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December 2005

 

Beach erosion at Quiet

- Carel

The beach in front of Quiet, the Auroville Healing Centre, is under imminent threat of being eroded. Auroville Today reported on the problem in November 2002. The situation has worsened since.

 

 

The problem of coastal erosion originated in 1986, when the Government of Pondicherry gave the green light to develop a new harbour at the mouth of the Ariyankuppam Estuary, south of Pondicherry.
Satellite photo of the Pondicherry coastline showing the breakwater and the enlarged beach south of itAs part of the New Harbour , two long breakwaters – rocky wall-like structures that protrude from the shore into the sea – were built. These breakwaters interfere with the coastal currents and processes. As a result, a very significant process of coastal erosion was triggered off. It started south of Pondicherry , from the mouth of the New Harbour , and gradually advanced north. Every year another large chunk of beach is lost to the sea. In little more than a decade, all six kilometres of the beach of Pondicherry town disappeared. Now a rocky seawall extends all the way from Ariyankuppam from the south of Pondicherry to Kottakuppam in the North. In 2002, the coastal village of Kottakuppam between Auroville and Pondicherry saw the erosion of a huge part of its beach and hundreds of fishermen lost their homes. Today, the problem has moved further north and is now threatening the Quiet beach and other beaches further north.

In fact, the beach erosion in front of Auroville's communities has already started. In the last decade, the beaches have changed considerably. There used to be a sandbar, a so-called “underwater island,” about 15-30 meters away from the shore. It no longer exists. The beach itself has become more and more steep. The beach sand is now coarse as the finer grains have been gradually washed away while the heavier and larger particles have been left behind. These are the first symptoms of beach erosion.
The dramatic encroachment of the sea into fishermen settlements Now the beaches have started to recede. And this will go from bad to worse as long as the problem caused by the New Harbour breakwaters is not corrected.

Dutch expert Jeen Kootstra judges that the erosion process will not stop unless proper measures are taken. The best course would be if the Pondicherry Government could be convinced to rectify its breakwaters. But it does not appear to be interested in taking this initiative. Instead, anti-erosion measures have been taken that, Kootstra believes, will soon be useless. One make-shift solution is poles that are tied together, with bags filled with sand behind it (see photo). Kootstra believes that this structure will hold initially, but that the waves will soon undercut the poles and then the whole structure will be washed away. He believes that another solution, to create barriers of trunks of Palmyra trees parallel to the beach, will not be very efficient either.
The Dutch solution: rows of long poles  staked perpendicular to the coast Instead, Kootstra proposes the Dutch and time-tested solution of installing rows of 6 m long poles, 4 m into the sand and 2 m above the beach, perpendicular to the coast to prevent longshore drift and sand transport. (see photo) At the upstream end, sand will be deposited and at the downstream end, sand will be eroded. Of course, this solution implies that the erosion will start further downstream, and this will necessitate the placement of subsequent lines of poles.

A better but more costly solution would be the construction of groynes, small rock-filled dams, also perpendicular to the coast. A last, but even costlier option, is to construct groynes in the sea parallel to the beach at about 150 m distance. On the lee side of the groynes, sand will be deposited. In between the groynes, the water will get deeper. It would result in a pleasant coastal morphology, but due to the large amount of material required to be deposited in the sea, the expense would be considerable. These measures proposed are based on general engineering judgement and one afternoon visit. Precise dimensions and cost will have to be worked out in a beach erosion study based on data on wind, waves and current.

A make-shift solution: poles tied together, with bags filled with sand behind itThe beaches in India belong to the Government, so any solution for the Auroville beaches will need the involvement of the Governments of Tamil Nadu and Pondicherry . The Auroville Working Committee has informed the Governing Board of the Auroville Foundation of the seriousness of the matter and has requested it to contact the concerned authorities for a solution.


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