Context: Kallakkadal, a coastal flooding phenomenon caused by distant ocean storms, has recently affected Kerala, India. The current event, triggered by a low-pressure system from South Atlantic Ocean, has flooded hundreds of houses in Alappuzha, Kollam, and Thiruvananthapuram districts.

Kallakkadal differs from tsunamis and can now be predicted by the INCOIS Swell Surge Forecast System. The swell surge is expected to continue for the next two days before weakening.

Kallakkadal

• Kallakkadal is a Malayalam term that combines “Kallan” (meaning thief) and “Kadal” (meaning sea). This term was formally approved by UNESCO in 2012.
• It refers to the phenomenon of coastal flooding during the pre-monsoon season (April-May) along the southwest coast of India, caused by ocean swells generated by distant storms.
• The latest instance of Kallakkadal took place after a low atmospheric pressure system moved over the region around March 25 from the South Atlantic Ocean — 10,000 kilometres off the Indian coast.
• Swell surge is another term used to describe the coastal flooding caused by Kallakkadal.

Causes and Formation

• Energy transfer from air to water during distant storms
  • Kallakkadal events are triggered by the energy transfer from air to water during distant storms, such as hurricanes or intense low-pressure systems.
  • During these storms, winds can reach speeds of over 100 km/h, leading to the formation of high waves.
• Wave propagation
  • The high waves generated by distant storms can travel thousands of kilometers from the storm center to eventually reach the shore.
  • Swell waves associated with Kallakkadal can propagate at speeds of up to 50 km/h and cover distances of over 10,000 km.

Affected Areas

• Kerala: The state of Kerala, particularly the districts of Alappuzha, Kollam, and Thiruvananthapuram, is among the worst affected by Kallakkadal. During these events, hundreds of houses are flooded, and relief camps are opened to accommodate the affected population.
• Lakshadweep: The low-lying coral atolls of Lakshadweep are vulnerable to sea-level rise and coastal flooding associated with Kallakkadal events. The unique geography of these islands makes them particularly susceptible to the impacts of swell surges.
• Tamil Nadu coast: The Tamil Nadu coast, which has a coastline of over 1,000 km, is another region that is expected to be impacted by Kallakkadal events. INCOIS has stated high waves will move to the Tamil Nadu coast.

Early Warning System

• Swell Surge Forecast System by INCOIS (2020)
  • This system provides forewarning of Kallakkadal events seven days in advance, allowing coastal communities to prepare and take necessary precautions.
  • The forecast system uses numerical ocean models, observations, and artificial intelligence techniques to generate accurate predictions.
• Challenges in forecasting Kallakkadal
  • Forecasting Kallakkadal events is challenging because they often occur without precursors or local wind activity.
  • In such situations, the traditional knowledge of fishermen and coastal communities plays a crucial role in identifying and responding to these events.

Different between Tsunami and Kallakathal

INCOIS Alerts

• Indian National Centre for Ocean Information Services (INCOIS) has issued alerts for coastal areas vulnerable to sea erosion, advising communities to take necessary precautions and ensure the safety of their property and lives.
• It is observed that 33.6% of the Indian coastline was vulnerable to erosion, 26.9% was under accretion (growing), and 39.6% was in a stable state.
• This long-term shoreline analysis indicates that out of 550 km of coast in Odisha, 28% of the coast is eroding, 21% is stable, and 51% is accreting.
• To protect the coastal areas from erosion, initiatives such as mangrove plantation, shelterbelt plantation, and installation of Geo-Tubes in 500 m (Pentha Village Odisha) have been carried out.

Climate Change and Kallakkadal

• Rising sea levels due to climate change
  • According to NASA, the global mean sea level has risen by about 0.3 inches (0.76 centimeters) from 2022 to 2023, a relatively large jump due mostly to a warming climate and the development of a strong El Nino.
  • The total rise is equivalent to draining a quarter of Lake Superior into the ocean over the course of a year.
• Warmer ocean temperatures
  • Climate change is also leading to warmer ocean temperatures, which can contribute to more intense storms and larger swell waves.
  • As the ocean surface warms, it provides more energy for storms to intensify, potentially leading to stronger winds and higher waves.
• Increased risk for coastal communities
  • The extent of coastal flooding has increased over the past 20 years as a result of sea level rise, meaning 14 million more people worldwide now live in coastal communities with a 1-in-20 annual chance of flooding.

Mitigation and Adaptation Measures

• Strengthening early warning systems and disaster preparedness
• Coastal protection and management measures can help reduce the vulnerability of coastal areas to flooding and erosion.
• Hard engineering structures, such as seawalls and groins, can be built to protect the shoreline from the impact of waves and current.
• Nature-based solutions, like mangrove restoration and beach nourishment, can also help to buffer the coast against erosion and provide additional ecosystem benefits.
• In the long term, mitigating climate change by reducing greenhouse gas emissions is essential to limit the extent of sea-level rise and ocean warming.
• Promoting sustainable development and climate-resilient infrastructure in coastal areas
• On the international level, India updated its climate action plans at the CoP26 Leader’s Summit, demonstrating a renewed commitment to the Paris Agreement’s goal of reducing GHG emissions intensity of GDP by 33-35 percent by 2030.