Aeolian Dynamics on the Windward Slope of a Reversing Transverse Dune, Alexandria Coastal Dunefield, South Africa

  1. K. Pye2 and
  2. N. Lancaster3
  1. J. R. Burkinshaw and
  2. I. C. Rust

Published Online: 8 APR 2009

DOI: 10.1002/9781444303971.ch2

Aeolian Sediments: Ancient and Modern

Aeolian Sediments: Ancient and Modern

How to Cite

Burkinshaw, J. R. and Rust, I. C. (1993) Aeolian Dynamics on the Windward Slope of a Reversing Transverse Dune, Alexandria Coastal Dunefield, South Africa, in Aeolian Sediments: Ancient and Modern (eds K. Pye and N. Lancaster), Blackwell Publishing Ltd., Oxford, UK. doi: 10.1002/9781444303971.ch2

Editor Information

  1. 2

    Reading, UK

  2. 3

    Reno, Nevada, USA

Author Information

  1. Institute for Coastal Research, Department of Geology, University of Port Elizabeth, PO Box 1600, Port Elizabeth 6000, South Africa

Publication History

  1. Published Online: 8 APR 2009
  2. Published Print: 27 MAY 1993

ISBN Information

Print ISBN: 9780632035441

Online ISBN: 9781444303971

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Keywords:

  • aeolian dynamics on windward slope of reversing transverse dune;
  • intrusion of aeolian bedform into atmospheric boundary layer - acceleration of flow on upstream side of dune form;
  • sand transport rates determined by surface shear stress;
  • sand transport equations - for wind blowing over flat surface;
  • aeolian dynamics of reversing transverse dune;
  • wind speed data at measuring stations with respect to wind speed above dune crest;
  • erosion pin and gradient data;
  • airflow response - adjusting to changing shape of dune

Summary

Few empirical measurements describing the inter-relationship between wind shear, sediment flux and dune shape have been reported. We compare the results from two of several detailed field experiments conducted as part of a study of airflow on the windward slope of a 7 m high reversing transverse coastal dune. The seasonal reversal of the dune in response to opposing summer and winter wind regimes provides an ideal opportunity to study the relationship between dune shape and airflow characteristics.

The wind speed profile, erosion and deposition rates and values of surface gradient were recorded along a section line normal to the crest line of the dune. Our paper deals specifically with wind speed measured at 6 cm above the surface. The two experiments were conducted 3 weeks apart at the start of the summer wind season on the east flank of the dune. Wind conditions were similar but the difference in the crestal geometry of the dune resulted in contrasting erosional responses.

Variation in sediment flux can be related not only to the absolute gradient of the dune surface but also to changes in gradient. We recognize three phases in the erosional response of the dune which are determined by change in the rate of change of gradient, and which give an insight into the self-regulatory relationship between form and flow. Erosion pins act as a sensitive measure of variation in shear stress on the dune surface, and could possibly be used in future shear stress determination once a data base of variables related to shear stress has been acquired.