Experts noted that it was imperative to clear silt from the river mouth to maintain its ecology. M.V. Ramanamurthy, Director, National Centre for Coastal Research, said dredging the river mouth between June and September was essential for smooth tidal exchange and better water quality. Littoral drift pattern along the coast caused siltation and closure of the mouth, he said.
The department had cleared nearly two lakh cubic metres of silt and dumped them for nourishment on the beach of northern side near Srinivasapuram last year.
Officials of the WRD said the exercise would mean spending around ₹11 crore every year. However, they added, silt blockage occurred rapidly after the exercise and the department was looking to address the issue.
Sources in the NIOT said they had considered all alternatives and found dredging the river mouth between June and September to be the best and most sustainable option. Physical interventions such as training walls along the waterways would not resolve the issue of siltation. Other measures may lead to erosion in other areas. NIOT had made site-specific solutions to dredge the Adyar river mouth and nourish eroded coastline on the northern side.
Meanwhile, residents said water hyacinth disrupting the water flow had also turned the stretch of the river near Lock Street into a mosquito breeding ground since January.
Krishna Mohan, member of Madras Boat Club, said the aquatic weeds choking the river would be a safety hazard for children taking part in the summer rowing camp. Though the trash booms installed in some parts were effective in preventing the weeds and garbage from floating down the river, the structures, which were moved aside during the monsoon, were not restored.
WRD officials said the river was cleared of floating waste and hyacinth before the onset of Northeast monsoon to ensure free flow of floodwater. The Greater Chennai Corporation was also engaged in clearing hyacinth.
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