Development of a GIS-based Open Source Simulation Tool for Modelling General Avalanche and Debris Flows over Natural Topography

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Catastrophic granular and debris flows occur in many mountain areas all over the world. Snow avalanches, rock or rock-ice avalanches, debris flows, lahars and pyroclastic flows are only some examples. An adequate management of the risk related to these phenomena requires a detailed and reliable analysis of the mechanisms involved in such processes. Even though much work has been done on this subject, and a number of physically-based models with a varying degree of complexity do exist, some problems still remain unsolved: (1) Flow over arbitrary topography, the role of viscous pore fluid or two-phase nature of flow, and particle and/or fluid entrainment have not yet been accounted for in an appropriate way. (2) Until now, no successful attempts have been made to build easy-to-handle Open Source applications of these complex models, which would be essential to make them available to a broader group of users in universities and public services.This proposal offers an effective, innovative and unified solution to these two problems. It is therefore concerned with rapid geophysical mass flows, including avalanches and real two-phase debris flows, from a known initiation zone through the flow path along natural mountain topography into the deposition zone. For a given amount of mass and its distribution in the initiation zone, we are interested in the motion and geometric deformation along the track down the arbitrary topography, including the processes of erosion and deposition of mass along the track and the ultimate distribution of the deposited mass. This will also include the effect of dynamically evolving pore fluid pressure and/or evolution of the solid and the fluid components. An equally important focus shall be put onto the development of a user-friendly and freely accessible application of the developed model. This application will build upon the GIS software GRASS, which is available as an Open Source product under the GNU General Public License. The new software will be evaluated using physical model tests and well-documented mass flow events. These tests will cover a broad range of processes and process chains including debris flows, debris avalanches and avalanches of snow or rocks.