The study by Swiss Re Group said that the extreme rainfall volume over a short duration paralysed Chennai with major disruption to critical infrastructure. “The event highlights the vulnerability of rapidly growing urban areas to flash floods originating from heavy rains,” the report said. 

Chennai was paralysed November and December in 2015 after accumulated rainfall of more than 500 mm with some areas receiving more than 250 mm rainfall in just 24 hours. Of the total losses, insured losses were USD 0.8 billion, making the floods the second costliest insurance event in India on sigma records. 

The report also pointed out that a large part of the losses originated from commercial lines as Chennai is home to several manufacturing companies, particularly in the motor industry. 

Swiss Re Economic Research & Consulting ranked Chennai floods as 14th among the 20 costliest insurance losses in the world in 2015. The flash floods were also ranked 14th among the 20 worst catastrophes in terms of victims with 289 killed in the catastrophe.