The Role of Overbank Flow in Governing the Form of an Anabranching River: The Fitzroy River, Northwestern Australia

  1. N. D. Smith2 and
  2. J. Rogers3
  1. C. F. H. Taylor

Published Online: 17 MAR 2009

DOI: 10.1002/9781444304213.ch7

Fluvial Sedimentology VI

Fluvial Sedimentology VI

How to Cite

Taylor, C. F. H. (1999) The Role of Overbank Flow in Governing the Form of an Anabranching River: The Fitzroy River, Northwestern Australia, in Fluvial Sedimentology VI (eds N. D. Smith and J. Rogers), Blackwell Publishing Ltd., Oxford, UK. doi: 10.1002/9781444304213.ch7

Editor Information

  1. 2

    Department of Geosciences, 214 Bessey Hall, University of Nebraska, Lincoln, NE 68588-0340, USA

  2. 3

    Cape Town, South Africa

Author Information

  1. Department of Geography, University of Western Australia, Nedlands, Western Australia 6907

Publication History

  1. Published Online: 17 MAR 2009
  2. Published Print: 7 OCT 1999

ISBN Information

Print ISBN: 9780632053544

Online ISBN: 9781444304213

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Keywords:

  • role of overbank flow in governing form of anabranching river - the Fitzroy River, northwestern Australia;
  • better understanding of modern fluvial processes and their sedimentary styles is needed to predict impact of future modification to river systems;
  • climate and flood hydrology;
  • contemporary planform characteristics;
  • Fitzroy floodplain - topographic floodplain;
  • main channel and Cunningham anabranch;
  • processes of planform development;
  • controls on planform development

Summary

The 85 000 km2 Fitzroy River catchment lies in the semi-arid tropics of north-western Australia. Monsoon-associated rainfall events inundate the Fitzroy's largely unconfined, 300-km-long floodplain, with flows of 30 000 m3 s−1 ranking as 1 in c. 35 yr events. Adjustment of the main Fitzroy channel to convey these large flows efficiently is restricted by a low-gradient valley, an erosion-resistant floodplain, and both gradual and episodic constriction of the channel by sediment and vegetation. To compensate for the restricted capacity of the main channel, auxiliary channels form in response to water excesses, with high-magnitude overbank flows reactivating atrophying channels and/or scouring elongate depressions on distal floodplain, which can become preferred flow paths and eventually new channels. The planform of channels is governed by the interaction between the frequency and magnitude of overbank events and vegetation, and by the texture of channel banks and floors. An anabranching river results, which can exhibit adjacent braided, sinuous and straight channel reaches.