Relevance of tectonic and structural parameters in Triassic bedrock formations to landslide susceptibility in Quaternary hillslope sediments

Abstract

Important controlling factors of mass movements are generally soil water and geometric-topographic terrain factors such as inclination, curvature type and degree, and the relative position of unstable slopes and embankments. In addition, various geologic parameters that have a direct or indirect connection to soil-mechanical properties of slide masses are also of importance. Some studies also emphasise tectonic parameters in the context of susceptibility to mass movements. This study considers the relevance of tectonic and structural parameters in bedrock formations for landslides in periglacial hillslope sediments on top of the bedrock. The research area is part of the southern Solling anticline, a saddle structure in the Middle Bunter Sandstone formation in northern Hesse and southern Lower Saxony (Germany). In this geologic formation, sandstone, siltstone, and mudstone are interbedded with impermeable strata. Uplift of the Solling anticline, in particular during the Quaternary, resulted in a partially intensive dissection of the Bunter Sandstone plateau into separate blocks with disrupted, tilted, and partially rotated layers. The structural conditions have an indirect impact upon landslides in the superposed hillslope sediments. Water flow along strata and joints above water impermeable strata cause water infiltration and moistening of the periglacial hillslope sediments on top of the bedrock. Mass movements are frequently linked to sites of outcrop springs and occur after long periods of rainfall. A GIS-based analysis was used to statistically evaluate possible factors controlling landslides. Factors were weighted and included in an empiric-statistical model that allows spatial description of hazard potentials due to mass movements. In addition to morphologic parameters, the structural parameters of the bedrock are of utmost importance for the occurrence of landslides.