By Arun B Shrestha, Narendra R Khanal, Mandira Shrestha, Hari Krishna Nibanupudi, and David Molden on 04 Aug 2014
In the early hours of 2 August 2014, a landslide occurred above Jure village, about 1.4 km upstream from the Sun Koshi Hydropower project’s intake site. In an instant, a 1.9 km long slope of land perched 1,350 m above the river bed collapsed, burying two dozen houses, taking the lives of at least thirty-three people, and injuring many more. Over 150 people are still missing.
The massive landslide created a high dam across the Sun Koshi River. A river gauging station of the Department of Hydrology and Meteorology (DHM) at Pachuwarghat downstream of the landslide dam showed a rapid decline in water flow three hours after the landslide, after which the flow of water completely stopped for approximately 12 hours (Figure 1). An inflow of about 160 m3/sec of water quickly created a large lake behind the dam. Within 13 hours the newly formed lake – which rapidly grew to a volume of an estimated 7 million cubic metres – extended about 3 km upstream, completely submerging the 2.6 MW Sanima Hydropower station. Had Nepal’s security forces not taken timely action to release some of the stored water through controlled explosions, the backwater would have extended further upstream and caused great damage in Barabise, the nearest upstream town. However, the risk that the dam will breach still remains, bringing with it the threat of a catastrophic flood. The Home Ministry has declared the area a ‘flood crisis zone’, and has issued a warning to communities downstream, with many vulnerable villages being evacuated.