Urban Literacy: Chennai must learn to read its landscape

Chennai does not forget its floods. It forgets what made them inevitable.

Each northeast monsoon brings familiar photographs: inundated streets, stranded vehicles, families climbing stairs as water enters their homes. We call the rain extraordinary. Yet the deeper question is ordinary: what happened to the land that once held the water?

Rainfall matters, enormously, and Cyclone Arnab last week was no exception. During Cyclone Michaung in December 2023, the India Meteorological Department recorded 291.6 millimetres in 24 hours at Perungudi on December 4. No drainage system can make such rainfall harmless.

But rainfall alone cannot explain why exposure accumulates in the same low-lying landscapes. A hazard becomes a disaster when land-use decisions place people and property in its path.

Consider Pallikaranai. The Tamil Nadu State Wetlands Authority identifies its Ramsar-designated marsh at 1,247.54 hectares. More revealingly, the authority says its drainage system serves roughly 250 square kilometres of south Chennai, encompassing 65 wetlands, before discharging towards the sea. This is not vacant land awaiting economic use. It is working infrastructure, supplied by geography rather than concrete.

Older estimates of the marsh's extent vary with definitions and historical boundaries. That uncertainty does not erase the documented pressure from settlements, roads, institutions and commercial development around it. Nor does a Ramsar boundary describe the entire hydrological system that sustains it. A legally protected patch can still be undermined when surrounding channels are narrowed, or its catchment is paved.

Chennai once relied on networks of tanks, lakes, canals, marshes and rivers. These were not interchangeable ornaments on a map. They stored rainfall, slowed runoff and connected water to outlets. Urban expansion has interrupted parts of that network. The Comptroller and Auditor General's audit of the 2015 floods recorded, among other failures, encroachments along waterways and obstructions to flood flows. It found that 30.2 kilometres of the Adyar's 85 kilometres of banks were encroached upon at the time examined.

That is an institutional finding, not a metaphor. This matters particularly as the metropolitan region plans further growth: land converted today creates risks that future taxpayers, tenants and emergency workers may inherit for decades.

Yet the debate repeatedly narrows to the size of stormwater drains. Chennai needs functioning drains, desilted channels, maintenance and reliable flood warnings. But expanding drainage while allowing storage areas and flow paths to disappear is an expensive exercise in chasing consequences. Water travels across administrative boundaries; municipal budgets and planning approvals rarely do.

The property market exposes the same mismatch. Buyers compare square footage, connectivity, schools and resale potential. Banks examine repayment capacity and collateral values. Approval documents establish compliance with specified rules. None of these, by itself, tells a household how rainwater moved through that parcel before construction, or whether upstream development has changed its future flood risk.

This is not an argument that residents knowingly bought disaster, or that any construction in Velachery, Perumbakkam or Sholinganallur stands on former marshland. Such sweeping claims require parcel-level evidence. It is an argument that critical environmental information is too difficult to obtain, interpret and contest before irreversible decisions are made.

The ‘Chennai Climate Action Plan’ already demonstrates why that information matters. Its flood modelling projects inundation across substantial areas under different rainfall scenarios, while acknowledging limitations arising from terrain data and subsequent infrastructure changes. Risk maps are estimates, not guarantees. Precisely for that reason, they should be periodically updated and publicly scrutinised, rather than left to specialists after each emergency.

There is a larger failure here: education has taught us to recognise the price of urban land without understanding its ecological function. An engineering graduate may understand software and structures without learning the watershed beneath a neighbourhood. A management student may calculate investment returns without pricing flood exposure. A lawyer may master title and approval procedures without examining whether those procedures adequately disclose environmental hazards. These are gaps in training, not indictments of individual graduates.

Urban literacy should therefore become practical, not ceremonial. Schools could use neighbourhood maps to trace tanks, canals, contours and drainage routes. Universities could require students in engineering, law, economics and management to work together on real local planning problems. A floodplain is not merely an environmental topic; it is also a question of contracts, insurance, public finance and distributive justice.

Government must make that knowledge actionable. First, publish searchable, regularly updated parcel-level flood-risk and historical land-use information, clearly stating uncertainty. Second, require a standard flood-risk disclosure before major property sales and development approvals, without pretending disclosure substitutes for regulation. Third, assess projects cumulatively at catchment scale, including downstream effects, rather than approving each plot in isolation.

Fourth, protect and reconnect wetlands, tanks and natural channels through enforceable land-use rules, maintenance budgets and independent public monitoring. Fifth, put existing residents, particularly lower-income households, at the centre of mitigation: safer housing and credible rehabilitation matter more than indiscriminate eviction. A city's memory must not become an excuse to punish those with the fewest choices.

These reforms are more demanding than another promise of wider drains. They also offer something infrastructure alone cannot: better decisions before risk is built into the landscape.

Chennai cannot prevent the northeast monsoon, and climate change increases the urgency of preparing for rainfall extremes. It can, however, stop treating every flood as an unexpected visitor.

The city has begun to map its risks. The next test is whether those maps will govern approvals, investments and everyday choices. Before asking how quickly Chennai can build, shouldn't we ask what its water remembers?

Thakur is Professor & Director, Centre of Excellence (CoE) for Public Policy, Sustainability, and ESG, Alliance University, Bengaluru