The effect of floodplain grass on the flow characteristics of meandering compound channels

Liu, Chao; Shan, Yuqi; Liu, Xingnian; Yang, Kejun; Liao, Huasheng

doi:10.1016/j.jhydrol.2016.07.037

Cited by 44 publications

(16 citation statements)

References 52 publications

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“…The cell then rapidly decays after the apex section and disappears before the formation of a new cell (see Fig. 8b in Liu et al 2016a). A similar development process of secondary current cells was reported based on experimental observations (e.g., Shiono et al 2008) and numerical simulations (e.g., Jing et al 2009).…”

Section: Introductionsupporting

confidence: 79%

“…However, when river flood occurs, the floodplains on the two sides of the main river are inundated, forming a meandering compound channel in which the floodplain water and main channel water have different depth-averaged two-dimensional flow directions in the meandering belt, particularly within crossover sections (Shiono et al 2009;Liu et al 2014). Numerous previous studies have investigated the complex three-dimensional flow patterns along meanders in meandering channels with overbank flows (e.g., Shiono and Muto 1998;Lyness et al 2001;Spooner 2001;Wormleaton et al 2004;Shiono et al 2008Shiono et al , 2009Liu et al 2016a) and found that the upstream floodplain flow can significantly affect the main channel flow in crossover sections. For example, the mean velocity in a meandering main channel reaches a maximum at the apex section and a minimum in crossover sections because of the influence of upstream floodplain flows (Liu et al 2014(Liu et al , 2016a.…”

Section: Introductionmentioning

confidence: 99%

“…Numerous previous studies have investigated the complex three-dimensional flow patterns along meanders in meandering channels with overbank flows (e.g., Shiono and Muto 1998;Lyness et al 2001;Spooner 2001;Wormleaton et al 2004;Shiono et al 2008Shiono et al , 2009Liu et al 2016a) and found that the upstream floodplain flow can significantly affect the main channel flow in crossover sections. For example, the mean velocity in a meandering main channel reaches a maximum at the apex section and a minimum in crossover sections because of the influence of upstream floodplain flows (Liu et al 2014(Liu et al , 2016a. Floodplain roughness (e.g., vegetation) is an important factor that affects the flow pattern along a meander (Shan et al 2017).…”

Section: Introductionmentioning

confidence: 99%

“…Floodplain roughness (e.g., vegetation) is an important factor that affects the flow pattern along a meander (Shan et al 2017). For example, under low-flow conditions, roughened floodplains enhance the conveyance capability of the main channel but reduce the conveyance capability of the entire channel (Shiono et al 2009;Liu et al 2016a). These studies provide insights to better understand the evolution of the flow along a meander.…”

Section: Introductionmentioning

confidence: 99%

“…A secondary current cell is a typical flow feature found in a meandering main channel and has been extensively investigated (Sellin et al 1993; Shiono and Muto 1998;Wormleaton et al 2004;Liu et al 2014Liu et al , 2016aShan et al 2017). In half of a meander (from one apex section to the next apex section), a secondary current cell initially appears next to the inner corner in the section after the apex section.…”

Section: Introductionmentioning

confidence: 99%

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Estimation of flow direction in meandering compound channels

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Section: Introductionsupporting

confidence: 79%

Section: Introductionmentioning

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Estimation of flow direction in meandering compound channels

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et al. 2018

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An analytical model for transverse velocity distributions of overbank flows with submerged and emergent vegetated floodplains

Liu

Bai

et al. 2023

Hydrological Processes

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The emergence of floodplain vegetation enhances the local drag and affects the velocity distribution of the overbank flow in a two-stage channel. Numerous analytical models (e.g., the modified SKM models) have been established to simulate the transverse velocity distributions of overbank flows with vegetation. However, the dimensionless eddy viscosity (λ) was simplified to be a constant in these models when quantifying transverse momentum exchange. In this paper, we develop a novel analytical model to simulate the depth average velocity profiles of overbank flows with floodplain vegetation. Considering a micro-hexahedral element on a vegetatedbed area for a two-stage rectangular channel, the governing equation of the vegetated overbank flow is derived. An improved eddy viscosity model that considers the transverse variation of the λ is employed to quantify the transverse momentum transfer, and a linear empirical function simplifies the secondary current. The simulated depth average velocities agreed well with the published measurements. In comparison with existing models, the proposed model shows better prediction accuracy, particularly in the shearing layer domain. More importantly, for the optimized model parameters, we found that the dimensionless eddy viscosity plays the most influential role when simulating depth-averaged velocities in the shearing layer domain, whereas the drag force dominates for vegetated floodplains. This study provides a convenient method for predicting the flow velocity in overbank floods with vegetation.

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Turbulent flow structure in a vegetated non‐prismatic compound channel

Mehrabani

Mohammadi

Ayyoubzadeh

et al. 2020

River Research & Apps

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The presence of vegetation on the floodplains of compound channels affects the structure of mean flow, increases flow resistance and turbulence intensity, and impacts sediment transport. In prismatic compound channels, the shear stress at the interface between the flows in the main channel and lateral floodplains has a strong influence in the cross sectional velocity distribution and thus conveyance of the channel. Due to mass transfer between subsections, these effects are enhanced in non‐prismatic channels. In the present study, the three‐dimensional turbulent flow structure in a vegetated non‐prismatic convergent compound channel is experimentally investigated. The main purpose is to clarify the explicit influence of the combination of two factors (floodplain vegetation and convergent floodplains) on mean flow and large‐scale turbulence. The experiments were conducted for relative depths (i.e., the ratio between floodplain and main channel flow depths) equal to 0.21 and 0.31 and floodplain convergence angles equal to 7.25° and 11.3°. The results obtained in straight compound channel with vegetated floodplains were used as a reference. The analysis of the Acoustic Doppler Velocimeter measurements shows that due to convergent floodplains, a transverse current is directed from the floodplains to the main channel from both sides, generating two helical secondary currents. Investigations of the vegetation influence on Reynolds stresses shows that there is a significant vertical and lateral spreading of the shear region towards the main channel side slope. As the convergence angle increases, the floodplain flow proportion decreases. In this case, the presence of vegetation in the floodplain leads to a suppression of the momentum exchange between main channel and floodplains causing the discharge distribution between sub‐sections to be significantly different from what would be without floodplain vegetation.

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The effect of floodplain grass on the flow characteristics of meandering compound channels

Cited by 44 publications

References 52 publications

Estimation of flow direction in meandering compound channels

Estimation of flow direction in meandering compound channels

An analytical model for transverse velocity distributions of overbank flows with submerged and emergent vegetated floodplains

Turbulent flow structure in a vegetated non‐prismatic compound channel

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