Multiscale analysis of surface roughness for the improvement of natural hazard modelling

Abstract. Surface roughness influences the release of avalanches and dynamics rockfall, debris flow, but it is often not objectively implemented in natural hazard modelling. For two study areas, a treeline ecotone windthrow-disturbed forest landscape European Alps, we tested seven algorithms using photogrammetric digital surface model (DSM) with different resolutions (0.1, 0.5 1 m) moving-window areas (9, 25 49 m2). The vector ruggedness measure algorithm performed best overall distinguishing between categories relevant for modelling (including shrub forest, high windthrow, snow rocky land cover). results m resolution were found to be suitable distinguish interest, performance did increase higher resolution. In order improve calculation along flow direction, directional approach that improved reliability computation channelised paths. We simulated on elevation models (lidar-based) observe potential influence DSM terrain (DTM) simulation tool Rapid Mass Movement Simulation (RAMMS). this way, accounted based instead DTM, which resulted shorter avalanche runouts by 16 %–27 % areas. above treeline, comparison represented within RAMMS, therefore underestimated. conclude DSM-based combination DTM-based considering promising achieving better assessment an alpine landscape, might