A catastrophic landslide in the high Himalayas of Nepal's Gorkha district on 11 October 2026 triggered devastating floods along the Budhi Gandaki River, releasing energy equivalent to a 3.5-magnitude earthquake, according to a preliminary technical assessment by Nepal's Department of Mines and Geology. The disaster left at least five people missing and caused widespread destruction to hydropower infrastructure, roads, and bridges.

How the Disaster Unfolded

The incident began at approximately 4:20 am in the upper reaches of the Ungdilung Khola, a tributary of the Budhi Gandaki River, in Chumnubri Rural Municipality — an area bordering China, situated between Chamar Himal and Syerangi Himal. According to the department's report, an avalanche originated at roughly 6,000 metres altitude in the Tibetan Tethys Himalaya, a zone characterised by relatively weak rock formations, with a landslide occurring at around 5,500 metres.

The massive slide — comprising a mixture of snow, water, and glacial debris — swept southward along the Ungdilung Khola, depositing a large volume of debris at the narrow confluence of the Ungdilung Khola and Syar Khola, another Budhi Gandaki tributary, at an altitude of approximately 2,000 metres. The debris repeatedly blocked and released river flows, potentially generating successive flood surges downstream.

Scale of the Flood Surges

The National Disaster Risk Reduction and Management Authority (NDRRMA), citing the department's findings in a social media post, said the Budhi Gandaki experienced repeated flood surges in a single day. The largest surge reached an estimated height of 20 to 25 metres. The first mud-laden flood reached the Salleri area — where a construction camp for the 341-MW Budhi Gandaki Hydroelectric Project was located — at around 4:30 am. The largest surge arrived at the hydropower camp at approximately 6:30 am, sweeping the camp away entirely.

The report notes that the enormous volume of debris carried by the Ungdilung Khola played a more significant role in generating the largest flood surge than the water that had accumulated behind the blockage of the Syar Khola. Field observations further indicated that the Syar Khola's flow had stopped roughly one hour before the largest surge arrived, with water accumulated over a stretch of around 1.5 kilometres in its upper reaches. Smaller surges reportedly continued even after the peak event had passed.

Infrastructure and Community Damage

The powerful surge caused major damage downstream, particularly in the Jagat area along the Budhi Gandaki River, where several buildings were affected. Permanent bridges over the Soti Khola and the Budhi Gandaki River were among the damaged structures, the report said. Several hydropower projects, roads, and bridges were destroyed, according to the NDRRMA.

Context: Second Major Disaster in Six Weeks

This comes amid a broader pattern of escalating flood disasters in Nepal's river systems. The 11 October flooding was the second major riverine disaster in roughly six weeks, following catastrophic floods that struck the Bhote Koshi and Trishuli rivers on 26 August. That earlier disaster killed nearly 1,500 people and left more than 5,000 missing, while devastating communities, hydropower plants, roads, and bridges along both rivers. The recurrence underscores the acute vulnerability of Nepal's high-altitude river corridors — and the infrastructure built within them — to glacial and snow-related mass movements, particularly as climate pressures on Himalayan glaciers intensify.

What Comes Next

The department's report is described as a preliminary assessment; a fuller technical investigation is expected. The fate of the 341-MW Budhi Gandaki Hydroelectric Project — a long-planned, high-stakes energy project — will be closely watched, as will any government response regarding early-warning systems for high-altitude glacial and debris-flow events in Nepal's northern river catchments.