It was an uncharacteristically sunny day for the monsoon, with blindingly clear skies. Namgye Chumbi was weeding his potato garden in Phakding by the Dudh Kosi on the morning of 4 August 1985.
There weren't too many trekkers on the trail. The Dudh Kosi was tumbling noisily over boulders nearby. Around two in the afternoon, the river went quiet. Namgye sensed danger.
"I noticed that the white water had turned muddy brown, and in the distance I heard a thundering sound like an approaching helicopter," recalls the 50-year-old farmer. "I looked upstream and saw this huge wall of dark brown water approaching very fast."
Namgye indicates the level of the river with his left hand and raises his right hand over his head like a cobra to illustrate what he saw.
He dropped everything and began to run up the mountain. His wife, Sherkima, had more presence of mind, and picked up their two young children Hira and Tsering and followed her husband. They reached a ledge as the thunderous flood raced by beneath their heels. The ground was shaking, and the sound was deafening.
The family lost everything. If they had been just a few seconds slower, they would have lost their lives as well. Their millet farm upstream was cut in half, as the river changed its course and started flowing through its terraces.
Nearly 25 years later, Namgye has built a new house higher up the mountain, where his married children and four grandchildren live together today. Namgye points out one boulder the size of his house in the middle of the Dudh Kosi that was brought down by that terrible flash flood.
The Dudh Kosi deposited debris up to 15 metres high downstream. The water stayed muddy and high for two weeks until it finally started to recede. Villagers in Jorsale and Phakding were puzzled that there was a flood when there had been no rain; they only found out later that a glacial lake called Dig Tso had burst upstream in the Bhote Kosi Valley.
Namgye Chumbi still doesn't know the reason for the flood. He does know there is another large lake called Imja Tso that may burst at any time.
This was what scientists call a Glacial Lake Outburst Flood (GLOF). There is a major GLOF on a Himalayan river every ten years or so. A major flood in 1983 caused by a glacial lake burst in Tibet washed away 25 km of the Kodari Highway and put the Sun Kosi hydropower plant out of action. The frequency of these floods is increasing because of climate change.
Kunda Dixit in Khumbu