Mechanisms of anabranch avulsion within gravel-bed braided rivers: observations from scaled physical models

J.O. Leddy, Philip Ashworth, J.L. Best

Research output: Chapter in Book/Conference proceeding with ISSN or ISBNChapter

Abstract

The physical modelling of gravel-bed braided rivers, using a 1:20 Froude scale model, permits analysis of the types and relative occurrence of different avulsion mechanisms. Anabranch avulsion within braided rivers involves three main mechanisms: choking avulsion caused by blockage of one channel by a sediment lobe, constriction avulsion produced by deflection, confinement and subsequent diversion of the flow by a barform and apex avulsion following erosion at the outside of sinuous thalwegs and confined meander bends. Each avulsion mechanism is described and analysis of the abundance of each type illustrates choking avulsion to be predominant without braided rivers. Three factors are found to control anabranch avulsions, namely flow discharge, sediment flux and floodplain topography. These are briefly discussed together with the implications of avulsion type for the alluvial architecture of gravelly braided alluvium.
Original languageEnglish
Title of host publicationBraided rivers
EditorsJ.L. Best, C.S. Bristow
Place of PublicationLondon, UK
PublisherSpecial Publication, Geological Society of London
Pages119-127
Number of pages9
Volume75
ISBN (Print)0903317885
DOIs
Publication statusPublished - 1 Jan 1993

Publication series

NameGeological Society Special Publications

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avulsion
braided river
gravel
meander
deflection
alluvial deposit
sediment
floodplain
topography
erosion

Cite this

Leddy, J. O., Ashworth, P., & Best, J. L. (1993). Mechanisms of anabranch avulsion within gravel-bed braided rivers: observations from scaled physical models. In J. L. Best, & C. S. Bristow (Eds.), Braided rivers (Vol. 75, pp. 119-127). (Geological Society Special Publications). London, UK: Special Publication, Geological Society of London. https://doi.org/10.1144/GSL.SP.1993.075.01.07
Leddy, J.O. ; Ashworth, Philip ; Best, J.L. / Mechanisms of anabranch avulsion within gravel-bed braided rivers: observations from scaled physical models. Braided rivers. editor / J.L. Best ; C.S. Bristow. Vol. 75 London, UK : Special Publication, Geological Society of London, 1993. pp. 119-127 (Geological Society Special Publications).
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Leddy, JO, Ashworth, P & Best, JL 1993, Mechanisms of anabranch avulsion within gravel-bed braided rivers: observations from scaled physical models. in JL Best & CS Bristow (eds), Braided rivers. vol. 75, Geological Society Special Publications, Special Publication, Geological Society of London, London, UK, pp. 119-127. https://doi.org/10.1144/GSL.SP.1993.075.01.07

Mechanisms of anabranch avulsion within gravel-bed braided rivers: observations from scaled physical models. / Leddy, J.O.; Ashworth, Philip; Best, J.L.

Braided rivers. ed. / J.L. Best; C.S. Bristow. Vol. 75 London, UK : Special Publication, Geological Society of London, 1993. p. 119-127 (Geological Society Special Publications).

Research output: Chapter in Book/Conference proceeding with ISSN or ISBNChapter

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T1 - Mechanisms of anabranch avulsion within gravel-bed braided rivers: observations from scaled physical models

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AB - The physical modelling of gravel-bed braided rivers, using a 1:20 Froude scale model, permits analysis of the types and relative occurrence of different avulsion mechanisms. Anabranch avulsion within braided rivers involves three main mechanisms: choking avulsion caused by blockage of one channel by a sediment lobe, constriction avulsion produced by deflection, confinement and subsequent diversion of the flow by a barform and apex avulsion following erosion at the outside of sinuous thalwegs and confined meander bends. Each avulsion mechanism is described and analysis of the abundance of each type illustrates choking avulsion to be predominant without braided rivers. Three factors are found to control anabranch avulsions, namely flow discharge, sediment flux and floodplain topography. These are briefly discussed together with the implications of avulsion type for the alluvial architecture of gravelly braided alluvium.

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Leddy JO, Ashworth P, Best JL. Mechanisms of anabranch avulsion within gravel-bed braided rivers: observations from scaled physical models. In Best JL, Bristow CS, editors, Braided rivers. Vol. 75. London, UK: Special Publication, Geological Society of London. 1993. p. 119-127. (Geological Society Special Publications). https://doi.org/10.1144/GSL.SP.1993.075.01.07