Nepal Floods and Their Relationship with Glacial Lake Outburst Floods (GLOFS): Spatial Patterns, Environmental Impacts and Risk-Reduction Strategies

Flooding is one of the most recurrent and damaging natural hazards in Nepal because of the country's steep topography, intense monsoonal rainfall, highly dissected drainage network, unstable slopes and rapidly changing Himalayan cryosphere. In the high mountain environment, conventional rainfall-induced floods increasingly interact with glacier-related processes, including glacial lake formation, glacier retreat, ice avalanches, landslides and glacial lake outburst floods (GLOFs). A GLOF occurs when water stored in a glacial lake is suddenly released, producing a high-energy flood wave that may transport large quantities of sediment, boulders, ice and debris into downstream valleys.
This paper examines the relationship between floods and GLOFs in Nepal, with particular emphasis on the role of glacier retreat, glacial-lake expansion, triggering mechanisms, downstream vulnerability and cascading hazards. The study uses a secondary-data and geospatial approach based on published literature, satellite-based glacial-lake inventories, government reports and assessments by ICIMOD, UNDP and other institutions. Historical events including the Nare GLOF of 1977, Nagma Pokhari GLOF of 1980, Zhangzangbo GLOF of 1981, Dig Tsho GLOF of 1985, Chubung GLOF of 1991, Tam Pokhari GLOF of 1998 and the Thame Valley GLOF of 2024 are examined alongside major rainfall- and river-related floods. The analysis demonstrates that Nepal's flood risk cannot be understood through a single hazard category
The study concludes that GLOF risk reduction requires an integrated approach combining remote sensing, GIS-based hazard mapping, continuous glacial-lake monitoring, early warning systems, structural mitigation, ecosystem-based measures, community preparedness and transboundary cooperation. The findings have implications for climate adaptation, mountain development planning and disaster-risk management in Nepal.

Nepal, GLOF, glacial lakes, glacier retreat, floods, climate change, Himalaya, remote sensing, disaster risk, Thame Valley

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