Evaluating Pre- and Post-Damages of Hydro-Hazard Dynamics in Talidas Valley under Climate Change due to Glacier Lake Outburst Flood

The glacier lake outburst floods (GLOFs) are a growing hydro-hazard in northern Pakistan's glacier-fed mountain valleys, where glacier retreat and moraine-dammed lake expansion can generate sudden flood waves through steep, downstream channels. This study used Sentinel-2C imagery, RGI v6-v7 glacier inventories, a 12.5 m ALOS PALSAR DEM, and high-resolution Google Earth Pro imagery to map glacier retreat, lake area change, catchment pathways, and downstream exposure before and after the 22-08-2025 GLOF event in Talidas Valley in the Ghizer district in northern Pakistan. Multi-temporal Sentinel-2 imagery from 2017 to 2025 showed sustained glacier retreat and changes in the associated proglacial lake system, suggesting continued glacier shrinkage and increased downstream hazard potential. Hydrodynamic simulations using HEC-RAS quantified flood extent, depth, and flow velocity, while overlay analysis with high-resolution imagery assessed exposure along the river corridor. The glacier analysis using RGI v6 and v7 shows that the glacier area of 0.158 km² (2017) declined to 0.093 km² (2023) and further decreased to 0.041 km² (2025), and NDWI-based mapping showed that the upstream lake area decreased by 0.0348 km² after the event, and simulated inundation intersected settlements and infrastructure along the valley floor. The results indicate the high physical exposure of settlements and infrastructure along the downstream river corridor and demonstrate that satellite-based glacier lake monitoring combined with HEC-RAS modeling can support GLOF risk mapping and early-warning planning in data-scarce glacier-fed valleys of northern Pakistan.