Climate Change

Chennai may break its own record for November rainfall

Lack of climate-resilient infrastructure and encroachment of water bodies has proved costly as floods ravage Chennai     

By Hariprasad Radhakrishnan
Published: Thursday 11 November 2021
Tamil Nadu Chief Minister MK Stalin's convoy wades through the flooded streets of Chennai. Photo @mkstalin / Twitter__

Chennai could break its own record for the maximum volume of rainfall it usually receives for the month of November, according to a popular city-based weather blogger.

The megacity has received rainfall above 1,000 millimetres during November only thrice during the past 200 years, Pradeep John tweeted November 11, 2021.

These dates are: 1985 (1,101 mm), 1918 (1,088 mm) and 2015 (1,049 mm). The city had already recorded 709 mm of rainfall till 2.00 pm November 11 and more than 19 days of the month were still left, he added.

Chennai has already been reeling under the intense rainfall it witnessed on the intervening night of November 6 and 7.

The India Meteorological Department (IMD) said in a press meeting November 11 evening that a depression over the Bay of Bengal had started making landfall between southern Andhra Pradesh and northern Tamil Nadu.

The depression is expected to last for a few hours. S Balachandran, deputy director-general of meteorology said the red alert for extremely heavy rainfall issued for Chennai had been revoked — meaning the worst was over for the city. However, a red alert for heavy to very heavy rainfall and high wind speed remains active.

He added that Nungambakkam, one of the prime locations in south Chennai, recorded the maximum rainfall of 6 centimetres November 11. 

No lessons learnt?

The rainfall has left residents marooned in their houses, as streets and subways remained heavily waterlogged. At least 11 of the 18 subways in the city were partially or fully submerged in the rains. Power outages and fallen trees were also reported in many parts of the city.

A senior official at the Greater Chennai Corporation told this reporter that 160 relief camps had been set up across the city. “About 2,000 people are currently staying at the centres. The numbers continue to fluctuate and more people are expected to move in soon,” he said. 

Less rainfall was witnessed this November compared to 2020 when Cyclone Nivar made landfall. But the high intensity cloudbursts spread over a very short span of time have been one of the major reasons for the floods.

The inadequate and unscientific construction of stormwater drains (SWD) and the encroachment of water bodies too have been responsible.

For instance, a SWD project worth several hundred crores, came under severe criticism as it was constructed on the seaward side of the East Coast Road, where the easy natural percolation of water precludes the need for artificial systems.

On the other hand, SWD systems in T Nagar and Kodambakkam — areas located in the heart of the city — failed to deliver as waterlogging continued for days. According to media reports, the civic body had spent Rs 2,500 crore on stormwater drain projects since 2015.

Arappor Iyakkam, an anti-corruption non-profit, has demanded the master plan for the stormwater drain system across the city be released in the public domain.

Chennai has also expanded over the years, with buildings encroaching upon water bodies, thereby obstructing the flow and percolation of water — one of the primary reasons for the 2015 Chennai floods. However, it is clear that the city has not learned its lessons yet.     

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