CHENNAI: Several areas in Manali and Madhavaram in North Chennai have been under water since Saturday morning as the water resources department (WRD), in an attempt lower storage levels ahead of the anticipated rains, opened sluice gates the Puzhal and Poondi reservoirs on Dec 12, releasing water at 1,000 cusecs and 12,000 cusecs. However, civic negligence including delays in stormwater drain projects and failure to build bunds along surplus channels has worsened flooding.
The 13.5-km-long surplus channel from Puzhal, which is 70 metres wide in most parts, is designed to carry excess water to the Kosasthalaiyar River in Manali, but a 1.5 km stretch near Sadayankuppam village lacks boundary walls, leading to ankle- to knee-deep flooding in Manali and nearby areas that house more than 5,000 families. This was flagged last year by a central govt team. “WRD has not built the walls for over a year. If these areas flood with an inflow at just 1,000 cusecs, the damage will be worse during heavy rains,” said A V Arumugam, zonal chairman, Manali, Greater Chennai Corporation (GCC).
Compounding the problem is the Kosasthalaiyar River, into which water at 12,000 cusecs is flowing from the Poondi reservoir. This has caused heavy inundation at the confluence point in Manali, where the Puzhal surplus meets the river.Kosasthalaiyar’s capacity is 30,000 cusecs but WRD has only opened 12,500 cusecs from Poondi which is less than half the river’s carrying capacity. Yet, areas like MFL in Manali flooded due to bund breaches.
Further bottlenecks occur in locations such as MFL and Sadayankuppam, where the surplus channel, with an inflow capacity of 12,500 cusecs, narrows to just 20m in width.
In Madhavaram, the WRD has delayed constructing a 2 km long, 3-metre-wide channel from Retteri Lake to the Puzhal surplus. “Water flows through a chain of lakes from Avadi, Ambattur, Korattur, and Retteri, but there is no link from Retteri to the Kosasthalaiyar. This leaves Madhavaram neighbourhoods in between flooded,” said Gowri Shankar, WRD assistant engineer. The ₹750 crore project, which requires land acquisition, has been awaiting government approval for months.
Besides, WRD is conducting a study to implement an alternative drainage mechanism at Manali. The existing Puzhal surplus channel is 1.5 metqres below the sea level at Manali, allowing Kosasthalaiyar backwaters to push water back into the channel, worsening the flooding.
