FLASH FLOOD (Syllabus: GS Paper 3 – Disaster Management)

News-CRUX-10     5th October 2023        
Samadhaan

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.
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