Worst-case glacial lake flood scenarios in a transboundary Himalayan basin

Assessing Glacial Lake Outburst Flood Risks

A study investigated the potential for glacial lake outburst floods (GLOFs) in a transboundary Himalayan basin, considering both existing dangerous lakes and the formation of new ones. The research focused on the Galongco and Jialongco lakes, as well as a hypothetical future lake upstream of Nyalam, to simulate worst-case outburst events.

Simulated Worst-Case Scenarios

The simulations revealed that large rock or ice avalanches could trigger GLOFs, producing discharges at the Nepal border more than 15 times greater than previously observed or anticipated from gradual breach simulations. These catastrophic events would result in extremely short warning times: 5-11 minutes for the Tibetan town of Nyalam and 30 minutes for the border with Nepal.

Limitations of Current Mitigation Efforts

Recent efforts to lower water levels at Jialongco would have minimal effect on downstream impacts from a very large-magnitude GLOF. This is particularly concerning for Nyalam, where significant infrastructure development has occurred directly within the high-intensity flood zone, increasing vulnerability.

Recommendations for Disaster Risk Management

The findings emphasize the need for a comprehensive disaster risk management approach. This includes implementing robust early warning systems, establishing effective land use zoning regulations, and developing programs to build local response capacities. Such measures are crucial for addressing current GLOF risks and preparing for more frequent catastrophic events under a warming climate.