Numerical modelling of a debris-flow fan in Eastern Italian Alps

The knowledge of flow rheology, the accurate prediction of runout distances, and velocities, can reduce the casualties and property damage produced by debris flows, providing a means to delineate hazard areas, to estimate hazard intensities for input into risk studies and parameters for the design of control works. The application of models which describe the propagation and deposition of debris flow for the hazard delineation and estimation, requires detailed topography, hydrological and rheological data that are not always available In the Tolmezzo area, Eastern Italian Alps, a wide, complex shaped debris flow fan is built by a torrent and its several tributaries. the material transported by these events invaded a very busy national road We compared the results of simulations carried on with two different single-phase, non Newtonian models, the two-dimensional FLO-2D and IDRA2D DF, in order to test the reliability to simulate the dynamic behaviour of the design debris flow. Data from field topographic surveys and from the rain gauges of the valley are used in order to build a trustworthy numerical model for deposition simulation. FLO-2D model creates a more accurate representation of the hazard area in terms of flooded area, but the results in terms of runout distances and deposits thickness are similar to the open-source IDRA2D DF results. Parameters obtained through back-analysis with both models can be applied to predict hazard in other areas characterized by similar geology, morphology and climate.