Flow structure and channel morphodynamics of meander bend chute cutoffs: A case study of the Wabash River, USA

Zinger, J. A.; Rhoads, Bruce L.; Best, James L.; Johnson, Kevin K.

doi:10.1002/jgrf.20155

Cited by 106 publications

(88 citation statements)

References 94 publications

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“…This is likely the case at the majority of bifurcations where one channel branches off to the side because due to the acceleration of the flow toward the diversion the approaching channel scours near the bank from where the flow is diverted, while the deceleration of the flow causes the deposition of a bar at the opposite bank. This has also been observed at chute cut‐offs (Zinger et al., ). We think that in general, the slope of the bed has a weaker influence on the division of suspended sediment than assumed because the slope primarily affects the sediment that is transported as bedload (Ikeda, ).…”

Section: Discussionsupporting

confidence: 59%

Flow and Suspended Sediment Division at Two Highly Asymmetric Bifurcations in a River Delta: Implications for Channel Stability

Kästner

Hoitink

2019

JGR Earth Surface

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The division of sediment at river bifurcations results from the complex interaction between three‐dimensional flow, planform, and channel bed morphology, as well as the heterogeneity of the bed material. Sediment division processes cannot be incorporated in their full complexity in scale experiments and are difficult to reproduce with numerical models. Field measurements are thus necessary to advance our understanding of those processes in river deltas. However, such measurements are rare. We present measurements of the flow and sediment division at two tidally influenced bifurcations of the Kapuas River, a large sand‐bedded suspended load‐dominated river in West Kalimantan, Indonesia. At both bifurcations, a smaller channel branches off from the side of the main river, which makes the planform strongly asymmetric. The planform of both bifurcations has been stable at least since the end of the nineteenth century when the region was mapped for the first time. Based on our measurements, we explore possible factors that stabilize the bifurcations. We measure the flow velocities with a boat‐mounted acoustic velocity profiler and determine the sediment concentration from acoustic backscatter, calibrated against water samples. The side branch of the first bifurcation receives a proportionally lower fraction of sediment than water. In contrast, the side branch at the second bifurcation receives a proportionally higher fraction of sediment than water. A comparison of flow velocity and suspended sand concentration indicates that the bed material sorting strongly influences the division of sediment, in particular at one of the bifurcations, which is situated in a meander bend.

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Section: Discussionsupporting

confidence: 59%

Flow and Suspended Sediment Division at Two Highly Asymmetric Bifurcations in a River Delta: Implications for Channel Stability

Kästner

Hoitink

2019

JGR Earth Surface

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“…Best & Reid 1984;Rhoads & Kenworthy 1995;Rhoads & Sukhodolov 2001;Yang et al 2009) andbifurcations (e.g. Bulle 1926;Neary & Odgaard 1993;Dargahi 2004 andZinger et al 2014). Numerous previous studies of bends, confluences and bifurcations have indicated that in all these configurations, a complex amalgamation of time-averaged and turbulence processes, including the pressure gradient force and secondary flow associated with the change in flow direction, may or may not lead to flow separation.…”

Section: Discussion and Generalization Of Resultsmentioning

confidence: 92%

“…Bagnold 1960;Leeder & Bridges 1975;Ferguson et al 2003;Frothingham & Rhoads 2003;Nanson 2010;Rhoads & Massey 2012;Schnauder & Sukhodolov 2012), bifurcations (e.g. Bulle 1926, Neary & Odgaard 1993, Dargahi 2004and Zinger et al 2014, and confluences (e.g. Best & Reid 1984;Rhoads & Kenworthy 1995;Rhoads & Sukhodolov 2001;Yang et al 2009).…”

mentioning

confidence: 98%

Flow separation at convex banks in open channels

Blanckaert

2015

J. Fluid Mech.

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Laboratory experiments in an open channel bend provide insight into the physics of convex bank flow separation occurring in a variety of channel configurations, including confluences and bifurcations. The edge of the zone of flow separation is characterized by a shear layer, enhanced velocity gradients, tke, turbulent shear stresses and reversal of the streamwise vorticity and vertical velocity. The latter result from turbulence-induced secondary flow near the convex bank. When bankline curvature abruptly increases, flow tends to move away from the convex bank along a straight path, as represented by the inertial forces -including the centrifugal force -in the transverse momentum equation written in curvilinear coordinates. Mass accumulation at the opposite bank leads to a transverse tilting of the water surface, and a pressure gradient towards the convex bank that causes the flow to change direction. The pressure gradient force lags spatially behind the inertial forces, which promotes flow separation. Flow separation typically occurs downstream of the location of maximum change in the bankline curvature, because an abrupt increase in bankline curvature also leads to water surface gradients that cause local flow redistribution towards the convex bank that opposes flow separation. The zone of convex bank flow separation is shaped by the secondary flow induced by streamline curvature and turbulence. The latter is conditioned by the production rate of tke, which crucially depends on the accurate description of the Reynolds stresses. Hydrodynamic, geometric and sedimentologic control parameters of convex bank flow separation are identified and discussed.

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“…For sharp-bended offtakes, flow separation may occur (Bulle, 1926;Constantine et al, 2010a), and a useful threshold angle for such flow separation may well exist but remains as yet unknown (Blanckaert, 2011). Very sharp bends generally occur when the river banks are strong relative to the flow strength, as is the case in meandering rivers with somewhat cohesive banks or vegetated banks (e.g., Zinger et al, 2013), but not in braided rivers with noncohesive sediment. In more gently curved rivers, the angle asymmetry is therefore an artificial characterisation of the bifurcation planform that are more appropriately described as curved channels (Bridge, 2003).…”

Section: Factors Affecting Bifurcation Evolution At Chute Cutoffsmentioning

confidence: 99%

Bifurcation instability and chute cutoff development in meandering gravel-bed rivers

et al. 2014

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. (2014) 'Bifurcation instability and chute cuto development in meandering gravel-bed rivers. ', Geomorphology., Further information on publisher's website:http://dx.doi.org/10.1016/j.geomorph.2014.01.018Publisher's copyright statement: NOTICE: this is the author's version of a work that was accepted for publication in Geomorphology. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reected in this document. Changes may have been made to this work since it was submitted for publication. A denitive version was subsequently published in Geomorphology, 213, 15 May 2014, 10.1016/j.geomorph.2014.01.018. Additional information:Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. AbstractChute cutoffs reduce sinuosity of meandering rivers and potentially cause a transition from a single to a multiple channel river. The channel bifurcation of the main channel and the mouth of the incipient chute channel controls sediment and flow partitioning and development of the chute. Recent channel bifurcation models suggest that upstream bend radius, gradient advantage, inlet step, and upstream sediment supply at the bifurcation are important factors in the evolution of bifurcations. Our objective is to unravel the relative importance of these factors for chute cutoff success and development. We compare results from a morphodynamic three-dimensional (3D) model and a one-dimensional (1D) model with nodal-point relation with field observations of chute cutoffs in a meandering gravel-bed river. The balance between increased gradient advantage and flow curvature upstream of the chute channel bifurcation was systematically investigated with the 1D model. The 3D model runs and the field observations show the development of two types of chute cutoffs: a scroll-slough cutoff and a bend cutoff. The morphodynamic 3D model demonstrates that chutes are initiated when flow depth exceeds the floodplain elevation. Overbank flow and a significant gradient advantage result in a bend cutoff. The outcome of the 1D model shows that channel curvature at the bifurcation determines the success or failure of the chute cutoff when the chute channel is located at the inner bend, as in the case of scrollslough cutoffs. We conclude that chute initiation depends on floodplain characteristics, i.e., floodplain elevation, sediment composition, and the presence of vegetation. Chute cutoff success or failure is determined by the dynamics just upstream of the channel bi...

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Flow structure and channel morphodynamics of meander bend chute cutoffs: A case study of the Wabash River, USA

Cited by 106 publications

References 94 publications

Flow and Suspended Sediment Division at Two Highly Asymmetric Bifurcations in a River Delta: Implications for Channel Stability

Flow and Suspended Sediment Division at Two Highly Asymmetric Bifurcations in a River Delta: Implications for Channel Stability

Flow separation at convex banks in open channels

Bifurcation instability and chute cutoff development in meandering gravel-bed rivers

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