he Tamilnadu CM, M.K. Stalin recently announced the upcoming launch of the TN-Alert App which s is a real-time flood forecast system. This will have regular updates on rainfall and flood risks. Based on reports from the last four major floods in Chennai—2015, 2019, 2021, and 2023—the Greater Chennai Corporation (GCC) has identified over 4,000 roads across all 15 zones as being prone to flooding, particularly in low-lying areas. Despite existing stormwater drain systems, these areas are still expected to experience waterlogging. To mitigate this, it plans to interlink these vulnerable roads to additional stormwater drains and deploy more motor pumps to help pump out excess water, ensuring quicker drainage during heavy rains.

A technical committee has been established by Chennai Metro Rail Limited (CMRL) to inspect 30 potential problem areas and it has submitted a report to IIT-M for further review. The findings will be communicated to CMRL for implementation. In preparation for the rains, relief centres and decentralised kitchens are being readied, boats, and roping in volunteers. Around 388 Amma Canteens and 35 cluster kitchens would be fully functional.

Pradeep John popularly known as Tamilnadu Weatherman and is the one whom the city turns to for weather predictions during the monsoon. His levels of accuracy make it something we can go by. He says, “Last year, we had a very good South-west monsoon, we had good water storage. October was dry and November had good rains. Normally, December is not the wettest month, November is the wettest followed by October. In December, the waterbodies reach saturation point and then when the final rain is a big rain we get into floods. Last year Cyclone Michaung brought rain to every inch of the city.
“This year, we have to wait and see. Cyclonic storm is inevitable but whether it will turn into floods, we can’t say. The first event won’t be too big.”

When queried whether it was climate change that was to blame for flooding, he shared his take, “It’s not because of climate change, rainfall intensity has increased, this is the urbanisation effect. Warm air can hold lot of moisture.

“Urbanisation plays a big role in flooding, the waterbodies that were there 20 years ago are not there now. There are paved surfaces everywhere so everything will turn into a run-off, to disperse this there are only four exits Ennore – Kosathaliyar, Cooum River, Adyar River and Pallikaranai. In Pallikaranai Marsh, water moves to Buckingham Canal and Kovalam Sea. We must check if there can be more exits. Catchment area is almost 5000 sq ft of water there is no way to drain. The city can’t handle extreme rains, the maximum is 150 mm.

“Just water standing on the road during rains is not flooding. After the rains stop, water standing 3 to six hours or more is flooding. “There are some troublesome areas always. We should not destroy lakes, protect what we have.

“Complete desilting of rivers must be done and there must be connectivity from rain water drains to stormwater drains. Stormwater drains for instance carry water to Mambalam Canal and then meet Adyar River. People think that if there are storm water drains the water will just flow out. They don’t realise that there will be backflow when there is a lot of water in the river. When this happens, there must be flaps – so that water raises to a certain point and then does not come into the storm water drain.

“If it rains every day, people must take the initiative and move to safer areas, especially in areas such as Pallikaranai and Mudichur. Stay prepared, you know how the water pattern in your area is. If you are unable to leave the house for 4 to 5 days, do you have the resources like food, lights and so on.”

R. Arul, Secretary, Pasumai Thaayagam and an expert on environment issues says, “Climate change is a reality. 2023 was the hottest year in the past 125000 years. In the history of the world, June 2024 was the hottest month. The heavy usage of fossil fuels and deforestation have increased greenhouse gas emissions. As the heat increases, extreme floods, hurricanes, drought, water scarcity and so on happen.

What is the solution? The solution is that various measures need to be taken on a war footing for the next six years. The cost of mitigating climate change should not be pushed onto the poorer countries, rich nations should take charge. Fossil fuels should be reduced.

“To prevent flooding in Chennai, the following measures need to be taken. Right now, there is no adequate disaster management system and this has to be created. Chennai’s waterbodies are being destroyed and from the period of 1991 – 2021, they shrunk from 28.7 sq. kms to 5.7 sq. kms

The structural changes needed include diverting the direction of flood water, reclaiming lost land where waterbodies stood, strengthening river banks and ensuring free flow of water, restoring the mouth of rivers, rainwater harvesting, efficient stormwater drains, desilting and more. Non-structural changes needed are creating awareness about floods and health issues that can arise during the rainy season, disaster relief, continuous functioning of emergency services, facilities to quickly restore infrastructure after rains, compensation schemes and so on.

A Chennai Resilient City plan should be created to handle situations after disasters. This can draw elements mentioned in the Sendai Framework for Disaster Risk Reduction 2015 – 2030. An Integrated Water Resources Management plan for Chennai, Kancheepuram and Tiruvallur is essential and this must ensure that the waterway is able to flow smoothly and the mouth of the rivers are restored to full capacity. An Integrated Flood Risk Management plan needs to be put in place. The Chennai We Want plan by Pasumai Thayagam outlines in detail how floods can be reduced and adequate drinking water resources assured.”