Two-dimensional simulation of two viscous debris flows in Austria

Risk mitigation and hazard assessment in steep torrent catchments requires a high level of information about possible runout distances, depth, velocities and resulting impact forces of mass movement processes and its consequences to endangered areas. Two well documented debris flow events at Wartschenbach/Eastern Tyrol and Moschergraben/Styria enable to investigate possible applications of the FLO-2D computer model. The FLO-2D computer model was developed at the Colorado State University and is a grid-based physical process model which routes precipitation-runoff and flood hydrographs over unconfined surfaces and channels using either a kinematic, diffusive or dynamic wave approximation to the momentum equation. All transitions between water floods and fully developed debris flows can be simulated using topographic data files to build the grid elements, information about surface roughness and properties of the sediment water mixture. A quadratic rheological model is used to describe flow behaviour of viscous debris flows. The rheological properties of deposited debris flow material are determined using a rotational viscometer and a new developed conveyor-channel.

The simulation results and the gained experience are of great promise to the future of debris flow modelling.