Does the topographic data source truly influence the routing modelling of debris flows in a torrent catchment?

To cope with debris-flow hazards, a common practice is the mapping of threatenedareas through routing models. Considering the primary role of topography in affect-ing the mobility of gravity-driven flows, its proper representation through digital ele-vation models (DEMs) is a requirement in routing modelling applications. The‘quality’of DEMs mainly depends on the quality, resolution and spatial arrangementof the topographic measurements (i.e. on the employed survey technology). Never-theless, no attempt to systematically evaluate the influence of the topographic datasource on the behaviour of routing models has been carried out. To address this, weinitially assess the performances of both terrestrial- (i.e. global navigation satellitesystem, GNSS) and airborne-based (i.e. full-waveform LiDAR and structure-from-motion, SfM digital photogrammetry) survey technologies in characterizing thetopography of a debris-flow channel. Afterwards, we investigate whether the topo-graphic data source can effectively influence the behaviour of a geographic informa-tion system (GIS)-based cell routing model. Regarding the assessment of the surveytechnologies performances, the‘standard’statistic-based approach indicated thatGNSS and full-waveform LiDAR can provide an accurate digital representation of thegully. However, the analysis of the shapes stressed that the most faithful and finerreproduction of the topographic singularities is yielded by the photogrammetricallyreconstructed surface due to the extremely high data source resolution. Furthermore,the pairwise comparison of derived elevation models pointed out that meaningfuldiscrepancies among tested survey technologies can be detected in morphologicallycomplex areas because of the inherent limits of the terrestrial-based method. Here,this research showed how these discrepancies have the potential to affect simulatedflow dynamics, even if not in a meaningful way from a risk planning and managementpoint of view. Overall, it appears that the topographic data source does not truly rep-resent a determining factor in modelling applications of channelized debris-flowrouting.