Chennai waterlogged: Why is it raining so much, and is it normal? – The Indian Express

Chennai News

Chennai has been experiencing heavy rainfall since October 31, resulting in the deaths of two people, waterlogging in several parts of the city, and disruption of vehicular movement. The India Meteorological Department (IMD) has predicted more rainfall in the city and other parts of Tamil Nadu, Puducherry and Karaikal, over the next three days.

How much rain has Chennai received?

Chennai 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.

Officials at the RMC said Perambur and Chennai Collectorate received 17 cm of rainfall each from 8.30 am Monday to 8.30 am Tuesday.

Among other areas in Chennai, Sholinganallur, Cheyyur, MGR Nagar, Nungambakkam, and Ayanavaram recorded 13 cm of rainfall each. At least 15 places recorded very heavy rainfall and 21 areas experienced heavy rainfall in the past 24 hours.

Addressing the media, Regional Meteorological Centre (RMC) head S Balanchander said, “Today, Chennai’s Nungambakkam station recorded 8 cm rainfall.” Previously, the city recorded 13 cm of precipitation in 1990 and 11 cm in 1964 on the same day.

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.

The Tiruvallur district administration said the quantum of water to be released would be increased depending upon the inflows into the reservoirs. The authorities have urged the people living in low-lying areas to be on alert. 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.

What brings rain to Chennai at this time? Is it normal?


Yes, it is. Chennai is largely fed by the northeast monsoon, from October to December, with easterly winds starting from mid-October. The onset of the monsoon is usually between October 10 to 20. This year, however, it set in on October 29.

It is the northeast monsoon, also known as the ‘primary monsoon of Tamil Nadu’, that brings sufficient rains to the state. 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.


In an earlier press conference, Balanchander said that this year, the north-east monsoon arrived on the coast on October 19. “We are currently seeing an active spell. There will be a lot of changes for the entire season. We have made a forecast for this month,” he added. He also said that the RMC has recorded 20 cm of rainfall since October 1. “The average during this time is 28 cm. So it’s a -29% (deficit) rainfall,” he told reporters.

The meteorological department also predicts a likely formation of low pressure over the Bay of Bengal moving towards the northern Tamil Nadu coast with moderate rain in the coming days ahead of the formation of the low pressure.

Is the rains a reason to panic?

Absolutely not, said Balanchander, while speaking to “October to December is Chennai and Tamil Nadu’s monsoon period and it is natural that there will be rains during this time. Right now, we are having an active spell of rains which began on October 29 and is likely to go on until November 5 or 6.”

Every month has its own share of active and dry spells, but the intensity of rain also differs, Balanchander said. “For example, it didn’t rain as Wednesday today as it did Tuesday. The intensity will vary.”

When asked if the rains this year can be compared with that of November 2021, he said, “We cannot compare the measurement because this is just the first spell. We can only compare with the whole month’s data.”


Balanchander also said that Chennai and parts of coastal Tamil Nadu will receive light to moderate rainfall in the next few days, after which rainfall activity will be seen in interior parts of the state.

Has the govt’s stormwater drain project been successful?

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.

This year, following the project, many areas prone to flooding have seen a marked difference in terms of rainwater drainage. In the last 24 hours, areas including GN Chetty Road in T Nagar, Velachery and other areas have seen less waterlogging. However, in parts of North Chennai, including Perambur Barracks road (which was submerged in 2021), things did not seem to improve. The visited the area on Wednesday and noticed that Perambur Barracks road and Pattalam areas were severely waterlogged. Other parts including Perambur, Pulianthope, Pantheon Lane, Vadapalani and Saligramam experienced waterlogging.

What has the Tamil Nadu govt done?


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 Stalin gave to the officials during the meeting.

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Municipal Administration Minister K N Nehru said Chennai recorded 205.47 mm rainfall between October 31 and November 2. “Water did not stagnate in many areas due to the completion of stormwater drain works. Waterlogging in Kolathur and Thiru Vi Ka Nagar areas is due to excess rainfall,” the Minister told the media earlier in the day. Measures were being taken to drain the water in the inundated areas with high-power motors, he said. Of the 15 subways being maintained by the Greater Chennai Corporation, water logging was reported in 3 — Ganesapuram, Rangarajapuram and Manickam Nagar, he added.