Swell waves inundate coastal areas in Kerala 

News Excerpt:

Swell waves have inundated coastal areas in central and southern Kerala, giving anxious moments to coastal communities and prompting district-level disaster management machinery to be in alert mode.

More about the news:

  • Swell waves have flooded beaches along the coastal areas in Thiruvananthapuram, Kollam, Alappuzha, and Thrissur districts. 
  • The phenomenon is referred to as ‘Kallakkadal’ locally in Kerala.
  • According to the Kerala State Disaster Management Authority (KSDMA) it is likely to persist for one or two days along the Kerala coast.
  • The Indian National Centre for Ocean Information Services (INCOIS) has warned that the sea will be rough near-shore along the Kerala coast during the swell wave event.

What are swell waves?

  • A swell is a series of mechanical or surface gravity waves generated by distant weather systems that propagate thousands of kilometres across oceans and seas.
  • Swell waves are not generated by local winds blowing near the shore, Instead, they're the result of the interaction of severe storms with a large fetch of water that takes place in the open ocean, thousands of kilometres away from land masses.


  • ‘Kallakkadal’ is a colloquial term used by Kerala fishermen to refer to flash flooding events. 
    • In Malayalam, Kallan means thief or mischievous one and Kadal means sea.
  • Fishermen use the term ‘Kalla Kadal’ to refer to the unusual occurrence of high swell waves during good weather. 
  • According to weather experts, the phenomenon is triggered by storms as far away as the Antarctic region. 
    • Kallakkadal are caused by meteorological conditions in the Southern Ocean, south of 30°S.
  • After travelling thousands of kilometres across the ocean basin, the swell intensifies when it encounters a coastal current, a phenomenon known as remote forcing.
  • 'Kalla Kadal' usually occurs along the southern coast of India, mainly during the pre-monsoon period, in April and May during clear weather conditions.
  • In 2012, UNESCO formally accepted the term for scientific use.


Indian National Centre for Ocean Information Services (INCOIS)

  • INCOIS was established as an autonomous body in 1999 under the Ministry of Earth Sciences (MoES).
  • It is mandated to provide the best possible ocean information and advisory services to society, industry, government agencies and the scientific community through sustained ocean observations and constant improvements through systematic and focussed research.
  • Indian Tsunami Early Warning Centre (ITEWC) of INCOIS is a Regional Tsunami Service Provider (RTSP) to provide tsunami warnings to countries on the Indian Ocean Rim. 
  • It also provides daily advisories to fisher folk to help them easily locate areas of abundant fish in the ocean. 
    • These advisories called Potential Fishing Zone Advisories are issued in Hindi, English and 8 vernacular languages.