IIT Madras designs concrete models to save Vaan island off the Tuticorin coast

A team from IIT Madras has designed a cutting-edge method to save an eroding island off the coast of Tuticorin. The research and development started when the environment department of the Tamil Nadu government approached them to save the Vaan island, which is a part of the Marine Biosphere Reserve at the sounthernmost string of islands. The Gulf of Mannar, between India and Sri Lanka is the first marine biosphere reserve in Asia, built by the Indian Government in 1989. This included a chain of 21 islands and coral reefs off the coast of Ramanathapuram and Tuticorin forming the core.

According to a database provided by the Tamil Nadu Government in 2015, about 1/4th area of the island has already submerged due to the removal of coral reefs. It also stated heavy biotic interference and frequent fires caused by fishermen led to the degeneration of the coral growth around the island. In 2014, the state's Environment Department approached IIT Madras with a request to preserve the island without engineering structures.

H Malleshappa, director, Environment Department, Tamil Nadu, speaking to the Indian Express said, "The objective was to control the erosion of the island and to facilitate coral rehabilitation in surrounding areas. Coral mining was once rampant in this area, and that combined with rising sea levels have over the years harmed the island."

The design was such. A two-layer submerged reef breakwater system, comprising 9,000 small units of reinforced concrete structures, was lowered in the water and placed in a semi-circular fashion. Prof S A Sannasiraj, head, Department of Ocean Engineering, IIT Madras, said, "These concrete structures were previously used in other parts of the world to rehabilitate corals. But this was the first time it was being used to protect an island." While the first phase of the project was executed in 2015 at a cost of Rs 12 crore, teh second phase is expected to start soon. Sannasiraj said, "We worked out the design, the build, how to place it, studied waves and determined where to place the structures. The holes in the concrete structure was to achieve good water circulation, so as to achieve wave dissipation. The holes are also required for marine growth. It only took eight months for corals to start growing on these structures."

Experts believe that the island conglomerate is responsible for protecting the 170-km island stretch. Sannisaraj said, "Even though these islands are uninhabited, they perform a crucial role in dissipating wave energy before it reaches the coast of Tamil Nadu. The space between the islands and the coast is like a swimming pool, where fishermen often park their boats. The mainland is naturally protected by these islands."

The project is likely to be extended to the next island Koswari, which is also losing its land area to erosion. 

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