TXT-tool 3.386-1.1 Two-Dimensional Debris-Flow Modelling and Topographic Data Jošt Sodnik and Matjaž Mikoš Abstract Two-dimensional (2-D) debris-flow mathematical modeling is a useful und widely used tool when assessing debris-flow hazard. A high accuracy for 2-D model input parameters is essential for obtaining acceptable simulation results, especially for potential debris flows without a recent history of activity. The numerical grid in the debris-flow transport area is usually generated from available topographic data. In Slovenia, DEM5 and DEM12.5 are publicly available data. However, the morphological accuracy of those datasets is questionable because of their development methods and their low resolution. A better solution is using LiDAR-derived data with their higher resolution and a lot of options for further improvements using different methods and algorithms. 2-D debris-flow simulation results using LiDAR data, compared to less accurate DEMs, are more accurate and more useful for debris-flow hazard mapping. The modelled debris-flow depths and velocities are more accurate and better follow field conditions. Although using high-resolution topographic data results in much longer computational time, this shouldn’t be a problem for potential debris flows. For debris-flow endangered and populated torrential fans, modelling of the influence of built structures on flow is important. With adequate numerical modelling of such structures the obtained simulation results are more meaningful, with better expressed J. Sodnik (&) Tempos d.o.o., Cesta v Kleče 16, 1000 Ljubljana, Slovenia e-mail: jost.sodnik@gmail.com J. Sodnik  M. Mikoš Faculty of Civil and Geodetic Engineering, University of Ljubljana, Jamova C. 2, 1000 Ljubljana, Slovenia e-mail: matjaz.mikos@fgg.uni-lj.si © Springer International Publishing AG 2018 K. Sassa et al. (eds.), Landslide Dynamics: ISDR-ICL Landslide Interactive Teaching Tools, https://doi.org/10.1007/978-3-319-57777-7_11 235