Abstract ID: 3.11330 | Rejected | Talk/Oral | TBA | TBA

Debris flows are destructive events posing serious risks in the Himalayas. This study assesses susceptibility in the Trans-Himalayan Spiti Valley using an AHP-based multi-criteria analysis of eleven geo-environmental factors. The resulting susceptibility map, validated against landslide inventories, classifies the basin into four zones, with 3.8% and 19.3% of the area exhibiting very high and high susceptibility, respectively, at 79.8% model accuracy. A case study of a 7th July 2022 debris flow confirms these findings. Geomorphological mapping and climate analysis indicate that increased summer temperatures and extreme precipitation destabilize periglacial sediments. Field observations show that 0.33 km² was affected, damaging houses, vehicles, and National Highway 505, disrupting transport connectivity. To examine permafrost’s role in landscape evolution, high-resolution PlanetScope (2022) and declassified CORONA KH-4 (1982) imagery were used to create geomorphological maps. A Sankey diagram and cross-section analysis over 40 years (1982–2022) reveal significant degradation of solifluction lobes, protalus ramparts, and paleo-rock glaciers, indicating shifts from glacial to periglacial processes. Approximately 12% of active solifluction lobes degraded, while 82% of paleo-rock glaciers remained largely intact, with minor transitions. The study highlights permafrost degradation’s increasing role in debris flows, aligning with global alpine trends. While links between permafrost loss and debris flow initiation require further study, findings suggest warming-induced changes may intensify debris flow activity. Future research should explore subsurface thermal regimes and microfabric analysis to enhance understanding of permafrost dynamics in debris flow processes amid climate change.