Mechanisms of anabranch avulsion within gravel-bed braided rivers: Observations from a scaled physical model

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

Research output: Contribution to journalArticle

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 (US)
Pages (from-to)119-127
Number of pages9
JournalGeological Society Special Publication
Volume75
DOIs
StatePublished - Dec 1 1993
Externally publishedYes

ASJC Scopus subject areas

  • Water Science and Technology
  • Ocean Engineering
  • Geology

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