Chennai’s Monsoon Test

Call it a continuum or an early image-building exercise, Chief Minister C. Joseph Vijay, who also holds the urban administration portfolio, has already dispatched ministers and senior officials to start flood control work well in advance of the onset of the northeast monsoon. He instructed that all desilting and storm water drainage (SWD) works should be completed as soon as possible.

Official data shows that flood-vulnerable locations within the Greater Chennai Corporation (GCC) have declined from nearly 800 in 2015 to 389 in 2023. The number is 219 for the northeast monsoon of 2026. The list of vulnerable locations is continuously revised based on ground-level assessment, rainfall patterns and effectiveness of completed flood mitigation works, GCC officials said. The SWD micro level work is 95% complete but there are severe capacity constraints along Buckingham Canal, Adyar and Sholinganallur, officials added.

GCC Commissioner GS Sameeran said the civic body is coordinating with the Railways, Chennai Metro Rail Limited and other agencies for drainage and flood control work. “Some major infrastructure works may take longer. The GCC has put in place temporary solutions such as pumping facilities to manage the monsoon,” he said.

Mud, silt and garbage removal work by machinery was carried out by GCC in Buckingham Canal in Palavakkam Little Canal area under Perungudi Zone | Photo credit: Special arrangement

Lack of consultation

Mr. Sameeran and his team were on routine inspections – almost daily – of various works across the city. Nevertheless, there was talk of a lack of consultation and transparency in the implementation of flood control works. MDMK councilor S. Jeevan of Ward 35 in Perambur said, “Elected representatives do not know what is happening during flood preparedness checks. I cannot meet the assistant engineer for 10 days to discuss residents’ grievances. The risk of flooding is high this year due to delays in desilting canals like the Kodungaiyur canal.”

North Chennai Residents’ Welfare Federation president T. Shanmugam said residents are worried as officials have yet to share details about flood preparedness. Haris Sulthan, an activist in Padi, said most of the water bodies in and around Chennai and its suburbs have remained largely dry, with the five drinking water tanks together holding 4.5 TMC against a total capacity of 11.7 TMC.

He said that routine annual works are being carried out but apart from these works, no new major flood control operations have been carried out in many areas including Medavakkam, Chitlapakkam, Hasthinapuram, Kadaperi, Ambedkar Road, Jothi Nagar and Sunnambu Kolathur where prolonged flooding was reported earlier. He praised the cancelation/cancellation of tenders for “cosmetic development on the lake shore” by the newly elected TVK government while calling for further desilting, removal of water hyacinth and increasing the depth of the lake.

Urbanization challenge

According to a senior GCC official, Chennai’s monsoon vulnerability, particularly in the south of the city, is largely due to uncontrolled urbanization and that flooding in many parts, such as near Perumbakkam, is “100% man-made”. Pointing out the built-up areas and encroachments around the Pallikaranai, Perungudi and IT corridor wetlands, he said natural waterways are blocked and canals in T. Nagar and Mambalam are heavily polluted as “the entire waterway is a sewer due to illegal sewage connections”.

KP Subramanian, an urban planner, pointed out that while flood resilience has improved in Velachery, areas like Kuber Nagar, Karthikeyapuram and parts of Madipakkam still face risks due to urban development and sewage pollution. Recommends periodic silting and zoning ordinances to designate floodplains, rivers, and lakeshores as no-development zones.

D. Raghunandan, a climate researcher at the Delhi Science Forum, said the SWD network in Chennai and its suburbs must be redesigned to handle extreme rainfall such as 100-200 mm or more in a few hours, rather than just evenly distributed volumes of rain. Instead of a haphazard pattern of urbanization, buildings, roads and flyovers must be planned to ensure natural drainage and not affect the connectivity of rainwater draining into the three main rivers flowing through the city and ultimately to the sea.

As a precautionary measure to mitigate flooding, GCC hired diesel-powered water pump tractors. They are parked in 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 decreased compared to previous years. Increasing the capacity of water bodies would help store excess rainwater or drain it naturally into the sea, he suggested. “These are long and costly overhaul processes that need to be systematically addressed over time, but would pay back by offsetting losses during frequent urban flooding,” he noted, noting that similar measures were needed in all major cities, not just Chennai.

S. Janakarajan, president of the South Asian Consortium for Interdisciplinary Water Resources Studies and former professor at MIDS, said water conservation must be a priority as short and heavy downpours are the new norm. He said 70% to 80% of rainfall flows into the sea because ministries divert water in an uncoordinated manner and suggested the state focus on conservation to mitigate floods and droughts. “There are 4,100 lakes in the three adjoining districts (Tiruvallur, Chengalpattu and Kancheepuram), apart from numerous temple tanks and ponds, which can help raise surface water and improve groundwater recharge. Also, temporary detention ponds could be created in educational institutions, parks, playgrounds and government lands, while large private lands could also be considered to serve as a sponge.

Monsoon preparedness

Meanwhile, the WRD is set to complete the first phase of its annual desilting exercise in a week. However, extensive swaths of water hyacinths, which prevent the free flow of flood water in waterways, remain a challenge this year. While the department has expedited work to clean 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 dredges, to clean water courses, including the Adyar, Cooum, Kosasthalaiyar and Araniyar rivers, as well as the Buckingham Canal, as well as clean sand in various estuaries.

Officials noted that the ₹42 crore project would help minimize flooding in rivers and backflow into micro drains by 70% to 80% during monsoon. The rivers would be able to handle the flows without overflowing even with 200 mm of rainfall per day.

Sewage networks

To reduce sewage-related complaints during the ensuing northeast monsoon, Chennai Metro Water has completed the second phase of cleaning the city’s sewerage network. The network was cleaned over 41,996 manholes during this phase, which ran from July to September.

Since floodwater often enters the sewer network during heavy rain, the water agency plans to carry out a third phase of cleaning between October and December to minimize 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 overflow. Robotic equipment is also used to detect leaks and damage to drinking water pipes.

Energy infrastructure

Tamil Nadu Power Distribution Corporation Limited (TNPDCL) covers flood mitigation works in 22 categories. The monsoon preparation work is being carried out on a large scale this year, said a senior TNPDCL official.

Tree felling was completed at 6.75 lakh places, exposed underground cables were buried at 1,762 places, damaged insulators were replaced at 85,000 places and low sag overhead lines were repaired at 54,387 places. Maintenance is taking place at 2,650 substations and 3,840 pole boxes. TNPDCL is also replacing 40,000 damaged concrete poles and frayed wires at 2,500 locations. Distribution transformer structures are maintained at 60,000 locations, according to data shared by TNPDCL.

Maintenance work is almost complete in distribution regions except Chennai North, Central, West and South-I. More than 90% of the monsoon preparation work is being done in Chennai South-II, Kancheepuram and Tiruvallur, data shows. The work is fast-tracked in central Chennai (T. Nagar, Anna Salai, Teynampet, Royapettah, Triplicane and Mylapore) where only 52% of the work has been completed. In the western region comprising Ambattur, Avadi, Maduravoyal, Anna Nagar and Kolathur, 56% work is complete.

“Early readiness is key”

“Local bodies in Tamil Nadu have been directed to complete monsoon works by October 10. In Chennai, desilting has been going on for two-and-a-half months, with one cycle covering nearly one lakh silt catchment pits being completed. The second cycle is underway. Similar instructions have been issued to other corporations, municipalities and city panchayats,” said Municipal Administration and Water Supply (MAWS) Minister Gagandeh “Very high rainfall in a short period and inflow stormwater from adjacent suburban areas would put more pressure on SWD systems, so early preparedness is key,” he told department heads at a recent meeting.

(With contributions from K. Lakshmi, R. Srikanth and Aloysio Xavier Lopez)