Record rain on 1-2 December 2015 triggered the Chennai floods, but the CAG's 2018 audit called them man-made, citing reservoir releases, encroached water bodie…
Heavy rain after the northeast monsoon began gave Nungambakkam 157.8 mm in 24 hours, and Kathivakkam over 300 mm. Most stagnation cleared by Sunday morning.
Nungambakkam recorded 530 mm over three days. At least 17 people died and the airport closed on 4 December.
India and the ADB agreed funding for 588 km of new stormwater drains and 23,000 catch pits in the Chennai-Kosasthalaiyar basin.
Report No. 4 of 2017 faulted reservoir management, building on water bodies, delayed desilting and a disaster authority that never met.
The airport closed on 1 December. Cargo partly resumed on 5 December and passenger flights on 6 December.
The CAG said 29,000 cusecs flowed for 21 continuous hours, after the release was raised from 12,000 to 20,960 cusecs on 1 December.
Meenambakkam recorded 345 mm in 24 hours, beating the December record of 262 mm set in 1901.
The CAG said an emergency should have been declared when Chembarambakkam reached 21 feet at noon on 16 November.
A depression formed on 8 November and crossed the coast near Puducherry on 9 November. Neyveli recorded 483 mm.
Tamil Nadu's rainfall ran 47% above normal to 30 November, over record-warm Bay of Bengal waters and El Nino conditions.
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