Long-term morphological developments of river channels separated by a longitudinal training wall

Le, T.B.; Crosato, Alessandra; Uijttewaal, W.S.J.

doi:10.1016/j.advwatres.2018.01.007

Cited by 27 publications

(33 citation statements)

References 28 publications

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“…Van der Mark and Mosselman, 2013;van Dijk et al, 2014;Le et al, 2018aLe et al, , 2018bSalter et al, 2018). Van der Mark and Mosselman, 2013;van Dijk et al, 2014;Le et al, 2018aLe et al, , 2018bSalter et al, 2018).…”

Section: The Forced Bifurcationunclassified

“…'Instability' has been indeed used to indicate: (i) the situation whereby an equilibrium bifurcation configuration is unstable; (ii) a systematic change in the discharge distribution over time (e.g., Kleinhans et al, 2013); (iii) a bifurcation that evolves towards a highly unbalanced configuration and eventually produces the complete closure of one of the two bifurcates (e.g., Burge, 2006;Le et al, 2018b). 'Instability' has been indeed used to indicate: (i) the situation whereby an equilibrium bifurcation configuration is unstable; (ii) a systematic change in the discharge distribution over time (e.g., Kleinhans et al, 2013); (iii) a bifurcation that evolves towards a highly unbalanced configuration and eventually produces the complete closure of one of the two bifurcates (e.g., Burge, 2006;Le et al, 2018b).…”

Section: The Meaning Of 'Instability' Within Bifurcation Dynamicsmentioning

confidence: 99%

“…River bifurcations have been extensively studied through laboratory-scale physical models (Federici and Paola, 2003;Bertoldi and Tubino, 2007;Bertoldi et al, 2009;Le et al, 2018b), and mathematical models based on 1D (Wang et al, 1995;Bolla Pittaluga et al, 2003;Kleinhans et al, 2013;Salter et al, 2018), 2D (Edmonds and Slingerland, 2008;Siviglia et al, 2013;Le et al, 2018aLe et al, , 2018b and 3D approaches (Kleinhans et al, 2008). Along with field observations (e.g.…”

Section: Introductionmentioning

confidence: 99%

“…Upstream effects comprise mechanisms that feed the bifurcating node with a topographically driven uneven distribution of flow and transport rate, like the curvature of the upstream channel (Kleinhans et al, 2008;Hardy et al, 2011;Sloff and Mosselman, 2012) and the occurrence of migrating bars (Bertoldi et al, 2009;Bertoldi, 2012) or steady bars (Le et al, 2018b). Forcing factors include both upstream and downstream effects.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Free and forced morphodynamics of river bifurcations

Redolfi

Zolezzi

Tubino

2019

Earth Surf Processes Landf

128

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Water and sediment distribution by river bifurcations is often highly unbalanced. This may result from a variety of factors, such as migration of bars, channel curvature and backwater effects, which promote an uneven partition of flow and sediment fluxes in the downstream branches, which we call ‘forcings’. Bifurcations also display an intrinsic instability mechanism that leads to unbalanced configurations, as occurs in the idealized case of a geometrically symmetric bifurcation, which we call ‘free’, provided the width‐to‐depth ratio of the incoming flow is large enough. Most frequently, these free and forced mechanisms coexist; however, their controlling roles in bifurcation dynamics have not been investigated so far. In this paper we address this question by proposing a unified free‐forced modelling framework for bifurcation morphodynamics. Upstream channel curvature and different slopes of downstream branches (slope advantage) are specifically investigated as forcing effects typically occurring in bifurcations of alluvial channels. The modelling strategy is based on the widely used two‐cell model of Bolla Pittaluga et al. (Water Resources Research, 2003, 39(3), 1–13), here extended to account for the spatially non‐uniform fluxes entering the bifurcation node. Results reveal that the relative role of free and forced mechanisms depends on the width‐to‐depth ratio falling above or below the resonant threshold that controls the stability of free bifurcations: when the main channel is relatively wide and shallow (super‐resonant regime) the bifurcation invariably evolves towards unbalanced configurations, whatever the combination of curvature and slope advantage values, which instead control the bifurcation response under sub‐resonant conditions. Detection of the resonant aspect ratio as a key threshold also releases the modelling approach from the need for parameter calibration that characterized previous approaches, and allows for interpreting under a unified framework the opposite behaviours shown by gravel‐bed and sand‐bed bifurcations for increasing Shields parameter values. © 2018 John Wiley & Sons, Ltd.

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Section: The Forced Bifurcationunclassified

Section: The Meaning Of 'Instability' Within Bifurcation Dynamicsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Free and forced morphodynamics of river bifurcations

Redolfi

Zolezzi

Tubino

2019

Earth Surf Processes Landf

128

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“…Eekhout et al () and Rodrigues et al () discussed this ambiguity of using the term “forced bars” for two types of bars, albeit without proposing a new terminology. To resolve the old ambiguity, the Delft School introduced the term “hybrid bars,” which was then gratefully adopted by Duró et al (), Le, Crosato, Mosselman, and Uijttewaal (), Le, Crosato, and Uijttewaal (), and Scorpio et al (). This second and more recent classification distinguishes two types of periodic bars: free and hybrid bars.…”

Section: Introductionmentioning

confidence: 99%

Numerical Study of Alternate Bars in Alluvial Channels With Nonuniform Sediment

Cordier

Tassi

Claude³

et al. 2019

Water Resources Research

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Rivers typically present heterogeneous bed material, but the effects of sediment nonuniformity on river bar characteristics are still unclear. This work investigates the impact of sediment size heterogeneity on alternate bars with a morphodynamic numerical model. The model is first used to reproduce a laboratory experiment showing alternate bar formation with nonuniform bed material. Subsequently, the influence of sediment size heterogeneity on alternate bars is investigated distinguishing hybrid from free bars, definition based on the presence/absence of morphodynamic forcing, considering the results of nine scenarios. In four of them, a transverse obstacle is used to generate forcing. The computations are carried out with the Telemac‐Mascaret system solving the two‐dimensional shallow‐water equations with a finite element approach, accounting for horizontal and vertical sediment sorting processes. The results show that sediment heterogeneity affects free migrating and hybrid bars in a different way. The difference lies in the presence/absence of a migration front, so that distinct relations between bed topography, bed shear stress, and sediment sorting are obtained. Sediment sorting and associated planform redistribution of bed roughness only slightly modify free migrating bar morphodynamics, whereas hybrid bars are greatly impacted, with decreased amplitude and increased wavelength. Increased sediment size heterogeneity increases the degree of sediment sorting, while the sorting pattern remains the same for both free and hybrid bars. Moreover, it produces averagely higher, longer, and faster free bars, while in the case of hybrid bars their wavelength is increased but no general trend can be determined for their amplitude.

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The influence of the development of dunes on the stability of bifurcations in sand‐bed rivers

Jing

Qin

2023

Earth Surf Processes Landf

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Channel bifurcations are common features observed in fluvial landforms from upstream gravel-bed rivers to downstream deltas. Extensive research has been carried out to study the stability and equilibrium configurations of bifurcations in the last two decades. However, existing studies generally employed oversimplified flow resistance equations, and the influence of the development of bedforms on the stability of bifurcations is rarely explicitly considered. The morphological features of bedforms in sand-bed rivers vary with flow conditions, which in turn affect flow resistance and sediment transport processes. Such a mutual feedback process is expected to exert a significant influence on the evolution of a bifurcation. A theoretical one-dimensional (1D) model is built, based on the classical model proposed by Bolla Pittaluga et al. in 2003, to evaluate the influence of the development of dunes on the stability of bifurcations. Results show that the development of dunes

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Long-term morphological developments of river channels separated by a longitudinal training wall

Cited by 27 publications

References 28 publications

Free and forced morphodynamics of river bifurcations

Free and forced morphodynamics of river bifurcations

Numerical Study of Alternate Bars in Alluvial Channels With Nonuniform Sediment

The influence of the development of dunes on the stability of bifurcations in sand‐bed rivers

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