River Bedforms: Progress and Problems

  1. J. D. Collinson and
  2. J. Lewin
  1. J. R. L. Allen

Published Online: 29 APR 2009

DOI: 10.1002/9781444303773.ch2

Modern and Ancient Fluvial Systems

Modern and Ancient Fluvial Systems

How to Cite

Allen, J. R. L. (1983) River Bedforms: Progress and Problems, in Modern and Ancient Fluvial Systems (eds J. D. Collinson and J. Lewin), Blackwell Publishing Ltd., Oxford, UK. doi: 10.1002/9781444303773.ch2

Author Information

  1. Department of Geology, The University, Reading RG6 2AB, UK

Publication History

  1. Published Online: 29 APR 2009
  2. Published Print: 7 FEB 1983

ISBN Information

Print ISBN: 9780632009978

Online ISBN: 9781444303773

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Keywords:

  • River bedforms - progress and problems;
  • sediment transport in rivers and kinds of bedform;
  • bedform existence fields;
  • bedform lag;
  • mechanisms of lag;
  • granular bed stability beneath sediment-laden stream

Summary

Despite great recent advances in our understanding of river bedforms and related phenomena, much remains to be done. Our knowledge of bedform existence fields under steady-state equilibrium conditions needs improvement by more work at extreme grain sizes and sediment transport stages, each of which calls for the use of deeper currents. Bedforms in natural environments are shaped by varying flows. The influence of flow non-uniformity and unsteadiness will not be understood until we have many more well-documented case histories and parallel attacks from theory and experiment. An understanding of the factors that determine the size and shape of bedforms that have grown to quasi-equilibrium requires a shift of emphasis in mathematical studies away from the rather restricted conditions that seem to govern the initial instability of granular beds. Experimental studies still have much to contribute, since we have little empirical knowledge of sediment entrainment and transport conditions at sloping beds, and many aspects of turbulent fluid flow over wavy surfaces have yet to be completely defined.