Kallakkadal

What’s in today’s article?

• Why in News?
• What’s in Today’s Article?
• Kallakkadal
• What causes Kallakkadal?
• Kallakkadal – challenges in early preparedness
• Why is Kallakkadal different from tsunami?

Why in news?

Recently, hundreds of houses have been flooded in several coastal areas of Kerala due to high sea waves, also known as swell waves. The worst affected regions include Alappuzha, Kollam, and Thiruvananthapuram districts.

Such flooding events are called swell surge or Kallakkadal in Malayalam.

What’s in today’s article?

• Kallakkadal

Kallakkadal

• About
  • Kallakkadal is essentially coastal flooding during the pre-monsoon (April-May) season by swell waves on the southwest coast of India.
• Meaning
  • The term Kallakkadal, used by local fishermen, is a combination of two Malayalam words, including Kallan and Kadal.
  • Kallan means thief and Kadal means sea. Meaning ocean that arrives as a thief.
  • In 2012, the term was formally approved by the United Nations Educational, Scientific and Cultural Organization (UNESCO).

What causes Kallakkadal?

• Ocean swell and role of distant storms
  • Kallakkadal is caused by waves that are formed by an ocean swell, hence the name swell surge.
  • Ocean swells occur not due to the local winds, but rather due to distant storms like hurricanes, or even long periods of fierce gale winds.
  • During such storms, huge energy transfer takes place from the air into the water, leading to the formation of very high waves.
  • Such waves can travel thousands of kilometres from the storm centre until they strike shore.
• Formation of Kallakkadal
  • Kallakkadal is a consequence of the strong winds in the southern part of the Indian Ocean, where an ocean swell is generated.
  • These generated waves then travel north to reach the coast in two/ three days.
• Recent incidents of Kallakkadal
  • The latest instance took place after a low atmospheric pressure system moved over the region around March 25 from the South Atlantic Ocean — 10,000 kilometres off the Indian coast.
  • The arrival of the pressure system resulted in strong winds, which led to the formation of swell waves of up to 11 metres in height.

Kallakkadal – challenges in early preparedness

• Kallakkadal occurs without precursors or any kind of local wind activity and as a result, it has been very difficult for the coastal population to get an advance warning.
• However, early warning systems like the Swell Surge Forecast System gives forewaring seven days in advance.
  • This system was launched by the Indian National Centre for Ocean Information Services (INCOIS) in 2020.

Why is Kallakkadal different from tsunami?

• Kallakkadal is a flash flood event that occurs without any noticeable change in local winds. On the other hand, tsunami is a series of enormous waves created by an underwater disturbance.
• Other differences include:
  • Cause: Kallakkadal is caused by strong winds, while tsunamis are caused by earthquakes.
  • Wave height: Tsunamis have a small wave height offshore.
  • Wavelength: While ocean waves have a wavelength of only 30 or 40 meters, Tsunamis have a very long wavelength often hundreds of kilometers long.

Q.1. What is Indian National Centre for Ocean Information Services (INCOIS)?

The Indian National Centre for Ocean Information Services (INCOIS) is an autonomous organization of the Government of India that provides ocean information and advisory services to society, industry, government agencies, and the scientific community. INCOIS was founded in 1999 and is located in Pragathi Nagar, Hyderabad.

Q.2. What are swell waves?

Any random disturbance that can occur in the sea. Swell waves are specific kinds of deep-water, linear, long-range wind-driven waves that emanate or filter out of a random wave system during an external weather event due to wave dispersion. Waves can be of any form, type, shape, height, period, direction, and speed.

Source: What is Kallakkadal, which has flooded houses in Kerala’s coastal areas?