Nepal Floods Triggered By Massive Ice-Rock Avalanche, Not Heavy Rainfall: Scientists

A preliminary report by Nepalese scientists suggests that the devastating floods in Nepal's Bhotekoshi-Trishuli corridor were triggered by a massive ice-rock avalanche rather than heavy rainfall, according to a report released on Sunday by the Nepal Environment Society. The death toll from the flash floods has risen to 903 as bodies continue to be recovered.

The avalanche originated in the Langtang-Lirung area at an elevation of about 5,200 meters, falling onto the Lhende River and traveling downstream through the Bhotekoshi and Trishuli, generating a powerful debris-laden flood. The study found no evidence of a glacial lake outburst flood (GLOF), despite initial thoughts. Satellite imagery, hydrological and meteorological data, terrain characteristics, and elevation and slope changes along the river system were analyzed to reach this conclusion.

The ice-rock mass traveled at an estimated average speed of 167 kmph, reaching the town of Rasuwagadhi in just over seven minutes. Despite slowing down, the flood still carried a huge quantity of rock, sediment, and soil. The disaster caused extensive damage to hydropower infrastructure, with 13 hydropower projects and one solar project affected, taking around 431 MW of generation capacity out of the system.

Preliminary government assessments estimate economic losses at around Rs 3 trillion, although detailed sector-wise assessments are still underway.