Abstract
Experiments were conducted in a straight channel that widens from a single channel to a compound channel based on a real navigation channel with a similar shape in a mountainous region of China. Flow entered the single channel and then the compound channel with vegetated floodplains. The channel widened at the interface between the single and compound channels, resulting in different flow depths between the single and compound channels. An equation was proposed to estimate the percentage that the flow depth decreased from the single channel to the compound channel. Vegetation increased the floodplain resistance, causing more water to flow in the main channel and yielding a greater mean velocity in the main channel relative to the nonvegetated case. The velocity reached a maximum and gradually decreased until reaching a constant in the compound channel. Sediment motion (bedload vs. deposition) was determined by the local bed shear and the critical bed shear. Sediment was deposited in the compound channel at the position where the local bed shear was smaller than the critical bed shear. When the floodplains were vegetated, the increase in the main channel velocity enhanced the local bed shear, which surpassed the critical bed shear; thus, deposited sediment was reinitiated and moved downstream, and no deposition was observed.
Similar content being viewed by others
Abbreviations
- A :
-
Channel area
- A fp :
-
Floodplains channel area
- A mc :
-
Main channel area in the compound channel
- A sc :
-
Channel area in the single channel
- a :
-
Frontal area of vegetation per unit volume
- B :
-
Compound channel width
- B f :
-
Floodplain width
- B m :
-
Main channel width
- B s :
-
Single channel width
- Dr :
-
Relative flow depth in the compound channel
- d :
-
Stem width
- d s :
-
Particle diameter
- d * :
-
Dimensionless particle parameter
- Fr :
-
Channel Froude number
- g :
-
Local gravitational acceleration
- H :
-
Flow depth in the single channel or in the main channel of the compound channel
- H cc :
-
Flow depth at fully developed flow region in the main channel of the compound channel
- H f :
-
Flow depth at fully developed flow region on the floodplain of the compound channel
- H sc :
-
Mean flow depth at #-3.5 and #-3 in the single channel
- h :
-
Bankfull depth
- \(\overline{h}\) :
-
Mean flow depth
- h v :
-
Grass height
- K :
-
Velocity ratio
- N :
-
Grass density
- n :
-
Manning’s coefficient
- Q :
-
Upstream discharge
- Q fp :
-
Floodplain discharge at fully developed flow region in the compound channel
- Q mc :
-
Main channel discharge at fully developed flow region in the compound channel
- R :
-
Hydraulic radius
- Re :
-
Channel Reynolds number
- s :
-
Bed slope
- U d :
-
Depth-averaged velocity
- U fp :
-
Floodplain velocity at fully developed flow region in the compound channnel
- U mc :
-
Main channel velocity at fully developed flow region in the compound channel
- U sc :
-
Mean single channel velocity at -3.5# and 3# in the single channel
- U(x):
-
Main channel velocity at measurement transects
- u :
-
Measured velocity
- u * :
-
Local shear velocity
- u *c :
-
Critical shear velocity
- u *cc :
-
Local shear velocity in the compound channel
- u *sc :
-
Local shear velocity in the single channel
- x, y, z :
-
Longitudinal, lateral and vertical directions, respectively
- δ 0 :
-
Viscous sublayer thickness
- ε r :
-
Absolute relative error
- v :
-
Kinematic viscosity
- ρ :
-
Flow density
- ρ p :
-
Sediment density
- τb :
-
Bed shear stress
- τz :
-
Spatially averaged shear stress
- τzx :
-
Total shear stress
- τzx Rey :
-
Reynolds shear stress
- τzx vis :
-
Viscous shear stress
- τ*c :
-
Critical Shields parameter
- β :
-
Scale factor
References
Bousmar D, Proust S, Zech Y (2006) Experiments on the flow in an enlarging compound channel. In: Proceedings River Flow 2006 Conference, pp 323–332. https://doi.org/10.1201/9781439833865.ch32
Chen YK, Hu J, Song DD, Liu HT, Bao MJ (2015) Mathematical model and verification of reef-blasting regulation for Tongluoxia reach of Yangtze River. Port Waterway Eng (in Chinese) 6:131–136. https://doi.org/10.3969/j.issn.1002-4972.2015.06.027
Chlebek J, Bousmar D, Knight DW, Sterling M (2010) A comparison of overbank flow conditions in skewed and converging/diverging channels. In: River flow international conference, pp 503–511
Devi K, Khatua KK (2017) Flow distribution in an unsymmetrical compound channel. Ish J Hydraul Eng 24(1):16–24. https://doi.org/10.1080/09715010.2017.1340096
Ervine DA, Babaeyan-Koopaei K, Sellin RHJ (2000) Two-dimensional solution for straight and meandering overbank flows. J Hydraul Eng 126(9):653–669. https://doi.org/10.1061/(ASCE)0733-9429(2000)126:9(653)
Gao YS, Wang SY, Zhou SF, Wang XK (2014) Numerical study on the effects of flow motion on channel evolution in gradual width river. Adv Eng Sci (in Chinese) 46(2):14–19. https://doi.org/10.15961/j.jsuese.2014.02.004
Hu CH, Ji ZW, Guo QC (2010) Flow movement and sediment transport in compound channels. J Hydraul Res 48(1):23–32. https://doi.org/10.1080/00221680903568600
Huai WX, Gao M, Zeng YH, Li D (2009) Two-dimensional analytical solution for compound channel flows with vegetated floodplains. Appl Math Mech (English Edition) 30(9):1121–1130. https://doi.org/10.1007/s10483-009-0906-z
Huai WX, Wang WJ, Zeng YH (2013) Two-layer model for open channel flow with submerged flexible vegetation. J Hydraul Res 51(6):708–718. https://doi.org/10.1080/00221686.2013.818585
Julien PY (2010) Erosion and sedimentation. Cambridge University Press, Cambridge
Liu C, Luo X, Liu XN, Yang KJ (2013) Modeling depth-averaged velocity and bed shear stress in compound channels with emergent and submerged vegetation. Adv Water Resour 60:148–159. https://doi.org/10.1016/j.advwatres.2013.08.002
Liu C, Liu XN, Yang KJ (2014) Predictive model for stage-discharge curve in compound channels with vegetated floodplains. Appl Mathe Mech (English Edition) 35(12):1495–1508. https://doi.org/10.1007/s10483-014-1884-6
Liu C, Nepf H (2016) Sediment deposition within and around a finite patch of model vegetation over a range of channel velocity. Water Resour Res 52(1):600–612. https://doi.org/10.1002/2015WR018249
Liu C, Shan YQ, Liu XN, Yang KJ, Liao HS (2016) The effect of floodplain grass on the flow characteristics of meandering compound channels. J Hydrol 542:1–17. https://doi.org/10.1016/j.jhydrol.2016.07.037
Liu C, Shan YQ (2019) Analytical model for predicting the longitudinal profiles of velocities in a channel with a model vegetation patch. J Hydrol 576:561–574. https://doi.org/10.1016/j.jhydrol.2019.06.076
Nepf H, Ghisalberti M (2008) Flow and transport in channels with submerged vegetation. Acta Geophys 56(3):753–777. https://doi.org/10.2478/s11600-008-0017-y
Nepf H (2012) Flow and transport in regions with aquatic vegetation. Annu Rev Fluid Mech 44(1):123–142. https://doi.org/10.1146/annurev-fluid-120710-101048
Nelson PA, Brew AK, Morgan JA (2015) Morphodynamic response of a variable-width channel to changes in sediment supply. Water Resour Res 51(7):5717–5734. https://doi.org/10.1002/2014WR016806
Paola C, Straub K, Mohrig D, Reinhardt L (2009) The Unreasonable effectiveness of stratigraphic and geomorphic experiments. Earth-Sci Rev 97(1–4):1–43. https://doi.org/10.1016/j.earscirev.2009.05.003
Peng W, Shuai CF, Xin X (2010) Yangtze River: China’s golden waterway. Civ Eng 163(5):15–18. https://doi.org/10.1680/cien.2010.163.5.15
Proust S, Rivière N, Bousmar D, Paquier A (2006) Flow in compound channel with abrupt floodplain contraction. J Hydraul Eng 132(9):958–970. https://doi.org/10.1061/(ASCE)0733-9429(2006)132:9(958)
Proust S, Bousmar D, Rivière N, Paquier A, Zech Y (2010) Energy losses in compound open channels. Adv Water Resour 33(1):1–16. https://doi.org/10.1016/j.advwatres.2009.10.003
Rameshwaran P, Shiono K (2007) Quasi two-dimensional model for straight overbank flows through emergent. J Hydraul Res 45(3):302–315. https://doi.org/10.1080/00221686.2007.9521765
Rezaei B, Knight DW (2009) Application of the Shiono and Knight Method in compound channels with non-prismatic floodplains. J Hydraul Res 47(6):716–726. https://doi.org/10.3826/jhr.2009.3460
Rezaei B, Knight DW (2011) Overbank flow in compound channels with non-prismatic floodplains. J Hydraul Eng 137(8):815–824. https://doi.org/10.1061/(asce)hy.1943-7900.0000368
Sun X, Shiono K (2009) Flow resistance of one-line emergent vegetation along the floodplain edge of a compound open channel. Adv Water Resour 32(3):430–438. https://doi.org/10.1016/j.advwatres.2008.12.004
Shiono K, Chan TL, Spooner J, Rameshwaran P (2009) The effect of floodplain roughness on flow structures, bedforms and sediment transport rates in meandering channels with overbank flows: Part I. J Hydraul Res 47(1):5–19. https://doi.org/10.3826/jhr.2009.2944-I
Shan YQ, Liu C, Luo MK (2015) Simple analytical model for depth-averaged velocity in meandering compound channels. Appl Math Mech (English Edition) 36(6):707–718. https://doi.org/10.1007/s10483-015-1943-6
Shan YQ, Liu XN, Yang KJ, Liu C (2017) Analytical model for stage-discharge estimation in meandering compound channels with submerged flexible vegetation. Adv Water Resour 108:170–183. https://doi.org/10.1016/j.advwatres.2017.07.021
Shan YQ, Zhao T, Liu C, Nepf H (2020). Turbulence and bed-load transport in channels with randomly distributed emergent patches of model vegetation. Geophys Res Lett. https://doi.org/10.1029/2020GL087055
Wang SY, Zhou SF, Zhao XE, Liu XN, Wang XK (2013) Experimental study on the flow characteristics at local diverging-converging sections in mountain lotus root shape channel. Adv Eng Sci (in Chinese) 45(Supp2):51–54
Wang WJ, Huai WX, Li SL, Wang P, Wang YF, Zhang J (2019) Analytical solutions of velocity profile in flow through submerged vegetation with variable frontal width. J Hydrol 578:1–9. https://doi.org/10.1016/j.jhydrol.2019.124088
Wang YC, Chen XB, Borthwick AGL, Li TH, Liu HH, Yang SF, Zheng CM, Xu JH, Ni JR (2020) Sustainability of global Golden Inland Waterways. Nat Commun 11(1):1–13. https://doi.org/10.1038/s41467-020-15354-1
Yang KJ, Cao SY, Knight DW (2007) Flow Patterns in Compound Channels with Vegetated floodplains. J Hydraul Eng 133(2):148–159. https://doi.org/10.1061/(ASCE)0733-9429(2007)133:2(148)
Yang JQ, Kerger F, Nepf H (2015) Estimation of the bed shear stress in vegetated and bare channels with smooth beds. Water Resour Res 51(5):3647–3663. https://doi.org/10.1002/2014WR016042
Yang ZH, Li D, Huai WX, Liu JH (2019) A new method to estimate flow conveyance in a compound channel with vegetated floodplains based on energy balance. J Hydrol 575:921–929. https://doi.org/10.1016/j.jhydrol.2019.05.078
Acknowledgements
This project was supported by the National Natural Science Foundation of China (51879175), the Fok Ying Tung Education Foundation (171067) and Ministry of Education Chunhui Project (2020-703-3). The longitudinal profiles of flow depths and velocities are all shown in Supporting Information.
Author information
Authors and Affiliations
Corresponding author
Additional information
Publisher's Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Supplementary Information
Below is the link to the electronic supplementary material.
Rights and permissions
About this article
Cite this article
Li, F., Shan, Y., Huang, S. et al. Flow depth, velocity, and sediment motions in a straight widened channel with vegetated floodplains. Environ Fluid Mech 21, 483–501 (2021). https://doi.org/10.1007/s10652-021-09783-9
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s10652-021-09783-9