Abstract
The planting of the vegetation on the floodplain helps the ecological restoration, which is the main form of the river’s ecological corridor. Therefore, the current research of the river dynamics focuses on the water movement under a compound channel with the vegetated floodplains. Two simulated vegetation species are selected in this paper for the flume simulation experiments of the floodplain vegetation, and the compound channel is divided into three subregions in the transverse direction. The Navier-Stokes equation and the eddy viscosity theory are applied to obtain the transverse distribution of the depth-averaged velocity and the results agree well with the experimental data. This paper proposes a new method based on the analytical solution of the flow velocity distribution to calculate the average flow velocity in each section. Calculation results can effectively simulate the average flow velocity of the measured sections. The description of the pollutant transport processes in a moving stream requires a refined determination of the dispersion coefficients in the compound channel. The process of the pollutant concentrations in each zone and the reasons for their occurrence are elucidated on the basis of the experimental results. Simultaneously, the measured values of the longitudinal dispersion coefficients are obtained by the “routing procedure,” and a two-zone model of the pollutant dispersion is constructed on the basis of the hydrodynamic study. The prediction method for the longitudinal dispersion coefficients is also presented. Applying the predicted and measured section average flow velocities to the two-zone model to predict the longitudinal dispersion coefficient, and the average relative errors are only 4.17%, 7.15%, respectively. This result indicates that the two-zone model can effectively predict the longitudinal dispersion coefficients. The calculation methods for the longitudinal dispersion coefficients from—various studies are compared. The results reveal that the predicted values of these calculation methods are all larger than the measured values, indicating that the vegetation has a considerable influence on the dispersion process. This study comprehensively shows the dispersion features of the pollutants and provides a theoretical basis for the planning and the design of the vegetated ecological corridors.
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References
Liu C., Shan Y. Impact of an emergent model vegetation patch on flow adjustment and velocity [C]. Proceedings of the Institution of Civil Engineers-Water Management, 2022, 175: 55–66.
Huai W. X., Li S., Katul G. G. et al. Flow dynamics and sediment transport in vegetated rivers: A review [J]. Journal of Hydrodynamics, 2021, 33(3): 400–420.
Wang W. J., Huai W. X., Thompson S. et al. Steady nonuniform shallow flow within emergent vegetation [J]. Water Resources Research, 2015, 51(12): 10047–10064.
Sun X., Shiono K. Flow resistance of one-line emergent vegetation along the floodplain edge of a compound open channel [J]. Advances in Water Resources, 2009, 32(3): 430–438.
Huai W., Zhang J., Katul G. G. et al. The structure of turbulent flow through submerged flexible vegetation [J]. Journal of Hydrodynamics, 2019, 31(2): 274–292.
Liu C., Shan Y., Sun W. et al. An open channel with an emergent vegetation patch: Predicting the longitudinal profiles of velocities based on exponential decay [J]. Journal of Hydrology, 2020, 582: 124429.
Li Y., Wang Y., Anim D. O. et al. Flow characteristics in different densities of submerged flexible vegetation from an open-channel flume study of artificial plants [J]. Geomorphology, 2014, 204: 314–324.
Fernandes J. N., Leal J. B., Cardoso A. H. Improvement of the lateral distribution method based on the mixing layer theory [J]. Advances in Water Resources, 2014, 69: 159–167.
Wang W. J., Huai W. X., Li S. et al. Analytical solutions of velocity profile in flow through submerged vegetation with variable frontal width [J]. Journal of hydrology, 2019, 578: 124088.
Wu Z., Singh A., Foufoula-Georgiou E. et al. A velocity-variation-based formulation for bedload particle hops in rivers [J]. Journal of Fluid Mechanics, 2021, 912: A33
Murphy E., Ghisalberti M., Nepf H. Model and laboratory study of dispersion in flows with submerged vegetation [J]. Water Resources Research, 2007, 43(5): 687–696.
Huai W., Shi H., Song S. et al. A simplified method for estimating the longitudinal dispersion coefficient in ecological channels with vegetation [J]. Ecological Indicators, 2018, 92: 91–98.
Liu X., Huai W., Wang Y. et al. Evaluation of a random displacement model for predicting longitudinal dispersion in flow through suspended canopies [J]. Ecological Engineering, 2018, 116: 133–142.
Sonnenwald F., Stovin V., Guymer I. A stem spacing-based non-dimensional model for predicting longitudinal dispersion in low-density emergent vegetation [J]. Acta Geophysica, 2019, 67(3): 943–949.
Shiono K., Knight D. W. Turbulent open-channel flows with variable depth across the channel [J]. Journal of Fluid Mechanics, 1991, 222: 617–646.
Huai W., Xu Z., Yang Z. et al. Two dimensional analytical solution for a partially vegetated compound channel flow [J]. Applied Mathematics and Mechanics (Engilsh Edition), 2008, 29(8): 1077–1084.
Stone B. M., Shen H. T. Hydraulic resistance of flow in channels with cylindrical roughness [J]. Journal of Hydraulic Engineering, ASCE, 2002, 128(5): 500–506.
Schlichting H., Gersten K. Boundary-layer theory [M]. NewYork, USA: McGraw-Hill, 1979.
Pasche E., Rouvé G. Overbank flow with vegetatively roughened flood plains [J]. Journal of Hydraulic Engineering, ASCE, 1985, 111(9):1262–1278.
Fischer H. B. “Discussion of ‘simple method for predicting dispersion in streams’ by McQuivey R S and TN Keefer T” [J]. Journal of the Environmental Engineering Division, 1975, 101(3): 453–455.
Deng Z. Q., Singh V. P., Bengtsson L. Longitudinal dispersion coefficient in straight rivers [J]. Journal of Hydraulic Engineering, ASCE, 2001, 127(11): 919–927.
Zeng Y., Huai W. Estimation of longitudinal dispersion coefficient in rivers [J]. Journal of Hydro-Environment Research, 2014, 8(1): 2–8.
Wang Y., Huai W. Estimating the longitudinal dispersion coefficient in straight natural rivers [J]. Journal of Hydraulic Engineering, ASCE, 2016, 142(11): 04016048.
Boxall J. B., Guymer I. Longitudinal mixing in meandering channels: New experimental data set and verification of a predictive technique [J]. Water Research, 2007, 41(2): 341–354.
White B. L., Nepf H. A vortex-based model of velocity and shear stress in a partially vegetated shallow channel [J]. Water Resources Research, 2008, 44: W01412.
Nepf H. M. Vegetated flow dynamics [J]. The Ecogeomorphology of Tidal Marshes, 2004, 59: 137–163.
Nepf H. Drag, turbulence, and diffusion in flow through emergent vegetation [J]. Water Resources Research, 1999, 35(2): 479–489.
Fischer H. B. Dispersion predictions in natural streams [J]. Journal of the Sanitary Engineering Division, 1968, 94: 927–943.
Rominger J. T., Nepf H. Flow adjustment and interior flow associated with a rectangular porous obstruction [J]. Journal of Fluid Mechanics, 2011, 680: 636–659.
Liu C., Nepf H. Sediment deposition within and around a finite patch of model vegetation over a range of channel velocity [J]. Water Resources Research, 2016, 51: 600–612.
Acknowledgements
This work was supported by the Research project of China Three Gorges Corporation (Grant No. 202103399), the Talent Program of China Institute of Water Resources and Hydropower Research (Grant No. WE0199A052021) and the Basic Scientific Research Expense Project of IWHR (Grant No. WR0145B022021).
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Project supported by the National Key Research and Development Program of China (Grant No. 2019YFD1100205), the National Natural Science Foundation of China (Grant Nos. 51809286, 52209083, 51809288, 41501204 and U1802241).
Biography: Yan-fang Zhao (1996-), Male, Master
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Zhao, Yf., Fan, Jj., Wang, Wj. et al. Dispersion features of pollutants in a compound channel with vegetated floodplains. J Hydrodyn 34, 1095–1105 (2022). https://doi.org/10.1007/s42241-023-0084-1
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DOI: https://doi.org/10.1007/s42241-023-0084-1