Tamil Nadu's beautiful long sandy beaches are a beloved treasure. Not only do these beaches provide recreational spaces for the public, but are also a resting space for migratory birds, and nesting spaces for turtles and protect coastal areas from natural calamities. But the 1,076 kilometre coastline is under threat.

According to the latest shoreline changes assessment report, about 42.7 per cent, that is 422 kilomteres of Tamil Nadu's coastline is eroding. Experts say that these alarming statistics are a result of man-made structures like groynes, seawalls and breakwaters, apart from a large number of ports and harbours across the coastline.

The study, conducted by the National Centre for Coastal Research (NCCR) also revealed that Tamil Nadu ranked fourth in coastal erosion, just behind West Bengal, Puducherry and Kerala, which means that erosion is happening across the country's coastline at an alarming rate.

So what is erosion and how does it happen? Probir Banerjee, founder of PondyCAN (Pondy Citizen's Action Network), a non-governmental organisation that has been trying to restore Puducherry's beaches, says that to understand erosion, we must first understand how beaches are formed. Most of India's beaches are formed by sand that is transported from the inland through rivers.

About one billion tonnes of sand is transported every year along the Indian coastlines. However, the sand doesn't stay in one place. It continues to move along the coast, depending on the wave action, a process called longshore drift.

As long as the sand is moving and distributed evenly, it protects coastal areas from natural calamities. But over the years, due to construction activities on the beach, the sand has been eroding. “Sand is constantly moving, but if you put up any structure, it will block the movement of sand on the southern side, while the sand on the northern side of the structure will continue to move. This will result in a vacuum and the sea water will come in,” explained Probir.

Puducherry beach is a classic example of erosion due to man made structures. In order to build the fishing harbour in 1986, two breakwaters were constructed. Breakwaters are long strips of boulders jutting out into the sea to protect the ships from the mighty waves.

As a result, sand started accumulating on the southern side.

Meanwhile, the northern side continued to experience longshore drift but without sand to replace it. Over the years, the northern side started eroding. Similarly, sandbars are a small island formed further off into the shore, where the waves break and slowly come to the shore. But when erosion happens, that sand bar is gone. The waves then hit the rocks hard and pull the sand from below when it goes back.

Ironically, the solution that most coastal dwellers and authorities jump to is also the cause of the problem. When a particular village or area is facing erosion and wants to protect themselves, they immediately resort to placing sea walls or groynes. But the moment they do that, they are simply passing on the problem to their neighbours and destroying the entire ecosystem.

Probir explains, "When the sea walls go down, you've to keep placing rocks. it makes a deeper and deeper hole outside the wall. As a result, there's a huge crevice. What the beach needs is sand, as long as it has sand, it is healthy. The moment you deprive it of sand, there is a problem. That is erosion."

He added, "In Puducherry, we had an National Green Tribunal order that these structures shouldn't be built and that a proper shoreline management plan should be in place. But no one has done anything about it. When we were in Pillaichavady, we had a meeting in Auroville about the restoration project. Houses were collapsing and the community wanted to put up some walls. But the people in Kalapet were protesting against it because if they built walls in Pillaichavady, Kalapet would suffer.

"The problem is that the government will wait till the houses are collapsing and then as emergency measures, they will put up some walls and that will cause problems in the next area," he added.

So what is the solution? According to Ramanthan V, Group Head, Coastal Processes & Shoreline Management, "Coastal engineers suggest hybrid solutions, a combination of soft and hard structures."

PondyCAN has shown the rest of the country a successful approach in preventing erosion by using soft structures or natural structures. Instead of hard structures like sea walls, Probir and his team set up a submerged reef which will arrest the sand. This reef allows just as much sand as required, after which it will spill over and go to the next stretch.

In case of groynes and seawalls, it goes two-three metres above the water level. So even if you have the required quantity of sand, it cannot jump over the groyne and go to the other side. In contrast, a submerged reef allows only whatever sand is required. The whole idea of nature based solutions is sand nourishment. Tamil Nadu-based environmentalist Jayshree suggested that marine plantation is another alternative solution that could prevent erosion.

Erosion affects the entire ecosystem: the village, beach, sea, lugworms in the sea, the small and bigger fish. When erosion happens, there are no lugworms and the entire chain disappears. “People don't understand the ecosystem, they just want to protect their house. The fact that you are destroying the entire ecosystem is not their concern,” said Probir.It also has other environmental impacts. For instance, mountains are continuously blasted to get rocks.

So if there are alternate natural solutions that are safer, why then are fishing communities and authorities resorting to hard structures? One reason is the lack of awareness about its multi-fold impact. The Tamil Nadu coastline is prone to natural disasters like Tsunamis and fishing communities have suffered over the years due to its impact.

They have been demanding that sea walls or groynes be put up to protect their ships and their houses. In some cases, the communities have started building walls themselves. This is because people are panicking and want immediate solutions.

The other reason, according to Probir, is that, "It's a big money making racket. Why would authorities put sand when they can put rocks? There's a lot of vested interests. We have had several workshops with fishermen. They were all initially demanding walls. I posed the question ‘do you want a beach or a wall?’ and they said beach. The beach was their home, a part of their life. But who will give them the beach? The government would say why should we do dredging?

“If we put sand, the sand will move, we have to do it again. But they don't realise that if they put up structures, it will trigger erosion, and until they remove it, they will have to keep doing it artificially. That needs a lot of money too."

According to Jayashree, "Intense development and manipulating the terrain is the problem. There's no plan whatsoever. If you take Chennai, the problem is we don't treat it like a coastal city. Chennai's coast is not limited to the 500m high tide line. We treat it as a flat city, that's how the planning is. We forget that we have a fragile vulnerable coastline which can spill from 500 m to 13 kilometres inland. We plan all our development as if that doesn't exist. That's a lot of pressure on the coast.

"I'm not convinced that groynes help against disasters. We also need to ensure that the coast is open only to the fishing community. Everything else needs to be removed."

According to the NCCR report, "Tamil Nadu has three major ports, seven government captive ports, 16 minor ports, more than 20 fishing harbours and several coastal industries like nuclear and thermal power plants." All these activities have put tremendous pressure on the coast as well."

While fishermen across the coast have been demanding sea walls and other structures to protect themselves, environmental activists are saying providing natural solutions, creating awareness about it and preventing any further man-made structures are the need of the hour. Let the sand move.