Are area changes the primary indicator for predicting glacial lake outburst Risks?——A case study of the HMA region

Abstract

Glacial lake outburst floods (GLOFs) have received substantial attention owing to their catastrophic potential. Thus, accurate susceptibility assessments are crucial for disaster prevention and mitigation. These assessments primarily depend on the characteristics of glacial lakes and their surrounding environments. While some studies highlight glacial lake area expansion as a key indicator, quantitative analyses remain limited. This study investigates 94 reported GLOF events in High Mountain Asia (HMA) since 1998, confirming 40 precise events through literature review, remote sensing imagery, and geomorphological analysis. By constructing year-by-year boundary data for these 40 glacial lakes and analyzing their area changes, we identified three key findings: (1) Relationship between lake size and outburst frequency: Smaller lakes are more prone to outbursts. The mean glacial lake area was 0.25 km², with 42.5% being <0.1 km² and only 2.5% >1 km². (2) Complex area change patterns: Area changes before outbursts were categorized into four types: expanding, stable, shrinking, and fluctuating. Notably, 45% of lakes showed expansion trends, while 15.56% exhibited significant shrinkage. (3) Regional differences in susceptibility: In the Himalayas, pre-outburst area changes were highly variable, making area growth an unreliable indicator of GLOF susceptibility. Conversely, lakes in the Nyainqentanglha Mountains were either stable or expanding before outbursts, suggesting that continuous expansion could serve as a potential trigger and warrants close monitoring. These findings underscore the need for comprehensive, region-specific approaches to GLOF risk assessment, emphasizing the complexity of area changes and the importance of tailored monitoring strategies.