Nepal Glacier Lake Flood Risk Map
29 April 2015
At least 10,000 people live directly in the path of the three very unstable glacial lakes, Imja Tsho, Thulagi and Tsho Rolpa. These areas include the dozens of towns on the main trekking route to Mt Everest Base Camp. These lakes are extremely vulnerable to Glacial Lake Outburst Floods (GLOF) from aftershocks following the 7.8 Ricther earthquake on Saturday, 25 April 2015.
GLOFs occur when earth structures damming large glacial lakes collapse. Formed out of deposited rocks and mud these dams are inherently unstable and can be ruptured by a single landslide or avalanche into the lake. Past floods have obliterated small hydro electric plants in their path. In 1980 a GLOF in north eastern Nepal devastated villages over 70km downstream.
The UN and World Bank have a number of development projects in place to improve warning systems about GLOFs, but they have not been adequately successful. Most towns have limited awareness of these risks and few (if any) have evacuation plans. Due to lack of resources many of the monitoring systems that did exist have degraded. The glacier lakes themselves serve as major tourist attractions, so locals’ incomes rely on remaining in endangered areas. In fact, as visitor numbers to Mt Everest have increased significantly over the past ten years, the local population living the the path of the Imja glacier lake has swelled.
Local District Disaster Relief Committees generally have very little knowledge about climate change or GLOF risk management. There is also insufficient coordination between different agencies for systematic information sharing on GLOF risk management and no efficient mechanism for communicating GLOF warnings effectively. UNDP Report September 2012
The natural moraine banks that form the dam for these lakes are unstable and are vulnerable to earthquakes. This instability is exacerbated by the fact that the volume of the glacial lakes has been increasing due to climate change.
Government and disaster management authorities have limited understanding and experience of managing growing climate risks, including current variability and the projected impacts of climate change, that are increasing the range and magnitude of disasters that Nepal is having to cope with UNDP Report September 2012
As these lakes only began forming in the late 1950s, they were not a threat when Nepal last experienced major earthquakes in the 1930s. Given the volume of water and steep terrain, World Bank flood models predict walls of water and debris up to 10 metres high, even 100km from the source. There is also a chain reaction risk where a comparably small lake, situated above larger lake, causes a sudden surge of water that then bursts the larger lake’s moraine dam.
Nouveau Eco created this risk map because we want people in this zone, both local and international first responders, to be made aware of the risks facing them so that they can take steps to prevent further disaster in this already devastated region.