Electrical resistivity tomography and digital aerial photogrammetry in the research of the “Bachledzki Hill” active landslide – in Podhale (Poland)

Abstract

Podhale is a region in Poland at high risk of landslide. Sudden activation of landslides is the greatest threat to the local infrastructure. This work describes the joint use of electrical resistivity tomography (ERT) and aerial photogrammetry in the study of the active “Bachledzki Hill” landslide. In order to determine landslide dynamics, a digital version of stereo-pairs of aerial images from 1972 and 2004, as well as the airborne laser scanning (ALS) results from 2014 were used. Based on the data, first, three photogrammetric digital elevation models were generated. Then, in the ArcGIS software two differential models were generated (2004–1970 and 2014–1970) ground surface displacements in the landslide area and two other models illustrating the volume of the displaced material. Our research has shown that the landslide has been active to varying degrees since 1970. The landslide geometry, as well as the structure and lithology of the flysch bedrock were characterized using the ERT method. The resistivity images allowed the interpretation of the faults and lithology of the bedrock, as well as the determination of the depth and geometry of the landslide slip surface. Areas with water-logged rocks or rocks containing clay in the structure of the landslide are located. In this areas further movements may be generated. In addition, a voxel 3D ERT model of landslide and a model of rupture surface were generated. Both models allowed the spatial interpretation and visualization of the landslide structure and the geological structure of flysch rocks, as well as the spatial imaging of the surface rupture. The results of geophysical surveying made it possible to understand the cause of the activity of the landslide. The proposed comprehensive application of geophysical researches, geological modeling and digital aerial photogrammetry methods may become a common research methodology in the detailed study of landslides. • The aim of the photogrammetric research was to describe and understand the kinematics of landslides. • Geoelectrical methods, such as Electrical Resistivity Tomography, can be successfully used in landslide studies. • The 3D ERT voxel model facilitated geological interpretation. • Based on geophysical data and archival wells the surface of rupture model was developed using geostatistical methods.