The Hindu 09.09.2009
New ‘sand vent’ coming up
S. Ganesan
| At Pulivalam to restrict flood discharges into city |
— PHOTO: R.M. RAJARATHINAM. 
PROJECT: Construction of the ‘sand vent’ under way near Tiruchi.
TIRUCHI: A new regulatory system being built near the inflow point of the Nangam Kattuvari along the Uyyakondan river at Pulivalam about 20 km from here is expected to restrict the surplus discharges from various drainage channels which often flood Tiruchi city during the monsoon.
The ‘sand vent,’ replacing a much smaller and ancient structure of the same kind, is one of the important components of the Rs.253-crore flood control project currently being executed by the Public Works Department. The project, apart from strengthening the bunds of the Cauvery and Coleroon in Tiruchi, Karur and Perambalur districts, also envisages improvements to the Uyyakondan and Kudamuritti rivers and other channels.
PWD officials point out that one of the major objectives of the project is to restrict the surplus flows from rivers, irrigation and drainage channels into Tiruchi city from far off places. Several drainage channels flowing down from Karur district join the Uyyakondan river at various places.
Through the construction of a bigger sand vent at Pulivalam, the surplus flow from the Nangam Kattuvari could be regulated and diverted through the Kodingal channel to restrict the water flow in the Uyyakondan river that runs across Tiruchi city, says K.K. Palanisamy, Executive Engineer, PWD, RC Division.
Apart from the Nangam Kattuvari, the surplus waters from a dozen drainage channels also flow into the Uyyakondan river. At times of floods, the drainage channels carry about 7,000 cusecs of water, sending the Uyyakondan river in spate.
A substantial portion of this flow would now be diverted through the Kodingal channel, which ultimately flows into the Cauvery near the confluence point of the Kudamuritti river along the Karur Highway at the entry point to Tiruchi city.
The old sand vent, built about 70 to 80 years ago, was too small to help effective regulation of the surplus flow. The shutters of the structure had also been damaged compounding to the problem.
The new structure with three vents (against the existing two) and shutters is being built at a cost of Rs.1.55 crore. The sand vent would also serve as a bridge for the locals to cross over the channel.
The foundation of the structure has already been raised and the sand vent would be fully completed well before the monsoon season next year.