Application of airborne laser scanning and electrical resistivity tomography in the study of an active landslide and geology of the cliff, Jastrzębia Góra, Poland

Abstract

The cliff in Jastrzębia Góra is one of the most an active landslide areas along the Polish Baltic coast. The aim of these studies was to determine the dynamics of displacements in an active landslide and to identify the geology of the cliff. Two methods, ALS (Airborne Laser Scanning) and ERT (Electrical Resistivity Tomography), were used for this purpose. Multitemporal ALS data were used to determine the geomorphological changes within the cliff and find the causes of the rapid rate of cliff edge landslides. ALS differential models were the sources of new information about the dynamics of vertical displacement in the landslide and helped calculate the volume of displaced rock masses that occurred over 12 years. The cliff was found to become significantly an active in 2010. This process was observed by analysing the relief of multitemporal digital elevation models, differential models, AND morphological sections and by conducting long-term field observations. The ERT surveys made it possible to generate two 3D ERT electrical resistivity models that provided much new information about the geological structure of the cliff. Additionally, a 2D ERT profile was made through the landslide. The internal structure of the landslide was recognized, and the depth of the slip surface was estimated. The results permitted clarifying the cause of the high landslide activity and the rapid rate of retreat of the cliff edge over the past 12 years. In addition, by means of the results of electrical resistivity surveys and the use of archival boreholes, it was possible to extrapolate a model of the surface relief of the clay hill using geostatistical methods. It was found that at the boundary with the active landslide—the top of the clay layer—is tilted towards the north, i.e. towards the sea, which favours the activation of the landslide. The proposed research methodology, as well as the obtained information, may be of significant assistance in further diagnosis and prognosis of the dynamics of landslide development and the causes of landslide formation within cliff coasts.