Engineering Geological Assessment and Landslide Hazard Zonation Using the Slope Stability Susceptibility Evaluation Parameter Method Around Gidole Town, Southern Ethiopia

Gidole Town and its surrounding areas have experienced repeated landslide events that have damaged roads, farmland, and settlements, yet detailed engineering geological investigations and quantitative hazard assessments remain limited. This study investigates the engineering geological factors controlling slope instability and develops a landslide hazard zonation map using the Slope Stability Susceptibility Evaluation Parameter (SSEP) method. The research integrates detailed geological and geomorphological mapping, structural discontinuity measurements, landslide inventory mapping, laboratory testing of representative soil samples, and Geographic Information System (GIS)-based spatial analysis. The results show that highly weathered basalt, unconsolidated colluvial deposits, steep slopes, groundwater seepage, and intense seasonal rainfall are the primary controls on landslide occurrence in the study area. The hazard zonation model classified 67.7% of the area as high hazard, 29.0% as moderate hazard, and 3.4% as low hazard. Model validation using the mapped landslide inventory indicated that approximately 74% of documented landslides fall within the predicted high-hazard zones, demonstrating the robustness and reliability of the SSEP approach. The resulting hazard map provides a scientific basis for land-use planning, infrastructure development, slope stabilization, and disaster risk reduction in southern Ethiopia. The findings further demonstrate that the SSEP method is an effective and practical tool for landslide hazard assessment in data-constrained mountainous regions.