Effect of the DEMs resolution on landslide runout models

Abstract

Dynamical runout models are essential tools in landslide hazard and risk assessment, because they allow us to simulate the motion of past landslides and to predict the motion of future landslides. Runout distances obtained from these models, combined with expert-knowledge, are used to delineate the landslide hazards zones and consequently create hazard maps. Digital Elevation Models (DEM) are widely used in landslide runout models. The accuracy of the models depends on the source and resolution of the DEM data. By assessing the DEMs ability to interpret the terrain, and the DEM resolutions’ effect on the runout models, it will be possible to evaluate the influence of the DEM resolutions. To evaluate how DEM resolution influences results from numerical runout models, three case studies of flow-type landslides that occurred in Norway in distinct slope typologies were back-analysed with the runout models RAMMS and DAN3D by applying DEMs with 1m and 10m resolution. The results of this study showed that the DEM resolution influence the behaviour of the runout models. By increasing the resolution of the DEMs from 10m to 1m resolution, the accuracy of the runout increased. It was shown that 1m DEMs generally provided the most accurate shape and runout length that were the most identical to the real event. This was also the case for the flow height and velocity, where the 1m DEMs provided the most accurate results. However, DAN3D obtains more varied results compared to the results obtained from RAMMS, which better complies with the real events. It was also noticed that the 10m DEMs required higher friction parameters to back-analyse debris avalanches, but there was no clear trend for the debris flows.