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REPORT: Rapidly growing Chennai submerged by rare extreme rainfall event

This factsheet, from the Raising Risk Awareness initiative, examines the impacts of the 1 December 2015 flood in Chennai.

Chennai is a coastal mega-city that has encountered explosive and largely unplanned growth over the past 15 years. The city of 8.2 million is one of the largest in South India and has a booming IT sector. Chennai is topographically at with two rivers, the Adyar and Cooum, running through the Chennai Metropolitan Area (CMA). The majority of rainfall occurs during the north-east monsoon from October to December, which is followed by a dry winter.

Key messages:

  • On 1 December 2015, a very rare extreme rainfall event in Chennai, India, led to devastating floods that killed over 470 people and brought the city to a standstill.
  • No measurable effect of human-caused emissions was detected in the extreme one-day rainfall in Chennai on 1 December 2015, highlighting the need for more effective management of the built environment to prevent such impacts in the future.
  • The country’s Parliamentary Standing Committee on Home Affairs acknowledged the lack of timely desilting, the inadequate flood zone planning, and large-scale settlements in low-lying areas as major contributors to the impacts on the city.

Download the factsheet here.

Image credit: Asian Development Bank