Man-made floods
Chennai observes massive seasonal peaks of rainfall. Storm water management treats this rain as if it was sewage to be dispensed of as quickly as possible in large systems of pipes. Overwhelmed by the amount of rainfall, clogged by silt and sewage, these systems have many times failed to protect citizens. The deluge of monsoon rains has led to hundreds of fatalities and caused billions of dollars in damage in recent years. Climate predictions suggest that, while Chennai will experience on average less rainfall per year in the coming century, rain will come in more intense bursts. The bandage to the problem offered is more expensive drains. However, these solutions ignore the real cause of floods in Chennai. Direct human interventions have contributed the most to increasing flood risk, next to climate change in general (also partly caused by human influences). The tarmacking of two-thirds of the city has sealed the ground surface with buildings and impermeable roads. Historic tanks and ponds that once captured rainfall have been built over, largely due to real estate pressure.

Neglect of abundant resources

Recent droughts have made Chennai look further afield for fresh water. As local fresh water reservoirs dry up, the municipality increasingly relies on expensive and unhealthy desalinated water as well as long-distance sources. Yet it cannot keep up with growing demands. In response, borewells dig deeper to tap underground aquifers for illegal commercial extraction. Depleting an already exhausted resource leads to sea water infiltration. However, on average the yearly amount of rain that falls on Chennai ever year greatly exceeds water demand—it just varies greatly by month and year. In expelling rainwater directly to the sea, storm water sewers rob Chennai of a precious resource. Used water is also expelled to rivers. Around 50% of this water is potentially recyclable. If these capacities were used to replenish groundwater, the city’s water problems would be greatly eased.

An inefficient centralized system
Chennai has turned its back to water bodies because of offensive pollution. Informal settlements are often the scapegoat, leading to resettlement schemes and barricaded rivers. But in reality, slums are only responsible for a small fraction of pollution. Less than half of the city’s sewage is treated in wastewater treatment stations, while the rest is expelled to rivers and storm drains, eventually polluting the shallow aquifers and making their water unsafe for consumption. In response the municipality plans to increase the capacity of its five treatment stations. Capacity problems are not only caused by the system itself though, but also by its insufficient maintenance and management. Nearly 3,000 kilometers of sewer mains are in place to convey sewage across long distances,2 depending on hundreds of unreliable pumps to move sewage across Chennai’s flat topography. The invisibility and complexity of this underground system makes efficient and accountable central maintenance and management near to impossible. Rapid and often informal urban growth further impedes the success of a solely centralized approach.