Tamil Nadu - Chennai

Much water has not flowed under the bridge

WATERY CURSE: (From left) These pictures recapture how Madipakkam reeled under the groundswell of water, buffeted by the monsoon’s furious onslaughts in 2002, ’05 and ’08.

CHENNAI: In 2005, after heavy rain, the Virgumbakkam canal overflowed and the 100 feet wide Jawaharlal Nehru (Inner Ring) Road was cut off. This time after the rain, the same canal overflowed and the same section of road was shut down for a few days. Suburbs such as Madipakkam too get inundated year after year after a heavy spell of rain.

Desilting of canals, removal of encroachments and cleaning of riverbeds are regular post-monsoon activities in the city. None of this will help unless a long-term comprehensive drainage plan is implemented for the city and its suburbs.

The city of Chennai is a relatively flat site and depends on natural waterbodies for draining rainwater. The Cooum river, the Adyar river, Buckingham Canal and various open channels and waterbodies save the city from flooding.

The challenge for the Chennai Corporation is to drain the surface water from the 2,870-km length of the streets within city to these waterbodies.

At the moment there are only 881 km of roadside service drains.

The water in the other areas has to depend on the surface runoff along the contours.

Continuous re-laying of roads and construction of bridges have damaged the natural contours that facilitate the flow. Corporation sources explained that the West Mambalam area is often flooded because a culvert that drains the water flowing along the natural slope from this area towards Usman Road has been blocked.

The Chennai Corporation needs to now develop a series of drains parallel to the railway track to drain the water. Similarly, areas beneath the recently built flyovers in T.Nagar have no drainage facility and lead to flooding of junctions.

Corporation Commissioner Rajesh Lakhoni said the civic body has appointed a consultant to come out with a master plan for city drainage.

Government sources told The Hindu that about Rs.600 crore would be spent to improve the drainage network. However, it is learnt that the proposed plan overlooks the contours of the city surface and is, instead, based on the levels taken on the existing roads.

This does not reflect the true lay of the land and such levels will continue to alter as the roads are re-laid and houses raise their site levels. The contour mapping of the city at a 30-50 cm interval is currently under way and the results have to be incorporated in the plan, says the government source.

The situation in the suburbs is worse than the city. The Veerangal Odai that connects the Adambakkam Lake with Pallikaranai marsh ends abruptly after 550 m from its origin and the remaining part is missing. This causes inundation in places such as Puzhithivakkam, Madipakkam and AGS Colony.

The Thoraipakkam and Perungudi areas face prolonged inundation because the proposal for a new canal from Okkiyam Maduvu to the sea has been delayed for many years. When contacted, PWD officials said that a consultant has been appointed and a detailed proposal for the straight cut canal would be ready soon. Land has been obtained from the Highways Department to re-lay the Veerangal Odai, they added. At the moment there is no plan to evolve a comprehensive stormwater drainage plan in any of the municipalities in the suburbs. Senior CMDA officials said the second Master Plan had identified these issues but they could not take up projects as the local bodies were in charge of implementation. However, they would be willing to draw up a comprehensive plan, if requested, said an official. Even if the local bodies desire to take up the stormwater drainage plan, the proliferating violation of layout rules leading to narrow roads would hamper construction of stormwater drains. In addition, many layouts that have come up on the agricultural lands have filled all the natural valley lines necessary for draining the runoff. The planners explained that a proper contour survey of the suburbs must have preceded layout and infrastructure such as roads and drains developed parallel to the natural valley points. The ad-hoc and unplanned growth of suburbs will only perpetuate the problem. After a few years the situation will worsen and an extensive and expensive reengineering would be required to correct the situation.

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