Glacial Lake outburst

The Uttarakhand government has decided to evaluate the risk posed by five potentially hazardous glacial lakes in the region. These lakes are prone to Glacial Lake Outburst Floods (GLOFs), the kind of events that have resulted in several disasters in the Himalayan states in recent years.

What is Glacial Lake outburst?

• When the boundary around unstable glacial lake breaks, and huge amounts of water rush down the side of the mountains, which could cause flooding in the downstream areas.
• This is called glacial lake outburst floods or GLOF.
• Factors causing GLOF:
• GLOF can be triggered by several reasons, including earthquakes, extremely heavy rains and ice avalanches.
• These lakes are also often found in steep, mountainous regions, which means landslides or ice avalanches can sometimes fall directly into the lakes and displace the water, causing it to over-top the natural dam and flood downstream.
• Features of GLOF:
  • They involve sudden (and sometimes cyclic) releases of water.
  • They tend to be rapid events, lasting hours to days.
  • They result in large downstream river discharges (which often increase by an order of magnitude).