Examining Otteri Nallah

Urban Drainage, Public Health, and the Limits of Short-Term Flood Mitigation in Chennai

Thisai’s analysis of Otteri Nallah foregrounds a crucial argument: urban flooding and health crises cannot be addressed in isolation from the ecological and governance systems that produce them. The Nallah’s condition exemplifies how mismanaged urban waterways become sites where environmental degradation, infrastructural stress, and social vulnerability intersect.

From Drainage Channel to Bottleneck: Encroachment, Waste, and Regulatory Failure

Image on left: Still of Otteri Nallah, spurce: The Hindu. Right: Sub-basin of Otteri Nallah, source: adapted from CMDA

Otteri Nallah is a major stormwater channel within the Cooum River basin, draining runoff from densely populated neighbourhoods such as Anna Nagar, Villivakkam, Perambur, and surrounding areas before discharging into the Cooum River. Unlike natural rivers with relatively stable widths and floodplains, urban nallahs like Otteri are highly variable systems, expanding as they collect water from multiple sources and contracting where constricted by development. This variability demands careful spatial planning and continuous maintenance. However, Otteri Nallah has instead been treated as residual infrastructure—something to be managed episodically during crises rather than integrated into long-term urban planning. The result is a drainage channel that is perpetually overwhelmed during moderate to heavy rainfall events.

Residents along Otteri Nallah, particularly in parts of Anna Nagar, experience recurring floods that disrupt daily life and damage property. These floods are often framed in public discourse as inevitable consequences of heavy rainfall. Yet, our research points to a different conclusion: flooding is largely a product of inadequate silt removal, unchecked dumping of waste, and poorly regulated sewage discharge into stormwater drains. Desilting is frequently proposed as the primary solution. While necessary, it is increasingly deployed as a one-size-fits-all response, detached from the specific hydrological dynamics of Otteri Nallah. The Nallah’s flow characteristics differ significantly from conventional stormwater pipelines. Its width, depth, and carrying capacity fluctuate as it receives water from secondary drains and surface runoff. Treating it as a static conduit rather than a dynamic system undermines the effectiveness of routine desilting operations.

One of the most striking aspects of Otteri Nallah’s degradation is the scale and persistence of solid waste dumping. Construction debris, household waste, and animal carcasses accumulate both within the channel and along its banks. These materials obstruct water flow, reduce effective channel depth, and accelerate siltation, turning sections of the Nallah into stagnant pools rather than a flowing drain. Encroachments further compound these issues. As buildings, compound walls, and informal structures press against the channel’s edges, they reduce its functional width and eliminate buffer zones that could otherwise absorb excess water. The Nallah is thus forced to perform beyond its diminished capacity, leading to overflows that disproportionately affect adjacent residential areas.

Importantly, these physical obstructions are not random but symptomatic of weak enforcement. Despite existing regulations prohibiting dumping and construction near waterways, violations remain widespread, pointing to a persistent gap between policy and practice.

Recent interventions have included the use of drone-based larvicide spraying to address mosquito proliferation along Otteri Nallah. While such measures may temporarily reduce mosquito populations and mitigate disease risks, they are explicitly identified as short-term solutions. Spraying does little to address the underlying conditions—stagnant polluted water, unmanaged waste, and industrial runoff—that create breeding grounds in the first place. This reliance on reactive public health interventions reflects a broader tendency in urban governance to manage crises rather than prevent them. Mosquito control becomes a recurring expense and logistical challenge precisely because the environmental conditions that sustain mosquito populations remain unchanged.

A more effective approach, as highlighted in the analysis, would integrate waste management, sewage treatment, and drainage planning. Without addressing these root causes, public health measures risk becoming cyclical, offering temporary relief while leaving structural vulnerabilities intact.

Rethinking Solutions: Beyond Desilting

Recent efforts by the Greater Chennai Corporation (GCC) to impose spot fines for garbage dumping and illegal sewage discharge represent an important shift toward accountability. Fines ranging from ₹1,000 for waste dumping to ₹25,000 for illegal sewage connections signal an acknowledgment of the role everyday practices play in degrading waterways like Otteri Nallah.

However, enforcement alone cannot compensate for systemic shortcomings. Penalties are effective only when monitoring is consistent and alternatives—such as accessible waste disposal systems and functioning sewage infrastructure—are in place. In the absence of these supports, punitive measures risk targeting symptoms rather than transforming behaviour at scale.

A key intervention proposed is mandatory rainwater harvesting (RWH) for all buildings along the Otteri Nallah. This recommendation is particularly significant because it reframes the Nallah not as a channel meant to carry all forms of water, but specifically as a conduit for excess rainwater. By decentralising runoff management, RWH can reduce peak flows into the Nallah during rainfall events, easing pressure on an already stressed system. Regular canal maintenance is another essential measure, but it must extend beyond periodic desilting. Invasive vegetation, debris accumulation, and informal dumping require continuous monitoring and community engagement. Importantly, maintenance must be coordinated across departments responsible for water, sanitation, and solid waste, rather than treated as an isolated technical task.

Otteri Nallah as an Urban Mirror: From Short-Term Control to Systemic Repair

Otteri Nallah reflects the broader trajectory of Chennai’s relationship with its waterways. Once integral to the city’s drainage and ecological systems, such channels have been progressively reduced to utilitarian drains—expected to absorb runoff, waste, and sewage without adequate investment or protection. This transformation has social consequences. Communities living along the Nallah bear the brunt of flooding, pollution, and health risks, revealing how environmental degradation intersects with questions of equity and urban justice. The Nallah thus becomes not just an infrastructural problem, but a spatial manifestation of uneven urban priorities.

The analysis presented here makes a compelling case for moving beyond reactive, fragmented solutions in addressing the challenges of Otteri Nallah. Desilting, larvicide spraying, and fines may be necessary, but they are insufficient on their own. What is required is a systemic shift—one that recognises urban waterways as dynamic, living systems embedded within social, ecological, and infrastructural networks.

Restoring Otteri Nallah’s capacity and function will demand integrated planning, strict regulation of waste and sewage, decentralised rainwater management, and sustained public engagement. Without such a shift, the Nallah will continue to oscillate between neglect and crisis management, reinforcing the very vulnerabilities the city seeks to overcome. In this sense, Otteri Nallah is not an anomaly but a warning. How Chennai chooses to respond will shape not only the future of this single waterway, but the resilience of the city as a whole.