Sting in the tail: on Cyclone Ditwah, its impact Politics & News

During its slow crawl over Sri Lanka in November, Cyclone Ditwah was a rain machine that repeatedly swept over the same areas for days, eventually precipitating a national disaster with widespread flooding. Fourteen lakh people were affected, and at least 474 were killed. After crossing Sri Lanka, the system re-entered the Bay of Bengal and briefly reintensified, bringing heavy rains to north Tamil Nadu and south Andhra Pradesh. By December 1, the storm’s remnant parked itself off Chennai’s coast as a deep depression. The next day, after around 18 cm of rain over 24 hours, the city woke to flooded streets and widespread waterlogging. While that much rain would test any urban drainage system, public frustration has mounted. That Ditwah was tricky to predict made matters worse. Chennai’s storm water network has been rebuilt and extended after the 2015 floods, and again since 2023, but it cannot be flood-proof. Integrated projects in local basins are designed to handle intense bursts rather than hours of heavy rain. The GCC has said that it has spent ₹5,200 crore over four years to add around 1,100 km of new drains, with three-fourths of the work done. A separate endeavour to fix smaller broken links is incomplete, leaving many streets waterlogged. Chennai’s flat layout, increasing paved area, and the three rivers running through it from catchments in Tiruvallur and Kancheepuram also mean that when a storm system inundates those basins and Chennai together, water levels will rise quickly. Recent floods in north Chennai exposed the encroachment and shoddy desilting of the Kosasthalaiyar. With its ability to tolerate flooding diminished, the GCC had to shut some drains and pump stagnant waters against reverse flow. By lingering near Chennai, the new storm had similar effects.

The Thiruppugazh Committee appointed after the 2021 floods produced a 600-page report with basin-wise recommendations and numerous measures. The State government has cited this report while justifying design changes and drain upgrades, building artificial water bodies, and seeking central funds for an ‘Integrated Urban Flood Management’ project, yet the report remains out of public view. There is also no verifiable consolidated implementation plan with a deadline. Flood maps and elevation models exist for the Chennai basin but they are not a shared reference for enforcement and relief efforts, while proper zoning and limits on construction continue to elude residents. Thus, the rains underline an unresolved story while spotlighting gaps in infrastructure and transparency. As the upgrades take shape, the State must publish the report and ensure hazard maps and basin-wide coordination efforts as well as temporary solutions such as pumps keep pace with the storms that routinely test them.