On August 5, 2025, Dharali village in Uttarakhand, India, witnessed a debris-flow event along the Kheer Gad watershed, considered one of the most severe catastrophic geomorphic disasters in the Himalaya in 2025. Intense rainfall induced the failure of the thick, unconsolidated moraine deposits, initiating mass mobilization into the Kheer Gad. The subsequent interplay of channel morphology and the descending debris promoted significant erosion and entrainment, leading to a marked amplification of flow mass and momentum. This fast-moving descending flow engulfed buildings and people, resulting in extensive destruction in the Dharali market area, with 7.5- to 15-m-thick debris deposits spreading over 20 hectares. This event represents a classic example of debris flow in a mountainous watershed, in which geomorphological attributes govern flow dynamics under hydroclimatic forcing. The observations emphasize the need for comprehensive geomorphological assessments of debris-flow-prone watersheds, especially those posing significant risks to life, livelihoods, and infrastructure at watershed outlets. This study integrates available information and satellite images with detailed morphometric assessments of the Kheer Gad watershed and its hydroclimatic responses to infer the key factors governing the event’s evolution and transformation. It became evident that the watershed morphometric characteristics, high erosion potential along the flow channel during hydrometeorological events, low valley floor width-to-valley height ratios, moderate to high stream length–gradient indices, and the presence of knickpoints might have amplified the flow volume. Furthermore, infrastructure encroachment at the debris fan base substantially increased the severity of damage. This study also mentions possible mitigation measures that could be undertaken in similar geomorphological settings across the Himalaya and other mountainous regions to mitigate the future risk posed by such events.