Context:
Recent high sea waves, commonly referred to as swell waves or Kallakkadal in Malayalam, have caused extensive flooding in coastal areas of Kerala. Hundreds of houses in regions like Alappuzha, Kollam, and Thiruvananthapuram districts have been affected by these swell surges. The flooding highlights the vulnerability of Kerala’s coastal communities to natural events and emphasizes the need for effective disaster preparedness and response measures.
Relevance:
GS III: Disaster Management
Dimensions of the Article:
- Kallakkadal
- Challenges in Early Preparedness for Kallakkadal
- Differences Between Kallakkadal and Tsunami
Kallakkadal
Definition and Origin
- Kallakkadal refers to coastal flooding occurring during the pre-monsoon season (April-May) due to swell waves on the southwest coast of India.
- The term “Kallakkadal” originates from two Malayalam words: “Kallan,” meaning thief, and “Kadal,” meaning sea, translating to “ocean that arrives as a thief.”
- In 2012, UNESCO formally approved the term, acknowledging its significance among local fishermen.
Causes of Kallakkadal
Formation of Swell Waves
- Kallakkadal is primarily caused by waves formed through ocean swells, hence the name “swell surge.”
- These ocean swells are not generated by local winds but are a result of distant storms such as hurricanes or prolonged periods of intense gale winds.
- During these storms, a significant transfer of energy occurs from the air to the water, leading to the creation of exceptionally high waves.
- These waves can travel vast distances from the storm center until they reach the coastline.
Role of Southern Indian Ocean Winds
- Kallakkadal results from the powerful winds in the southern part of the Indian Ocean, generating ocean swells.
- These waves then travel northward, reaching the coast within two to three days.
- A recent instance occurred when a low atmospheric pressure system moved over the region around March 25, originating from the South Atlantic Ocean approximately 10,000 kilometers away from the Indian coast.
- This atmospheric pressure system caused strong winds, resulting in the formation of swell waves reaching heights of up to 11 meters.
Challenges in Early Preparedness for Kallakkadal
Lack of Precursors
- Kallakkadal often occurs without any precursors or local wind activity, making it challenging for coastal communities to receive advance warnings.
Swell Surge Forecast System
- Despite the inherent difficulties in predicting Kallakkadal, the Swell Surge Forecast System offers early warnings up to seven days in advance.
- Launched by the Indian National Centre for Ocean Information Services (INCOIS) in 2020, this system aids in providing timely alerts to coastal populations, enhancing preparedness and response measures.
Differences Between Kallakkadal and Tsunami
Nature of Occurrence
- Kallakkadal: It is a flash flood event that occurs suddenly without any noticeable change in local winds.
- Tsunami: Tsunami is a series of massive waves generated by underwater disturbances, typically earthquakes.
Cause
- Kallakkadal: It is primarily caused by strong winds.
- Tsunami: Tsunamis are predominantly caused by earthquakes, although they can also result from volcanic eruptions, landslides, or meteorite impacts.
Wave Characteristics
- Kallakkadal:
- Wave height varies based on the strength of the wind causing the swell.
- Originates due to ocean swells formed by distant storms or prolonged periods of intense gale winds.
- Tsunami:
- While tsunamis have a relatively small wave height offshore, they can gain enormous height as they approach the coast.
- Tsunamis are characterized by their long wavelength, often extending hundreds of kilometers, which distinguishes them from regular ocean waves with wavelengths of only 30 to 40 meters.
-Source: Indian Express
