Shifting sands

An interesting article on the beaches of India getting affected by climate change -

As a student in the '60s, Satish Shetye recalls sprinting down sandy, golden stretches on Miramar with his friends. In about 20 seconds , they would Until the construction of a port in the erstwhile Madras Presidency, the stretch of sand that ringed the city was narrow. It was a large breakwater that hastened the change cover the distance from the road to the point where the waves would begin licking their feet. Today, even Usain Bolt would find it difficult to get to the shoreline that fast - because Miramar beach, part of the Aguada Bay, has grown more than three times in breadth over the last four decades.

According to Shetye, who's now head of the National Institute of Oceanography in Goa, the Miramar stretch, now growing by more than one metre every year - a tad slower than it used to - is but one of many Indian beaches which are either expanding or shrinking at a discernible rate. The Marina in Chennai, for instance, was spreading at an astonishing 20 metres a year in the 1940s, but it has now stabilised at an accretion level of about two metres per annum.

In many places, the change has altered the landscape. The Pondicherry beach is almost gone; Pavin Kurve in Karnataka is fast disappearing; and Bandra in Mumbai is believed to have been a beach that has shrunk over the years into a rocky shoreline. At times the rate of accretion or erosion can be so rapid that your favourite vacation spot may not look the same after a couple of decades.

Experts agree that a combination of natural and manmade factors is redrawing the country's 7,517-km coastline. Sediment transport along the coast may be the primary reason for the change, but a lot more remains to be understood . "It is a chaotic process," says Shetye. "Some beaches grow, some shrink, some others grow and shrink alternately. The reasons are waves, tides, currents, winds and a lot more we don't know about. We need a comprehensive study by experts from different streams to understand the process better."

India made a beginning in this direction in 2002, when the Chennai-based Integrated Coastal and Marine Area Management (ICMAM) project directorate roped in several institutes to begin studies . The initial results now trickling in indicate damage due to an element of human intervention. "Results of three studies conducted in Kayankulam in Kerala, Ullal near Mangalore and Ennore near Chennai show manmade structures have caused erosion," says ICMAM project director B R Balasubramanian. Groynes to arrest erosion on a stretch of Kayankulam beach and the construction of a jetty in Ullal caused partial submergence of land at other spots.

On the flip side is the expansion of stretches like the Marina, already one of the biggest beaches in the world, with a width of 500 metres at some points. S A Sannasiraj, scientist at the department of ocean engineering, IITMadras , says the Marina's unceasing growth can be attributed to sediments transported by currents along the Bay of Bengal from south to north and deposited at Chennai due to development on the coastline.

This growth, according to scientists, may have been triggered by the construction of a 1,100-ft pier in 1861. As the pier expanded into a port with quays added through the early 1900s, it coincided with an increase in accretion on the beach. "In the 1940s, when the length of the breakwater was increased for the creation of the inner harbour, the Marina grew exponentially, up to 20 metres a year. It could have been almost a visible growth," says Sannasiraj who predicts that the beach would continue to grow for another 50 years at a rate of two metres per year.

Sannasiraj, however, says beaches like Miramar and Marina are not on an unbroken path of expansion. "In fact, both accretion and erosion happen to the same beach within a year. We should calculate the results at the end of the year. For example, along the Marina, sediment moves northwards during the south-west monsoon and southwards during the north-east monsoon. With the northward movement much more predominant than the other, the net result is that the sediments get deposited on the shore, resulting in the growth of the beach," says the scientist.

Part of the process by which the sea shapes the land is also determined by the flow of rivers that empty into it. According to NIO scientist Sanil Kumar, pollution can alter the amount of sediment deposited at the mouth of a river. "When the river discharge changes due to urban interference, and the river deposits fewer sediments, the sea tries to make up for the loss, taking away sediments from the beach," says Kumar, referring to a study done at the mouth of Sharavati river in Karnataka. 'Urban interference' here could be construction of dams upstream, dumping of garbage, or construction of sea walls.

Scientists say such accretion and erosion along the east coast of India is easier to study than those on the west coast. "This is because 'longshore' currents on the east coast are fairly clear to us, but the west coast presents a mixed trend with different observations at different locations," says Balasubramanian , adding that a proposal is under consideration of the ministry of water resources to take up comprehensive studies based on real time observations and mathematical predictions.

But that's easier said than done, for Indian research institutes face a shortage of quality scientists. "We need an interdisciplinary study involving institutes and scientists dealing with geology, oceanography, ocean engineering, physical oceanography for this. But where are the scientists? Young and bright scientists ask what their prospects would be after they complete such a study," sighs Shetye. We need to find answers - as much to address the scientist's concern as to explain nature's wonders.

LIFE IS A BEACH

Expanding...

MIRAMAR:

Part of the Aguada bay and located within Panaji city, it has widened more than three times over the last four decades. Civic authorities have tried to use some form of fencing to keep sand from being thrown up on to the road adjoining the sea

MARINA:

Was spreading at an astonishing 20 metres a year in the 1940s when the adjoining port was being expanded. Construction of a breakwater is said to have caused changes in the pattern of sediment deposits along the Chennai coast. It is now growing at a slower rate of two metres per annum

Shrinking...

BANDRA:

Once dotted with fishing villages and small sandy stretches, Bandra's shoreline has changed completely in the last 50 years. The sea has advanced closer and sand deposition is less. Intensive development along the Mumbai coastline, especially around Mahim creek, is said to have altered tidal patterns

PONDICHERRY:

The entire stretch of the beach within the erstwhile colonial enclave has disappeared. The erosion, estimated to the extent of 100 metres, is attributed to the construction of a minor fishing harbour on the southern end. It is said to have blocked the process by which sand gets deposited.

By Arun Ram, TOI Link -
http://timesofindia.indiatimes.com/h...ow/5329819.cms

Interesting article...