Slope Stability assessment of a roadside landslide along Khodpe–Chainpur Road Section (NH-64), Sudurpashchim Province, Nepal

Roadside landslides pose critical challenges to transportation infrastructure in Himalayan corridors, threatening connectivity to remote communities and causing significant economic losses during monsoon seasons. Yet systematic investigation frameworks integrating geophysical characterization with quantified stability assessment and mitigation evaluation remain limited. This study demonstrates such a framework applied to the Baluwatar landslide along the Khodpe-Chainpur Road (NH-64) in Bajhang District, Sudurpashchim Province, Nepal. This study employed Electrical Resistivity Tomography, borehole investigations, and Limit Equilibrium modeling to characterize subsurface structures and conduct slope stability analyses. Results identified critical low-resistivity zones, indicating water-saturated colluvial deposits and potential slip surfaces located at 25–30 m depth. Boreholes confirmed loose, sandy colluvium and a shallow groundwater Table (1–2 m). Under simulated monsoon conditions, the current Factor of Safety (FOS) values are 1.179 (hillside) and 1.124 (valley side), denoting marginal stability driven by saturation and road undercutting. Modeled mitigation strategies, including high-strength mesh with soil nailing, catch drains, and a gabion retaining wall, successfully raised the FOS to 1.969 (hillside) and 1.328 (valley side), demonstrating significant stability improvement. This framework provides a scalable Disaster Risk Reduction approach for global road corridors in steep mountainous terrains, emphasizing the importance of groundwater management for stability.