FLASH FLOOD (Syllabus: GS Paper 3 – Disaster Management)
Context: Recently, a glacial lake outburst in north Sikkim's Mangan district, caused flash floods and breached Sikkim's Chungthang dam, the state's largest hydropower project.
Flash flood
- Meaning: A flood caused by heavy or excessive rainfall in a short period of time, generally less than 6 hours known as a flash flood.
- Conditions for occurrence: It can occur either within minutes or a few hours of excessive rainfall.
o It can occur even if no rain has fallen, or after a sudden release of water by a debris or ice jam.
o It happens more where rivers are narrow and steep, so they flow more quickly.
o It can occur in urban areas located near small rivers since hard surfaces such as roads and concrete do not allow the water to absorb into the ground.
- Causes: It may be caused by
o Heavy rain associated with a severe thunderstorm, hurricane, tropical storm, or meltwater from ice or snow flowing over ice sheets or snowfields.
o It also occurs due to Dam or Levee Breaks, and/or Mudslides (Debris Flow).
o Occur on or near volcanoes, after eruptions, when glaciers have been melted by the intense heat.
Key Points
- The burst led to the breach of Sikkim’s Chungthang dam (Teesta 3 HEP), the biggest hydropower project in the state.
- The Himalayan region is part of a seismically active zone.
- The dam is part of the 1,200 megawatts (MW) Teesta Stage III Hydro Electric Project. The dam breach in the Himalayan state has raised serious concerns about a deluge in the downstream areas.
