Kathmandu, The devastating floods in Nepal that swept through the Bhotekoshi–Trishuli corridor were triggered by a massive ice-rock avalanche in the high Himalayas, not by conventional rainfall, according to a preliminary report by Nepalese scientists.
The surge then travelled downstream through the Bhotekoshi and into the Trishuli, generating a powerful debris-laden flood, My Republica reported. The study concluded that the disaster was not caused by a glacial lake outburst flood . The researchers analysed satellite imagery, hydrological and meteorological data, terrain characteristics and changes in elevation and slope along the river system. No evidence of a GLOF, the report added. The study also found no evidence of exceptionally heavy rainfall in the upper watershed that day, weakening the assumption that the disaster was caused solely by extreme rainfall or a cloudburst. The disaster also caused extensive damage to hydropower infrastructure.
The study found that a huge mass of ice, rock and debris fell from around 5,200 metres in the Langtang–Lirung area of Rasuwa and entered the Lhende River. The study found that the ice-rock mass travelled about 22 kilometres to Rasuwagadhi in just over seven minutes, reaching an estimated average speed of 46.3 metres per second, or 167 kilometres per hour, it said. Citing preliminary Nepal Electricity Authority data, the study said 13 hydropower projects and one solar project were affected, taking around 431 MW of generation capacity out of the system.
The ice-rock mass began falling from the northern part of Langtang–Lirung at around 8:37 am Wednesday, according to the study. It descended steep terrain from about 5,200 metres before reaching the Lhende River at around 2,930 metres.
