It has always been an open secret, discussed and debated after the December floods last year. But now it has emerged that as the city expanded, more than 150 water bodies, that were part of a flood mitigating system in the city and its suburbs, were encroached and turned into human habitation. The result was there to see: Plum real estate ventures in Mudichur and Tambaram went under water. According to a study done by Care Earth Trust (a Chennai-based biodiversity research organisation), only 15% of the city’s wetlands are left, down from the 80% when Chennai’s area was lesser. The researcher, Prem V , has analysed the spatio-temporal variations, specially focusing on wetland and built-up land of the Chennai metropolitan area from 1980 to 2010.
As per the findings, the built-up area of the city was 47.62 sqkm in 1980, only 20%, while the wetlands were spread over 186.30 sqkm (see maps). In 1991, the built-up area increased three-fold, 152.33 sqkm, and almost equaled the wetland spread which in the 11 years had come down to 159.41 sqkm. The IT boom at the turn of the millennium triggered a construction boom in the southern parts of the city to accommodate offices; and to house techies the real estate business flourished in the vicinity. Over the years, the city expanded and outskirts like OMR and Perungudi transformed. As concrete replaced the shrublands and dry lake beds, the built-up area increased. In 2000, it was 250.58 sqkm (68%) when compared to the 117.48 sqkm of the wetlands. A decade later, the built-up area touched 402.10 sqkm (85%) and the wetlands had shrunk to 71.05 sqkm (15%).
The study found that most of the water bodies affected were in the southern and western suburbs. The areas where the water bodies were encroached, some institutionally, included Tambaram, Perungalathur, Vandalur, Ramapuram, Manappakkam, Valasaravakkam, Ambattur, Alandur and Adyar. Incidentally, several of these areas were hit hard by the December deluge. According to the study, buffer areas of a lake are the first casualties of rapid urbanisation. Known as ‘odai porambokku’ and ‘yeri porambokku’ in Tamil – meaning rivulet across a wasteland and lake on a wasteland respectively – these buffer areas connected lakes and drained excess water from one water body into another. These channels formed an integral part of a natural flood mitigating system, but over time, with the lakes dry, these were encroached upon, the study said. Also, pastoral land adjoining the lakes acted as floodplains during monsoon. With the channels and farmlands gone, flooding was imminent. As a conservation-oriented study, the research provides a road map for the government to protect the wetlands from further degradation. Six years ago the Union ministry of environment and forests enacted Wetlands (Conservation and Management) Rules 2010. One of the key features of this legislation was powers vested in the state machinery to determine the “wise” use of water bodies. May 2016, Tamil Nadu set up wetland authority to protect the water bodies. How effective it will be remains to be seen.
Article published in ToI as SINKING REALITY – Why Chennai & suburbs went under water?