Moctar Dembele¹, Gregoire Mariethoz¹ and Bettina Schaefli^2,3, (1)Institute of Earth Surface Dynamics (IDYST), Faculty of Geosciences and Environment (FGSE), University of Lausanne, Lausanne, Switzerland, (2)Institute of Earth Surface Dynamics, Faculty of Geosciences and Environment, University of Lausanne, Lausanne, Switzerland, (3)Now at: Institute of Geography (GIUB), University of Bern, Lausanne, Switzerland