Glacial Lake Outburst Floods in the Sagarmatha Region

Glacial lake outburst floods (GLOFs) are common natural hazards in the Himalaya. These floods, usually of large magnitude, can severely affect fragile mountain ecosystems and their limited economic activities. In this study, GLOF hazard in the Sagarmatha region (national park and buffer zone) was assessed using dam break and hydrodynamic modeling. The available data from the Dig Tsho GLOF of 1985 were used to validate many of the model outputs. The technique was further applied to GLOF hazard assessment of Imja Lake, the largest and potentially most dangerous glacial lake in the region. The peak outflow discharge of an Imja GLOF is estimated at 5463 m3/s. The peak discharge attenuates to about 2000 m3/s at the boundary of the buffer zone at about 45 km from the outburst site. Finally, a GLOF vulnerability rating map was prepared and an assessment of vulnerable settlements was carried out. The study was found to be a cost-effective means of obtaining preliminary information on the extent and impact of possible GLOF events—information that is useful for developing plans for early warning systems and implementing management plans.