Flash Flood in Sikkim
Publish Date : 01/11/2023
Sikkim recently experienced a Flash Flood. The South Lhonak Lake, a glacial lake located at an altitude of 17,000 feet in the state’s northwest, experienced a rupture as a result of continuous rainfall.
- Consequently, water was discharged into the downstream regions, causing flooding in the Teesta River and impacting four districts of Sikkim: Mangan, Gangtok, Pakyong, and Namchi, as reported by the Sikkim State Disaster Management Authority (SSDMA).
- This flooding also caused the Chungthang Hydro-Dam in Sikkim (on Teesta river) to breach, worsening the overall situation.
What is a Flash Flood?
- About:
- A Flash Flood is a sudden and potentially catastrophic flood that occurs when water stored behind a glacier or a moraine (a natural accumulation of ice, sand, pebbles, and debris) is released rapidly.
- These floods happen when glacial lakes formed by melting ice accumulate water behind weak moraine dams.
- Unlike sturdy earthen dams, these moraine dams can fail abruptly, releasing large volumes of water in minutes to days, leading to devastating downstream flooding.
- The Himalayan terrain, with its steep mountains, is particularly vulnerable to Flash Flood.
- Climate change, accompanied by rising global temperatures, has expedited the process of glacier melting in the Sikkim Himalayas.
- The region now boasts more than 300 glacial lakes, with ten identified as susceptible to outburst floods.
- Flash Floods can be triggered by several reasons, including earthquakes, extremely heavy rains and ice avalanches.
- Climate change, accompanied by rising global temperatures, has expedited the process of glacier melting in the Sikkim Himalayas.
- Impact:
- Flash Flood can result in catastrophic downstream flooding. They have the potential to release millions of cubic meters of water in a short period of time.
- Peak flows during Floods have been recorded as high as 15,000 cubic meters per second (as per National Disaster Management Authority).
- Flash Flood can result in catastrophic downstream flooding. They have the potential to release millions of cubic meters of water in a short period of time.
- A Flash Flood is a sudden and potentially catastrophic flood that occurs when water stored behind a glacier or a moraine (a natural accumulation of ice, sand, pebbles, and debris) is released rapidly.
How Susceptible is South Lhonak Lake to Flash Flood?
- The South Lhonak lake in northern Sikkim is situated about 5,200 meters above sea level.
- Scientists have previously warned that the lake had been expanding over years, possibly from the melting of the ice at its head.
- Notably, seismic activities, including a 2011 magnitude 6.9 earthquake, escalated the Flood risk in the area.
- In 2016, the Sikkim State Disaster Management Authority and other stakeholders launched a critical plan to drain excess water from South Lhonak Lake.
- Visionary innovator Sonam Wangchuk led the effort, employing High Density Polyethylene (HDPE) pipes to siphon off water from the lake.
- This initiative successfully reduced the lake’s water volume by approximately 50%, mitigating the risk to some extent.
- However, the recent tragedy is believed to be caused by an avalanche originating from the ice-capped feature surrounding the lake.
What Actions be Taken to Reduce the Risk of Flash Flood?
- Glacial Lake Monitoring: Establishing a comprehensive monitoring system to track the growth and stability of glacial lakes in vulnerable regions.
- Satellite imagery, remote sensing technology, and field surveys through drones can be used to regularly assess changes in glacial lakes and their associated moraine dams.
- Early Warning Systems: Early warning systems that can provide timely alerts to downstream communities in the event of a Flash Flood.
- Also, there is a need to complement it with flood protection measures, such as constructing protective barriers, levees, or diversion channels to redirect floodwaters away from populated areas.
- Public Awareness and Education: There is a need to raise public awareness about the risks of Flash Flood and educate communities living downstream about evacuation procedures and safety measures, as per NDMA’s guidelines related to these floods.
- Conduct drills and training programs to ensure that residents know how to respond in case of a Flood of this kind.
- International Cooperation: India can collaborate with neighboring countries in the Himalayan region, as Flash Floods can have transboundary impacts.
- Sharing information and best practices for flood risk reduction and management with neighboring countries can help to mitigate the risk.