The entire stretch of the Kerala coast could be vulnerable to inundation caused by tsunami waves originating from different sources, a numerical modelling study of tsunami propagation in the South East Arabian Sea (SEAS) has revealed.
The modelling results summarised that sea level rise caused by climate change could aggravate tsunami inundation in some of the stretches like Neendakara and Thottapally marked by low backshore elevation, whereas the impact might not be significant in the central and northern sectors of the coast.
The results of the study showed strikingly different run-up (the height of the water pushed onshore by a tsunami) and inundation characteristics for the Kerala and Lakshadweep coasts. Simulation experiments revealed that Cochin Harbour was largely immune to the amplification of tsunami waves because of the presence of good natural channels.
The study was undertaken by Praveen S.S., project scientist at the Ministry of Earth Sciences, Chennai, for his Ph.D. in physical oceanography awarded by the Cochin University of Science and Technology. The investigation, done under the guidance of N.P. Kurian, Director, Centre for Earth Science Studies, covered the Kerala coast and the Androth, Chetlat, Kadmat and Kavaratti Islands of Lakshadweep.
It involved numerical simulations for three different sources, namely the tsunami unleashed by the Sumatra earthquake in 2004, the Makran earthquake-induced tsunami in the Arabian Sea in 1945 and a hypothetical potentially worst case from Makran.
It was seen that the Lakshadweep Maldive Ridge (LMR), a major oceanic feature in the Arabian Sea, could increase the tsunami amplitude (wave height) in the case of a Sumatra 2004-like tsunami originating from the east. The increase in run-up was found considerably high in the case of southern Kerala when compared to northern Kerala.
In contrast, simulations carried out for a Makran 1945-like tsunami showed that the LMR impeded the run-up and inundation to a certain extent. However, the Lakshadweep Islands did not appear to be vulnerable to tsunami inundation.
The investigation found that though the hypothetical Makran source was not likely to generate a run-up as high as the Sumatra 2004 along the Kerala coast, it could leave a major part of the coast inundated. This anomaly has been attributed to the beach elevation characteristics.
The paper stresses the need to carry out numerical simulations for the extreme sea level rise scenarios for the whole coast.
Dr. Pradeep said the study assumed importance in the light of ongoing efforts at the global level to understand, analyse and combat the effects of climate change.