Some considerations on the application of the FLO-2D model for debris flow hazard assessment

The two-dimensional flood routing model FLO-2D, with the capabilities of simulating non-Newtonian sediment flows, is becoming more widely used to route debris flows over alluvial fans of alpine torrents and to delineate hazard areas of inundation. Nevertheless the different applications described in literature are not comparable, because they base on different assumptions related to the numerous parameters governing the debris flow simulation. This paper reports the applications of the FLO-2D computer model and discusses the assumptions made for the replication of two well documented debris flow events at Fiames (Belluno) and Rio Dona (Trento) in the Eastern Dolomites. The simulations results are consistent with the field observations in terms of maximum flow depths and extent of the inundated areas in the two study sites. These two applications have enhanced the experience for the requirements of model input data in small alpine catchments, in particular the assessment of the main rheological parameters of flows, that are crucial in the design of debris flow countermeasures; they lead to propose a simplification in choosing the FLO-2D rheological parameters; and facilitate the results comparison and their interpretation among different FLO-2D simulations.