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| Titel |
Sand availability control on dune shape and orientation |
| VerfasserIn |
Xin Gao, Clement Narteau, Olivier Rozier, Sylvain Courrech du Pont |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250104724
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| Publikation (Nr.) |
 EGU/EGU2015-4156.pdf |
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| Zusammenfassung |
| An increasing body of evidence indicates that sand availability does not only control dune
type but also the underlying dune growth mechanism. Consequently, the same wind regime
can produce different bedform orientations. Here, we use numerical simulations
with different conditions of sand availability to predict dune shape and alignment
in asymmetric bimodal wind regimes. In zones of abundant sand supply, linear
dunes grow in height and propagate selecting the orientation for which the normal
to crest components of transport reaches a maximum. In zones of limited sand
supply, linear dunes grow by extension in the direction of the resultant sand flux.
Considering these two independent dune growth mechanisms, we find good agreement
between numerical and analytical models, and estimate the magnitude of wind
velocity acceleration up the dune stoss slopes. In the extensional mode of linear
dune formation, there is no abrupt change in dune trend when the divergence angle
between the two winds crosses 90°. Instead, there are systematic transitions in
dune type from linear to barchan for critical values of the divergence angle that
depend on the transport ratio. We show how the growth rates of the two dune growth
mechanisms may be used to infer the dune field morphology in zones of low sediment
availability. |
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