Zmienność kształtu wydm gwiaździstych w obszarach o bimodalnym reżimie wiatru

Contemporary morphological changes of star dunes are observed mainly in certain parts of these dunes. They occur as lateral migration of crestlines of dune arms and modifications of inclination of their slopes. The aim of the research was to determine annual variability of shapes of compound and complex star dunes in bimodal wind regime. Precise measurements of 5 star dunes were performed with use of GPS RTK in March, 2011, and March, 2012, on Erg Chebbi (Morocco). Based on these measurements, 3D models of the dunes were created, which in turn, allowed for calculation of annual magnitude and direction of crestlines migration of star dune main arms. The results show that the resultant drift direction was in accordance with long-term regime of active wind in the study area. Both, the resultant drift direction and its magnitude were similar in all studied dunes. Variability of star dune shapes occurred to be independent from their stage of development (size of a dune) or its type. The most important feature determining morphodynamics of the star dune arms are: i) the angle between the arms and the active wind, and ii) slope inclination of the arms.