Key Mountain Development Institute Warns Of Second Flood In Nepal

A powerful flash flood that tore through Nepal's Rasuwa district on Wednesday has triggered fresh fears of another disaster, with scientists warning that a blockage remains lodged upstream near the Nepal-China border and could unleash a second surge of floodwaters.

The warning comes from the International Centre for Integrated Mountain Development (ICIMOD), the Kathmandu-based intergovernmental organization that serves the eight countries of the Hindu Kush Himalayan region -- India, Nepal, Bhutan, China, Pakistan, Bangladesh, Myanmar and Afghanistan.

Founded in 1983, ICIMOD is one of the leading scientific institutions studying mountain environments, glaciers, climate change and disaster risks across the Himalayas.

According to ICIMOD, which released a detailed statement, a flood struck suddenly on August 26, sending a massive torrent of water, sediment and boulders down the Bhote Koshi and Trishuli river systems. Water levels rose dramatically within minutes, leaving officials and scientists racing to understand what caused the catastrophe and whether more danger lies ahead.

Areas further downstream in Nuwakot and Dhading districts are also being monitored.

ICIMOD's strongest warning came from Qianggong Zhang, Head of Climate and Environmental Risks at the organisation. "The same site devastated by last year's Rasuwa flood is once again under threat. An ice avalanche in the Lhende Khola is the suspected trigger, but the cause remains unconfirmed. With a blockage still lodged upstream on the Nepal-China border, authorities warn a second flood is imminent and evacuation orders are now in place for Jilong port," Zhang said.

The warning is particularly alarming because the affected region suffered a similar disaster last year.

ICIMOD scientists note that the same section of the basin which experienced severe flooding in 2024 has once again become the focus of concern.

Areas further downstream in Nuwakot and Dhading districts are also being monitored because of the potential for continued impacts.

According to preliminary assessments, the latest event has once again damaged infrastructure and hydrological monitoring systems while threatening communities and river valley settlements downstream.

The flood reportedly began around 9 a.m. local time, when water levels in the Bhote Koshi basin rose rapidly. The floodwaters swept downstream through the Bhote Koshi River into the Trishuli River system.

A key hypothesis is that a large ice-rock avalanche occurred high in the mountains.

Hydrological measurements reveal the extraordinary power of the event. Water levels in the Trishuli River at Galchchi reportedly surged by as much as nine metres within just 30 minutes. At Malekhu, river levels climbed by seven metres over a similar period. Such rapid rises are indicative of a sudden release of enormous volumes of water and debris from upstream.

Scientists are now investigating multiple possible explanations for the disaster.

One leading hypothesis is that a large ice-rock avalanche occurred high in the mountains.