The rains in Chennai have reportedly broken a 100-year record (374 mm in just 24 hours).

Unregulated urbanization behind the crisis in Chennai CSENishanth Krish
news Chennai Rains Thursday, December 03, 2015 - 18:51

Even as the world discusses climate change in Paris, Chennaiites are perhaps experiencing it firsthand. The rains in Chennai have reportedly broken a 100-year record (374 mm in just 24 hours).

According to a Centre for Science & Environment (CSE) press-note, rapid urbanization in Chennai, Mumbai and other Indian cities has destroyed natural drainage systems, increasing their vulnerability to flooding.

CSE director-general Sunita Narain said that Indian urban sprawls 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, blocking the smooth flow of water. Wetlands are rarely recorded under municipal land laws. Planners see only land, not water. Greedy builders then take over,” she observed.

Chennai had over 600 water bodies in the 1980s, but now only a fraction survives. Climate change-induced unnaturally heavy rains could have exacerbated the problem. Chennai has only 855 km of storm-water drains, most of which are clogged as against 2,847 km of urban roads. Thus, even a marginally heavy rainfall causes havoc in the city.

Excessive construction leads to poor recharge of groundwater aquifers and blocking of natural drainage systems. “While Chennai has been struggling to meet its water needs and has even been desalinating seawater at a huge expense, it allowed its aquifers to get depleted,” observed CSE officials.

There are natural canals and drains that directly connect the city with wetlands, water bodies and rivers such as Cooum and 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 river 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).

Scientific research has already linked such intense weather phenomena to changing climate. An Inter-Governmental Panel on Climate Change Report clearly says that frequency and intensity of such excessive rainfall will increase in the future. 

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