Morphology and Facies Models of Channel Confluences

  1. M. Marzo and
  2. C. Puigdefábregas
  1. C. S. Bristow1,
  2. J. L. Best2 and
  3. A. G. Roy3

Published Online: 14 APR 2009

DOI: 10.1002/9781444303995.ch8

Alluvial Sedimentation

Alluvial Sedimentation

How to Cite

Bristow, C. S., Best, J. L. and Roy, A. G. (1993) Morphology and Facies Models of Channel Confluences, in Alluvial Sedimentation (eds M. Marzo and C. Puigdefábregas), Blackwell Publishing Ltd., Oxford, UK. doi: 10.1002/9781444303995.ch8

Editor Information

  1. Barcelona, Spain

Author Information

  1. 1

    Department of Geology, Birkbeck College, University of London, Malet Street, London WC1E 7HX, UK

  2. 2

    Department of Earth Sciences, University of Leeds, Leeds LS2 9JT, UK

  3. 3

    Départment de Geographié, Université de Montréal, Quebec H3C 3J7, Canada

Publication History

  1. Published Online: 14 APR 2009
  2. Published Print: 16 SEP 1993

ISBN Information

Print ISBN: 9780632035458

Online ISBN: 9781444303995



  • Alluvial facies;
  • presenting morphological data from channel junctions;
  • tributary mouth-bars;
  • combination of confluent flows;
  • confluence separation zone bars;
  • post-confluence mid-channel bars;
  • potential for mouth-bar progradation


Channel confluences represent points of significant change within river networks that are of importance to geomorphologists, sedimentologists and engineers. At scales varying over four orders of magnitude confluences are characterized by distinct areas of scour and deposition: (i) tributary mouth-bars, (ii) a deep confluence scour, (iii) bars within areas of flow separation and (iv) post-confluence mid-channel bars. The morphology of these elements and their depositional facies are controlled predominantly by confluence angle, the discharge ratio between the two channels and modifications which occur at low stage. A review of confluence morphology from flume and field studies is presented alongside examples from the Brahmaputra River; these are then used to present tentative facies models which suggest that junctions may be represented by a unique assemblage of bedforms and sedimentary structures. Sedimentation at channel junctions is particularly important in multichannel braided or anastomosed rivers where channel confluences are most abundant and their likelihood of preservation is at its highest. Complete preservation of confluence sediments may be achieved by abandonment of one channel and domination of the confluence by the other channel or, more rarely, complete abandonment of the entire junction. Partial preservation of the deeper portions of confluence scour and fill at the base of channel sandstones is more likely.