It was a wall of water and mud traveling at such speed that it engulfed buildings in seconds. In the wake of the Nepal flood disaster, questions were being asked about whether the deadly torrent could have been predicted or detected quicker to give communities downstream more time to evacuate.
Geologists say they believe the flash floods in Nepal and Tibet were set off by a dual high-altitude landslide and glacial avalanche that unleashed huge volumes of water. Disaster experts say such events are difficult to forecast.
Most monitoring and early-warning systems for glacial hazards focus on a specific area of risk. For example, water levels in flood-prone glacial lakes — which form when a glacier retreats and meltwater fills the hole left behind — can be monitored for unexpected rises.
Eran Hood, professor of environmental science at the University of Alaska, has spent years studying glacial lake outburst floods from the Mendenhall Glacier and their impact on the city of Juneau, where flooding occurs annually.
He said that scientists relied on real-time video monitoring, laser measurements of water levels and frequent field observations to try to predict when the area might flood and what the risks might be to communities downstream.
But experts in disaster response said the Nepal flooding would have been harder to predict because the collapse was sudden. Forecasting such an event would have required intensive and resource-heavy monitoring across vast areas, they say.
