IIT team revives dying island

In 1989, the Indian government had created the first marine biosphere reserve in Asia comprising the Gulf of Mannar, between India and Sri Lanka with the chain of 21 islands and adjoining coral reefs off the TamilNadu coast. However, rampant coral reef mining, heavy biotic interference due to its nearness to Tuticorin town” and “frequent fires” caused by fisherman led to drastic changes in Vaan island, the southernmost in the string of islands, in the Marine Biosphere Reserve.  This was noticed by the Tamil Nadu Government’s Department of Environment three years ago. They approached IIT Madras with a request to find a solution to protect the island which had shrunk from 16 hectares in 1986 to 1.5 hectares in 2015. The IIT team launched a study of the island and designed and built small models that were studied and developed in the IIT labs. Then they designed a “two-layer submerged reef breakwater system”. The first phase involved lowering  9,000 small units of reinforced concrete structure with holes into the sea, 250m off the island’s shoreline, and placed in a semi-circular fashion. Prof S A Sannasiraj, head, Department of Ocean Engineering, IIT Madras, who is steering the project said that such concrete structures have been used earlier in some parts of the world to rehabilitate corals, but this is the first time it was being used to protect an island. Within just eight months corals have started growing on these structures. Today, these “artificial reefs” have helped it “gain mass” by 7.6 per cent. With the success of the Vaan island which is gradually growing, the project may soon be extended to the next island Kosawari, which is losing ground due to erosion.