Context: Glacial lake bursts in Sikkim have led to the death of Seven people and many missing reports. South Lhonak Lake suddenly overflowed into the Teesta River, creating flash floods that destroyed the Chungthang dam.
Location of Disaster
South Lhonak Lake is a glacial-moraine-dammed lake, located in Sikkim’s far northwestern region. It is one of the fastest expanding lakes in the Sikkim Himalaya region.
- A glacial lake is a body of water that originates from a glacier. It typically forms at the foot of a glacier but may form on, in, or under it.
- Types – Lakes form when meltwater ponds and this can happen on the ice surface (supraglacial lakes), in front of the ice (proglacial lakes), or even underneath the ice (subglacial lakes).
Glacial Lake outburst Flood (GLOF)
- GLOF is the term used to describe the incident when the water levels of glacial lakes breach their boundaries, causing large amounts of water to flow into nearby streams and rivers.
- These also create flash floods.
- Experts often attribute GLOFs to climate change and the increase of anthropogenic footprints on glaciers.
Reasons for GLOF
Possible reasons for triggering the GLOF can be any geophysical phenomenon that destabilizes the water level in the glacial Lake, which subsequently results in the breach of boundaries.
When a glacial lake bursts, its water flows into downstream areas at extreme speed. This causes massive damage to the infrastructure. GLOFs remain a persistent threat to downstream communities and infrastructure, besides flora and fauna.
In June 2013, Uttarakhand received an unusual amount of rainfall leading to the melting of the Chorabari glacier and the eruption of the Mandakini river. The floods affected large parts of Uttarakhand. Reportedly, the worst hit was the Kedarnath valley in Uttarakhand, as the flood left behind a death toll of more than 5,000.
Guidelines on Risk Reduction
- Identifying Potentially Dangerous Lakes:
Potentially dangerous lakes can be identified based on field observations, records of past events, geomorphologic and geotechnical characteristics of the lake/dam and surroundings, and other physical conditions.
- Use of Technology:
Promoting use of Synthetic-Aperture Radar imagery (a form of radar that is used to create two-dimensional images) to automatically detect changes in water bodies, including new lake formations, during the monsoon months. Methods and protocols could also be developed to allow remote monitoring of lake bodies from space.
- Channeling potential floods:
To manage lakes structurally, the NDMA recommends reducing the volume of water with methods such as controlled breaching, pumping or siphoning out water and making a tunnel through the moraine barrier or under an ice dam.
- Uniform Codes for Construction Activity:
Developing a broad framework for infrastructure development, construction and excavation in vulnerable zones. There is a need to accept procedures for land use planning in the GLOF-prone areas.
- Enhancing Early Warning Systems (EWS):
The number of implemented and operational GLOF EWS is very small, even at the global scale. In the Himalayan region, there are three reported instances (two in Nepal and one in China) of implementation of sensor- and monitoring-based technical systems for GLOF early warning.
- Training Local Manpower:
Apart from pressing specialized forces such as National Disaster Response Force (NDRF), ITBP and the Army, NDMA has emphasized the need for trained local manpower. It has been observed that over 80% of search and rescue is carried out by the local community before the intervention of the state machinery and specialized search and rescue teams. The local teams could also assist in planning and setting up emergency shelters, distributing relief packages, identifying missing people, and addressing the needs for food, healthcare, water supply etc.
- Comprehensive Alarm Systems:
Besides classical alarm infrastructure consisting of acoustic alarms by sirens, modern communication technology using cells and smartphones can complement or even replace traditional alarm infrastructure.
- In 2020, National Disaster Management Authority (NDMA) issued detailed guidelines on how to reduce and deal with disasters caused by GLOFs/Glacial Bursts.
- NDMA guidelines suggest that risk reduction can be done by identifying and mapping potentially dangerous lakes, taking structural measures to prevent their sudden breach, and establishing mechanisms to save lives and property in times of a breach.