Glacial lake outburst floods are sudden and terrifying, as anyone who has seen one can tell you. Heading down valley, Tenzing and I stop in the hamlet of Ghat, along a river named the Dudh Kosi, about five days' walk below the Everest base camp. We park our rucksacks at the lodge of an old friend, Lama Dorje, whom I came to know while working as a UNESCO consultant, nearly 20 years ago. Sweeping a length of robe over his shoulder, Lama Dorje, now 78, emerges from the Buddhist chapel attached to his lodge and summons us into his kitchen. He sets a teakettle over the open hearth and blows on the fire, then recounts the 1985 flood that washed away half of his village.
During the monsoon season, a gargantuan chunk of the Langmoche Glacier, perched above the southwestern end of a lake called Dig Tsho, a day's walk upriver from Ghat, detached and crashed into the lake. The resulting wave hurdled the lake's natural moraine, displacing enough rubble and ice to cause an outburst.
"My wife and I were drinking tea at the hearth of our old house, below here," Lama Dorje says, running his fingers across his head. "We heard a low, whirring rumble that gradually grew in volume, like an approaching helicopter. I scrambled down the stairs, stepped outside, and looked upriver. It was right there, coming toward us -- a wall of gray and brown water with what looked like steam or dust swirling crazily around it and above it. The wave itself was filled with boulders, dirt, firewood, and whole trees. The trees would run into an obstacle, be forcefully upended, and be tossed downriver, over and over again, like a kid kicking a stick down a trail.
"When the wall of water reached the bridge just downstream from here, it simply picked up the bridge and took it away. Then it car-ried away four of our livestock, then our neighbors' livestock. When it reached the houses located below ours, it swept those away too. We could only stand there helplessly."
Over the next six hours, the entire volume of the mile-long lake careered furiously down the narrow valley, destroying a nearly completed 500-kilowatt hydropower station, sweeping away 14 bridges, and erasing stretches of the Everest trek route. By the time it surged across the Indian border, 100 miles downstream, four people had drowned. The flood occurred during daytime, fortunately, when valley residents could escape to higher ground; otherwise there would almost certainly have been more casualties.
