Climate change: Tamil Nadu coast may witness heavy spells of rain in next decade – Times of India

CHENNAI: Hot, dry and dusty. That’s the popular perception of Chennai. But for three days this November, 500 streets in the city were under water. Some suburbs were flooded for a couple of weeks.
Climate experts called the downpour on the November 6-7 weekend, which brought the city to its knees, unusual in the year of La Nina, when rainfall is generally poor.

However, a new study involving three popular climate models has forecast that Tamil Nadu’s 1,076km coast, including Chennai, may witness extreme spells of rain during the northeast monsoon in the 2020 to 2030 decade due to El Nino or the warming of the Pacific. That’s in 2022-2023, 2023-2024, 2024-2025 and 2026-2027.
“The probability of occurrence of extremes is high,” said K Palanivelu, corresponding author in the study conducted by the Centre for Climate Change and Disaster Management, Anna University, department of physics, Anna University, and Chennai Institute of Technology. The researchers said other global and local parameters should also be analysed. However, it’s clear dry Chennai is turning wet.
But is the city prepared for this? Chennai has several lakes, three major rivers and a canal cutting across the city. And after the 2015 floods, there was a flurry of activity to build storm water drains.
But this November proved that all the infrastructure built in the past 15 years after calculating just the road run-off and allowing for 5cm per hour rainfall was inadequate. Witness what happened in areas such as Pullianthope, Velachery, Alandur and Thiru Vi Ka Nagar. Worse, several projects planned for the next few years, including the Kosasthalaiyar integrated storm water drain network, have been designed to cater to a maximum of 7cm rainfall per hour. But the city may witness 20cm per hour rainfall frequently in future.
“The government needs to rework the projects keeping these forecasts in mind. Crores of rupees may go down the drain if the Greater Chennai Corporation doesn’t reassess,” said S Kumararaja, coordinator of south west federation of Velachery.
Activists who audited the city drains after the recent floods noted that they didn’t cater to the areas they were supposed to. The drain infrastructure marred by faulty engineering may just not be enough to save the city, said Jayaram Venkatesan of Arappor Iyakkam, an anti corruption NGO.
Activists and residents say urban planners should think beyond their jurisdictions — such as Greater Chennai Corporation limits or Chennai metropolitan area or a panchayat area — when looking at combating flooding.
“Since floods are part of a watershed, planners need to look at the entire catchment area that includes the rivers, lakes and canals and calculate the volume of run-off based on a 100-year return period. Hydrological models to estimate where the carrying capacity is exceeded should be run. Just constructing box-like concrete structures with other utilities crisscrossing won’t resolve the flooding issue,” said an environmental engineer with the state government.
“Acquifer recharge to slow down run-off, harvesting structures, local man-made tanks and lakes should also be considered to collect the rainwater,” said Raghukumar Choodamani, a resident of Perambur.
Experts said local administrations should look at permanent solutions and not just place pumps and build drains on particular streets. “We need to make room for the water to flow and that can happen only if all departments coordinate and work as a team,” said S Saroja, executive director of Citizen Consumer and Civic Action Group.