Nepal, Sept. 7 -- On the morning of August 26, Prime Minister Balendra (Balen) Shah was preparing to answer lawmakers' questions in the House of Representatives when news of a devastating flood in Rasuwa's Bhotekoshi River reached him.

Shah immediately sought details and instructed the concerned agencies to alert people living along the riverbanks. Local administrations and police began using loudspeakers to warn residents to move to safer areas.

But the first sign that something far more serious was unfolding had already appeared in the sky.

At 8:55 am, an Altitude Air helicopter had taken off from Kathmandu for Timure in Rasuwa to pick up Indian tourists. As the pilot approached Dhunche, however, he saw what appeared to be a huge cl...