Uttarakhand floods: Satellite images show disappearance of buildings, roads

Experts from the National Disaster Management Authority (NDMA) have said they were examining the possibility of a glacier collapse

The National Remote Sensing Centre’s post-flash flood satellite images of the upper reaches of Uttarakhand indicate the accumulation of debris in and around Dharali, the disappearance of buildings, roads, and plantations, and sediments and debris covering a stretch of Bhagirathi and Kheer Ganga rivers. A bridge and what appear to be orchards are also inundated.

Rescuers at the scene of the mudslide and flash floods. (AFP)

Experts from the National Disaster Management Authority (NDMA) have said they were examining the possibility that a glacier collapse upstream of the channel feeding the Kheer Ganga triggered the floods.

Anil Kulkarni, a distinguished visiting scientist at the Indian Institute of Science’s Divecha Center for Climate Change, said past satellite images have helped understand the glacier dynamics. “Kheer Ganga river originates from glaciated terrain. Satellite imagery from September 2022 was analysed. It is useful imagery as during this time snow had mostly melted and glacier ice and landforms can be seen clearly.”

He said the satellite imagery indicates that glacier ice is mostly melted. He added that glacier ice can be seen in a very small area. “... well-developed deglaciated valley can be seen,” Kulkarni said in a note on Thursday.

He added that the outlet of the deglaciated valley is bounded by an end moraine, and a small river passes between the end moraine and the side wall. “Upstream of the end moraine, a meandering stream pattern was observed. It indicates flat terrain and also the formation of a lake in the past.” Kulkarni said. “The flash flood mud flow may have been caused by to outburst of the lake.”

Satellite images of Dharali Village in Uttarkashi district taken on June 2024 (left) and August 2025.

NDMA officials were awaiting cloud-free satellite imagery to get further details on the glacier feeding Kheer Ganga. “There are indications that a glacial snout at 6700 m detached some days ago...,” said NDMA advisor (mitigation) Safi Ahsan Rizvi on Wednesday. “...large glacio-fluvial debris deposits collected. Incessant rain over the past few days is believed to have led to the loosening of the debris. Once critical mass was crossed, the massive collection of debris cascaded downstream with water in the Kheer Ganga, accelerating due to the steep gradient up to Dharali.”

Rizvi said that it is clear that none of the 195 at-risk glacial lakes are in the Dharali catchment. “As per the National Remote Sensing Centre (NRSC) Atlas of 2023, there are 7500 glacial lakes greater than 0.25 ha in the Himalayas. Of these, NDMA categorised 195 as at-risk.”