Sandeep Kumar, Mohd Shawez, Tariq Anwar Ansari, Haritabh Rana, Devanshu Ghildiyal
The North-western (NW) Himalaya is highly vulnerable to climate-driven hazards, where glacial retreat, unstable slopes, and extreme rainfall exacerbate disaster risks. On 5 August 2025, a catastrophic debris flow from the Kheer Ganga Valley devastated Dharali village in Uttarkashi, resulting in 61 deaths, 84 missing persons, and 94 injuries. Persistent rainfall may have triggered a debris flow on the moraine slope at the foot of Shrikanth glacier, mobilizing large volumes of unconsolidated moraine and colluvial sediments. The high-energy flow buried parts of Dharali under 12 – 18 m with the debris of ∼ 251,000 tons, destroyed nearly 60% of its infrastructure, and caused partial damming of the Bhagirathi River. Field surveys confirmed channel avulsions, extensive sediment deposition, and significant geomorphic changes. Furthermore, a debris flow simulation model was computed using the widely recognized HEC-RAS software, employing the non-Newtonian Bingham approach. The results showed that the debris flow velocity, flow depth, and flow pressure reached up to approximately 26 m/s, 19.4 m, and 190 kPa, respectively, at Dharali and nearby areas. Anthropogenic interference, particularly unplanned settlement expansion on paleo-debris fan deposits and river encroachments, greatly exacerbated the disaster’s impact. The Dharali event underscores the urgent need for monitoring the stability of glacial moraines, strict land-use regulation, and community-based preparedness to mitigate future risks.