Remote sensing and spectral indices-based rapid impact assessment of the Talidas GLOF event in Gilgit–Baltistan, Pakistan

Glacial lake outburst floods (GLOFs) have emerged as a significant cryosphere hazard in High Mountain Asia (HMA). Particularly, the Gilgit-Baltistan and Chitral regions of northern Pakistan have witnessed a significant increase in GLOFs due to accelerated glacial melt resulting from climate change. This study presents a rapid impact assessment of the August 2025 Talidas GLOF event, based on Sentinel-2 imagery and ALOS PALSAR 12.5 m DEM datasets. The water inundation and depletion were mapped using dNDWI and dMNDWI, with validation demonstrating strong performance, achieving accuracies of 92.32% and 90.56%, respectively. Results reveal nearly complete drainage of glacial lakes, extensive debris deposition, a 195 m channel shift, and the sudden formation of a 0.628 km2 debris-dammed lake. This study presents a rare, empirically grounded rapid impact assessment of a GLOF event in a geographically underrepresented region, addressing a significant knowledge gap in high-mountain hazard research. It further underscores the critical value of near-real-time, satellite-based methods as indispensable tools for evaluating cascading hazards in data-scarce regions undergoing rapid glacier retreat.