Event Reconstruction and Hydroclimatic–Cryospheric Context of the 2018 Badswat Debris Flow–River Blockage, Pakistan

High Mountain Asia is undergoing rapid warming, with consequences for snow, ground thermal conditions, runoff, sediment availability, and water-related mass-movement hazards. This study combines watershed-scale hydroclimatic and cryospheric diagnostics with an event-scale reconstruction of the 17 July 2018 Badswat debris flow–river blockage in Gilgit–Baltistan, Pakistan. Snow-cover area (MODIS MOD10A1; 2000–2025), surface frost-number terrain (MODIS MOD11A2; 2001–2025), air temperature (ERA5-Land; 1950–2025), and precipitation (CHIRPS; 1981–2025) were analyzed in Google Earth Engine. The event was reconstructed in RAMMS-DF with Voellmy–Salm rheology (μ = 0.09, ξ = 500 m s−2) on a 12.5 m grid. Air temperature increased by 0.13 °C decade−1 (p < 0.001). Snow-cover and permafrost-favorable extents were negatively associated with temperature (r = −0.74 and −0.78), but neither showed a significant temporal trend over the shorter satellite record. CHIRPS precipitation increased by 1.7 mm yr−1 (p < 0.001), mainly in summer, although its annual variability agreed poorly with ERA5-Land and the trend is therefore product-specific. The calibrated scenario reproduced the mapped runout path, river-blockage location, and depositional zone, and yielded maxima of 15.17 m flow height, 33.82 m s−1 velocity, 2544 kPa impact pressure, and 81 kPa basal shear stress, with about 352,540 m3 of deposition. Because dynamic outputs lack independent measurements and joint parameter uncertainty was not quantified, they are scenario estimates rather than design values. The study provides an uncertainty-explicit event reconstruction and separates long-term environmental context from the unresolved event-scale trigger.