Effects of helical flow in one‐dimensional modelling of sediment distribution at river bifurcations

Mark, C.F. van der; Mosselman, E.

doi:10.1002/esp.3335

Cited by 49 publications

(41 citation statements)

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“…In particular, he found a more frequent occurrence of branch abandonment for branches with a larger bifurcation angle deviation from the upstream branch. Although flume experiments of Federici and Seminara [2003] and numerical modeling by Van der Mark and Mosselman [2012] indicated no correlation between bifurcation angle asymmetry and bifurcation evolution, it is a plausible correlation and deserves further investigation. Furthermore, Koomen [1992], Ashworth et al [2000] and Schuurman et al [2013] found that the relative length of bar-tail limbs is an indicator of bifurcation asymmetry, and thus shortterm evolution: the dominant channel creates the longest bar-tail limb.…”

Section: Introductionmentioning

confidence: 91%

Bar dynamics and bifurcation evolution in a modelled braided sand‐bed river

Schuurman

Kleinhans

2015

Earth Surf Processes Landf

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Abstract.Morphodynamics in sand-bed braided rivers are associated to simultaneous evolution of mid-channel bars and channels on the braidplain. Bifurcations around mid-channel bars are key elements that divide discharge and sediment. This, in turn, may control the evolution of connected branches, with effects propagating to both upstream and downstream bifurcations. Recent works on bifurcation stability and development hypothesize major roles of secondary flow and gradient advantage. However, this has not been tested for channel networks within a fully developed dynamic braided river. A reason for this is a lack of detailed measurements with sufficient temporal and spatial length, covering multiple bifurcations. Therefore we used a physics-based numerical model to generate a dataset of bathymetry, flow and sediment transport of an 80-km river reach with self-formed braid bars and bifurcations. The study shows that bar dissection due to local transverse water surface gradients is the dominant bifurcation initiation mechanism, although conversion of unit bars into compound bars dominates in the initial stage of a braided river. Several bifurcation closure mechanisms are equally important. Furthermore, the study showed that nodal point relations for bifurcations are unable to predict short-term bifurcation evolution in a braided river. This is explained by occurrence of non-linear processes and non-uniformity within the branches, in particular migrating bars and larger-scale backwater-effects, which are not included in the nodal point relations. Planform morphology, on the other hand, has predictive capacity: bifurcation angle asymmetry and bar-tail limb shape are indicators for near-future bifurcation evolution. Remote sensing data has predictive value, for which we developed a conThis article is protected by copyright. All rights reserved.ceptual model for interactions between bars, bifurcations and channels in the network. We conducted a preliminary test of the conceptual model on satellite images of the Brahmaputra.

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Section: Introductionmentioning

confidence: 91%

Bar dynamics and bifurcation evolution in a modelled braided sand‐bed river

Schuurman

Kleinhans

2015

Earth Surf Processes Landf

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“…First, we used Delft3D to systematically test scenarios. Delft3D is a physicsbased numerical model and simulates hydrodynamics, sediment transport, and morphodynamics and has been used in several fluvial, estuarine, deltaic, and tidal applications (e.g., Lesser et al, 2004;Edmonds and Slingerland, 2008;Kleinhans et al, 2008Kleinhans et al, , 2010van der Wegen and Roelvink, 2012;Schuurman et al, 2013) and is extensively used and verified in engineering practice. The model schematisation was inspired by the River Allier.…”

Section: Numerical Modelling Approachmentioning

confidence: 99%

“…So, the effects of helical flow driven by flow curvature on bed shear-stress direction were parameterized (Struiksma et al, 1985). Computation of morphodynamics included sediment transport induced by the flow and the longitudinal and transverse bed slope (Struiksma et al, 1985;Lesser et al, 2004;Kleinhans et al, 2008), bank erosion (van der Wegen and Roelvink, 2012), and bed level change because of gradients in sediment transport. Sediment transport was predicted by the Engelund and Hansen (1967) equation . At the inflow boundary, the input of sediment was kept equal to the local sediment transport capacity.…”

Section: Model Descriptionmentioning

confidence: 99%

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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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“…Within this special edition flow structures have been investigated in a simple configuration of a bifurcation through either the application of a physical scale model (Thomas et al, 2011) or through a full three-dimensional (3D) flow model utilizing a parametric study of how flow structures and partitioning are dependent upon geometric characteristics bifurcation . The effect of the predicted helical flow is considered by Van der Mark and Mosselman (2012) who develop a semi-analytical relationship for nodal points in a 1D framework to account for bedload sediment division due to the flow curvature at bifurcations and offtakes. However, these bifurcations consider immobile, smooth boundaries which will not represent natural features including inlet steps or bed ramps.…”

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confidence: 99%