The State government is contemplating two options – the formation of a “cut and cover” channel from Pallikaranai marshland to the sea and regular dredging of the marsh – to address the problem of flooding in Velachery and the southern outskirts of the city.
The first option was mooted nearly 20 years ago and dropped in October 2014. While the second is also nothing new, authorities would like to tread their path carefully in view of possible objections from green activists.
Last week’s torrential rain caused by Cyclone Michaung left Velachery and the city’s southern suburbs flooded. Also called “straight cut”, the cut and cover” channel was to complement the existing arrangement of water draining from the marsh into Muttukadu backwaters through South Buckingham Canal and Okkiyam Maduvu. Its carrying capacity was to be 3,500 cubic feet per second (cusecs).
When the idea was mooted during the 2005 flood, the cost was estimated at ₹63 crore, including ₹30 crore for land acquisition, said a report published by The Hindu on November 8, 2006. Eventually, the cost was revised as ₹131.9 crore four years later. In 2012, the Water Resources Department (WRD) proposed to drop the work as the alignment would pass through a private resort-cum-amusement park, and this would increase the land acquisition cost to ₹100 crore.
In October 2014, the State government agreed with the proposal and scrapped the project, according to the Comptroller and Auditor General’s (CAG) report of 2017 on the flood of 2015. The CAG had even pulled up the government for “lack of seriousness” in fulfilling the objective of providing a permanent solution to the inundation problems of thickly populated Velachery.
However, about 10 years ago, improvements were made to the South Buckingham Canal from Okkiyum Maduvu to Muttukadu backwaters to carry 9,000 cusecs, a fact that had been acknowledged by the CAG. Last week, a maximum of 11,000 cusecs would have flown through the marsh. The proposed “cut and cover” channel can carry at least 4,500-5,000 cusecs, says a senior official.
As for the other option, the State government, in September 2021, gave an undertaking before the Madras High Court that no dredging work would be undertaken in future, except when such a necessity arises out of removal of encroachments from the waterbody. This was in response to a public interest litigation petition filed by an environmental activist. At that time, the government also told the court that the removal of silt from the Pallikaranai marshland was done in the past, “after obtaining expert advice, only to maintain better water level in the wetland.”
The official says the accumulation of silt and semi-solid substance in the marsh has reduced the capacity of the wetland to absorb floodwater, which comes from about 30 tanks in and around the city. The government is keen on ensuring that the ecosystem of the marsh does not get disturbed even as it plans to undertake dredging, which is for the purpose of providing relief to people in Velachery and surrounding areas, the official adds.
