Battered by another round of rain, India’s fourth largest city Chennai is battling unprecedented floods – pointing to extreme weather events as a result of climate change and also the folly of unplanned, unrestrained development
By Gopikrishna Warrier
Map Attribute: To get a
clearer picture of how the Chennai has been affected, Sanjay, Aruna and Arun built a
map based tool to report flooded streets using OpenStreetMap data. One can zoom
into a locality, visualize which streets are reported as flooded (pink), and further one can click on a street and mark it as flooded too / Click on the Image to visit the source site.
If the runway of a city’s airport is built over a dry river, there is that once-in-a-lifetime possibility of the river running over its banks and flooding the airport. On Tuesday, December 1, that’s exactly what happened when the otherwise dry and stagnant Adayar river that runs under the secondary runway of the international airport overflowed its banks and water spilled all over the tarmac and aprons. This was in addition to the torrential rain that submerged one of India’s biggest cities and left many thousands stranded.
The airport
was declared closed, first for three days and later extended for five days. As
this is written, the airport has been declared shut till December 6. This is
unprecedented in the history of the busy airport, a hub for southern India,
which has been declared closed during heavy showers but never flooded and been
inoperable for so many days at a stretch.
Train traffic
was similarly disrupted and major roads caved in as the heavy rains inundated
the teeming urban centre of more than four million people and low lying areas
went under water. The armed forces had to be called in for rescue and relief.
The Indian Navy sent in INS Airavat to join in the operations. Essentials such
as drinking water, food and medicines were in short supply.
Scores of
people were reported killed in the unprecedented heavy rainfall that lashed the
coastal capital of Tamil Nadu in November and ran into December. The end result
was that during the northeast monsoon of 2015, starting from October 1, Chennai received rainfall of
1,506.9 mm, which is in excess of the city’s annual average rainfall of 1,468
mm. In November 2015, the precipitation was 1,197.3 mm, which was more than the
earliest highest in the century level of 1,088 mm recorded in 1918.
In the 24 hours
between December 1 and 2, the city reportedly recorded 294 mm and 345 mm in two
observatories, the highest rainfall since 1901.
The deluge
that followed was literally Chennai Floods Version 2.0 — the city had taken a
sunny respite of just a few days and was coming back to life after the heavy
rains of mid-November. Version 2.0 had an additional complication. The floods
were being caused not only by the rainwater falling on the city, but also due
the administration being forced to release water that was overflowing the
city’s storage reservoirs.
Thus, when the
Chembarambakkam reservoir had to be eased to release excess water, it flowed
through its natural drainage into the sea – the Adayar river. It flowed into
the Chennai airport. The walled premises of the airport became a temporary open
reservoir for the water.
Aircrafts
destined for Chennai could not land, and those at the airport could not leave.
In the touch down and take off world of commercial aviation, having a few
aircrafts locked up at the Chennai airport meant disturbance of schedules all
over the country. And since the outside of the airport terminal was one of the
areas badly inundated, those inside the buildings could not reach their homes
in different parts of the city and outside.
What caused
these unusually copious rains in Chennai during this northeast monsoon season?
“Even as the
world discusses climate change in Paris, Chennai is perhaps experiencing its
impact – the unprecedented deluge that the city has been subjected to is a
reminder of increasing frequency of such freak weather events across the Indian
sub-continent,” the Centre for Science and Environment (CSE) said in a press
note.
“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,”
CSE director general Sunita Narain said.
According to
Skymetweather.com, these rains were caused due to a combination of the El-Nino and
the positive Indian Ocean Dipole phenomena.
“El-Nino is an
oceanic-atmospheric phenomenon where sea surface temperatures of East Pacific
Ocean warm up, while the Indian Ocean and the Bay of Bengal have relatively
cool temperatures,” noted Skymetweather, which has become a quick go to site
for nuanced weather information. “For the development of any cyclone or strong
weather system, we require warm sea surface temperatures (SST). As a result,
central Bay of Bengal did not witness any weather systems this year on account
of cooler SST.”
However, the
positive Indian Ocean Dipole added a different dimension. The Indian Ocean
Dipole system is a periodic oscillation of SST within the Indian Ocean. During
a positive Indian Ocean Dipole year there is a greater than average warmth over
the sea surface resulting in the western part of the ocean leading to the
development of low-pressure areas. This resulted in the development of three
strong weather systems developing in South Andaman Sea this season resulting in
back-to-back rains in Chennai and other parts of coastal Tamil Nadu and Andhra
Pradesh.
Prone to Flooding
Chennai city
is prone to flooding. It is a topographically flat city, with altitude ranging
from 2 m to 15 m above sea level. Four rivers run from west to east into the
sea cutting through the city. Of this, two rivers – Cooum and Adayar – are
within the main city area. Since the city is otherwise water-deficient, these
rivers are blocked with bunds upstream of the city and their flow stored in four
reservoirs.
According to
CSE, Chennai had more than 600 water bodies in the 1980s, but a master plan
published in 2008 revealed that only a “fraction of the lakes could be found in
a healthy condition. According to records of the state’s Water Resources Department,
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”.
Chennai Flood
2.0 was more severe than the previous one because water was being released from
the reservoirs that otherwise are used to store water. This led to flooding of
all the areas which were either in the path of the rivers that originated from
reservoirs, or were in the lower parts of the city. Thus, settlement along the
banks of the Adayar and Cooum rivers, and those in the vicinity of swamps and
lakes got high flooding.
Somewhere in
its growth, the residents of the city forgot the natural contours of their
habitat, built along and across rivers, filled up lakes and ponds and massively
encroached upon the Pallikarnai Swamp. Resultantly, the once in a century event
became a huge nightmare.
For the
rain-weary Chennai and adjoining areas, three nearly back-to-back events have
caused much suffering and anguish, and the hope is that the weather will blend
into a pleasant winter sooner than later.
The ability of
the city to deal with events such as this is decreasing. Indirectly
proportional to this ability is the city’s vulnerability to climate
change-related extreme weather events, as and when they happen.
About The Author:
Gopikrishna
Warrier is Regional Environment Manager with Panos South Asia.
Publication Details:
This article was originally published at The Third Pole under Creative Common License 2.0 UK