Geomorphology- and geophysics-based recognition of stages of deep-seated slope deformation (Sudetes, SW Poland)

Abstract

Slopes of the Kamienne Mountains, SW Poland, have been affected by a variety of slope deformations, from DSGSDs through rock slope collapses, rotational and translational landslides sensu stricto, to valley-confined earth flows. Variable geomorphic expression suggests that major slope deformation events are of different ages and some slope deformation may be ongoing. In this paper we use the combination of landform mapping and Electrical Resistivity Tomography profiling to characterize two settings, considered to represent early stages of slope deformation and advanced stages of ridge collapse. Landform recognition involved field geomorphic mapping and interpretation of high-resolution LiDAR DTM. Diagnostic features of early stages of deformation are open cracks, minor and rather subdued scarps in the upper slope, and lower slope bulging. Irregular hummocky topography, ruiniform relief and closed depressions typify the late stages. ERT results are generally consistent landform interpretation and show weakening of bedrock, evolving failure planes, as well as subsidence of rigid caprock blocks into deformable sedimentary series for the late stage. The combined geomorphological-geophysical approach performed fairly satisfactorily and both methods can be used to cross-check interpretations, even in areas not subject to recent mass movement events, poorly accessible due to dense forest cover and lacking clear morphological evidence.