Addressing policy challenges from Chennai’s 2015 extreme rainfall event

The December 2015 extreme rainfall event in Chennai, India, which saw a record 494 mm of rain in 24 hours, was determined by climate attribution studies to be a 1 in 600–2,500 year event not caused by anthropogenic global warming. While the event's rarity would have overwhelmed most cities, its impact was exacerbated by poor land-use planning, including the encroachment of wetlands and riverbeds, and a clogged drainage system. The document recommends that Indian cities integrate wetland protection, river basin approaches, and vulnerability-focused disaster action plans into their urban development to build resilience against increasing extreme weather trends.

• Climate attribution studies concluded that the extreme rainfall event in Chennai on 1 December 2015 was not caused by human-induced climate change.
• The rainfall event was an exceptionally rare occurrence with a return time estimated between 600 and 2,500 years, meaning the annual probability of such an event at any given station is less than 0.2%.
• Contrary to global trends, sea surface temperatures in the western Bay of Bengal have not risen over the last 35 to 40 years, a phenomenon attributed to the 'brown cloud' of air pollutants (aerosols) that block sunlight.
• The severity of the disaster was increased by urban management failures, specifically the lack of timely desilting of drains, inadequate flood-zone planning, and the encroachment of construction onto riverbeds and wetlands.
• The economic cost of the extreme rainfall event to the Indian economy is estimated at US$3 billion.
• Vulnerability was highest among people in informal settlements and those living in flood plains, with more than 2.6 million houses in low-lying areas being submerged.

APA

Climate and Development Knowledge Network (2017). Addressing policy challenges from Chennai’s 2015 extreme rainfall event. https://cdkn.org/sites/default/files/files/CDKN_RRA_ChennaiFlood_PB_Pr1Final_WEB.pdf

Chicago

Climate and Development Knowledge Network. Addressing policy challenges from Chennai’s 2015 extreme rainfall event. 2017. https://cdkn.org/sites/default/files/files/CDKN_RRA_ChennaiFlood_PB_Pr1Final_WEB.pdf.

Wikipedia

{{cite report |author=Climate and Development Knowledge Network |title=Addressing policy challenges from Chennai’s 2015 extreme rainfall event |date=2017 |url=https://cdkn.org/sites/default/files/files/CDKN_RRA_ChennaiFlood_PB_Pr1Final_WEB.pdf |access-date=17 August 2026 |via=Climate Insights Directory}}

BibTeX

@techreport{climateanddevelopmentknowledgenetwork2017addressing, author = {{Climate and Development Knowledge Network}}, title = {{Addressing policy challenges from Chennai’s 2015 extreme rainfall event}}, institution = {Climate and Development Knowledge Network}, year = {2017}, url = {https://cdkn.org/sites/default/files/files/CDKN_RRA_ChennaiFlood_PB_Pr1Final_WEB.pdf}, urldate = {2026-08-17}, note = {Indexed by Climate Insights Directory} }