Chennai’s stormwater drain network is approaching the northeast monsoon with major sections still incomplete, unconnected or inadequately maintained. The Greater Chennai Corporation has completed 1,045km of work across three ongoing projects covering 1,093km, but the remaining 48km is concentrated in densely populated areas where even short missing links can disrupt drainage across an entire neighbourhood.
The immediate problem is visible on roads across the city. In Anna Nagar Second Avenue, an open stormwater drain runs through multiple locations between Thirumangalam and Roundtana, while key junctions remain unconnected. Arcot Road is dug up along stretches in Kodambakkam and Valasaravakkam, with work progressing in fragments. Similar conditions have been reported on PT Rajan Salai in KK Nagar, while a section near the KP Park tenements in Pulianthope has been cordoned off for drain construction.
These locations illustrate why the length of unfinished work does not fully measure the risk. The civic body is yet to complete missing-link work at 68 of 105 identified locations. A drain network is continuous only when its separate sections connect to one another and discharge through functioning downstream infrastructure. A short unconnected section can therefore prevent water from moving out of a much larger catchment, leaving roads and neighbourhoods vulnerable during intense rain.
The unfinished work is also tied to coordination problems between public agencies. Contractors have said that the Tamil Nadu Generation and Distribution Corporation Limited has not helped shift electrical junction boxes that obstruct drain construction. The Greater Chennai Corporation has also been criticised for not coordinating sufficiently with the electricity utility. Metro construction on Arcot Road has affected existing pipelines and stormwater drains at several points, adding another layer of disruption to an already fragmented road and drainage system.
The city’s current approach has consequently placed considerable weight on pumping. The corporation has procured 1,000 dewatering motors and is relying heavily on pumps in affected areas. But pumps cannot substitute for a connected gravity-based drainage network. If drains do not carry water to their intended outlets, or if missing links and blocked inlets interrupt the system, additional pumping capacity can address only part of the problem. The supplied report notes that the motors will have limited use unless the remaining drain work is completed.
Maintenance is another weakness. The corporation is yet to desilt at least 500km of its overall 1,682km drain network. Only 59% of silt catch pits have been desilted. These pits are entry points through which rainwater reaches the drains, so their condition affects whether the network can receive water efficiently even where the main drain has been built.
The distinction between construction and functionality is important. A newly built drain may not reduce flood risk if its inlets are blocked, its connections are incomplete, its gradient is faulty or its outfall is unable to carry the additional flow. The report says two of the three ongoing projects are nearly five years old and were funded by the Asian Development Bank and KfW Development Bank. They have faced funding problems, tendering malpractices, gradient issues and coordination difficulties between departments.
Those delays have left the final phase of the work concentrated in neighbourhoods including Tiruvottiyur, Manali, Madhavaram, Thiru Vi Ka Nagar, Anna Nagar, Alandur, Perungudi and Sholinganallur. Several of these areas are densely built, meaning construction itself can create access problems while incomplete work leaves residents exposed to flooding. The reported road closures, dug-up corridors and open drains show how infrastructure delivery can impose immediate costs before its promised protection becomes operational.
The larger issue is that stormwater drainage cannot be planned as a collection of isolated road works. Former Thiruppugazh flood committee member S Janakarajan said stormwater drains carry sewage, industrial waste and solid waste, eventually discharging into the city’s canals and rivers instead of treatment plants. He argued that the capacity of the drains must be studied and that new infrastructure should follow a masterplan mapping watersheds and natural slopes.
His remarks point to a fundamental planning challenge: water does not follow administrative boundaries or project packages. It moves according to terrain, catchment and available outfalls. If a drain is designed without understanding the watershed it serves, or if downstream canals cannot accommodate the flow, a completed stretch may transfer the problem rather than solve it. The report specifically identifies the Buckingham Canal as an important destination for diverted drains and says the canal itself has not been desilted.
Janakarajan also questioned the rebuilding of existing stormwater drains in narrow streets and said that some larger streets now have drains with low capacity. Bhuvana Raj, head of Eco Watch, a volunteer-led environmental monitoring group formed by the Federation of OMR Resident Associations, described cut-and-cover drains as patchwork used to fill missing links. She also questioned how residents could assess whether drains were scientifically designed when project reports were not publicly available.
The concerns therefore extend beyond whether work is progressing. They concern the information and institutional systems used to design, approve and monitor the projects. Without publicly available project reports, residents may know where roads are dug up but not the design capacity, catchment served, intended outfall, construction schedule or reason for delay. That makes it difficult to distinguish a temporary construction disruption from a design or coordination failure.
The project history reinforces the governance problem. The three ongoing projects involve a very large network, but delivery has been divided across funding arrangements, contractors, utilities and transport construction. The reported delays show how a stormwater project can be slowed by issues outside the civic body’s immediate control, while the absence of coordination leaves citizens facing the consequences. The responsibility for a functioning drainage system, however, ultimately depends on the agencies working as one network rather than as separate departments.
The corporation’s desilting and missing-link targets also reveal a capacity problem. Of the 105 identified missing-link locations, work remains at 68. Of the total 1,682km drain network, at least 500km still requires desilting. These figures describe different stages of the system: construction, connection and maintenance. Completing one does not automatically complete the others. A drain can be structurally present but disconnected, connected but silted, or maintained but undersized.
The evidence supplied does not establish how much additional capacity each drain requires, how the outstanding works are prioritised or whether all identified project reports have been made public. It does establish that the city’s flood preparedness depends on a set of interlocking tasks that remain unfinished. The corporation’s 1,000 dewatering motors are a response capacity, but they do not resolve the underlying network gaps.
Tamil Nadu Chief Secretary M Sai Kumar has directed officials to complete all northeast monsoon-related works by September 30. That deadline places the remaining construction, missing-link connections and maintenance work within a defined administrative window. Whether the deadline results in a functioning network will depend not only on physical completion, but also on coordination with the electricity utility, metro authorities and agencies responsible for canals and outfalls.
Chennai’s stormwater challenge is consequently not simply a story of 48km of unfinished drains. It is a test of whether the city can plan drainage by watershed, coordinate infrastructure projects across departments, maintain the network it has built and make design information available to the public. The immediate measure of preparedness will be whether the remaining works are completed; the longer institutional question is whether the drainage system is treated as one connected urban utility rather than a series of road-level projects.
