Context-

• The floods that occurred in Chungthang in Sikkim, the north-eastern state of India, have spread rapidly to other districts.
• The flood was caused by the Glacial Lake Outburst Flood (GLOF) at South Lhonak Lake in North Sikkim.
• This resulted in loss of lives and considerable damage to public property and infrastructure such as; The Chungthang Dam, built on the Teesta River producing 1200 MW power, has broken down, the investment cost of which is around Rs 25 thousand crores.

Background -

• This affected area of North Sikkim is located near the India-Nepal border. This place has been considered geographically sensitive.
• The study conducted in the year 2021 was published in the journal ‘Geomorphology’.
•  It was highlighted that the level of South Lhonak Lake has increased significantly over the past decade due to glacial melting and the risk of glacial lake outburst floods (GLOFs) has increased.
• Researchers from the Indian Institute of Technology, Roorkee and the Indian Institute of Science, Bangalore have found that these lakes are mainly located in remote and mountainous valleys but can cause loss of life and property up to 10 kilometers downstream.

GLOF -

• The main reason for glacial lake outburst flood is the weak structure of the moraine dam.
• Moraine is actually a deposit of dust and soil fallen on the surface of the glacier which acts like a dam, in which water keeps collecting.
• When it breaks, it suddenly causes rapid flooding in low-lying areas.

 Reason:

• GLOFs can be triggered by many causes, including earthquakes, extremely heavy rainfall, and snow avalanches.

 Other recent GLOF incidents in India:

• In June 2013, unusual amounts of rainfall in Uttarakhand caused the glacier to melt and the Mandakini River to burst.
• Flood from glacial lake in Gaya village of Ladakh in August 2014.
• GLOFs were believed to be the cause of flash floods in the Chamoli district of Uttarakhand in February 2021.

 Important Facts:

Sikkim -

• Capital: Gangtok
• Chief Minister: Prem Singh Tamang
• Accession to the Union: 16 May 1975

Sikkim state border-

• To the north and north-east: from the Tibet Autonomous Region of China,
• To the south-east: from Bhutan,
• In the south: from West Bengal,
• In the west: It borders Nepal.

 Chungthang Hydro-Dam -

• The dam is an integral part of the 1200 MW Mega Teesta Phase III Hydroelectric Project developed by Teesta Energy.
• With a gross head of 817 meters and a net head of 778 metres, it is an important source of power generation.