Swell Waves (Kallakkadal)

Context

The Indian National Centre for Ocean Information Services (INCOIS) issued a red alert for coastal districts of Keralam due to the risk of Kallakkadal, which can cause sudden coastal flooding even without strong local winds.

About Swell Waves

1. Definition: Ocean waves generated by distant storms and strong winds that travel long distances across the sea.
2. Kallakkadal: A local term used by fishermen in Keralam for sudden coastal flooding caused by swell surges.
3. Difference from local wind waves: Swells have more regular wave periods and directions than locally generated wind waves.

Formation and Characteristics

1. Formation: Strong winds during distant storms transfer energy to the sea, generating swell waves.
2. Long-distance travel: Swells can travel thousands of kilometres from their source.
3. Wavelength: Usually below 150 metres, but may exceed 700 metres during severe storms.
4. Unexpected arrival: Swell surges can affect coastlines without strong local winds or rainfall.

Impacts of Swell Surges

1. Coastal flooding: Inundation of low-lying coastal areas.
2. Coastal erosion: Damage to beaches, homes and coastal infrastructure.
3. Livelihoods: Disruption of fishing and other marine activities, posing risks to coastal communities.

Early Warning System in India

1. Indian National Centre for Ocean Information Services (INCOIS): An autonomous institution under the Ministry of Earth Sciences that provides ocean information and forecasts.
2. Swell Surge Forecast System: Launched by INCOIS in 2020, it provides warnings of swell-related coastal hazards around 2–3 days in advance, helping authorities prepare for potential flooding.
3. Swell-surge Inundation Vulnerability Advisory System (SIVAS): INCOIS currently provides this forecasting system for the Kerala coast. It simulates coastal water levels and wave-driven inundation and provides forecasts up to 3 days in advance in English, Hindi and Malayalam.

FAQs

Q1. What are swell waves?

Ans. Swell waves are ocean waves generated by distant storms or strong winds that travel far from their place of origin.

Q2. Which organisation forecasts swell surges in India?

Ans. The Indian National Centre for Ocean Information Services (INCOIS), under the Ministry of Earth Sciences, provides swell-surge forecasts and warnings.

Q3. How do swell waves differ from locally generated wind waves?

Ans. Swell waves originate from distant weather systems and can reach a coast even when local winds are weak. Wind waves form mainly due to winds acting on the nearby sea surface.