On the origin of meandering and braiding in alluvial streams

Engelund, Frank; Skovgaard, Ove

doi:10.1017/s0022112073001163

Cited by 176 publications

(84 citation statements)

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“…These influences are largely expressed through the aspect ratio (γ = W / H) and this ratio has been used as a criterion for characterizing the threshold between meandering and braided patterns (Engelund and Skovgaard, 1973;Fredsoe, 1978;Fukuoka, 1989;Howard, 1996). If channel banks are largely unvegetated and composed of cohesionless sediment, channels will be wide, γ will be high (N50), and a braided pattern will tend to develop because of channel bed instabilities related to development of multiple alternate bars (Engelund and Skovgaard, 1973;Parker, 1976;Fredsoe, 1978;Fukuoka, 1989;Seminara and Tubino, 1989;Howard, 1996;Dade, 2000;Crosato and Mosselman, 2009). On the other hand, if banks are cohesive (e.g.…”

Section: Conditions For Meandering and Floodplain Formationmentioning

confidence: 99%

River meandering on Earth and Mars: A comparative study of Aeolis Dorsa meanders, Mars and possible terrestrial analogs of the Usuktuk River, AK, and the Quinn River, NV

et al. 2015

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Section: Conditions For Meandering and Floodplain Formationmentioning

confidence: 99%

River meandering on Earth and Mars: A comparative study of Aeolis Dorsa meanders, Mars and possible terrestrial analogs of the Usuktuk River, AK, and the Quinn River, NV

et al. 2015

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“…We adopt a simple power-law form of transport for noncohesive sediment of uniform grain size [7], and include the downslope gravitational transport component that generalizes ideas going back to the earlier work of [11]. Thus, we close (2.3) with…”

Section: Sediment Continuity Equationmentioning

confidence: 99%

A discontinuous Galerkin finite element model for river bed evolution under shallow flows

Tassi

Rhebergen

Vionnet

et al. 2008

Computer Methods in Applied Mechanics and Engineering

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“…The first is a functional explanation relating the occurrence of braiding to a particular combination of externally imposed environmental factors such as stream discharge, channel or valley gradient, sediment particle size, and bank resistance, and exemplified by Leopold and Wolman's (1957) recognition of a threshold slope for braiding. Alternatively, explanations have been sought through stability analysis of channel-scale bed forms in two-phase flow (Engelund and Skovgaard 1973;Parker 1976;Fredsoe 1978). Neither of these approaches explicitly considers the physical sedimentary processes accompanying the onset of braiding, which need careful description and analysis before any complete explanation of the phenomenon is possible (Carson 1984a;Fujita 1989).…”

Section: Introductionmentioning

confidence: 99%

How do gravel-bed rivers braid?

Ashmore¹

1991

Can. J. Earth Sci.

335

279

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Sedimentary processes and bed forms leading to the onset of braiding were observed in small-scale hydraulic models of gavel-bed streams. The laboratory streams had a variety of combinations of (constant) discharge and slope but identical bed-material particle-size distrihutions. From initially straight channels, braiding occurred by four different processes: deposition and accurnuIation ol'a central bar, chute cutoff of point bars, conversion of single transverse unit bars to mid-channel braid bars, and dissection of multiple bars. In these experiments the chute cutoff mechanism was the most common, but the predominant braiding mechanism depends upon sediment mobility (excess bed shear stress) and the bed-form regime. At very low excess bed shear stress the central bar process dominates, but at higher excess bed shear stress slip-face unit bars are more common, bed scour at confluences is more pronounced, and propogation of alternate convergence (scour) and divergence (deposition) is more likely; thus chute cutoffs and bar conversion dominate. The multiple bar mechanism is restricted to channels with very high widthldepth ratio. All of these processes, along with avulsion, are significant for maintenance of an established braided channel.The direct physical sedimentary cause of primary braiding is essentially the same in all these processes: local aggradation (often by stalling of bed-load sheets) and loss of competence in a lateral flow expansion. The chute cutoff process occurs in a morphologically distinctive setting and may be aided by other factors, but it is usually triggered by the local thalweg shoaling that is the fundamental physical mechanism causing the onset of braiding by the other processes. Local short-term pulses in bed-load supply are often the trigger for the initiation and maintenance of braiding, regardless of the exact braiding process.Les processus sedimentaires et les formes de litage qui sont associCs au dCveloppement d'un rCseau anastornos6 ont Ct C observks par modClisation hydraulique de fdets d'eau sur lit de gavier, une khelle rCduite. Les filets d'eau utilisds en laboratoire combinaient diverses conditions de debit (constant) et de pente, cependant les distributions granulomCtriques du mathiel du lit de sCdiment Ctaient toujours les memes. Quatre processus ont modifiC les chenaux rectilignes initiaux et ont contribuC 2 crCer un rkseau anastornos6 : dCpBt et accumulation d'une barre centrale, recoupement transversal des lobes de mkandre, transformation de barres transversales individuelles en barres anastomosCes B chenaux multiples, et dissection des barres multiples. Le processus le plus souvent observC dans cette expkrimentation fut le recoupement transversal des lobes mkandriques, toutefois le mCcanisme dominant dans la formation du rCseau anastornos6 dCpend de la mobilitk du sediment (force supCrieure au seuil de cisaillement du lit) et du rCgime des formes de litage. Le processus de formation des barres centrales pridomine en prksence d'une trks faible force exctdante au seuil ...

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On the origin of meandering and braiding in alluvial streams

Cited by 176 publications

References 10 publications

River meandering on Earth and Mars: A comparative study of Aeolis Dorsa meanders, Mars and possible terrestrial analogs of the Usuktuk River, AK, and the Quinn River, NV

River meandering on Earth and Mars: A comparative study of Aeolis Dorsa meanders, Mars and possible terrestrial analogs of the Usuktuk River, AK, and the Quinn River, NV

A discontinuous Galerkin finite element model for river bed evolution under shallow flows

How do gravel-bed rivers braid?

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