Thursday, September 8 2005 14:17 Hrs (IST) - World Time -

New Delhi: The tsunami last year might have caused greater destruction to Tamil Nadu coast had it not been for Sri Lanka, according to a post-tsunami survey report by Indian Department of Ocean Development.

The island nation of Sri Lanka has blocked and deflected the approaching tsunami waves and hence the coastal areas of the districts of Pudukottai, Ramanathapuram, Tuticorin and Tirunelveli were saved, says the DOD report.

It said when high-energy tsunami waves traversed horizontally across Indian Ocean, the east coast of Sri Lanka absorbed the devastating tsunami energy and only the refracted waves with low energy reached the west and south-east coast of Tamil Nadu.

"This was confirmed by wave modelling studies," DOD said.

It is for this reason Tuticorin, although it is situated south of Rameswaram, witnessed tsunami almost an hour after it hit Chennai coast. Thus, much of the southern coastal belt of Tamil Nadu, shadowed by Sri Lanka, was less affected.

The DOD report said because of the deflection of the waves, the water had receded temporarily in some places before returning to normal. For instance, the rocky bed which used to be always under water in Tiruchendur coast (near Tiruchendur temple) got exposed because of the receding water up to 50 metres from the normal low tide mark.

The DOD survey also concluded that, contrary to fears, the impact of tsunami waves on either the corals or on the ecosystem was only minimal.

It said underwater surveys using Line Intercept Transect Method (LIT) revealed there were no appreciable changes in the biophysical status of corals in the Gulf of Mannar. Coral species of the family Acroporidae, which are vulnerable to natural disturbances, did not show any damage in their structures after the tsunami waves in the Gulf of Mannar.

The report said that the massive corals and associated fishes, algae and sea grass beds were not affected by the tsunami waves.

There was only slight displacement of the coral rubble walls lying near the edges on the seaward side of some of the islands of the Gulf of Mannar.

"Indications are that sediment load might have increased due to the sudden flushing effect of the tsunami waves and hence there is a need to make a complete survey of all the coral reef habitats," the report said.

The tsunami had left one positive effect, however. It benefited the Pulicat Lake by opening its mouth wide, the report said.