Monitoring the Potoška planina landslide (NW Slovenia) using UAV photogrammetry and tachymetric measurements

This paper summarizes the observation of the Potoška planina landslide, which is located in the Karavanke mountain range in NW Slovenia. The landslide lies at the tectonic contact between the Upper Carboniferous and the Permian clastic rocks, and the Upper Triassic to Lower Jurassic carbonate rocks. Due to active tectonics, the clastic rocks are heavily deformed and, consequently, highly prone to fast and deep weathering. The carbonate rocks are also highly fissured due to tectonic disturbances, which result in large quantities of talus and scree material covering the part below the crown. A greater spatial density of springs and wetlands, supplied from the infiltration, is evident at the contact between scree and clastic rocks. Due to prevailing geological, tectonic and hydrological conditions, the Potoška planina area is highly prone to different slope mass movements. This paper presents the monitoring of surface movement patterns at the toe of the Potoška planina landslide. The sliding mass is composed of tectonically deformed and weathered Upper Carboniferous and Permian clastic rocks covered with a large amount of talus material, which is unstable and prone to landslides. Additionally, the Bela torrent causes significant erosion and increases the possibility of mobilization of the sliding mass downstream. Based on said conditions and field survey work, the toe of the landslide is considered to be the most active part of the landslide. In order to estimate surface movement patterns over a monitoring period of 22.5 months and five reconnaissance campaigns, periodic monitoring was conducted using unmanned aerial vehicle (UAV)-based photogrammetry, which provides high-resolution images and tachymetric geodetic measurements that enable accurate control of photogrammetric analysis of surface displacements. Using the results of said periodic monitoring, analyses of UAV-based displacement patterns, surface elevations and volume changes were all modelled for four observation periods. According to our results, the movement pattern at the toe of the Potoška planina landslide indicates a steadily downslope movement of the entire area with localized surges superficial slips.