The steel structure, weighing 900 tonnes, was immersed 2.5 metres below sea level to aid in restoration of sandy beaches and prevent erosion

In a first in the country, the National Institute of Ocean Technology (NIOT) on Thursday successfully immersed a triangular wedge-shaped offshore reef 2.5 metres below sea level on the northern side of the coast. The aim is to ensure restoration of the town’s sandy beach. The construction of the 900 tonne reef, measuring 125x100 metres, began in May 2017.

Sanctuary Beach, a Singapore-based consultant with expertise in beach restoration across various countries, was selected for the nourishment plan for the promenade stretch starting from the northern side of the harbour.

The work to immerse the reef began at around 7.00 a.m. About 26 air bags were placed at the bottom of the massive structure to ensure that its nose did not hit the seabed. Three winches with multi-sleeve pulleys along with two fishing vessels were deployed off the coast to ensure the reef’s controlled movement into the sea.

Daunting task

The air bags, each 10 metres long, were designed to detach automatically from the reef and ensure that it had its own buoyancy in water. The structure was immersed at the designated location at 6.00 p.m.

According to a senior NIOT official, the reef will reduce wave activity and allow sand to freely move towards the north and prevent erosion along the coastline. About 70% of the sand will be bypassed to the north in the first year, followed by 100% from the next year. As per NIOT design, around 2 lakh cubic metres of sand has already been nourished, while about 3 lakh cubic metres of sand is still pending.

Now, the Puducherry government has to ensure that the accumulated sand from dredging is transported to the sand deficit zones to get the desired results. The construction of a seawall from the harbour’s northern side for 5 to 6 km had resulted in the loss of about 200 metres of the coastline’s sandy beach over the years.

“The role of the Puducherry government is to start bringing in the remaining sand required to start the nourishing process. The beach is not going to widen till the hole, created in the last 20 years due to the blockage of sand movement, gets filled. We hope that this is done soon so that we will have a beach in front of the town,” said Sunaina Mandeen, a member of the NGO, Pondy Citizen’s Action Network (PondyCAN).

Ms. Mandeen pointed out that the Puducherry harbour had been chiefly responsible for the coastline’s devastation going northward. Puducherry’s moral responsibility will only end when it has made sure that all the beaches are restored. The coastline’s realignment has to take place to ensure that the submerged sand flows northward and the beaches on the northern side get nourished. This whole exercise is a very major step in that process, she said.