Chennai: In the last 50 years, Chennai has faced at least one flood every 10 years. But that interval seems to be narrowing since 2000 the city experienced floods in 2005, 2015, and 2023. Will what weathermen call ‘extreme weather events’ become more frequent in the future because of climate change?
Experts say unplanned expansion of the city and encroachments on waterbodies were the main reasons for floods during ‘extreme weather events’ such as Cyclone Michaung.
But such events could become more frequent. Climate studies project an increase in the frequency and intensity of northeast monsoon rainfall in the future.
M Rajeevan, former secretary, Ministry of Earth Sciences, says IPCC climate models have projected rainfall from cyclones to become severe. And more cyclonic storms may form over the northern latitude as the ITCZ (inter tropical convergence zone) may shift. The ITCZ is a belt of low pressure that circles the Earth generally near the equator where the trade winds of the northern and southern hemispheres come together.
“Climate change could have contributed to it. Climate change is happening everywhere, and there is an obvious change in the intensity and frequency of cyclones. In the future, we may see more extreme weather events leading to floods,” says Rajeevan.
A 2020 study by the Indian Institute of Tropical Meteorology, Pune, showed there may be a 5% increase in northeast monsoon rainfall between 2020 and 2049, and it may increase to 21% from 2070 to 2099 even if measures are taken to control greenhouse gas emissions.
The study projects an increase in frequency and intensity of rainfall, intense 24-hour rainfall and consecutive five-day rainfall events, a drop in the number of consecutive dry days, and a rise in the number of very wet.
The last three floods in the city happened during years of El Nino, the warming of the eastern equatorial Pacific Ocean, considered favourable for the northeast monsoon. As oceans absorb the additional heat from global warming, El Nino may become more frequent. Studies show north Indian Ocean temperatures are projected to rise by 2.7C to 3.2C by the end of this century. “Flooding was severe this time because the ground was already saturated from the monsoon. Whenever cyclones occur during the rainy season, the chances of flooding are quite high,” says Prof Vimal Mishra, climate expert at IIT Gandhinagar.
G Sundarrajan of Poovulagin Nanbargal says the interval between years with annual rainfall of more than 200cm is shortening. He says to prevent flooding in Chennai, the government must protect the Pallikaranai marsh, develop a climate model for the city, and shift factories further away.
“The government must put on hold Chennai Masterplan 3 and the Parandur airport project. Chennai grew by destroying water bodies and farmlands. If the city is allowed to expand further to Kanchipuram, Tiruvallur, Chengelpet, and Arakkonam, around 4,000 water bodies in these areas will get destroyed,” says Sundarrajan. Explore Your Financial Landscape with Personalized Credit Insights.