Emergent vegetation flow with varying vertical porosity

Zhao, Meirong; Fan, Zi-long

doi:10.1007/s42241-018-0083-9

Cited by 8 publications

(2 citation statements)

References 25 publications

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“…The presence of emerged vegetation changes the velocity distribution in open channels. Numerous theoretical and empirical formulas have been proposed to approximate the vertical distribution of velocity in a vegetated channel (Gu et al, 2007;Huai et al, 2009a;Klopstra et al, 1997;Zhao and Fan, 2019).…”

Section: Velocity Distributionmentioning

confidence: 99%

Flow resistance of emergent rigid vegetation in steady flow

Wang,

Liu,

Sun

et al. 2024

Journal of Hydrology and Hydromechanics

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Enhanced understanding of flow resistance in open channels with emergent vegetation is essential for flood management and river ecosystem restoration. The presence of vegetation can significantly alter bed resistance, leading to a challenge in accurately predicting flow discharge, water levels, sediment transport, and bed deformation. Previous studies on vegetated flows have focused on vegetation resistance, on which the impact of vegetation has been ignored or poorly estimated. This study proposes a new analytical model, built upon the momentum conservation law, to predict flow resistance to vegetated zones in a plain bed without bed forms, explicitly quantifying bed resistance and vegetation resistance in a corollary manner. The proposed model is benchmarked against five typical sets of laboratory experiments. It is demonstrated that the present model using a modified logarithmic velocity distribution performs best, whereas that assuming a uniform velocity profile considerably overestimates the vegetation resistance and neglects the effect of vegetation on bed resistance. The ratio of bed resistance to the total resistance is shown to range between 5% and 40%, and it decreases with increasing vegetation density and decreases with water depth. Therefore, bed resistance cannot be ignored when modelling shallow water flow with sparsely distributed vegetation. It is also revealed that vegetation arrangements significantly affect flow resistance, and therefore a model incorporating the effect of vegetation arrangement performs better. Overall, the present model facilitates a viable and promising tool for quantifying flow resistance in emergent vegetated channels.

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Section: Velocity Distributionmentioning

confidence: 99%

Flow resistance of emergent rigid vegetation in steady flow

Wang,

Liu,

Sun

et al. 2024

Journal of Hydrology and Hydromechanics

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“…In‐channel aquatic vegetation exerts drag on the surface flow (Cheng & Nguyen, 2011; D’Ippolito et al., 2019), which creates spatial heterogeneities in near‐bed mean flow velocity (Zhao & Fan, 2019), shear stress (Salvador et al., 2007; Yang et al., 2015), turbulent kinetic energy (Xu & Nepf, 2020), and pressure (Nepf & Koch, 1999; Yuan et al., 2021). In addition, vegetation drag extracts energy from the mean flow and converts it to turbulent kinetic energy

{k}_{t}\,

(Nepf, 1999, 2012; Tanino & Nepf, 2008).…”

Section: Introductionmentioning

confidence: 99%

Impacts of Emergent Vegetation on Hyporheic Exchange

Huang

Yang

2022

Geophysical Research Letters

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Hyporheic exchange, or the exchange of water and solutes between surface and subsurface water at the sediment‐water interface, regulates water quality and biogeochemical cycle in aquatic ecosystems. Vegetation, which is ubiquitous in nature, is known to impact hyporheic exchange; yet how vegetation impacts hyporheic exchange remains to be characterized. Here, we show that at the same spatially and temporally‐averaged flow velocity U $U$, vegetation increases the rate of hyporheic exchange by a factor of four. By tracking the movement of fluorescent dye in a flume with the refractive‐index‐matched sediment and translucent vegetation dowels, we demonstrate that the vegetation‐induced hyporheic exchange can be characterized by an effective hyporheic exchange velocity, VH ${V}_{H}$. We further demonstrate that VH ${V}_{H}$ correlates with the total near‐bed turbulent kinetic energy kt ${k}_{t}$ rather than U $U$, when kt<6×10−40.25emm2/s2 ${k}_{t}< 6\times {10}^{-4}\,{\mathrm{m}}^{2}/{\mathrm{s}}^{2}$, indicating that turbulent kinetic energy is a better metric than flow velocity for predicting hyporheic exchange in regions with vegetation.

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