Chennai paid the price for loss of wetlands and open spaces: study

Chennai’s resilience to the recent deluge has taken a severe beating as nearly a quarter of its wetlands, open space and flood plains have given way to concrete structures. Months before the series of depressions and “freak” weather developments hit the city, researchers at the Centre for Ecological Sciences in the Indian Institute of Science (IISc), Bengaluru, tabulated the “worrisome” growth patterns of the coastal city.

The research, which is to be published in the Journal of the Indian Society of Remote Sensing, shows that since 1991, the city’s concrete structures have increased nearly 13 times. Correspondingly, flood plains and open areas have been reduced by a fourth.

The results were tabulated through a combination of satellite imagery, which was then superimposed over topological maps of the Survey of India as well as from the Chennai municipality.

“In cities like Chennai and Kolkata, marshes and flood plains play a very important role in draining out overflowing rivers. This doesn’t seem to have been understood by urban planners. One can’t encroach the buffer around rivers without consequences,” says T.V. Ramachandra, who authored the study.

A disaster foretold

An IISc study attributes the severity of flooding caused by the recent rains to Chennai's worrisome growth patterns


  • In 1971: 0.3 million; population density, 769 persons 769 persons per
  • In 2011: 8 million; population density, 2,109 persons per

Area Studied

  • Chennai city area:
  • Buffer zone: 10km (peri-urban towns)
  • Built up area gone up from 1.46% to 18.6%
  • Area under vegetation gone down by 22%

Exploding growth since 1991


open spaces, marshy land and flood plains reduced by 18.14%

Predicted growth in 2026

  • Built up area to increase to 36.6% of total city mass
  • Open spaces, marshy land and flood plains to reduce to just 33.1%

Unplanned growth

Satellite images and predictive modelling show that the northwest and southwest zones of Chennai are seeing the most unplanned growth — an observation that correlates with not only the levelling of marshlands, but also the areas worst affected by the recent floods. “Is it worth sanctioning Rs.1,000-crore projects here, while spending more than Rs. 15,000 crore to restore normalcy to a flood-ravaged city?” asks Mr. Ramachandra.

Growth outlook

The outlook, predicted through the modelling of current growth along with planned and unplanned expansion of the city, looks grim. Built-up area of asphalt, concrete and metal is set to nearly double in size over the next decade, while open spaces will decline by a third.

“Significant changes can be seen in areas which fall within the CMDA [Chennai Metropolitan Development Authority] boundary such as the Korattur and Cholavaram lake bed, the Red Hills catchment area, the Perungalathur forest area, and the Sholinganallur wetland area,” the study says.

The metro tops the list in emissions

While bad planning and destruction of marshy lands may have only exasperated the devastation of the floods, IISc researcher T.V. Ramachandra is quick to point out that along with other major metros, Chennai must address its greenhouse emissions that contribute to climate change.

His recent research on carbon footprints in major metros of the country, shows that Chennai tops the list in emissions per capita. The city releases nearly 4.79 tones of CO2 per person per year, while Kolkata comes a distant second at 3.29 tonnes per capita. The highest contributor is industrial emission, where 4.4 million tonnes of CO2 in the year studied.

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Printable version | May 14, 2021 3:41:52 PM |

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