The shoreline north of the Adyar river’s mouth, including near Srinivasapuram, is eroding with every passing year, according to a study on shoreline change analysis by IIT-Madras.
On an average, a two-km stretch of coastline, particularly near Srinivasapuram, is eroding at the rate of one to five metres every year.
The study had surveyed the extent of erosion between Chennai port and Palavakkam, for a distance of 15 km.
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Taking the shoreline during 1990 as the baseline for the study, the Department of Ocean Engineering, IIT-Madras, had observed the shoreline oscillation in 303 transects at an interval of 80 metres.
According to the study analysing data between 2000 and 2019, the sand, which is moving gets trapped near the Adyar river’s mouth. This has led to sand being eroded along the shoreline near Srinivasapuram. The Adyar river’s mouth is dynamic and the instability of the river mouth has resulted in the eroding coastline on the northside.
Moreover, the breakwater structure near the Cooum river mouth has helped sand accretion. On an average, the stretch near Marina beach experiences a sand accretion of up to 2.2 metres every year. Groynes constructed at the Cooum river mouth have helped in the formation of the beach. After Marina beach, the sand deposit rate reduces along the shoreline even near Mylapore.
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Dr. V. Sundar, Professor Emeritus, Department of Ocean Engineering, IIT Madras said, “We noticed that the erosion beyond Adyar river mouth is more between June and September. The maximum rate of coastline erosion was noticed up to 10 metres in a year a few times. The coastline has had a maximum of accretion of 5.35 metres per year.”
Cost-effective solution
Disposal of sand was also important along with the dredging of the Adyar river mouth.
Encroachment near the Adyar river was another issue. The study suggested that the dredged sand could be filled in geosynthetic materials and used in constructing a training wall into the river.
This could be a cost-effective solution.
A technical study must be done for the stretch between the Cooum and Adyar river mouths to find a suitable solution for coastline protection. Some of the solutions could be use of geosynthetic materials for constructing groyne fields like near Ennore, offshore detached breakwaters or submerged reefs, he said.