Chennai could have avoided floods: CSE

The CSE director general said rampant construction across the city led to the blocking of natural flood discharge channels of the lakes

The Centre for Science and Environment (CSE) said Chennai could have fared better if it had protected and preserved its natural water bodies and drainage channels.

CSE director general Sunita Narain in a statement said: “We have repeatedly drawn attention to the fact that our urban sprawls such as Delhi, Kolkata, Mumbai, Chennai, Srinagar etc have not paid adequate attention to the natural water bodies that exist in them. In Chennai, each of its lakes has a natural flood discharge channel, which drains the spillover. But we have built over many of these water bodies, blocking the smooth flow of water. We have forgotten the art of drainage. We only see land for buildings, not for water.”

It was further stated destruction of wetlands in Chennai is a major concern. Wetlands are rarely recorded under municipal land laws, so nobody knows about them. Planners see only land, not water and greedy builders take over.

"A number of cities including Chennai are both water-scarce as well as prone to flooding. Both problems are related – excessive construction, which leads to poor recharge of groundwater aquifers and blocking of natural drainage systems," says Sushmita Sengupta, deputy programme manager with CSE’s water team.

"While Chennai has been struggling to meet its water needs and has been even desalinating sea water at a huge expense, it allowed its aquifers to get depleted.”

CSE’s research shows that Chennai had more than 600 waterbodies in the 1980s, but a master plan published in 2008 said that only a fraction of the lakes could be found in a healthy condition.

CSE quoted the state’s Water Resources Department and said the area of 19 major lakes has shrunk from a total of 1,130 hectares (ha) in the 1980s to around 645 ha in the early 2000s, reducing their storage capacity. The drains that carry surplus water from tanks to other wetlands have also been encroached upon.

The analysis also shows that the stormwater drains constructed to drain flood waters are clogged and require immediate desiltation. Chennai has only 855 km of stormwater drains against 2,847 km of urban roads. Thus, even a marginally heavy rainfall causes havoc in the city.

However, Chennai’s human-made drainage is no replacement for its natural drainage systems.

A CSE analysis shows that there are natural canals and drains that directly connect the city with wetlands, waterbodies and rivers such as the Cooum and the Adyar that run through Chennai. The Cooum is supposed to collect surplus water from 75 tanks in its catchment area within the Chennai Metropolitan Area, while the Adyar is supposed to carry the surplus water of about 450 tanks in its catchment area and also from the Chembarambakkam tank (which is not in its catchment).