Deadly Indian Himalayan flood likely caused by glacier collapse: Experts

A deadly wall of muddy water that swept away an Indian Himalayan town this week was likely caused by a rapidly melting glacier exacerbated by the rising effects of climate change, experts said on Thursday.

Scores of people are missing after water and debris tore down a narrow mountain valley, smashing into the town of Dharali in Uttarakhand state on Tuesday.

Several people could be seen in videos running before being engulfed as waves uprooted entire buildings, leaving others smothered in freezing sludge.

At least four people have been confirmed killed, with around 50 others still missing.

Government officials initially said the flood was caused by an intense “cloudburst” of rain. However, experts assessing the damage suggested that was only the final trigger, following days of prolonged rainfall that had already soaked and loosened the terrain.

P.K. Joshi, an expert on Himalayan hazards at New Delhi’s Jawaharlal Nehru University, said it appeared the flood was caused by the collapse of debris — known as moraine — that had dammed a lake of meltwater from a retreating glacier.

“Given the persistent rainfall over preceding days and the sudden discharge observed, a glacial lake outburst flood (GLOF) or collapse of a moraine-dammed lake is suspected as the primary trigger,” Joshi said.

That would have contributed to a “sudden high-energy flash flood,” he said, noting that glacial terrain upstream of the town included “unstable sediment zones.”

Cloud cover has obstructed satellite imagery to confirm the source of the debris, and Joshi cautioned that there is not yet enough satellite data for a definitive conclusion.

Safi Ahsan Rizvi, an adviser to the National Disaster Management Authority, also said it was “likely” that the cause was a “glacio-fluvial debris landslide.”

Sandip Tanu Mandal, a glaciologist at New Delhi’s Mobius Foundation, also pointed to the “possibility of a GLOF,” caused by “significant water accumulation in the lake due to increased melting and rainfall.”

Mandal noted that while the rainfall was heavy, it was “not very significant” compared to the vast volume of water that poured down the valley — suggesting a potentially collapsing glacial lake as the main cause.

Himalayan glaciers, which provide critical water to nearly two billion people, are melting faster than ever due to climate change, exposing downstream communities to unpredictable and increasingly costly disasters. The softening of permafrost is also raising the risk of landslides.

Joshi said the latest disaster “highlights the complex and interconnected nature of Himalayan hazards.” Rapid development downstream, he added, had magnified the destruction.

“The land use patterns in the floodplain exacerbated the disaster severity,” Joshi said.