Glacier Overflow Suspected in Uttarkashi Flash Floods, Say Experts
The recent flash floods and landslides that struck Uttarkashi district in Uttarakhand on Tuesday may have been triggered by a glacier collapse, according to preliminary assessments by disaster management authorities and glaciologists. Though conclusive evidence is still pending, the presence of a glacial snout and associated debris flow patterns have led experts to suspect a glacial lake outburst flood (GLOF) as the likely cause.
Safi Ahsan Rizvi, advisor (mitigation) at the National Disaster Management Authority (NDMA) and executive director of the National Institute of Disaster Management (NIDM), stated that the initial signs point to the detachment of a glacial snout at around 6,700 metres elevation. “The detachment likely occurred a few days prior to the incident. Continuous rainfall loosened glacio-fluvial debris that had accumulated behind the snout. Once the critical mass was breached, it surged down the Kheer Ganga stream with immense force,” Rizvi explained.
The steep topography between the glacier and the downstream regions, such as Dharali, would have intensified the speed and impact of the debris-laden water flow, he added. However, Rizvi emphasized that complete scientific analysis is still underway and satellite data is yet to provide definitive confirmation.
Nature’s fury at its worst. Horrifying footage of the moment the flash flood hit in Uttarkashi… People seen running away but are swept away in seconds pic.twitter.com/oMZp4q9d3I
— Akshita Nandagopal (@Akshita_N) August 5, 2025
Experts Highlight Periglacial Zone Risks
Supporting the glacier-related hypothesis, Anil Kulkarni, distinguished visiting scientist at the Divecha Center for Climate Change, Indian Institute of Science, said that the flood-struck area falls within a periglacial zone, where glacier involvement is “very likely.” Kulkarni referred to September 2022 satellite imagery, which showed a moraine — a buildup of glacial debris — in the upstream area feeding the Kheer Ganga.
He suggested that continuous rainfall in the area may have led to the formation of a temporary glacial lake behind this moraine ridge. “It is possible that a landslide near the lake outlet blocked drainage, causing water to accumulate. Eventually, this lake may have breached its boundaries, releasing both water and debris downstream,” he said.
This kind of phenomenon is not new to Uttarakhand. In 2021, a combination of glacial collapse and massive rockfall led to devastating floods in the Chamoli district, claiming over 200 lives and causing extensive damage to the Tapovan Vishnugad Hydropower project. That event, like the current one, also began in high-altitude glacier zones.
Scientific Confirmation Awaited
The Wadia Institute of Himalayan Geology (WIHG), a leading research body in the region, has not ruled out the possibility of a glacial lake outburst but maintained that current hypotheses remain speculative due to the absence of ground verification and high-resolution satellite imagery.
“Until we can confirm the presence of a lake that existed before the event and is now missing, all theories remain unverified,” said WIHG director Vineet Kumar Gahalaut. He noted that the area shows signs of older landslides as well, adding to the complexity of the investigation. “Some believe a cloudburst could have triggered the event; that, too, remains within the realm of possibility.”
Gahalaut emphasized that accurate conclusions depend on access to updated satellite imagery and field investigations, both of which are hindered by current weather conditions in the state.
Rainfall to Subside, Risk Remains
Uttarakhand has been experiencing continuous rainfall over the past few days, which has worsened conditions in fragile mountainous areas. The India Meteorological Department (IMD) has predicted a gradual reduction in rainfall from Thursday onward. However, the already destabilized terrain poses a lingering threat of additional landslides and flash floods.
As weather conditions begin to improve, on-ground teams are expected to access the affected areas and gather crucial data to confirm the root cause of the disaster. Meanwhile, local authorities have advised caution and suspended tourist movement in high-risk zones.
The event serves as another grim reminder of the fragile ecological balance in the Himalayan region, which is increasingly vulnerable to climate-driven events such as glacial melts, intense rainfall, and terrain destabilization.
