Researchers reveal how cyclone ‘Tauktae’ overtopped Kerala coast
During the 2021 Tauktae Cyclone, large-
scale flooding and erosion were found to be extremely high, especially along the
Chellanam region of Kerala, on India’s western coast. The Chellanam witnessed
coastal flooding, where waves from the ocean overtopped the coastal protection
measures inundating the houses and roads. In a joint study, researchers revealed
how Tauktae Cyclone overtopped Kerala regions despite low storm surge and low
tidal conditions.
Tauktae was located around 500 km away from Chellanam coast, and the area
had low tidal conditions. Despite the insignificant storm surge and low tidal
conditions, the waves overtopped the region in the early morning of 15 th May
2021, taking scientists by surprise.
A new model simulation observed the wave setup (a phenomenon that increases
the coastal water level due to the breaking of the waves) and low-frequency
waves (associated with storm waves) along with the storm wave to elevate the
coastal waters and overtopped the coastal villages at Chellanam.
It is also observed that the areas with steep bathymetry slopes are more severely
flooded, compared to regions with gently sloping bathymetry, as the steepness
increases the coastal water levels. The term ‘bathymetry’ refers to the ocean’s
depth relative to sea level, although it has come to mean as the depths and
shapes of underwater terrain.
Coastal wave models that can resolve wave properties like wave setup and low-
frequency waves (Infragravity waves) are used to simulate the coastal inundation
along the Chellanam coast. The spectral wave properties from operational Wave
Watch-III modeling technology at INCOIS are used as boundary conditions to force
the regional model of Chellanam. The simulation is carried out at different tidal
conditions and observed that the wave setup increases during low tidal conditions
near the steep coast at Chellanam region.
The study, jointly conducted by the researchers of the Indian National Centre for
Ocean Information Services (INCOIS), Hyderabad; Space Applications Centre (SAC),
ISRO, Ahmedabad; and Kerala University of Fisheries and Ocean Studies (KUFOS),
Kochi; has been published in the Scientific Reports journal.
“This study, done using numerical modelling techniques, show the significance of
storm waves and how the coastal water levels are elevated during the storm
surge due to the processes called wave setup associated with the storm waves.
The storm waves also induce another set of waves, a low frequency (period) wave
that increases the coastal water levels. The operational procedure for coastal
inundation during storm surge does not represent the wave setup and low
frequency waves, observed to be vital for inundation at Chellanam coast,” said Dr
Remya P.G., a researcher from Indian National Centre for Ocean Information
Services (INCOIS), Hyderabad.
Based on the current study, regional models along hot spots are proposed, where
numerical models can resolve the wave setup and infragravity waves.
Apart from Dr Remya, researchers associated with this study include
Ratheesh Ramakrishnan and Anup Mandal, SAC, ISRO, Ahmedabad; Dr
Prakash Mohanty, Dr R.S. Mahendra, and Dr T.M. Balakrishnan Nair of
INCOIS, Hyderabad; and Prince Arayakandy of Kerala University of Fisheries
and Ocean Studies (KUFOS), Kochi. (India Science Wire)
Keywords: Taukate, Cyclone, Flooding, Chellanam, Coastal region, Kerala,
Western coast