The Dharali debris flow on 5 August 2025, in Uttarakhand, India, was a catastrophic disaster that occurred in Kheer Gad, a tributary of the Bhagirathi river. It claimed approximately 60 lives and covered an estimated 3 hectares of apple orchards under debris. The damage also included at least 25–30 animals and a market comprising 65 hotels, over 30 resorts, and homestays. The present study involved the geomorphic characterisation of Kheer Gad to assess the debris flow potential of the catchment and debris flow simulation to ascertain the source, potential flow dynamics, and reconstruction. Findings reveal that the 17 km2 Kheer Gad catchment is inherently unstable, as suggested by Melton’s ruggedness number of 0.8, significantly above the 0.6 debris-flow threshold. The trigger was not a single event, but an antecedent rainfall of ∼195 mm/30 days, which saturated glacial and landslide-derived source materials. Debris flow simulation revealed 60 kPa flow pressure, velocities of 5–10 m/s, flow height of 5–10 m, spread area of ∼18 hectare, and volume estimate of 995,580 ± 200,000 m3–1,285,260 ± 126,000 m3 . These values are validated against field observations. Notably, the disaster was exacerbated by human vulnerability, given the doubling of built-up structures between 2011 and 2025, despite prior warnings in 2013. The present study provides a transferable methodology for assessing similar high-risk, glaciated basins to prevent such avoidable disasters.