What is Kallakkadal, which has flooded houses in Kerala’s coastal areas?
- April 3, 2024
- Posted by: OptimizeIAS Team
- Category: DPN Topics
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What is Kallakkadal, which has flooded houses in Kerala’s coastal areas?
Subject: Geography
Section: Indian Physical Geo
Context:
- Hundreds of houses have been flooded in several coastal areas of Kerala due to high sea waves, also known as swell waves, since Sunday.
More on news:
- The worst affected regions include Alappuzha, Kollam, and Thiruvananthapuram districts.
- Such flooding events are called swell surge or Kallakkadal in Malayalam.
What is Kallakkadal?
- Kallakkadal is essentially coastal flooding during the pre-monsoon (April-May) season by swell waves on the southwest coast of India.
- Kallakadal/Swell surge are flash flood events that take place without any noticeable advance change in local winds or any other apparent signature in the coastal environment.
- 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.
- In spoken language, these words were combined and pronounced as Kallakkadal, meaning ocean that arrives as a thief.
- In 2012, the term was formally approved by the United Nations Educational, Scientific and Cultural Organization (UNESCO).
Characteristics of kallakadal:
- This phenomenon occurs mostly during pre-monsoon season and sometimes during post monsoon.
- It continues for a few days and inundates the low lying coasts.
- During high tide the run-up, water level can reach as much as 3–4 m above Maximum Water Level (MWL).
What causes Kallakkadal?
- Kallakkadal is caused by waves that are formed by an ocean swell, hence the name swell surge.
- Kallakkadal events are caused by swells propagating from the Southern Indian Ocean of 30°S, from the region between Africa and Australia.
- 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 kilometers from the storm center until they strike shore.
- Usually, Kallakkadal is a consequence of the strong winds in the southern part of the Indian Ocean, where an ocean swell is generated, and the waves then travel north to reach the coast in two or three days.
- 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 —launched by the Indian National Centre for Ocean Information Services (INCOIS) in 2020 — give forewarning seven days in advance.
Why is Kallakkadal different from tsunami?
- Kallakkadal came under the spotlight after the 2004 tsunami that killed more than 10,000 people.
- Kallakkadal is often mistaken to be a tsunami, which is a series of enormous waves created by an underwater disturbance usually associated with earthquakes occurring below or near the ocean.
- Tsunamis are caused by landslides or earthquakes in the ocean bottom, whereas Kallakkadal are caused by meteorological conditions in the Southern Ocean, 30° South.