Modelling of debris-flow deposition: Terrain slope, mobility coefficient, and back-calculated basal friction coefficient

Numerous simulation models have become available for the hazard delineation of gravitational mass movements such as debris flows in the potential depositional area. This study compares the basal friction coefficients of two modelling approaches as they have been used in other studies to simulate mass movement deposition. We show that both back-calculated basal friction coefficients are related to the fan or terrain slope in the deposition region and to a mass flow mobility coefficient. The latter is characterized by the geometric scaling between the deposition area and the deposition volume as well as by process type. Intended as a preliminary study, we aim to initiate systematic investigations of different model applications to determine the runout pattern of mass movement processes, that could provide guidance for appropriate parameter selection.