Flood risks likely to reduce as mitigation works near completion

The long-pending issue of inadequate drain networks and culverts across arterial roads and rail tracks is likely to be resolved this year in several areas of the city as the Greater Chennai Corporation and other agencies are set to complete the construction soon.

Residents have been complaining for the past 10 years about flooding near the Police Commissioner Office on E.V.K. Sampath Salai at Vepery. “The culvert across the rail tracks near the Egmore railway station to drain water in the Cooum will be completed next week. This will prevent waterlogging on E.V.K. Sampath Salai and in the other areas of Vepery,” says an official of the Corporation.

Similarly, the construction of a push-through culvert at Ganeshapuram, which was delayed for several years, is expected to be completed soon. The work on the drain across the arterial Poonamallee High Road, near Barnaby Road, has been completed. Another drain has been constructed across Anna Salai to prevent flooding on General Patters Road.

In 2021, the Corporation shared a list of 25 locations with the Railways, where culverts must be built to prevent flooding of major residential areas near the rail lines. The work was delayed for more than three years in several areas. It is expected to be completed ahead of the onset of the northeast monsoon this year. Similarly, 27 locations in various parts of the city and the suburbs have been identified for construction of culverts by the Highways Department and other agencies. Some of the residential areas along Poonamallee High Road, Grand Southern Trunk Road, Grand Northern Trunk Road, and Outer Ring Road are yet to get the infrastructure for flood mitigation.

V. Rajasekaran, president, Federation of Varadharajapuram Welfare Associations, says Outer Ring Road from Vandalur to Minjur has become a barrier to the flow of floodwaters in their residential area. “After the 2015 floods, we demanded better culverts, storm water drains, and a wider bridge across the Adyar. Outer Ring Road still remains a barrier to the flow of floodwaters. Culverts have been closed at five or six locations from Muduchur junction to Kishkintha. The government should acquire 10 feet of land along Outer Ring Road on the left side from Vandalur to Minjur to prevent damage to culverts. The culverts have been closed for the construction of private buildings. The road has a 50-metre-wide piece of land on the opposite side. The width of the Adyar has reduced from 150 metres to 50 metres because of the Outer Ring Road bridge. We need a wider bridge,” he says.

At the zonal committee meeting held last week in the Ambattur zone, councillors flagged flood risks in the area ahead of the northeast monsoon. AIADMK councillor J. John said the 30-feet canal from the zero point in the Ambattur Lake narrows to five feet when it crosses the 100-Feet Road from Padi Flyover to Retteri near Wheels India. “The water from the Ambattur Lake to the Korattur Lake gets diverted to other residential areas because the culvert is narrow,” he said.

K. Kumar, former Chief Planner, Chennai Metropolitan Development Authority, says the absence of drainage systems that conform to the natural contours of Chennai has exacerbated flooding, especially during the monsoon. “When the CMDA was located on E.V.K. Sampath Salai between 1977 and 1988, the road used to be a decent one without flooding. I used to ride a bicycle from Perambur to the CMDA office on E.V.K. Sampath Road between 1977 and 1980. Perambur Barracks Road used to flood during the monsoon. The city’s flat terrain, combined with rapid urbanisation and inadequate storm water management, has led to significant water stagnation and flooding, especially in low-level areas,” he says.

“Many storm water drains in Chennai are not designed with appropriate gradients, causing water to stagnate rather than flow efficiently towards canals or the sea. This issue is compounded by blockages from debris and garbage, which can reverse the flow of water. The consequences are disastrous for traffic circulation, resulting in a multi-lane road operating with the capacity of a single-lane road. There are significant gaps in the connectivity between storm water drains and larger canals. This disconnect prevents effective drainage of rainwater, causing localised flooding when heavy rain occurs,” he says.

Stressing the need for a study of flooding in roads such as E.V.K. Sampath Salai, Mr. Kumar says, “Either a disconnect between the storm water drain and the larger canals or the changing urban fabric has severed the connection. The Corporation is working to address the missing links in the drainage network. But if the Corporation has drawn up a master drainage network plan conforming to the lie of the terrain is the moot question. If such a network is in place, the city might not be plagued by frequent flooding. Given to understand that the government of Tamil Nadu has made available to the Corporation the contour details at closer intervals through the Institute of Remote Sensing, Anna University, 10 to 15 years ago. The mixing of sewage in storm water drains further complicates drainage issues, as clogged drains can lead to health hazards and environmental degradation. Efforts to identify and penalise illegal sewage connections have been going on, but challenges remain,” he says.

“Culverts play a crucial role in drainage networks by facilitating the flow of water beneath obstacles such as roads, railways, and other infrastructure. They are essential for effective storm water management, particularly in urban areas where impervious surfaces increase the run-off. Culverts channel the surface run-off from one side of an obstruction to the other, preventing water from pooling on roadways and reducing the risk of flooding and erosion. By allowing water to flow freely, culverts help mitigate flood risks during heavy rainfall or storms, safeguarding infrastructure and ensuring public safety. Thus, culverts are pivotal in flood mitigation. Chennai needs to combat these challenges by implementing scientifically designed drainage systems that conform to the city’s contours, ensuring effective water flow and minimising stagnation, improving the integration of storm water drains with the canals to facilitate better drainage and prevent flooding, and conducting routine desilting and maintenance of drains and canals to ensure that they remain functional and free of blockages,” Mr. Kumar says.

Published - September 15, 2024 11:24 pm IST