Assessment of rainfall-induced slope failures at Chakargoan, Port Blair, India, using 2D ERT and self-potential techniques.

The Andaman and Nicobar archipelago receives substantial annual rainfall, averaging around 3000 mm, due to their distinctive geographical, geological, and climatic attributes. Landslides occur regularly as a result of heavy rainfall, and during severe to super cyclones, the risk of destructive landslips and debris slides becomes heightened. In the present study, various landslips and slope deformations triggered by heavy rainfall were investigated using integrated 2D electrical resistivity tomography (ERT) and self-potential (SP) geophysical techniques complemented by geological field surveys. A total of four 2D ERT profiles were performed using the Wenner array configuration to map the spatial distribution of subsurface electrical resistivities. The geoelectrical data candidly illustrates the spatial distribution of lateral and vertical resistivity contrasts and numerous low resistivity zones (5–100 Ωm), reflecting the various aspects of slope stability and associated hydrological characteristics. The negative self-potential anomalies (–0.2 to –0.34 mV) of the subsurface strata indicate flow dynamics and infiltration along the fractures as well as unstable weathered zones. Total station measurements illustrate the various surface characteristics of the slope failures, including potential slip surfaces, weak zones, and sliding mass. The integrated results involving 2D ERT, total station, and SP methods enable us to have a better understanding of the geometry of landslips, slope stability, and slope hydrology. Research highlights: Geophysical observations highlight the interplay of landslide occurrence and hydro-metrological events, shaping their occurrence. 2D Electrical Resistivity Tomography surveys detect subtle slope deformations and identify potential differential slope failures. The negative self-potential surveys indicate weathered zones and hydrological aspects of the slope failures. Massive deforestation and urbanization have significantly amplified the frequency of landslides in the Andaman and Nicobar Islands. [ABSTRACT FROM AUTHOR]