Evaluation of Slope Susceptibility Using 2D Electrical Resistivity Tomography Supplemented with Spatial Resistivity Change

Landslides, which are a serious geological hazard, occur commonly in the highlands. Anthropological activities, including the expansion of human settlements and the subsequent land use conversion, are considered important factors that can trigger landslides. In this study, to evaluate landslide susceptibility, we carried out a 2D Electrical Resistivity Tomography (ERT) survey along a hilly slope of the mountains to identify the lithological types of the subsurface layers. The lithological condition becomes the primary location at which a slip surface could eventually form and degree of saturation is the principal factor controlling slip surface formation. The interpreted 2D ERT indicated a significant resistivity contrast between the sediments/weathered rock material and the resistant bedrock at various depths (from 3 to 10 m). The MATLAB code of spatial resistance change (SRC) was used to analyze the resistivity change in the subsurface layers. The results revealed a high contrast in the SRC at the boundary between the dominantly low and high resistivities of the bedrock and the fracture features. Therefore, SRC analysis can enhance the ERT results and help delineate and categorize susceptible landslide zones effectively. In our study, the susceptibility zones related to ground modifications were located in the clusters of lodges, campground sites, and cabbage fields. Generally, in terms of the infiltration of drained rainwater, the load of a building having a shallow foundation can increase the likelihood of landslides. The occurrence gullies of the back slope may be an initial sign of a landslide.