Glacial Lake Inventory and Glacial Lake Outburst Flood Susceptibility Mapping Using AHP in Dudhkoshi Basin, Nepal

Considering the increasing climate variability and historical glacial lake outburst flood (GLOF) events that pose significant risks to downstream communities in the Himalayas, early basin-scale inventories and GLOF susceptibility maps are essential. This study focuses on the Dudhkoshi Basin in the Eastern Himalayas, recognized as one of the most densely populated areas with glacial lakes in Nepal. Utilizing Sentinel-2 satellite imagery, a comprehensive list of glacial lakes was created for the years 2016, 2020, and 2024, with an average mapping uncertainty of 1.12%. The inventories revealed 523 lakes in 2016, covering a total area of 16.0018 km²; 519 lakes in 2020, with a total area of 18.2293 km²; and the count increased to 537 lakes, with a total area of 20.8663 km² in 2024. The Analytic Hierarchy Process (AHP) was applied to assess susceptibility, considering critical parameters such as lake area, volume, expansion rate, freeboard, glacial proximity, slope, seismicity, and historical GLOF events. The potentially dangerous lakes were categorized into three levels of susceptibility: low susceptibility (0.250–0.550) with 40 lakes, medium susceptibility (0.550–0.700) with 15 lakes located between elevations of 4353 MSL and 5250 MSL, and high susceptibility (≥ 0.700) with 6 lakes situated between elevations of 4326 MSL and 4940 MSL. Given the challenges of field verification due to steep terrain and inaccessibility, this study provides a reliable baseline for hazard mapping and the prioritization of glacial lakes.