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Geological Society, London, Special Publications; 1993; v. 72; p. 25-36;
DOI: 10.1144/GSL.SP.1993.072.01.04
© 1993 Geological Society of London

Aeolian Mechanics and Dune Morphodynamics

Wind-speed profiles over a reversing transverse dune

Jennifer R. Burkinshaw, Werner K. Illenberger & Izak C. Rust

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

Wind-speed profiles were measured within 1.5 m of the surface on the windward slope of a 7 m high transverse dune that reverses seasonally with respect to summer easterly and winter northwesterly winds. The profiles were measure along section lines normal to the dune trend at different stages of dune reversal. An independent weather station recorded relatively undisturbed flow at 6 m elevation above the surface.

Flow deceleration at the base of the windward slope and flow acceleration against the middle to upper slope generate non-logarithmic wind-speed profiles. The shape of the dune and the strength of the wind play a major role in determining the behaviour of the wind-speed profile. Airflow compression is enhanced by steeper slopes, resulting in high surface shear stress that causes rapid erosion of the windward slope.

The wind-speed profile can be divided into three zones: a surface shear stress layer, an amplification layer and a recovery layer. It seems that the shear stress that governs sand transport is developed within 5 cm of the surface, in the surface shear stress layer. Future work should concentrate on measurements within this zone.