineering Department, College of Agriculture, Shiraz University, Shiraz, Iran

2 Department of Irrigation and Reclamation Eng., Campus of Agriculture and Natural Resources, College of Agricultural Engineering and Technology, University of Tehran, Karaj, Iran.

Abstract

Several factors affecting pollutant transport in rivers. Among those, vegetation is less studied by researchers. Due to the appropriate conditions in floodplains, such as adequate moisture and fertile sediments, it is possible to develop and grow different types of vegetation in these areas. Depending on the type of vegetation, their effect on the flow and subsequently on mass transfer is different. In this paper, the effects of flow depth, vegetation arrangement, and the interaction between the floodplain and the main channel on the longitudinal dispersion coefficient, K, in a compound channel has been studied. The results show that K is greater in the main channel rather than the floodplain. In addition, the interaction of the main channel and floodplain increases the K values up to 30 and 88% for non-vegetated and vegetated conditions, respectively, which are statistically significant. Similarly, the effect of vegetation arrangement on the K values are statistically significant, and K /U*iHi is greater for the staggered arrangement rather than tandem arrangement.

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References

Ahsan, N. (2008). Estimating the Coefficient of Dispersion for a Natural Stream. World Academy of Science, Engineering and Technology, 44:131-135.
Chatila, L. & Townsend, R. (1998). Modeling of pollutant transport in compound open channels. Canadian Water Resources Journal, 23, 259–271.
Crowder, D. & Diplas, P. (2002). Vorticity and circulation: Spatial metrics for evaluating flow complexity in stream habitats. Canadian Journal of Fish Aquatic Science, 59: 633–645.
Deng, Z., Singh, V. & Bengtsson, L. (2001). Longitudinal dispersion coefficient in straight rivers. Journal of Hydraulic Engineering, ASCE, 127(11): 919–927.
Elder, J.W. (1959). The dispersion of a marked fluid in turbulent shear flow. Journal of Fluid Mechanics, 5(4): 544–560.
Farzadkhoo, M., Keshavarzi, A., Hamidifar, H. & Javan, M. (2018b) A comparative study of longitudinal dispersion models in rigid vegetated compound meandering channels, Journal of Environmental Management, 217:78-89
Farzadkhoo, M., Keshavarzi, A. & Hamidifar, H. (2017). Estimation of Longitudinal Dispersion Coefficient in Compound Channels with Two Rows of Rigid Vegetation (tree) over Floodplain. Journal of Hydraulics, 12(1), 85-91. (In Farsi)
Farzadkhoo, M., Keshavarzi, A., Hamidifar, H., & Ball, J. (2018a). Flow and longitudinal dispersion in channel with partly rigid floodplain vegetation. In Proceedings of the Institution of Civil Engineers-Water Management (pp. 1-12). Thomas Telford Ltd.
Fischer, H.B., List, E.J., Koh, R.C.Y., Imberger, J. & Brooks, N.H. (1979). Mixing in Inland and Coastal Waters, Academic Press.
Hamidifar, H., Omid, M.H. & Keshavarzi, A. (2013) Mean Flow and Turbulence in Compound Channels with Vegetated Floodplains, Journal of Agricultural Engineering Research. 14(3):51-66 (In Farsi)
Hamidifar, H., Omid, M.H. & Keshavarzi, A. (2015). Longitudinal dispersion in waterways with vegetated floodplain. Ecological Engineering, 84:398-407
Hamidifar, H., Omid, M.H., Bahrami, M. & Amiri, M. (2016). Application of digital image processing technique for prediction of longitudinal dispersion coefficient in compound channels. Journal of Water and Soil Conservation, Vol. 23(4), 281-293.(In Farsi)
Iwasa, Y. & Aya, S., (1991). Predicting longitudinal dispersion coefficient in open channel flows. In: Proceeding of International Symposium on Environmental Hydraulic, Hong Kong, pp. 505–510.
Jael, A., Mousavi-Jahromi, S.H., Kashefipour, S.M., Soltani-Mohammadi, A. & Ghane, A. (2008). Estimating longitudinal dispersion coefficient in irrigation canals. In: Second Congress on Irrigation and Drainage Network Management, 28–30 January, Shahid Chamran University, Ahvaz, Iran. (In Farsi)
Kashefipour, S.M. & Falconer, R.A. (2002). Longitudinal dispersion coefficients in natural channels. Water Research. 36: 1596–1608.
Kim, D. (2012). Assessment of longitudinal dispersion coefficients using Acoustic Doppler Current Profilers in large river. Journal of Hydro-environment Research, 6: 29-39.
Lin, B., & Shiono, K. (1995). Numerical modelling of solute transport in compound channel flows. Journal of Hydraulic Research, 33(6): 773-788.
Liu, H. (1977). Predicting dispersion coefficient of stream. Journal of Environment Engineering Division, ASCE, 103(1): 59–69.
Nepf, H. M., Sullivan, J. A., & Zavistoski, R. A. (1997). A model for diffusion within emergent vegetation. Limnology and Oceanography, 42(8), 1735-1745.
Pourmoghadam, M. (2008). Spreading of nonreactive solutions in a compound channel. M.Sc. Thesis, Hydraulic Structures, Irrigation and Reclamation Engineering Department, University of Tehran. (In Farsi)
Rutherford, J.C. (1994). River mixing. New York: John Wiley & Sons, pp. 347.
Seo, I.W. & Cheong, T.S. (1998). Predicting longitudinal dispersion coefficient in natural streams. Journal of Hydraulic Engineering, 124(1): 25–32.
 
Simon, A. & Collison, A.J.C. (2002). Quantifying the mechanical and hydrologic effects of riparian vegetation on streambank stability. Earth Surface Processes and Landforms, 27: 527–546.
Windham, L., Weis, J.S., & Weis, P. (2003). Uptake and distribution of metals in two dominant salt marsh macrophytes. Estuarine Coastal Shelf Science, 56: 63–72.
Iranian Journal of Soil and Water Research
Volume 51, Issue 2
May 2020
Pages 479-488

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