Erosion: eco-friendly approach only way out FOCUS

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DANGEROUS MARCH: Sea waves menacingly advance towards the coast in Visakhapatnam on Tuesday.
DANGEROUS MARCH: Sea waves menacingly advance towards the coast in Visakhapatnam on Tuesday.

Nivedita Ganguly

Areas opposite INS Kalinga and stretch along Naval Coastal Battery the worst hit

Lack of sedimentation is a primary reason for beach erosion

One possible solution is building offshore breakwaters to reduce wave energy

VISAKHAPATNAM: That coastal systems are among the most vulnerable due to rapid global warming is a well-known fact. The threat looms large over the Vizag coast with coastal erosion threatening to chew away the beach of the region with every passing year. While the effect of beach erosion may be gradual, at stake is far more than a movie mogul’s mansion. The impact can be felt more strongly this year. Over the past few days, the sea has gouged out a 75-metre section of the R.K. Beach, blowing off three lamp posts.

Though the impact of the waves on the coast is more pronounced during the monsoon and high tide period, erosion occurs due to several important factors. Lack of sedimentation is one of the primary reasons responsible for beach erosion. While there are several governing factors for beach erosion, construction of structures on the beach, protruding hills and creeks act as barriers in the process of sedimentation eventually leading to erosion.

Scientists have been tirelessly campaigning at global fora for urgent steps to deal with the problem lest the coastal regions should be submerged forever. An extensive research done by scientists at National Institute of Oceanography (NIO) reveals the growing intensity of the process in the Southeast coast and the impending danger of the beach vanishing. Erosion and accretion trends for the entire coastal tract were studied. “The worst affected parts due to beach erosion in the Vizag coast are the parts opposite INS Kalinga at Bheemunipatnam, the stretch of beach near the Kursura Museum, the area opposite Hotel Taj and along the Naval Coastal Battery,” observed N.S.N. Raju, technical officer at the NIO who has been studying the phenomenon for the past few years. Similar studies conducted all along Southeast coast in several places of Karnataka, Tamil Nadu, Orissa, Kerala and Goa have revealed threatening consequences of beach erosion. Scientists have pointed out large-scale erosion of the nesting beaches of the Olive Ridley turtles along the famous Gahirmatha coast in Orissa.

While any coastal system is extremely dynamic and the process of erosion and beach formation is a continuous one, the scale of the erosion is reported to have been unprecedented in the last 18-odd months.

Tropical storms

According to reports, the intensity and frequency of tropical storms in the Bay of Bengal will increase in the post monsoon period as will the flooding in low-lying areas. While coastal agriculture will be largely affected, a 100-cm sea level rise could cost India a whopping US $ 1,259 million.

Oceanographic data collected by the Geological Survey of India reveals that a sea level rise by 7.5 metres in the next 50 years is envisaged. A 30 cm rise in the sea level would push the saline incursion in the major river courses by nearly 4 km. upstream of the sea.

A cost-effective and environment-friendly technology to prevent the erosion and promote beach nourishment for multifarious benefits is the need of the hour, said Mr. Raju. The study conducted by NIO has proposed a precautionary approach to check erosion.

“Sea walls prevent the landward migration of the beach. Wave energy would be dissipated over the region,” he pointed out. Building a rock wall perpendicular to the beach - a groin - would gather sand on the updrift side of the wall.

The structure slows down the long-shore currents that carry sand.

The result is that sand is deposited on the updrift side, depriving the downdrift side of sand.

Another possible solution is building offshore breakwaters to reduce wave energy before it reaches the beach. Breakwaters are long heaps of rocks dumped parallel to the shore to intercept waves.

He says that developing green vegetation of horseshoe creepers, casuarina plantation and other salt tolerant varieties is one of the ways of arresting beach erosion.

They do not allow penetration of sunlight and also prevent drifting of sand.



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