Glacial lake outburst flood hazard and downstream impacts: lessons from Afghanistan examples

Abstract Glacial lake outburst floods (GLOFs) pose a growing risk in high mountain regions as climate-driven glacier retreat accelerates lake expansion and new lake formation. In the Hindu Kush Himalaya, particularly in Afghanistan, triggering processes and GLOF propagation downstream are largely unstudied. This study evaluates two Afghanistan GLOFs (Peshghor 2018; Bam-Tanab 2021) using field observations and satellite imagery, and applies two-dimensional hydrodynamic simulation (BASEMENT-MD with BASEbreach) to the Kunj-Peshghor lake event to assess flood propagation, dam-breach dynamics, and downstream hazards under different scenarios. Both lakes formed and expanded over 33–42 days before catastrophic drainage, triggered by extreme temperatures, rapid-melt, ice-cliff collapse, and englacial tunnel failure. Both impacted Peshghor village downstream. The Kunj-Peshghor lake flood wave produced estimated peak velocities of 9 ms −1 and depths >10 m in confined valleys, associated with peak discharges >170 m 3 s −1 , high turbidity >800 NTU, and channel widening of up to 250 m. Secondary surges caused by temporary river blockages prolonged flooding and amplified downstream impacts. Hazard mapping indicates that ~46% of inundated zones in the Peshghor village fell within high to very high hazard levels, threatening settlements, roads, markets, and agricultural land. These findings provide the first quantitative GLOF propagation modeling for Afghanistan and highlight the need for site-specific monitoring, early warning systems, and mitigation measures. Both GLOFs were caused by the rapid formation and expansion of new lakes. This raises the question about whether current approaches to identifying dangerous lakes, based on remote-sensing of existing lakes are sufficient to detect all dangerous lakes and the associated hazards.