The morphodynamics of sand dunes and wind patterns (Case study: New and young Erg in southeast of Qom)

Document Type : Research Article

Author

• Naser Mashhadi

Geo Science Dept., International Desert Research Center (IDRC), University of Tehran

10.22067/geoeh.2022.76706.1227

Abstract

The study of dunes morphology provides a valuable tool in the investigation of wind systems and as result the identification of sand sources (removal region). The wind direction is the primary factor controlling the dune shape and elongation. In deserts exposed to wind from different directions and with comparable magnitude, dunes are formed to be different morphology. The sand dunes are either perpendicular or parallel to the wind direction.The purpose of this paper is to analyze the morphology of sand dunes under bimodal winds using conventional models. Observations showed that the linear (seif dune) dunes formation are due to the elongation of a barchan horn. So that, these dunes create by a bimodal wind regime with a strong peak from the result of northwest and west winds and a weaker peak from the east winds with a divergence angle of 135°. Sinuous crest lines of seif dune grow directly by west and east winds. Studies have also shown that the evolution trend of the sand dunes of the region, under the strong northwest wind, first shield dune transforms into a dihedral barchans. At this stage, Wind erosion on the back of the sand pile (shield dune) leads to the formation of a crest perpendicular to the wind direction and so to the formation of a slip face downwind. According to the effect of the magnitude and change of direction in the Westerly and Easterly winds, the western wing of barchan begins to extend and turns into a dentate seif dune.

Keywords

• Erg
• pre-Barchanic
• Sand dunes
• seif dune
• Shield dune

Main Subjects

• مخاطرات ژئومورفیک-هیدرولوژیک

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