Chennai seems to be perennially in danger of going under water. Yes, one reason is intensifying cyclones due to climate change. But the flooding is just as much a result of terrible infrastructure—a problem shared by cities across the country.
First, tell me all about this cyclone…
Cyclone Michaung—pronounced mig-jaum—formed over southwest Bay of Bengal on December 3. The “super-cyclonic storm” approached Chennai—and travelled along its coast—coming within 90 km of the city. No, Michaung didn’t actually make landfall in Chennai. It remained almost stationary off the coast for eight hours—gathering in intensity—and dumping vast amounts of rain. It eventually hit land in Andhra Pradesh. You can see its trajectory below:
You can see satellite images of the cyclone below:
The heavy rains: began on the evening of Sunday, December 3. By the next morning, most of the city had received more than 120 mm of rain—it was higher than 250 mm in some areas. Chennai had not received that volume of rain in such a short period of time in almost five decades, according to the state government. The numbers are higher than even the catastrophic 2015 floods—which killed more than 200 people.
The chaos: Chennai came to a grinding halt overnight. Great parts of the city were flooded—including the airport. The government cut electricity to minimise the risk of electrocution. There was zero internet and mobile connectivity. The death toll for Michaung so far is 17. But the damage has been considerable—making it hard for the city to just bounce back. CM MK Stalin said:
The damage is especially severe in areas under the corporation of Chennai. Infrastructure such as roads, bridges, and public buildings have suffered severe damage. The livelihood of lakhs of people has been affected.
The drone footage below gives you a sense of the flooding:
So this was a super cyclone caused by climate change, yes?
Yes—though you can’t entirely blame global warming for the flooding. But let’s start with warmer sea waters.
How cyclones form: They form over warm waters—that are at least 27°C—and therefore occur close to the Equator. It’s a complex phenomenon that depends on a number of factors. The Hindu happily offers this easy-to-understand explanation:
As air moves over such a warm sea, it also becomes warmer and laden with moisture, and begins to ascend. In the process, it becomes cooler, which condenses the vapour and forms clouds. Condensation releases heat, which makes the air lighter and causes it to ascend further. As it does, the surrounding air moves in underneath, creating the surface winds associated with cyclones.
An unusual storm: Every year, around five cyclones form over what is called the North Indian Ocean basin. On average, four develop over the Bay of Bengal and one over the Arabian Sea. These cyclones usually occur either before the monsoons (April-June) or after (October-December). But cyclones that form over the Bay of Bengal are usually not this intense or destructive. And high-intensity cyclones are rare at this time of the year.
Warming waters: As we said, cyclones are fueled by warm waters. Rising sea surface temperatures trigger more intense storms. We are entering a global weather pattern called El Niño—which results in hotter weather. But this year, the ocean temperatures have been exceptionally high—due to the added effect of climate change. And the air is getting warmer too—increasing its ability to hold water vapour. So a Cyclone Michaung is hardly surprising or an anomaly.
An escalating pattern: Over recent years, cyclones over the Bay of Bengal are increasing in frequency and intensity. This means extreme events—that occur once in a century—are becoming alarmingly common:
“We have seen record rainfalls in Chennai both in 2015 and 2023 now, within the span of nine years. And even between this Tamil Nadu has experienced intense cyclones,” Prabhakaran Veerarasu, an environmental activist said. Just one month ago, the Nilgiris district experienced the season’s most intense rainfall, recording a staggering 37 centimetres of rainfall in just 24 hours.
A 2020 study showed that tropical cyclones with wind speeds upwards of 185 km/hr have become 15% more likely since 1979.
Even more dire: Another 2017 study shows that once in a century events could occur every 5-10 years by 2100. More recent research claims that climate change is happening at a faster pace than expected. If true, that prediction will come true a lot sooner than the end of the century.
Rising sea levels: Of course, there are other ways to end up underwater. The other serious climate change effect is rising sea levels due to melting glaciers. And cyclones accelerate warming temperatures at the poles:
Cyclones draw heat from the sea and move it to the upper atmosphere, where winds carry it to the earth’s poles and warm them. An intensifying cyclone will do this more powerfully.
A World Bank study predicts that waters around India will rise to a higher level—due to our proximity to the Equator. A UN report warned 12 coastal cities will be underwater by the end of the century.
Ok, so what can we do about this?
Build climate change resiliency in our cities. But Chennai hasn’t even fixed basic infrastructure problems like storm drains—despite heavy investments:
Compared to earlier years, Chennai was theoretically better prepared as it had built a network of storm water drains (at a cost of Rs 4,000 crore). But due to the poor quality of construction and the massive amount of rain that Chennai received, it failed to evacuate the water in many parts of the city.
In November last year, the city again flooded for similar reasons—and there was no cyclone involved:
To prepare for the monsoon season this year, the local government carried out an ambitious project to build storm water drains—which would collect excess rains from the streets and drain them into the sea. But within three days of heavy rains in the first week of November, the city was entirely flooded, bringing life to a standstill.
Construction, construction, construction: It’s the same old story in every city and Chennai is no different. Rapid and unplanned development has choked water bodies—which helped drain rainwater. The spread of concrete doesn’t allow the ground to absorb water. According to State Planning Commission data, more than 80% of land in the city is under construction. Or as a geology professor puts it: "Most of Chennai has become buildings and roads.”
Point to note: Here’s a data point that reveals the city’s priorities:
According to municipality records, there are more than 30,000 interior roads and 471 bus route roads in Chennai that add up to close to 5,000 km and 300 km, respectively, but the city’s drainage network is present in just around 2,000 km. Many of these drains were built at least three decades ago.
These old drains can only handle 20 mm of rain per hour. So it isn’t surprising that even roads with drains on both sides are easily flooded. Now add corruption and indifference to the mix—we end up with new drains that are badly designed and poorly executed.
The bottomline: Our cities flood even when there isn’t a super-cyclone in town. Imagine how bad it will be as these events become frequent. How many times will we rebuild and restore—only to have it destroyed in the next torrential downpour?
UPenn’s Water Center has the most comprehensive analysis of Chennai’s water woes. BBC News offers a big picture view of the city—while this Hindustan Times deep dive looks specifically at infrastructure issues. The Hindu offers excellent visuals to explain Chennai’s problems. Also in The Hindu: An overview of Cyclone Michaung. The News Minute looks at the climate change angle.