GLOF (Glacial lake Outburst Flood) has recently been in the news after a major disaster in Nepal, with a lot of discussion happening around the same. A Glacial Lake is a huge water body with millions of litres of water and molten ice. It is a result of glacial melting which can be attributed primarily to global warming, leading to an increase in the number and size of glacial lakes across the globe. This is further aggravated by human intervention and development around glacial catchment areas. Many of these glacial lakes are susceptible to outburst floods, which has far-reaching consequences on downstream infrastructure and livelihoods.

Glacial lakes are formed through two different methods. Melting and retreat of glacier margin causes water to be collected between the glacier and the abandoned frontal rock debris, resulting in what is known as Moraine-dammed lake. The frontal rocky ridge or moraine acts as a dam for such a lake. The other scenario is that of Ice-dammed lakes where the movement of the glacier blocks the drainage and causes the resultant water to accumulate into a lake. As glacial lakes increase in size, they become hazardous since their support in the form of ice and sediment (moraine ridge) is quite unstable. The volatility of slopes and glacial lakes is further aggravated in young and seismically active mountains like Himalayas, where hazard chains and avalanches are a common occurrence.

Global Lake Outburst Flood is caused by the rupture of the dam holding back the glacial lake. The dam is either a moraine (ridge left behind by a receding glacier) or a glacier (which has blocked the flow of water). The dam rupture could be caused by any of the following reasons :•Sudden inflow of material into the lake, possibly due to avalanches, rockfalls or pieces of glacial ice-melts, causing displacement of water overtopping the moraine.•Rapid inflow of water from an upstream glacier.•Abnormal rainfall or snowmelt causing sudden increase in the water level of the lake.•Earthquakes.GLOF leads to release of abnormally huge quantities of water over a very short span of time. The extremely high flow of water coupled with river bed........

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