Why does Chennai get waterlogged every year? Is it extreme rainfall or the state govt's negligence?

Chennai: Tamil Nadu’s capital city Chennai continues to be water-logged following the heavy downpour of the last three days. Chennai has been experiencing heavy rainfall since October 31, resulting in the deaths of two people, waterlogging, and disruption of vehicular movement.

On Tuesday (November 1), Chennai reported the highest rainfall in more than three decades after the RMC recorded 8 cm rainfall in 24 hours. Previously, Chennai recorded 13 cm of precipitation in 1990 and 11 cm in 1964 on the same day.

The Regional Meteorological Centre (RMC), Chennai has predicted heavy to very heavy rains at Mayiladuthurai, Nagapattinam, Thanjavur, Thiruvarur, Pudukkottai, Sivaganga and Ramanathapuram districts of Tamil Nadu and Karaikal till Friday. An upper cyclonic circulation that lies over south Tamil Nadu and its neighbourhood, extending up to the upper tropospheric levels, is expected to bring the rains.

Record Rainfall

As the Northeast Monsoon had been active over the State, Chennai has received record rainfall on Tuesday (November 1); the Regional Meteorological Centre (RMC) recorded 8 cm in the 24 hours ending 8.30 am on Wednesday.

And in the last 24 hours one place had recorded extremely heavy rainfall, seven locations had registered very heavy rainfall and 20 locations, heavy rainfall. Sirkali had recorded 22 cm of rainfall, Thanjavur 18 cm, Chidambaram had recorded 15 cm, Sethiathope 13 cm, Kattumannarkoil 11 cm, Mamallapuram 9 cm, Maduranthakam 7 cm and Thiruporur 6 cm of rainfall.

Government's questionable efforts

Over the last six months, the Greater Chennai Corporation (GCC) has built 150 km long stormwater drains, costing about Rs 700 crore. While this stopped inundation in several hotspots in the city including T Nagar and Seethamal Colony, several pockets in the northern and southern parts collapsed.

As per reports, Greater Chennai Corporation is also working on a long term Rs 3,000 crore 750 km long storm water drains project, which when finished would fix these issues in northern and southern parts of Chennai as part of the River Kosasthalayar and Kovalam projects.

In 2015 and during many such extreme weather systems that Chennai has witnessed, it was mostly central and southern parts of the Tamil Nadu capital that bore the brunt. Ever since then, the Greater Chennai Corporation (GCC) initiated a stormwater drain (SWD) project and work has been taking place over the last few months in the city.

In the rains that have lashed Chennai in the past five days, North Chennai, the city’s congested neighbourhood with a largely working class population and several industries, is worst-affected.

The Northeast monsoon

The northeast monsoon, also known as the ‘primary monsoon of Tamil Nadu’, that brings sufficient rains to the state. The onset of the monsoon is usually between October 10 to 20. This year, however, it set in on October 29. Most of the other states in India depend on the southwest monsoon, that sets in from May and runs through September. The southwest monsoon, after a prolonged summer, helps Tamil Nadu maintain the ground water tables, while it is the North East monsoon that elevates the table.

Tamil Nadu’s coastal districts get 60% of the annual rainfall and the interior districts get about 40-50% of the annual rainfall from the North East monsoon.

Rapid rise in water levels in reservoirs

Heavy downpour in the city has led to a rapid rise in water levels in the reservoirs, leading to water from the Puzhal and Chembarambakkam dams, among the chief reservoirs providing drinking water to the metro, being released on Wednesday. The heavy downpour in Chennai, Kancheepuram and Tiruvallur districts caused heavy inflows into the reservoirs, and as a result 100 cusecs of water was released from Chembarambakkam and Puzhal dams.

Water level in Poondi, Cholavaram, Red Hills, Kannankottai Thervoykandigai and Chembarambakkam dams, with a combined capacity of 11,757 mcft, are fast filling up due to the northeast monsoon which set in on October 29. They account for a storage of 6,986 tmcft water with a combined inflow of 3,826 cusecs.

Tamil Nadu govt's action

Tamil Nadu Chief Minister MK Stalin conducted a meeting with officials. Shifting people from low-lying areas and those residing near the banks to safe areas, removing damaged and weak walls, taking steps to provide all the necessary basic facilities to those in the relief camps, coordinating with other departments and expediting required help, conducting medical camps to ensure people are not affected by any disease during monsoon seasons, providing awareness about electrocution during rains are some of the instructions.

Published on: Thursday, November 03, 2022, 05:56 PM IST