The study found that roads and buildings replace permeable surfaces, reducing rainwater absorption and increasing surface runoff.
The study found that between 2000 and 2024, Chennai’s built-up area grew 7.6%, vegetation cover declined 26.14% and water bodies shrank 22.54%. The study found that rainfall in 2015 exceeded its estimated 100-year return-period intensity, while the 2023 event was associated with a nearly 25-year return period. Meanwhile, revenue administration and disaster management commissioner B Chandra Mohan said Tamil Nadu had identified around 1,030 locations with high or very high vulnerability and another 1,003 with moderate vulnerability, based on experience, forecasts and water-stagnation depth. Between 2022 and 2025, 1,144.5km of stormwater drains had been laid, according to the corporation.
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Chennai: Rapid urban expansion, shrinking vegetation and water bodies, drainage gaps, and low-lying terrain contribute to flood risk, according to a University of Madras study. “Spatial analysis indicates that flood-prone areas are concentrated in low-lying coastal zones, western and southern peri-urban areas, and Adyar River floodplain, where urban expansion, high flow accumulation, and historical flood occurrences overlap,” said first author Rahul Debnath. It has also got a response plan,” he said.
The city’s flood-risk hotspots include Velachery, Pallavaram, Chromepet and surrounding southern localities, parts of western Chennai, Koyambedu, Villivakkam and areas around Tondiarpet. The study found that roads and buildings replace permeable surfaces, reducing rainwater absorption and increasing surface runoff. Drainage gaps in western and southern peripheral areas overlap with recent urban expansion, suggesting infrastructure has not kept pace with development. Areas more than 1km from mapped stormwater drains were classified as having drainage gaps. Researchers analysed Landsat satellite imagery from five years, elevation data, India Meteorological Department rainfall records and historical flood locations using GIS and remote sensing. The authors recommend integrating land-use planning, terrain characteristics and historical flood records into flood-risk management. They also call for assessing drainage coverage and capacity to identify priority areas for intervention. Teams assessed vulnerable locations and prepared mitigation and response plans. “Each particular location now has a plan that is being used for mitigation. These plans include water-level triggers for action and evacuation, specifying where people should be moved as water rises. the Greater Chennai Corporation (GCC) has expanded its stormwater drain network in recent years While the study identified gaps in drainage coverage. Download the TOI App.