Evaluating Slope Instability in a Volcanic Caldera Environment Using GIS-Based 3D Analysis: Mt. Bawakaraeng, South Sulawesi

Abstract

Landslides in volcanic terrains pose significant hazards to downstream communities, infrastructure, and watershed systems, particularly where steep slopes and complex geological conditions coexist. This study presents a GIS-based three-dimensional (3D) deterministic slope stability analysis to evaluate landslide susceptibility within the Mt. Bawakaraeng caldera, Sulawesi Island, Indonesia. The analysis integrates geotechnical, geological, hydrological, and topographic parameters obtained from field investigations, laboratory testing, remote sensing data, and a high-resolution 5-m Digital Elevation Model (DEM). Slope stability was evaluated using the factor of safety (FS), calculated through a Hovland-based 3D column method implemented within a GIS environment. Two critical collapse zones were identified and corresponded closely with documented historical landslide events. The calculated minimum FS values of 0.825 and 1.000 indicate unstable to marginally stable slope conditions, respectively. Numerical simulations indicate a progressive failure mechanism in which the collapse of a major slope unit can reduce the stability of adjacent slope units, potentially generating cascading landslide events. Monte Carlo simulations were additionally employed to identify critical slip surfaces and assess potential failure configurations. The simulated slip surfaces showed good agreement with observed landslide morphologies, supporting the reliability of the modeling approach. Potential failure volumes were also estimated to assess the downstream sediment hazard to the Jeneberang watershed. The results demonstrate that integrating GIS, high-resolution terrain data, and 3D deterministic modeling provides an effective framework for spatially explicit slope stability assessment in complex volcanic environments. The approach can support landslide hazard mitigation, watershed management, infrastructure planning, and sustainable development in mountainous regions prone to slope failure.