CHENNAI: The Adyar river mouth, a vital passage for the city’s floodwater to drain into the Bay of Bengal, is choked with lakhs of tonnes of silt deposits, putting the city at risk ahead of a monsoon that is only a few weeks away.
With the Water Resources Department (WRD) kicking off the annual flood mitigation work to tackle north-east monsoon, three earth-movers were seen in action on Friday, removing silt at the river mouth and Adyar creek. Locals told Express that work began about five days ago and had managed to create an opening of about 20 metres, allowing the Adyar river to flow into the sea. However, experts feel it is too late or rather symbolic.
The actual size of the river mouth is about 700 metres, which is choked now. “Going by the rate at which the work is being carried out, there is no way even a third of it can be opened. During the historic rain in 2015, the government deployed 32 earth-movers as water levels in upstream areas started rising due to blockage in the river mouth,” said A Kumar, local fisherman in Pattinampakkam.
There still remain two mountains of silt that piled up during the 2015 floods in the middle of the river mouth, but WRD officials claimed the mouth would be widened before the onset of the monsoon. “We will deploy more heavy machinery. Silt deposition is a natural phenomenon, and during monsoons, majority of it will be washed off by the strong currents. This year, we have started the work well in advance,” claimed an assistant executive engineer.
However, these last-minute efforts may not serve the purpose, opined experts. According to hydrologist J Saravanan, the river mouth should be kept open round the year. The flood-carrying capacity of the river is already limited and it is a disaster waiting to happen, he said.
“The authorities should scientifically study deposition in a year, the quantum of water flowing through the mouth and the silt to be dredged. There have been remarkable changes in rainfall distribution pattern, though the total rainfall figures have remained the same. Chennai, with its flat terrain unlike many other cities, is prone to flooding. We should have a strategic plan to mitigate the disaster, for which incorporating environmental aspects into city development plan is a must. But this unfortunately is not the case,” he said.
The unique properties of the estuarine ecosystem have been damaged by construction activities along the banks of the river, including high-rise apartments, a star hotel, and office complexes, alleged activist Jawaharlal Shanmugam.
Though rains were unprecedented in 2015, experts noted that the actual quantity of water released from the reservoirs was hardly unprecedented. Roughly every 10 years, Chennai has received high rainfall. In 1976, 28000 cubic feet per second (cusecs) water was released from Chembarambakkam into the Adyar river. In 1985, it was 63,000 cusecs. In 1996, the release from the three big reservoirs was 80000 cusecs — about the same as 2015. Even the most recent event — 2005 — witnessed a then record-breaking 40 cm of rainfall in a single day, with the Cooum taking 20,000 cusecs of flow and the Adyar 40,000.
“This is not unprecedented. It is just that we have systematically ignored the risk and prioritised real estate over sustainable development. It may not be possible to reset the clock to 1916, but having witnessed floods once every decade, it is time for us to insist that the city’s growth is planned systematically and scientifically, and that standards are not diluted in the name of profit and short-term growth,” said city-based historian TR Shashwath.