Cyclone Michaung | Assessment of stormwater drains to be done post flood relief measures by Greater Chennai Corporation

December 07, 2023 12:42 am | Updated 12:29 pm IST - CHENNAI

People wading through flooded Chinthadripet  street on December 5, 2023. File

People wading through flooded Chinthadripet street on December 5, 2023. File | Photo Credit: R. Ragu

The assessment of areas lacking stormwater drains (SWD) and damages can be done after cyclone-related relief works across the city are over, said officials of Greater Chennai Corporation.

A resident of Kavankarai in Puzhal, under Zone 3, said several areas were inundated but the level was lower than in 2015.  On the other end of the city, in Injambakkam, under Zone 15, residents suffered waterlogging in their homes since the morning of December 4. The Zonal official said two motor pumps were used for clearing the stagnation, but the water kept flowing in from other areas beyond Greater Chennai Corporation limits.

4000-crore project
The plan
The Greater Chennai Corporation took up the integrated stormwater drain (ISWD) project for the length of 1069.40 km in areas covering the Kovalam and Kosasthalaiyar basins, including the Adyar-Cooum basin.
As per the City Disaster Management Plan of the Greater Chennai Corporation - drains in Adyar and Cooum basins, spanning a length of 406 km completed with funds from the World Bank fund under the Tamil Nadu Sustainable Urban Development Project (TNSUDP).
Meanwhile, in the Kovalam Basin to benefit the South region, a few components are yet to be taken up for a length of 360 Km, with funds under the German Development Bank (KfW), and work is in progress in Kosasthalaiyar Basin for 769 km funded under Asian Development Bank (ADB) for people in North region.

Joint Commissioner (Works) G.S Sameeran said it was too early to comment on the status of the SWD as the GCC is focusing on relief. “An assessment can be done of areas lacking stormwater drains (SWD) and damages after the relief work... We must also check the rainfall in nearby districts such as in Poondi and areas close to Chembarambakkam,” he said.

Greater Chennai Corporation Commissioner J. Radhakrishnan said, “The stormwater drain has a capacity. Existing drains can withstand normal and above average rains of roughly 10 cm spread over 48-72 hours and not the incessant 50-cm rainfall that was recorded in Perumbakkam, Sholinganallur, Royapuram.”

“It should also be noted that for the rainwater collected from 35,000 streets, there are only four outlets. If not for this infrastructure, 70-75 % of the water across the city could not have been drained,” he added.

“Discussion post and pre-rains were on infrastructure. We must look into non-infrastructural solutions as well. Stormwater drains should not be looked at in isolation. While desilting the drains, we receive huge amounts of sludge and garbage. As mentioned in our City Disaster Management Plan, there are very low-lying areas that are historic and traditional settlements close to water bodies. Naturally, water percolates through these areas. Drains can handle normal showers. Whereas, during high tide, disaster-level rains, become ‘recepticles’,” said the Commissioner.

He said: For example, in Royapuram, the side routes along M.C Road, and 10-12 interior roads were flooded till calf-level water, for which a super-sucker motor has been allotted. It is a very peculiar situation since it is very close to the sea. Actual specific reasons have to be identified.”

Watershed regions

According to him: the challenge was also with Manali and Sadayankuppam - waterlogging due to suplus from Poondi and Puzhal reservoirs. Most of these places are watershed areas, he noted.

“Ground Zero as far as flooding is concerned is Pallikaranai and Madipakkam, apart from a few parts of Besant Nagar,” Dr. Radhakrishnan said, adding that the reasons for the former two locations could be due to an overwash - i.e a spillover - in Pallikaranai and Narayanapuram lakes or if water breached from some areas - this can be checked up with the Public Works Department (PWD) only after rains fully subside.

“Except for such hardcore places, the rest are draining. Slowly canals have been getting water out. We can say rivers are receiving water, as we saw 100% stagnation during incessant rains. Stagnation SIDCO Nagar under Zone 8 has been draining well now. Challenging portions in Anna Nagar, Mogappair and in Teynampet - Avvai Shanmugam Salai, Musiri Shanmugam Salai, Parthasarathy streets, 12 of 14 streets near Venus Colony including Poes Garden, parts of Radhakrishnan Salai and T.T.K Road - draining is ongoing,” he added.

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