Swell Surge and Coastal Hazards: An Emerging Challenge for India’s Coastal Regions

Why in News?

Recently, Swell Surge warnings were issued for coastal areas of Kerala and Karnataka. In the coastal weather bulletin issued in September 2026, Swell Waves with a period of 18–25 seconds and a height of approximately 1.0–1.7 metres were forecast for various coastal districts of Kerala. Such high and long-period waves can increase the risk of coastal inundation, erosion, and disruption of marine activities in low-lying coastal areas.

What is a Swell Surge?

• A Swell Surge is a marine phenomenon in which long-period Swell Waves generated in distant oceanic regions travel thousands of kilometres before reaching the coast. In Kerala, this phenomenon is locally known as Kallakkadal.
• A key feature of this phenomenon is that local weather conditions at the affected coast may remain relatively calm. Despite this, waves generated by distant ocean storms can reach the coast and cause an abnormal rise in seawater and coastal inundation.
• The Indian National Centre for Ocean Information Services (INCOIS) has developed the Swell-surge Inundation Vulnerability Advisory System (SIVAS), which can provide forecasts of potential Swell Surge-induced inundation along the Kerala coast up to three days in advance.

How are Swell Waves Formed?

Distant ocean storm/strong winds → Transfer of energy to the ocean surface → Formation of long-period waves → Propagation over long distances → Increased wave impact near the coast

• Swell Waves do not necessarily originate from strong local winds near the coast.
• High Swell Waves can therefore reach the coast even when local weather conditions are relatively calm.
• In 2024, INCOIS tracked a Swell Surge generated approximately 10,000 km away from the Indian coast in the southern Indian Ocean.
• The event involved high-energy waves with a period of about 22 seconds reaching the Indian coast.

Swell Surge vs Storm Surge

• Swell Surge: Associated with long-period waves generated by distant ocean storms.
• Storm Surge: An abnormal rise in sea level caused primarily by strong cyclone winds and low atmospheric pressure.
• Key Difference: Swell Surge is primarily associated with wave energy arriving from a distant source, whereas Storm Surge is mainly associated with an abnormal rise in sea level caused by a cyclone.

Coastal Vulnerability in India

• India’s long coastline and active marine weather systems in the Arabian Sea and Bay of Bengal make its coastal regions vulnerable to various marine hazards.

Major areas vulnerable to Swell Surge include:

• Kerala coast
• Karnataka coast
• Tamil Nadu coast
• Lakshadweep region

Major Impacts

1. Coastal Inundation: Long-period, high-energy waves can cause seawater to enter low-lying coastal areas.

2. Coastal Erosion: High-wave energy can remove beach sand and other sediments, increasing coastal erosion.

3. Fishing Activities: High sea waves can make small-boat operations hazardous and pose safety risks to fishing communities.

4. Coastal Infrastructure: Roads, houses, ports and other coastal structures can be affected by energetic waves and seawater inundation.

5. Tourism and Local Economy: Recreational activities on beaches may need temporary restrictions, affecting tourism-dependent livelihoods.

Coastal Hazards: A Broader Perspective

• Swell Surge is one component of India’s broader coastal disaster risk. Major coastal hazards include:
• Storm Surge - Tsunami - Coastal Flooding - Coastal Erosion - High Waves - Rip Currents - Saltwater Intrusion
• Each hazard has different causes and impacts. Therefore, coastal disaster management requires multi-hazard risk assessment rather than focusing on a single hazard.

Link with Climate Change

• Long-term sea-level rise increases the exposure and vulnerability of coastal areas. A higher baseline sea level can make a wave or marine event of the same height produce more severe coastal impacts.
• However, the immediate cause of a specific Swell Surge is generally associated with distant marine weather systems and the Swell Waves generated by them. Therefore, every Swell Surge event should not be directly attributed to climate change.

• Disaster Management and Early Warning

• The Indian National Centre for Ocean Information Services (INCOIS) plays an important role in monitoring and forecasting Swell Surge events in India.
• Through SIVAS, forecasts of potential Swell Surge-induced inundation along the Kerala coast are provided. The India Meteorological Department (IMD) also provides information on marine conditions and Swell Surge-related warnings through its coastal weather bulletins.

Key Risk-Reduction Measures

• Strengthen timely early-warning systems for coastal communities and fishermen.
• Move small vessels and fishing boats to safer locations during hazardous marine conditions.
• Impose temporary restrictions on recreational activities along beaches when necessary.
• Protect mangroves, coral reefs, sand dunes and coastal wetlands as natural barriers.
• Adopt risk-based land-use planning in highly vulnerable coastal areas.
• Integrate coastal inundation forecasts with local disaster-management plans.
• Continuously monitor distant Swell Waves using satellites, ocean buoys and oceanographic modelling.

Conclusion

The distinctive feature of a Swell Surge is that its source may be located far from the coastal area where its final impacts are observed. Therefore, India’s coastal disaster-management framework should integrate distant Swell monitoring, coastal inundation forecasting, local early-warning systems and ecosystem-based coastal protection. This can help reduce the vulnerability of coastal communities, fisheries, tourism and critical coastal infrastructure.

MCQ English

Q. With reference to Swell Surge, consider the following statements:

1. Swell Surge is associated with the arrival at the coast of long-period waves generated by distant ocean storms.
2. The presence of strong local winds near the coast is essential for a Swell Surge.
3. INCOIS has developed the Swell-surge Inundation Vulnerability Advisory System (SIVAS).
4. Storm Surge and Swell Surge are the same marine phenomena.

Which of the statements given above are correct?

(A) 1 and 3 only
(B) 1 and 4 only
(C) 2 and 3 only
(D) 1, 2, 3 and 4

Answer: (A) 1 and 3 only

Explanation:

• Statement 1 is correct. Swell Surge is associated with long-period Swell Waves generated in distant oceanic regions.
• Statement 2 is incorrect. Swell Waves can originate far from the affected coast, so strong local winds are not essential.
• Statement 3 is correct. INCOIS has developed SIVAS for forecasting potential Swell Surge-induced coastal inundation.
• Statement 4 is incorrect. Storm Surge and Swell Surge are distinct marine phenomena.