​Falling behind: On Mumbai and the monsoon

The southwest monsoon has been highly active over western India, with southwesterly winds loaded with moisture sweeping over the Western Ghats and delivering intense rains along the Konkan coast, while other weather systems offshore are routing more moisture over Mumbai and the surrounding areas. In urban areas in general, rainfall intensity matters more than volume. Mumbai itself can generally absorb moderate rainfall over several hours; however, its drainage — like in many Indian cities — cannot handle several hundred millimetres in short bursts. Heavy rainfall also overwhelmed river catchments in parts of Maharashtra, including around Nashik, while high tides reduced the efficiency of Mumbai’s stormwater drainage, worsening flooding in the city. Mumbai-Pune rail services were suspended after landslides in the Bhor Ghat and flights were affected. The closures of the Mumbai-Pune expressway and the Mumbai-Goa highway and significant flooding on the Mumbai-Ahmedabad expressway were disruptive, speaking to the increasing erraticity of monsoon rainfall, the vulnerabilities associated with linear infrastructure projects, and the ease with which the effects of natural disasters are compounded by cascading failures. A chawl collapse in Mankhurd took the lives of five children.

Mumbai lies on a peninsula built mostly on reclaimed land, former marshes, tidal flats, and low-lying coastal areas, creating the characteristic risk of higher flooding when rainfall coincides with high tide. It is compounded by decades of haphazard urbanisation that has encouraged water to run-off rather than be absorbed by the ground, forcing drains to handle more water than their design limits. After the July 2005 floods, when it received 944 mm in 24 hours, Mumbai launched the BRIMSTOWAD project and widened drains, installed pumping stations, and undertook premonsoon de-silting. Many of these works remain incomplete while some completed upgrades are based on assumptions about the monsoon that climate change has since undermined. Officials have also argued that pre-monsoon desilting helped reduce flooding in parts of Mumbai, but water on the Mumbai-Ahmedabad expressway, the chawl collapse, deadly tree falls in Kurla and Aarey, lack of redundancies in public transport, and the BMC’s belated advisory to builders to halt hazardous construction all suggest a governance lapse. Mumbai’s accountability also remains split across the BMC for local drainage and roads, the IMD for forecasting, the NDRF, two Railway zones, the State government, and highway authorities. Overall, the city has improved at shutting down to save lives and minimising the death toll — but as climate change and urbanisation evolve faster than infrastructure upgrades, simply waiting for system capacity to catch up to demand will be a failing strategy.