Kathmandu, Oct. 18 -- On the morning of August 26, Bal Bahadur Majhi, 50, was clearing firewood, rocks, and sand from the tunnel at the Rasuwagadhi Hydropower Project in Timure. The plant diverts part of the river into the tunnel and uses its steep drop to generate electricity.

Then he heard what he described as explosions in the distance. Before he could make sense of them, a landslide barrelled into the tunnel, and a slurry of mud, rocks, and water tossed him and pulled him under. When the water finally dropped to his neck, the tunnel was pitch dark and blocked.

"We never realised how dangerous it was," he said. "They had told us to go in a particular direction if there was a flood; there had been a small one last year, but we never i...