An integrated geohazard assessment approach for sustainable small hydropower projects: A case study from the Western Himalayan Syntaxes, Northern Pakistan

Geohazards, including landslides, debris flows, glacial lake outburst floods (GLOFs), and snow avalanches often pose a significant threat to the sustainability of small hydropower projects in the geologically young and tectonically active Himalayan Mountain chain. Traditional discipline specific geohazard studies often fail to adequately assess the diverse potential geohazards risks faced by these projects. This study investigates the role of the Integrated Geohazard Assessment Approach (IGAA) in ensuring the sustainability of the Rattu small hydropower project in Northern Pakistan. IGAA integrates various techniques, including engineering geology, geomorphology, social survey, and microwave remote sensing technique (Small Baseline Subset Interferometric Synthetic Aperture Radar (SBAS-InSAR)) for the evaluation and assessment of the potential risk from the frequently occurring various geohazards in the project area. Engineering geological assessment characterized the rockmass quality around the proposed project structures, while morphometric analysis differentiated sub-watersheds based on their debris flow or debris flood generating potential. SBAS-InSAR captured the slow kinematics of slopes composed of weak schistose rocks as well as debris fans/cones, validating the impact of geology and geotectonic structures on slope stability. Locale community consultation played a crucial role, leading to the identification of an undocumented snow avalanche event occurred in 2005. As a result, various proposed structures of the Rattu small hydropower project were relocated to safer areas, enhancing the project’s resilience. This study highlights the crucial role of IGAA in ensuring the sustainability of small hydropower projects, particularly during prefeasibility stage.