Ripple, Megaripple and Sandwave Bedforms in the Macrotidal Loughor Estuary, South Wales, U.K.

  1. S.-D. Nio,
  2. R. T. E. Shüttenhelm and
  3. Tj. C. E. Van Weering
  1. T. Elliott and
  2. A. R. Gardiner

Published Online: 29 JUN 2009

DOI: 10.1002/9781444303759.ch4

Holocene Marine Sedimentation in the North Sea Basin

Holocene Marine Sedimentation in the North Sea Basin

How to Cite

Elliott, T. and Gardiner, A. R. (2009) Ripple, Megaripple and Sandwave Bedforms in the Macrotidal Loughor Estuary, South Wales, U.K., in Holocene Marine Sedimentation in the North Sea Basin (eds S.-D. Nio, R. T. E. Shüttenhelm and Tj. C. E. Van Weering), Blackwell Publishing Ltd., Oxford, UK. doi: 10.1002/9781444303759.ch4

Author Information

  1. Department of Geology, University College of Swansea, Singleton Park, Swansea SA2 8PP, Wales, UK

Publication History

  1. Published Online: 29 JUN 2009
  2. Published Print: 23 DEC 1981

ISBN Information

Print ISBN: 9780632008582

Online ISBN: 9781444303759

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Keywords:

  • ripple, megaripple, sandwave bedforms;
  • two dimensional forms devoid of scour pits;
  • higher amplitude, shorter span, three- dimensional forms with scour pits;
  • The Loughor Estuary (or Burry Inlet);
  • seasonal variations in tides between equinox and solstice

Summary

The macrotidal Loughor Estuary in South Wales exhibits a wide range of ripple, megaripple and sandwave bedforms which, with one exception, are produced by tidal currents. The bedforms occur in ebb- and flood-oriented fields and are extensively exposed on channel floors, channel flanks and the intervening sand-bars following an ebb tide. Ripples are small scale bedforms which are either asymmetrical linguoid forms produced by the tidal currents, or straight crested symmetrical or asymmetrical forms produced by local wind-generated waves. Megaripples are intermediate scale bedforms which occur in two classes distinguished on a range of criteria: low amplitude, long span, two-dimensional forms devoid of scour pits (Type 1); and higher amplitude, shorter span, three-dimensional forms with scour pits (Type 2). Sandwaves are substantially larger, two–dimensional bedforms divisible into rippled and megarippled types. This suite of bedforms closely resembles that described from the Bay of Fundy, though there are several significant differences.

In addition, the megaripples and sandwaves display a range of modification features which result from several scales of unsteadiness in the tidal flow. Recognition of these features is an essential prerequisite to considering the bedforms as reflectors of the principal flow conditions.