Five. Forced Dunes

  1. Andrew Warren

Published Online: 27 MAR 2013

DOI: 10.1002/9781118295786.ch5

Dunes: Dynamics, Morphology, History

Dunes: Dynamics, Morphology, History

How to Cite

Warren, A. (2013) Forced Dunes, in Dunes: Dynamics, Morphology, History, John Wiley & Sons, Oxford. doi: 10.1002/9781118295786.ch5

Publication History

  1. Published Online: 27 MAR 2013
  2. Published Print: 20 MAY 2013

ISBN Information

Print ISBN: 9781444339697

Online ISBN: 9781118295786

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Keywords:

  • bluff obstacles;
  • cliff-top dunes;
  • climbing dune;
  • echo dune;
  • falling dunes;
  • forced dunes;
  • lee dunes;
  • sand;
  • wind

Summary

Forced dunes are those built around obstacles that have steep slopes facing the wind, like bushes, boulders or hills (‘bluff bodies’). Most climbing dunes accumulate in windward gullies, where, if the gully sides are steep, the windblown sand may be interleaved with rockfalls and coarse alluvium. Where the vortex loses strength, an ‘echo dune’ is formed, upwind of the hill. Cliff-top dunes have accumulated on the summits of some sea and lake cliffs. If there are no cliff-top dunes, or if sand escapes from them, it may be taken to falling dunes on the lee slope. The effects of gentle slopes on dune patterns have been analysed only recently. A wind-tunnel study of a wind blowing more or less at right angles over a ‘valley’ with gently sloping sides found that the wind was accelerated in a zone at least 1.5 valley widths upwind, and two valley widths downwind.