Geological Hazards in Pokhara Valley, Central Nepal: Types, Distribution, Impacts and Implications for Hazard Management

Abstract

Pokhara Valley is one of the most remarkable intermontane basins of the Nepal Himalaya and is characterized by a unique geological and geomorphological setting. The valley is occupied by extensive Quaternary sediments derived largely from catastrophic sediment-transport processes originating in the Annapurna region. The valley is traversed by the deeply incised Seti River and its tributaries and contains numerous terraces, gorges, caves, sinkholes, lakes and other distinctive geomorphic features. These geological and geomorphological conditions, together with active tectonics, steep surrounding slopes, intense monsoonal rainfall and increasing urbanization, make the valley vulnerable to a range of geological hazards. This study presents an integrated assessment of the major geological hazards in and around Pokhara Valley based on field observations, geological and geomorphological investigation, hazard inventory mapping, and interpretation of previous studies and review of published literature. The principal hazards identified include landslides, riverbank erosion and bank collapse, block fall, karstification and sinkhole development, flash floods and debris-flow-related hazards. Landslides occur mainly along the surrounding hill slopes and transportation corridors, whereas bank erosion and block failure are concentrated along the Seti River and its tributaries. Karstification is particularly important because the valley-fill sediments contain abundant calcareous materials, resulting in underground cavities, caves, solution channels, sinkholes and local ground subsidence. Flash floods represent a major high-impact hazard, as demonstrated by the 2012 Seti River disaster. The geological record of repeated large-scale debris-flow deposition also indicates that the Pokhara Valley has experienced catastrophic sedimentation events in the past and may remain susceptible to similar low-frequency but high-magnitude processes. The study emphasizes that geological hazards in Pokhara Valley should be considered within a multi-hazard framework. Detailed hazard zonation, systematic monitoring, improved drainage, control of unscientific river mining, land-use regulation, early warning systems and public awareness are essential for reducing future risk. The results provide a geological basis for hazard-sensitive urban planning and sustainable development in the rapidly expanding Pokhara Valley.