Simulation of the effect of wind speedup in the formation of transverse dune fields

Authors

  • Hiroshi Momiji,

    Corresponding author
    1. Department of Geography, University College London, 26 Bedford Way, London WC1H 0AP, UK
    • Department of Geography, University College London, 26 Bedford way, London WC1H 0AP, UK
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  • Ricardo Carretero-González,

    1. Centre for Nonlinear Dynamics and its Applications, University College London, Gower Street, London WC1E 6BT, UK
    Current affiliation:
    1. Department of Mathematics & Statistics, Simon Fraser University, Burnaby, BC, V5A 1S6, Canada
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  • Steven R Bishop,

    1. Centre for Nonlinear Dynamics and its Applications, University College London, Gower Street, London WC1E 6BT, UK
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  • Andrew Warren

    1. Department of Geography, University College London, 26 Bedford Way, London WC1H 0AP, UK
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Abstract

A computer simulation model for transverse-dune-field dynamics, corresponding to a uni-directional wind regime, is developed. In a previous formulation, two distinct problems were found regarding the cross-sectional dune shape, namely the erosion in the lee of dunes and the steepness of the windward slopes. The first problem is solved by introducing no erosion in shadow zones. The second issue is overcome by introducing a wind speedup (shear velocity increase) factor, which can be accounted for by adding a term to the original transport length, which is proportional to the surface height. By incorporating these features we are able to model dunes whose individual shape and collective patterns are similar to those observed in nature. Moreover we show how the introduction of a non-linear shear-velocity-increase term leads to the reduction of dune height, and this may result in an equilibrium dune field configuration. This is thought to be because the non-linear increase of the transport length makes the sand trapping efficiency lower than unity, even for higher dunes, so that the incoming and the outgoing sand flux are in balance. To fully describe the inter-dune morphology more precise dynamics in the lee of the dune must be incorporated. Copyright © 2000 John Wiley & Sons, Ltd.

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