India: West Bengal's climate change conundrum Part II: Changing rainfall patterns have left Kolkata vulnerable to flooding; here's why

By Chirag Dhara

[...]

A study by Haider Ali and co-workers from IIT, Gandhinagar, in 2014 analysing changes in rainfall at urban centers in India from 1900 to 2010 found that Kolkata is among the cities that has seen the largest increases in episodes of extreme rainfall. Intense rainfall events are contributing an increasing fraction to the total yearly rainfall in the city, which means that monsoon dry spells are lengthening. This is precisely what [Samir Chatterjee, a former table tennis and bridge champion] described, as did most others who were interviewed.

Kolkata is far from an isolated case. Increasing monsoon variability is a pan-Indian, pan-global phenomenon.

[...]

River discharge and land subsidence in river deltas combined with storm surges and rising sea levels make coastal and riverine cities extremely vulnerable to flooding.

Kolkata has been found to be one of the most flood-prone cities in the world because of its exposure to cyclones that form over the Bay of Bengal, and an exceptionally rapid rise in relative sea levels in these parts.

[...]

One of the reasons for Kolkata’s increasingly vulnerability to flooding is the rapid decline in the east Kolkata wetlands, the natural drainage system of the city. Wetlands are defined as areas that are covered in water for at least one season. They act as a natural sponge, soaking in water and holding it until it can slowly infiltrate into the ground.

Increasing population and rapid real estate development over these wetlands is robbing the city of its natural defense mechanism against floods.

[...]