Reconstruction of landslide activity using dendrogeomorphological analysis in the Karavanke mountains in NW Slovenia

Tree ring eccentricity was used to reconstruct landslide activity in the last 138 years in the Urbas landslide located at Potoška planina in the NW part of the Karavanke Mountains, Slovenia. The research was based on the dendrochronological sampling of Norway spruce (Picea abies (L.) Karst.) in areas of varying landslide intensity. Analysis of a sudden change in the eccentricity index of 82 curved trees concluded that there were 139 growth disturbances and 16 landslide reactivations between 1880 and 2015, with a landslide return period of 8.5 years. Using lidar data, changes in the surface of the digital terrain model (DTM) were compared with changes in the eccentricity index of trees at the same location in the period 2014–2017. On the basis of temporal changes in the eccentricity index and by using spatial interpolation, landslide activity was reconstructed for the period 1943–2015. During this period, landslide intensity increased in the central part of the landslide. Although categorization into seven categories of different stem curvature was proposed, no distinction between categories with respect to their eccentricity index was found