Call it the continuum or an early image-building exercise, Chief Minister C. Joseph Vijay, who also holds the Municipal Administration portfolio, has already deployed Ministers and senior officials to take up flood-mitigation works well ahead of the onset of the Northeast monsoon. He has instructed that all de-silting and stormwater drain (SWD) works be completed as early as possible.
Official data shows that the flood-vulnerable locations within the Greater Chennai Corporation (GCC) have dropped from nearly 800 in 2015 to 389 in 2023. The figure is 219 for the 2026 Northeast monsoon. The list of vulnerable locations is being continuously reviewed based on field-level assessments, rainfall patterns, and the effectiveness of the completed flood-mitigation works, said GCC officials. The micro-level SWD works are 95% complete, but there are severe capacity constraints along the Buckingham Canal, Adyar, and Sholinganallur, officials added.
GCC Commissioner G.S Sameeran said the civic body is coordinating with the Railways, Chennai Metro Rail Limited, and other agencies on drainage and flood-mitigation works. “Some major infrastructure works may take longer. The GCC has implemented temporary solutions, such as pumping facilities, for managing the monsoon,” he said.
Work to remove silt, mud, and garbage using machinery was undertaken by the GCC in the Buckingham Canal located in the Palavakkam Little Canal area under the Perungudi Zone | Photo Credit: Special Arrangement
Lack of consultation
Mr. Sameeran and his team have been on routine inspections – almost daily – of various works across the city. Even so, there has been talk about a lack of consultation and transparency in the conduct of flood-mitigation works. MDMK councillor S. Jeevan of Ward 35 in Perambur said, “Elected representatives do not know what is happening during flood preparedness inspections. I have not been able to meet the assistant engineer for 10 days to discuss residents’ complaints. The flood risk is high this year due to delays in desilting canals such as the Kodungaiyur Canal.”
Federation of North Chennai Residents Welfare Association president T. Shanmugam said residents were worried as officials had not shared details of flood preparedness yet. Haris Sulthan, an activist in Padi, said most waterbodies in and around Chennai and its suburbs remained largely dry, with the five drinking water reservoirs together holding 4.5 TMC against the 11.7 TMC total capacity.
He said routine annual works were being carried out, but no new major flood-mitigation interventions had been undertaken beyond these works in many areas, including Medavakkam, Chitlapakkam, Hasthinapuram, Kadaperi, Ambedkar Road, Jothi Nagar, and Sunnambu Kolathur, where prolonged inundation was reported previously. He appreciated the cancellation/reversal of tenders of “cosmetical lake-front development” works by the newly elected TVK government, while also calling for further desilting, the removal of water hyacinth, and increasing the lake depth.
Urbanisation challenge
According to a senior official in the GCC, Chennai’s monsoon vulnerability, particularly in the south of the city, is largely due to unchecked urbanisation, and that flooding in many parts like near Perumbakkam is “100% man-made”. Pointing to the built-up spaces and encroachments around the Pallikaranai marshland, Perungudi, and the IT corridor, he said that natural watercourses are choked, and canals in T. Nagar and Mambalam are heavily polluted because the “entire waterway is a sewer due to illegal sewage connections.”
K.P. Subramanian, an urban planner, highlighted that while flood resilience in Velachery has improved, areas like Kuber Nagar, Karthikeyapuram, and parts of Madipakkam still face risks due to urban development and drain silting. He recommends regular desilting and zoning regulations to designate flood plains, rivers, and lake margins as no-development zones.
D. Raghunandan, a climate researcher at Delhi Science Forum, said the SWD network in Chennai and its suburbs must be redesigned to handle extreme rainfall events such as 100-200 mm or more in just a few hours, rather than just evenly distributed volumes of rain. Instead of a haphazard pattern of urbanisation, the buildings, roads, and flyovers must be planned to ensure natural drainage and that the connectivity of stormwater drains to the three major rivers running through the city, and eventually into the sea, is not affected.
As a precautionary measure to mitigate flooding, diesel-powered water pump tractors were hired by the GCC. They are parked at the Valasaravakkam zone on Saturday | Photo Credit: B. Velankanni Raj
Chennai must protect its wetlands and lakes, such as in Perumbakkam and Pallikaranai; the depth of the Cooum and Adyar rivers has also reduced compared to yesteryears. Increasing the capacity of waterbodies would help store excess rainfall water or drain it naturally towards the sea, he suggested. “These are long and costly overhaul processes that have to be addressed systematically over time, but they would pay back by offsetting losses during frequent urban floods,” he noted, adding that similar measures were needed in all major cities, not just in Chennai.
S. Janakarajan, president of the South Asia Consortium for Interdisciplinary Water Resources Studies and former professor at MIDS, said water conservation must be prioritised since short, heavy downpours are the new normal. He said 70% to 80% of rainfall runs off into the sea because departments uncoordinatedly drain water, and suggested that the State focus on conservation to mitigate floods and droughts. “There are 4,100 lakes in the three adjoining districts [Tiruvallur, Chengalpattu, and Kancheepuram], besides numerous temple tanks and ponds that can help augment surface water and improve groundwater recharge. Also, temporary holding ponds could be created in educational institutions, parks, playfields, and government land, while large private land parcels could also be considered for creating sponge parks,” he said.
Monsoon preparedness
The WRD, meanwhile, is set to complete the first phase of its annual desilting exercise in a week. However, vast swathes of water hyacinth hindering the free flow of floodwater in waterways remain a challenge this year, too. While the department has accelerated work to clean the major and minor waterways ahead of the Northeast monsoon, residents of various parts of the city have urged the authorities to coordinate with other agencies to prevent sewage from entering the waterways.
The department has deployed about 400 machines, including floating excavators, to clean the waterways, including the Adyar, Cooum, Kosasthalaiyar, and Araniyar rivers, as well as the Buckingham canal, and also clear sand bars at the various river mouths.
Officials noted that the ₹42-crore project would help minimise flooding in the rivers and backflow into micro drains by 70% to 80% during the monsoon. The rivers would be able to handle the flows without spillover, even in the event of 200 mm of rainfall in a day.
Sewer networks
To reduce sewage-related complaints during the ensuing Northeast monsoon, Chennai Metro Water has completed the second phase of cleaning the city’s sewer network. The network was cleaned through 41,996 manholes during this phase, carried out between July and September.
As floodwater often enters the sewer network during heavy rain, the water agency plans to undertake a third phase of cleaning between October and December to minimise blockages and prevent sewer network failures, officials said.
Nearly 417 sewage pumping stations and sewage treatment plants have been equipped with IoT-based monitoring systems to help detect and prevent sewage stagnation and overflows. Robotic equipment is also being used to detect leaks and damages in drinking water pipelines.
Power infrastructure
The Tamil Nadu Power Distribution Corporation Limited (TNPDCL) covers flood mitigation works under 22 categories. The monsoon preparatory works are carried out on a massive scale this year, a senior official of the TNPDCL said.
Tree branch clearance was completed at 6.75 lakh locations, exposed underground cables were buried at 1,762 places, damaged insulators were replaced at 85,000 locations, and low-sag overhead lines were rectified at 54,387 places. Maintenance is under way at 2,650 substations and 3,840 pillar boxes. The TNPDCL is also replacing 40,000 damaged concrete poles and worn-out conductors at 2,500 locations. Distribution transformer structures are maintained at 60,000 places, according to data shared by the TNPDCL.
Maintenance works are nearly complete across distribution regions, barring Chennai North, Central, West, and South-I. Over 90% of monsoon preparatory works are done in Chennai South-II, Kancheepuram, and Tiruvallur, data showed. Works are expedited in central Chennai (T. Nagar, Anna Salai, Teynampet, Royapettah, Triplicane, and Mylapore), where only 52% of the works have been completed. In the western region covering Ambattur, Avadi, Maduravoyal, Anna Nagar, and Kolathur, 56% of the works are complete.
‘Early preparedness is key’
“Local bodies across Tamil Nadu have been directed to complete monsoon works by October 10. In Chennai, desilting has been under way for two and a half months, with one cycle covering nearly one lakh silt catch pits having been completed. The second cycle is under way. Similar instructions have been issued to other corporations, municipalities, and town panchayats,” said Municipal Administration and Water Supply (MAWS) Department Secretary Gagandeep Singh Bedi. “Very high rainfall in short duration and rainwater inflow from adjoining suburban areas would place more pressure on the SWD systems, so early preparedness is key,” he told the department heads at a recent meeting.
(With inputs from K. Lakshmi, R. Srikanth, and Aloysius Xavier Lopez)