Chennai is getting back on its feet after the devastating flood. It was 100 years ago when Chennai, then Madras, was faced with such a deluge. But, there were no floods.
A clearer picture
To understand the situation better we need to know more about Chennai. Located along the Bay of Bengal, Chennai and its surroundings had many rivulets and rivers with their catchments and flood plains and numerous natural depression wetlands. When it rained heavily in the catchments, the rain water flowed into rivulets and then on to the rivers and finally into the Bay of Bengal.
When the rain persisted, the rivers burst their banks and the water got into the adjoining flood plains and to the natural depression wetlands. The flood plain depressions retained the water and thus buffered the flood. The same flood plain wetlands provided a sanctuary for resident and migratory birds, fish, amphibians, reptiles and a host of aquatic vegetation. These flood plain wetlands took a long time to evaporate and while doing so, also recharged the groundwater helping flood plain agriculture.
From a rural agricultural landscape of natural wetlands and a myriad rivulets and rivers, Madras and its surroundings changed into an urban metropolis. In the process, it first reclaimed and filled up the flood plain natural wetlands, embanked the rivulets and rivers and channelised them into mere drains.
Our city planners replaced nature’s flood abatement architecture into non-porous and flat concrete jungles.
The volume of rain water that came down had no flood plain wetlands to hold them nor were there unchanged rivulets and streams to take the water into the rivers and then on to the sea. Instead the flat flood plains had to hold the flood water till they were drained out or gradually seeped into the ground, which is an extremely slow process.
With no legal prohibition and safeguard for the flood plains and catchments of water bodies including rivers in and around Chennai, abuse of it has been made easy in the name of “so called development”.
It is estimated that Chennai has lost majority of its 650 wetlands to such uncaring development. A classic example is the Chennai International Airport constructed over the active flood plains of the Adyar — one of the two lifeline rivers of Chennai.
As future citizens, you need to be aware of how environment has planned its landscape design to face nature’s fury. We also need to question our city planners as to why the provisions of natures were not taken care of.
While we ponder over these mistakes, let us at least make sure that we will not choke our streams and drains with polythene and other such material that will close the opportunity of excess rain water getting into the natural rivers.
The writer is a Principal Invigilator and Senior Advisor, Aquatic Systems, Wildlife Trust of India.
How the flood plain depression could have saved the city
To understand this, take a square meter of parchment paper and place it on a loose sandy surface. Using your fist, punch the paper in as many places as you can to create several hollow depressions. Pour water on the parchment and fill in the depressions. Measure how much water these depressions hold. Now, hold the parchment paper by the four corners and pull. See how it flattens out and the water floods out. This is what happens when the natural depressions of our flood plains are flattened for agriculture or urban development. It diminishes their ability to hold rain water, resulting in floods.
