GLOF are instances of large lakes formed from melting of glaciers, suddenly breaking free of their moraine natural dams that are formed from rock sediments and other debris.
The South Lhonak glacier located in north Sikkim is reportedly one of the fastest retreating glacier. The glacier receded nearly two kilometres in 46 years fro 1962 to 2008. There are an estimated 7500 glaciers in the Himalayas and GLOF has been associated with major disasters through the years. 2013 Kedarnath district outburst in Uttarakhand as a example of GLOF related disaster.
What triggered the Sikkim GLOF event:
The national disaster management agency reports that the primary reason for sudden surge appears to the likely combination of excess rainfall and a GOLF event. There is speculation that heavy rainfall might have tipped the moraine to collapse and triggering the floods,
What was the resulting damage:
The most visible consequence of the flooding was the destruction of the Chungthang dam.
All bridges of the downstream to the Testa v hydropower station were submerged or washed-out disrupting communication.
The floods destroyed 11 bridges in the state.
Are such events likely in the future?
Several studies have over the years warned of the risk from the GLOF events from the Himalayas. Both the frequency and severity of such events are going to increase in the future.
The Himalayan ecosystem is the most fragile in the world. Rising temperature is leading to wetter future.
GLOF is outcome of the warming of the region.
Way forward:
Testa River is source of hydropower generation for several power projects. The risk of GLOF like event require greater care in planning and executing dams and other infrastructure projects.
Also require early warning system, coordinated approach such as multiple agencies promptly sharing satellite images and network of sensors to provide adequate warning.