KATHMANDU, Oct. 12: A temporary blockage formed by a landslide near Chumchet in Gorkha district may have burst, triggering flooding in the Budhi Gandaki River on Sunday morning, according to a preliminary assessment by the International Centre for Integrated Mountain Development (ICIMOD).
Reviewing initial reports from Nepal’s government agencies, ICIMOD said the landslide had blocked the river, creating a temporary barrier that may have subsequently collapsed and unleashed the flood.
The flood is estimated to have begun at around 4 am Nepal Standard Time on Sunday, October 11, carrying mud, sediment and debris downstream. Fluctuations in water levels prompted authorities to alert communities along the Budhi Gandaki, Trishuli and Narayani river systems.
Preliminary reports indicate that several people are missing, houses have been swept away, bridges damaged and riverside infrastructure affected. The site of the 341-megawatt Budhi Gandaki Hydropower Project at Salleri, Gorkha, has also sustained damage.
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Authorities are assessing the extent of the destruction, while search and rescue operations, evacuations and relief efforts are underway.
ICIMOD Director General Pema Gyamtsho said the incident, following the recent Rasuwagadhi–Kerung disaster, underscored the vulnerability of mountain communities and settlements along river corridors to natural hazards.
“Response must be the immediate priority. However, understanding the causes of such floods will be crucial to reducing similar risks in the future,” he said.
Qianggang Zhang, ICIMOD’s strategic lead for climate and environmental risks, said the initial analysis pointed to a debris-laden flood triggered by the collapse of a landslide-dammed river.
He stressed the need for integrated monitoring of landslides and river systems in steep mountain catchments, where hazards can develop rapidly and affect downstream communities.
Similarities with 2024 flood
The latest incident follows a major flood-related event in the Budhi Gandaki region in April 2024, when a large avalanche from the terminus of the Manaslu Glacier displaced water from Birendra Lake, causing a sudden rise in the river’s flow.
A detailed ICIMOD-led study concluded that the event was not a glacial lake outburst flood (GLOF), but resulted from water displacement caused by the avalanche.
ICIMOD said the two incidents highlight how different natural processes can trigger destructive floods in Himalayan river systems. The incidents also underscore the need to account for landslides, river dynamics, vulnerable settlements, infrastructure and cascading hazards in future risk-reduction and reconstruction planning.
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