Topographic Data and Numerical Debris-Flow Modeling

The digital elevation models (classical DEM 5 and DEM 12.5), publically available in Slovenia, have been evaluated as a basis to prepare numerical square grids 5 × 5 m for 2D modeling of possible debris flows on torrential fans, using the model Flo-2D. Also recently available LiDAR data in their original resolution have been used, as well as their decreased resolution to the one of the numerical grid (e.g. 5 × 5 m). From our numerical results it seems obvious that the use of more precise LiDAR data over classical DEMs for numerical debris-flow modeling is fully justified. Better quality of input topographic data assures higher accuracy of results and therefore also accuracy of hazard maps produced in such a way. The LiDAR data promises better representation of torrential channels on torrential fans (narrow, deep channels) and computed results (velocities, depths) are generally better estimated. Using more precise data also increases computational times compared to using classical DEMs.