Kathmandu, October 11: A temporary river blockage caused by a landslide near Chumchet in Gorkha district may have collapsed, triggering the flash flood in the Budhi Gandaki River on Sunday morning, according to a preliminary assessment by the International Centre for Integrated Mountain Development (ICIMOD).

Based on initial reports from Nepal’s government agencies, ICIMOD said the landslide may have blocked the river, forming a temporary barrier that later burst and released a large volume of water, mud, sediment and debris downstream.

The flood is estimated to have started at around 4 am on Sunday, October 11. Fluctuations in river levels prompted authorities to issue alerts to communities along the Budhi Gandaki, Trishuli and Narayani river systems.

Preliminary reports indicate that several people are missing, while houses, bridges and riverside infrastructure have been damaged. The 341-megawatt Budhi Gandaki Hydropower Project site in Salleri, Gorkha, has also suffered damage.

Authorities are assessing the extent of the destruction as search and rescue operations, evacuations and relief efforts continue.

ICIMOD Director General Pema Gyamtsho said the incident, following the recent Rasuwagadhi–Kerung disaster, highlighted the vulnerability of mountain communities and settlements along river corridors to natural hazards.

He stressed that immediate response efforts should remain the priority, while understanding the causes of such floods would be essential to preventing similar disasters in the future.

Similarly, Qianggang Zhang, ICIMOD’s strategic lead for climate and environmental risks, said the preliminary findings pointed to a debris-laden flood caused by the collapse of a landslide-dammed river.

He emphasized the importance of integrated monitoring of landslides and river systems in steep mountain catchments, where hazards can develop rapidly and threaten downstream communities.

Similarities With the 2024 Flood Event

The latest incident has drawn comparisons with a flood-related event in the Budhi Gandaki region in April 2024, when a large avalanche near the terminus of the Manaslu Glacier displaced water from Birendra Lake, causing a sudden rise in river flow.

A detailed study led by ICIMOD concluded that the 2024 event was not a glacial lake outburst flood (GLOF). Instead, it resulted from water displacement caused by the avalanche.

ICIMOD said the two incidents demonstrate how different natural processes can trigger destructive floods in Himalayan river systems.

The centre has stressed the need to consider landslides, river dynamics, vulnerable settlements, infrastructure and cascading hazards in future disaster-risk reduction and reconstruction planning.