Rheological assessment of a debris flow from the laboratory experiments to the real scale modelling

In last decades, numerical models have been developed for the analysis of hydrogeological problems like mapping hazard areas, definition of velocities, depths and discharges of mud and debris flows. Even though many modelling tools offer consistent physical-based performances their truthfulness is strongly conditioned by the model-specific assignment of the rheological parameters. For example, viscosity, yield stress and Manning’s n describes the debris-flow mobility in the FLO-2D model, while RAMMS model needs two frictional-collisional parameters of the Voellmy's fluid. In the light of the scientific state of the art on this topic, investigations are still necessary to strengthen the rheology assignment. The mobility properties can be mainly obtained by means of two approaches: i) calibration via the back analysis of well documented debris-flow events; ii) upscaling laboratory measurements of the ‘measurable’ flow rheology at the field scale and for the numerical model in use. The term ‘measurable’ is to say that a sub-sample composed by the finest components of the expected debris flow can be often tested.