By Ratan Bhandari
Last month, the residents of Basari village in Nepal informed officials about a nearby landslide that damaged five houses. Rising to the call of duty, at half past seven in the morning the District Administration and Police Officers arrived and took stock of the situation. The nearby cracked surfaces served a reminder of the devastating Gorkha earthquake the previous month. More than 250 villagers were relocated to a safe spot.
More landslides ensued the following day as tents were provided for affected residents. Whilst sleeping in the temporary camp, the residents of Basari village got another rude shock at half past two in the morning. This time an even more colossal landslide formed a wall of mud and rock that blocked the Kali Gandaki River. There was pandemonium as people panicked fearing for their lives. Local police made announcements on loudspeakers asking people in Mustang, Myagdi, Baglung, Parbat, Gulmi, Syangja, Tanahun and Nawalparasi districts downstream to remain on high alert. The landslide dammed the river and blocked almost the entire flow, which resulted in a 2-km long artificial backwater lake. The landslide occurred as a nearby ridge had developed cracks after the earthquake.
The landslip buried 27 houses; thankfully there were no casualties as people had already been evacuated. People living in the downstream were moved to higher ground as road transportation was halted in the area. According to an Engineer at the Road Division Office in Baglung, the artificial dam at the landslide site was about 35 meter high.
The Kali Gandaki River is the main source of the Narayani River, known as the Gandak in India, and flows through one of the world’s deepest gorge between the Annapurna and Dhaulagiri ranges in Nepal. The steep gradients are favorable for ‘run-of-river’ hydropower, which divert water in to tunnels unlike ‘dam-toe’ storage projects.
Nepal’s largest hydro project happened to be located downstream of the dam caused by the landslide. Power generation of the 144 MW Kali Gandaki ‘A’ hydropower project was halted for several hours, fearing possible outburst upstream. All the gates at the Gandak barrage were opened amid flood fears. According to the Chief District Officer of Nawalparasi of Nepal, the authorities in India too were informed given the potential downstream impact.
This is not the first time the Gandaki has been impeded by a landslide. There are records that the river was blocked several times in the past, last recorded in September 1997. Authorities have maintained that the vulnerable cliffs at Bandarjung, Guithe, Bhurung, Gharkhola, Ghar and Ramche could pose great threat in the rainy season, more so in the aftermath of quakes. According to Deputy Superintendent of Police, Hira Gire, other massive landslides could occur in the area during the upcoming monsoon. The landslide prone zones coupled with the seismic activity can have a calamitous impact on downstream hydropower dam or barrage sites, and communities dependent on and living near the river.
In this case a disaster was averted after 15 hours as the impeded water in the dam started overflowing as the landslide induced reservoir slowly released water. The water level was two meters above the usual monsoon flow. Though floodwaters from the artificial dam entered houses near the banks at Beni, the district headquarter, there was no notable damage. Soon after, downstream settlers returned to their homes.
Ratan Bhandari is a Kathmandu based water resource activist, and can be reached at firstname.lastname@example.org
Source : International Rivers