INCOIS’ second Coastal Flood Monitoring System (CFMS) near Kollam port in Kerala to improve the accuracy of ‘Kallakkadal’ forecasts. | Photo credit: BY ARRANGEMENT
Hyderabad-based India’s National Center for Ocean Information Services (INCOIS) has installed a second Coastal Flood Monitoring System (CFMS) near Kollam port in Kerala to improve the accuracy of ‘Kallakkadal’ (surge wave) forecasts along India’s southwest coast.
Who is at risk from wave surges?
“Kallakkadal” events – sudden and powerful wave surges – pose a significant threat to fishing communities and coastal infrastructure. These waves are usually triggered by long-term swells generated by distant storms in the southern Indian Ocean, nearly 10,000 kilometers from India’s coast, INCOIS director TM Balakrishnan Nair said.
Swell shocks frequent during pre-monsoon
The first observational evidence of such waves in Indian waters was recorded during the initial deployment of the CFMS in Vizhinjam last year. The system was operated from February to May, covering the pre-monsoon period when these wave surges are most common.
Scientists have observed that these surges, with periods ranging from 30 to 300 seconds, can substantially raise coastal water levels. The goal, they said, is to identify patterns in Southern Ocean waves and refine forecast models for better accuracy.
The CFMS integrates a coastal automatic weather station with four high-frequency pressure sensors installed in shallow waters at depths of three to seven meters. This configuration enables accurate monitoring of nearshore wave transformation processes and provides valuable real-time data.
INCOIS is working to build a comprehensive understanding of the entire chain of processes – from wave generation in the open ocean to nearshore wave transformation and subsequent coastal inundation. This integrated approach is expected to strengthen early warning systems and improve the accuracy of ‘Kallakkadal’ forecasts.
Scientific basis of surge generation
About a decade ago, he established the scientific basis for the generation of tidal waves in the southern Indian Ocean, demonstrating how distant weather systems can create long-duration waves that travel thousands of kilometers before hitting the Indian coast. Subsequent research linked the “Kallakkadal” events to infragravity waves – low-frequency waves created by the interaction between shorter waves in the open ocean.
As these waves approach shallow water, their energy is amplified due to shoaling—a process in which wave height increases as waves move from deep to shallow areas. Coastal bathymetry, or underwater topography, further amplifies these waves and contributes to flash coastal flooding, the researchers said.
Kollam was selected for the second system due to its frequent exposure to such events. After installation, INCOIS conducted a community awareness program to improve preparedness and promote effective use of forecast information, said scientist Praveen Kumar. Through a combination of scientific research, advanced observations and community outreach, INCOIS aims to strengthen coastal resilience and reduce the risks posed by “Kallakkadal” events.
Published – May 13, 2026 12:36 PM IST
