The disaster management advisory panel, constituted by the Coimbatore City Municipal Corporation to recommend steps to prevent waterlogging in six major underpasses, submitted its report on Thursday.
The panel studied six underpasses - Saibaba temple ARC railway underpass, Kikani school railway underpass, Avinashi road flyover, Lanka Corner, Nirmala college road, Kaleeswara Mill railway underpass- in the city.
The panel has suggested reducing storage in Valankulam to ease water flow from the underpasses on Avinashi road and Lanka corner. The Avinashi road flyover underpass gets flooded during heavy rains and its maximum water level reaches 3 m to 3.5 m. The approximate volume of water accumulated during rain is around 60 - 70 lakh litres and it crosses one lakh LPM within an hour as flow from the nearby catchment area of 3 sq km.
The level difference between the lowest point of this underpass and Valankulam is only 2.6 m for a distance of 1500m. A slope that can be achieved is 1:600 only and it is not possible to drain the water by gravity, the panel observed. Bringing down the Full Reservoir Level of Valankulam by reducing the bottom outlet pipe of the Valankulam at Sungam junction, can achieve a slope of 1:400 and water will drain naturally. (Gradient slope ratio 1:400 means if the run length is 400 meters, the way would has to raise the length of 1 meter. Adjusting gradient ratio helps water flow).
To reduce waterlogging under the Avinashi road flyover, the panel has suggested maintaining the level of Valankulam 0.6 metres less which could help water from the underpass in Lanka corner to drain into the lake. Another option suggested is constructing a sump of 20 lakh litres capacity in addition to the existing sump could give a better solution, according to the report.
The panel has also suggested the construction of a drain channel in the ARC underpass and on Nirmala college road.