Flash Floods in Nepal’s Trishuli Valley Expose Risks of Rapid Hydropower Expansion

In late August, a glacier collapse over 3,800 ft wide fell into the Trishuli River valley, about 4,000 ft below its former position. The surge swept away a multistory border building, roughly 70 bridges and miles of highway, and buried 12 hydropower plants. Rescue teams have recovered about 1,400 bodies; more than 5,000 people remain missing. Among the buried facilities, 121 individuals were reported trapped, with only three survivors found.

NPR

The Trishuli basin, a key watercourse in the central Himalayas, hosts 36 hydro projects, including a dozen submerged by the flood. The region experiences frequent earthquakes and landslides, and accelerating glacier melt has increased slope instability. Prior to the disaster, the area endured deadly flooding for three consecutive years: extreme rainfall in 2024, a glacial-lake burst in 2025, and the 2026 glacier snap.

NPR

• Glacier width: > 3,800 ft; drop: ~4,000 ft.

NPR

• Infrastructure loss: 1 border building, ~70 bridges, miles of highway.

NPR

• Hydropower impact: 12 plants buried; 36 projects in the basin.

NPR

• Human toll: ~1,400 bodies recovered; > 5,000 missing; 121 trapped (Brig. Gen. Subas Jung Thapa).

NPR

• Upper Trishuli-1 project: cost > $0.5 billion; financed by ~$300 million from two World Bank arms and $60 million from the Asian Development Bank; estimated 50 people trapped, five bodies recovered.

NPR

• Brig. Gen. Subas Jung Thapa, Nepali army, said the army is leading rescue operations and estimated 121 people were trapped inside the plants.

NPR

• The World Bank said the Upper Trishuli-1 design reflected risk assessments available in 2018 and will review the flood’s implications for future risk assessment, monitoring, early-warning and emergency-response measures.

NPR

• The Asian Development Bank did not immediately respond to inquiries about a climate-resilience assessment.

NPR

• Arnold Dix, tunneling expert assisting rescue teams, argued that the underground infrastructure remained intact and that the glacier collapse was an unforeseen threat that will reshape design standards.

NPR

• Parineeta Dandekar, river expert with the South Asia Network on Dams, Rivers and People, accused the World Bank of a flawed risk-assessment report that omitted cumulative disaster risk.

NPR

• Dipak Gyawali, hydropower engineer at the Nepal Academy of Science and Technology, warned that “These risks have to be properly studied and assessed. Unfortunately, they have not been.”

NPR

• C.P. Rajendran, Indian geoscientist, emphasized that the disaster could recur elsewhere in the Himalayas, urging broader scrutiny of hydropower siting.

NPR

• Shyam Saran, retired Indian ambassador, argued that cumulative environmental impact assessments of entire river systems would reveal a markedly different risk picture.

NPR

• Austin Lord, disaster-risk specialist at the Stimson Center, highlighted the basin’s repeated flooding and cited a pre-flood warning paper that flagged the area’s vulnerability.

NPR

• “We need to understand what is happening now in Nepal can happen in other parts of the Himalayas,” — C.P. Rajendran

NPR

• “Why did it have to happen in the first place?” — Parineeta Dandekar

NPR

• “These risks have to be properly studied and assessed. Unfortunately, they have not been,” — Dipak Gyawali

NPR

The World Bank indicated it will consider the flood’s lessons when updating risk-assessment protocols for hydropower projects. No specific timelines for revised assessments or additional funding decisions have been announced.

NPR