The Shape of the Barchan Dune

G. Sauermann and H. J. Herrmann

Diploma Thesis

We work on models to describe the dynamics of the surface of a dry granular bed, like a desert. These models, based on coupled differential equations, can describe the formation and evolution of dunes. The simplest and the most well-known type of dunes is the Barchan dune which has the shape of a crescent and occurs if the wind always comes from the same direction and if there is not enough sand to cover the entire surface. They are encountered typically close to the ocean, for instance in Peru, Namibia and Morocco. On these fields hundreds of Barchans can be found, generally all of the same size. These dunes exist in heights between 1.5 m and 10 m, while their basis is typically 40 to 150 m long and 30 to 100 m broad. Field measurements have been performed in south Morocco near Laâyoune to compare with the numerical results. Figure  shows one of these measured dunes.

Fig 1:
Surface data of a real dune measured in Morocco. Axis dimensions are in meters. Length in the symmetry line: 53m, length including horns: 93m, height: 6.3m, width: 78m, volume: 10 800 m$^3$, date: 26. may 1999, UTM: 678001E 3008927N