Kathmandu, October 12
The International Centre for Integrated Mountain Development (ICIMOD) has made a preliminary assessment that a landslide near Chumchet in Gorkha temporarily blocked the flow of the Budhigandaki River, and that the breach of this blockage caused the destructive flood.
Analysing preliminary details of the flood, which began around 4 am on Sunday, ICIMOD said the temporary dam formed when the landslide blocked the river may have burst.
The National Disaster Risk Reduction and Management Authority (NDRRMA) had earlier made a similar estimate based on reporting by the Nepali Army.
Qianggong Zhang, ICIMOD’s Strategic Lead for Climate and Environmental Risks, also said that the preliminary analysis of Sunday’s Budhigandaki flood suggests a debris-laden flood caused by the breach of a temporary landslide blockage.
According to him, ICIMOD’s analysis is based on publicly available information up to 11:30 am Nepal time on Sunday. He said details of the incident and the damage may change as rescue and investigation work continues.
Reports say the destructive flood left some people missing, swept away houses, and damaged hydropower projects and bridges. Initial reports also indicate serious damage at the site of the 341-megawatt Budhigandaki hydropower project at Sellari in Gorkha.
The NDRRMA has said that although physical damage was extensive, human casualties have not been confirmed. However, precise details of the damage are yet to emerge.
The flood carried debris, including black soil and various kinds of wreckage, along the banks of the Budhigandaki and deposited it downstream. Communities along the Budhigandaki, Trishuli and Narayani river systems were put on alert as water levels fluctuated and risks increased.
Security agencies are active in the affected areas, carrying out search and rescue, relocating displaced people and arranging shelter.
A chain of risks, from landslide to flood
The Budhigandaki flood came shortly after the flood in the Rasuwa–Bhotekoshi area. According to ICIMOD, the Budhigandaki flood highlights the risk that one natural process in the mountains can trigger another disaster, compounding the loss of lives, property and infrastructure.
ICIMOD Director General Pema Gyamtsho said these events show that mountain communities and river corridors are highly exposed to sudden-onset, cascading natural hazards.
He said that while immediate rescue and relief must be the priority, identifying the cause of the flood will be important for reducing such risks in future and strengthening community resilience.
Budhigandaki also hit by a destructive flood in 2024
According to ICIMOD, a major flood event also occurred on the Budhigandaki in April 2024. At that time, a massive avalanche fell from the front of the Manaslu glacier into Birendra Lake, causing the lake’s water to surge out suddenly. This triggered a flash flood in the Budhigandaki River.
A detailed ICIMOD-led study concluded that the event was not a glacial lake outburst flood (GLOF) but was caused by the avalanche displacing the lake’s water.
According to Zhang, integrated monitoring and assessment of landslide-prone areas and river systems is needed in steep mountain regions, because natural processes there can develop rapidly and their effects can reach far beyond the site of the event.
ICIMOD stressed that future risk assessment, infrastructure planning and rehabilitation work should consider the various natural hazards, their triggers and their downstream impacts together.
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