The north-east monsoon has not started in full swing, yet the one-day rain on October 15, 2024, left Chennai and its suburbs almost paralysed. Floods that occurred in 2015, 2017 and 2023 also affected normal life in most parts of the city. Even after spending crores of rupees to improve the drainage system during the last one year or so, flooding in Chennai continues.
Unless serious action is taken to remove encroachments in water bodies in different locations, the flood problem in the city cannot be solved permanently.
Chennai gets heavy rains on a regular basis as it is located along the highly volatile coast of the Bay of Bengal. However, massive flooding and waterlogging following just a few days of torrential rain have become common in recent years. The primary causes for these are: global warming, uncontrolled growth, and reckless urban development with no coherent hydrological plan.
During heavy rainfall, natural lakes, ponds, tanks, rivers and interconnected drainage systems are expected to play a critical role in replenishing groundwater, holding excess water and gradually releasing the surplus into the ocean. Tamil Nadu has about 41,127 tanks and a vast network of small water bodies, and hence vast areas getting inundated is indeed mystifying.
Coming to Chennai, why are its major waterways, including the Cooum, Adyar and Buckingham Canal, no longer able to drain the excess rainwater efficiently? The Pallikaranai marshland, once a crucial natural sponge that absorbed surplus rainwater, has deteriorated. What has caused the decline of this essential ecosystem?
Choking lifelines
Lakes and marshy areas were once iconic symbols of Chennai. According to a 2015 report by the Centre for Science and Environment, the city boasted over 600 small water bodies in the 1980s, each equipped with natural flood discharge channels that effectively managed excess water. Today, however, only a small fraction of these water bodies remain in good health. They have not disappeared but have been systematically encroached upon to make way for concrete structures, undermining the city’s natural drainage systems.
Sites that were once tanks or ponds two or three decades ago have now been replaced by multi-storey residential and commercial complexes. Chennai’s airport is built entirely on the floodplains of the Adyar River, while stretches of the Buckingham Canal now support the city’s elevated railway. Although the actual number of encroachments is likely to be much greater, these developments have contributed to the shrinking of significant waterways, including the Cooum, Adyar, Velachery, Mogapair, Vilivakkam and Ambattur.
In its draft for the ‘Second Master Plan for Chennai Metropolitan Area, 2026’, the Chennai Metropolitan Development Authority emphasised the importance of the Pallikaranai swamp area for the region’s drainage system. It urged that this area be conserved and that all development activities be strictly prohibited to preserve its ecological function. Regrettably, the Pallikaranai marshland has become the largest site for solid waste disposal over the years. Areas that were once open and served as drainage paths have now been developed into residential zones. Given this situation, where will the rainwater run-off be directed? It is important to understand that rainwater doesn’t forget where it used to flow; it will gravitate towards its historical path, which could be a road or a building today.
The severe flooding and encroachments are not confined to Chennai; recent catastrophic floods in Mumbai, Ahmedabad, Hyderabad, Kolkata, Bengaluru, Delhi and Jaisalmer highlight failure to effectively manage their drainage systems. In the pursuit of developing smart cities, many major Indian cities have either overlooked or recklessly encroached upon their natural reservoirs.
Lessons not learnt
The flooding in most of the areas on October 15 indicates that the city has not learned any lessons from the 2015 and 2023 episodes. Proactive planning can significantly mitigate damages. Effective urban design, coupled with a robust drainage system, is essential. The State must take decisive action against encroachments on natural reservoirs, as these intrusions diminish water storage capacity, a primary contributor to flooding.
Reports indicate that many initiatives by the State have not achieved the desired results, largely due to the civic authorities and land mafia significantly disrupting the city’s hydrological cycle. This concern was echoed by the Standing Committee on Water Resources in its 16th report, ‘Repair, Renovation, and Restoration of Water Bodies’, which highlighted that a majority of water bodies in the country have been encroached upon by municipalities and panchayats.
Tamil Nadu has a notorious record of encroachment into water bodies. This is well-documented by the First Census on Water Bodies, released by the Ministry of Jal Sakthi in 2023, which underlined that Tamil Nadu accounts for about 22 per cent of the total encroached water bodies in the country. Strong legislation should be enacted soon to make such encroachments a cognisable offence. In a landmark judgment delivered on September 6, 2014, the Madurai Bench of the Madras High Court directed the government not to grant layout or building permission on lands located on water bodies. This should be implemented stringently.
Construction of buildings in water-spread areas reduces the storage capacities of the water bodies, which is one of the major reasons for flooding. While imposing a blanket ban on all construction works in the marshlands, developmental activities in urban areas should be strictly reviewed before approval. De-silting of small water bodies and drainages should be undertaken regularly. The rainwater harvesting method that was propagated some years back in the State needs a fresh thrust. Parks must have ponds and large development areas must have a large water retention area which can absorb the excess rain.
The Tamil Nadu government reportedly plans to construct three new water bodies on Madras Race Club land to store water and mitigate flooding. Similar initiatives should be taken in different parts of the city. Also, efforts should be taken to store the water where it was historically stored by removing the encroachments. Else, flood-related problems will continue.
Narayanamoorthy is former full-time Member (Official), CACP, New Delhi, and Alli is Associate Professor, Department of Economics, Vellore Institute of Technology, Chennai. Views are personal