Flash Floods

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    In News

    • Recently, there was a cloudburst near the holy cave shrine of Amarnath in south Kashmir Himalayas which triggered flash floods damaging the property and also killed several people.

    About the tragedy

    • Amarnath yatra which began on June 30 has been temporarily suspended in view of the tragedy.
      • The annual 43-day Amarnath yatra commenced from the twin base camps Nunwan-Pahalgam in south Kashmir’s Anantnag and 14-km shorter Baltal in central Kashmir’s Ganderbal.

     

    Cloudburst

    • A cloudburst is a sudden aggressive rainstorm falling for a short period of time, limited to a small geographical area.
    • It usually occurs in high-altitude areas due to the formation of a low-pressure area on the top of a mountain.
      • The low-pressure zone attracts clouds to the top of the mountain with great force. When they hit the peak, the moisture content is released in the form of rain
    • It can occur during heavy rainfall with size droplets 4-6 millimetres falling at a speed of 10 metres per second.
    • Cloudbursts are associated with thunderstorms and the air currents rushing upwards in a rainstorm hold up a large amount of water.
      • If these currents suddenly cease, the entire amount of water descends onto a small area with catastrophic force all of a sudden and causes mass destruction. This is due to a rapid condensation of the clouds.
    • The primary reason behind this is rising temperatures which in turn have led to an increase in precipitation across the Himalayas.
    • Topographical conditions like steep hills favour the formation of these clouds. Water flowing down steep slopes brings debris, boulders and uprooted trees with great velocity damaging any structure that comes in their way.

     

    Flash Floods 

    •  Flash Floods are highly localised events of short duration with a very high peak and usually have less than six hours between the occurrence of the rainfall and peak flood.
    • The flood situation worsens in the presence of choked drainage lines or encroachments obstructing the natural flow of water. 
    • Flash floods have a different character than river floods, notably short time scales and occurring in small spatial scales, which make forecasting of flash floods quite a different challenge than traditional flood forecasting approaches. 
    • Urban areas are more likely to experience this type of “surface water” flooding because they have a lot of hard surfaces.
      • When rain hits them it can’t soak into the ground as it would do in the countryside.

    Impacts

    • Death or Serious Injury
      • The very nature of flash floods makes them fast and very difficult to predict.
      • Since they can occur without warning, it is no surprise that people can be seriously injured or killed by these natural disasters.
    • Immediate Property Damage
      • In addition to the force of the water, flash floods can carry large debris such as boulders. This combination can cause heavy structural damage to homes making them uninhabitable and can carry away large pieces of property such as vehicles.
    • Loss of Critical Infrastructure
      • Large debris and flood waters can cause structural damage to bridges and roadways, making travel impossible.
      • Power, telephone, and cable lines can be taken out by flash floods as well.
      • Flood waters can disrupt or contaminate groundwater, making tap water unfit for consumption.
    • Deposited Sediment & Silt
      • Floods can leave behind large amounts of silt and other debris that can make travel difficult and can be costly to remove. 
    • Uninsured or Under-insured Homeowners
      • Being infrequent and unpredictable, many homeowners do not consider flash floods when insuring their homes.
    • Economic Losses
      • Depending on the damage caused, it may prevent local businesses from opening or keep customers from getting to those businesses.

    Initiatives in this direction

    • Flash Flood Guidance Services
      •  It is a robust system designed by the India Meteorological Department (IMD) to provide the necessary products in real-time to support the development of warnings for flash floods about 6-12 hours in advance at the watershed level for the flash flood-prone South Asian countries viz. India, Nepal, Bhutan, Bangladesh, and Sri Lanka.
    • South Asian Flash Flood Guidance System (FFGS)
      • The India Meteorological Department (IMD) launched the South Asian FFGS.
      • It is aimed at helping disaster management teams.
      • Helps governments make timely evacuation plans ahead of the actual event of flooding. 

    Way Forward 

    • There is a need for each member nation to improve their weather observational networks so that more data is available at the time of issuing warnings. 
    • Soil moisture data is also important and there is a need to augment the existing network.
    • These severe rainstorms appear in the summer, and in farming communities, they are sometimes welcomed, as a cloudburst can irrigate crops very thoroughly.

    Source:DTE