Nepal flash flood imaged by satellites

The catastrophic flash flood struck the Nepal–China border region on 26 August 2026, triggered by a rapid slope failure from a glacier collapse on Langtang Lirung in Langtang National Park. The impact of the collapsing glacier hitting the valley bottom generated energy equivalent to a 5.2 magnitude earthquake, producing a torrent of water, ice, and debris that gushed nearly 100 km downstream, overwhelming the Gyirong Port border crossing and devastating infrastructure along the Lende Kholā and Trishuli River valleys.

Satellite imagery from the Copernicus Sentinel-2 and US Landsat-9 missions revealed the scale of the disaster. A natural-color Sentinel-2 pair compared the day after the event (27 August) with a pre-event view (12 August), clearly showing a dramatic increase in river water. Additional shortwave-infrared processed images compared Landsat-9 data acquired approximately two hours after the collapse (26 August) with a pre-event Sentinel-2 image (24 August), helping distinguish water and ice from clouds in this frequently cloud-covered mountainous region.

The flood left hundreds dead and thousands missing, with rescue operations complicated by difficult mountainous terrain, cut-off areas, damaged infrastructure, weather, and the continuing risk of further flooding and landslides. The International Charter Space and Major Disasters and the Copernicus Emergency Mapping Service were activated to provide satellite imagery to aid emergency response. ESA, a co-founder of the Charter, supports the service by providing Sentinel satellite data and managing access to complementary Copernicus data.