Numerical simulation of slope stability and landslides under different loadings in the Karongi district, western Rwanda

Abstract

Slope stability and landslides are significant threats to human life, infrastructure, and socio-economic activities in the Karongi District of Western Rwanda, which is characterized by steep slopes, heavy rainfall, and seismic activity. It is very important to understand the dynamics of slope stability under variable conditions of loading for effective disaster mitigation and sustainable land management. This study investigates slope stability and landslide susceptibility under such conditions. Using the Limit Equilibrium Method (LEM), Scoops3D software, and QGIS for the analysis, high-resolution Digital Elevation Model (DEM), pore water pressure ratios, seismic forces, and detailed land use information are integrated in simulating and analyzing slope behavior. The findings of this study provide a better understanding of the strong influences of pore water pressure ratios, seismic activity, and land cover on slope stability. The higher pore water pressure ratios tend to decrease the Factor Of Safety (FOS) values, indicating the vital role of pore water pressure in increasing the slope instability. Similarly, the model representing areas with proximity to roads, bare or agricultural lands are most prone to instability. Slope instability in susceptible areas was exacerbated by seismic loading, which in this case was represented by a Peak Ground Acceleration (PGA) of 0.065g. Historical landslide data allowed the validation of the model, hence showing the reliability of identifying high-risk zones. The validation of the model’s predictive capability at the Karongi region based on the historical landslide data in eastern DRC, Rwanda, and Burundi within 2000-2019 shows quite good correspondence of historical landslide locations with areas with FOS less than 1.0. Notably, the model highlighted a horseshoe-shaped zone in the southeastern part of Karongi district that had shown low FOS values, with no recorded historical landslides. This area comprises bare ground with very little vegetation cover and thus is very susceptible to slope failure, particularly at high pore water pressure ratios. The present findings emphasize that predictive modeling for latent landslide risk is important; therefore, the area requires detailed geotechnical investigation and mitigation strategies in a proactive approach. These results identify potential uses of this model in early warning systems and disaster mitigation strategies. The research puts forward a step in understanding slope stability dynamics in high-risk regions and gives practical insights into sustainable land management and disaster risk reduction.