Rim Slope Instability of Reservoir and Mitigating Approaches

Abstract

Nepal is mountainous country with high potential of hydropower projects. Hence, steep and geologically complex terrain surrounding the reservoir poses a considerable risk of rim slope instability. This may compromise dam safety, reduce reservoir capacity through sedimentation during operation. The study area is Dudhkoshi Storage Hydroelectric Project in Khotang District. This study investigates the factors contributing to slope instability around the Dudhkoshi reservoir rim, emphasizing the influence of geological structures, seasonal rainfall, fluctuating water levels, and anthropogenic activities such as road construction and deforestation. A combination of geological survey, remote sensing data, and geotechnical analysis was employed to assess the stability of critical slopes. Preliminary results highlight several high-risk zones dominated by weathered rock masses, colluvial deposits, and active landslides and landslides prone areas. These conditions are further exacerbated by monsoonal precipitation and rapid drawdown events, which induce pore pressure changes and slope weakening. This study underscores the critical need for integrated slope management strategies to ensure the long-term stability and sustainability of the Dudhkoshi reservoir. The findings serve as a foundation for hazard mitigation planning and informed decision- making in large-scale hydroelectric infrastructure projects in mountainous regions.