Chennai: The flooding of Chennai city was not due to official indecision or mismanagement of release of water from the Chembarambakkam lake into the Adyar river, Tamil Nadu chief secretary K. Gnanadesikan said on Sunday.
In a statement issued here, Gnanadesikan said the flooding was caused primarily due to the very high rainfall in November, which was followed by more rain in Chennai, Kanchipuram and Tiruvallur districts on December 1.
Referring to media reports that the recent flooding of the Adyar river that killed many people and destroyed livelihood and assets of millions of people was the result of improper management of water releases from the Chembarambakkam lake.
Gnanadesikan said the India Meteorological Department (IMD) on November 30 and December 1 had issued advisories of isolated heavy rainfall and not 50 cm rainfall as reported by some media groups.
Gnanadesikan said that in meteorological terminology, ‘isolated’ means only in one or two places, heavy rainfall is between 6.4 cm to 12.4 cm, while very heavy rain means 12.4 cm to 24.4 cm.
He dismissed as “malicious” and “canards” the allegations that engineers present at the Chembarambakkam lake were waiting for instructions from the principal secretary of the Public Works Department and the chief secretary and the imputation that the officers were awaiting clearance from Chief Minister J. Jayalalithaa.
Gnanadesikan said the allegations were not supported by the water release data of the reservoir.
According to Gnanadesikan, as per the rules for flood regulation of the compendium of rules of regulation, the level of water reservoirs requires to be maintained at two feet below full tank level while monsoon is still active.
He said the rules balance the interests of water storage for the scarcity period, the need to control flooding in downstream areas and the safety of the reservoir.
Gnanadesikan said adequate flood warnings were issued to people living in low lying areas on December 1, and over 47,300 people were evacuated from those areas.
He said many tanks were breached due to heavy rains and the water flowed into the Adyar river.
“The flow in Adyar river reached its full capacity due to the surplus from Chembarambakkam tank, the inflow from the catchment areas of Adyar within Chennai city and the surplus received from the other tanks,” he said.
“In view of the heavy flow in the Adyar river, the high intensity runoff of local rainfall in Chennai city and adjoining urban areas could not fully drain into the Adyar and hence contributed to the inundation of the city,” he said.

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