IMD issues red alert for Chennai: Why floods are an annual affair in the southern city

Rapid urbanisation, lack of planning, destruction of wetlands and climate change are all contributing to the flood issue in the city

FP Staff November 18, 2021 16:55:48 IST
IMD issues red alert for Chennai: Why floods are an annual affair in the southern city

Firefighters evacuate with a boat residents of a waterlogged neighbourhood to a dry area during heavy monsoon rainfall in Chennai. AFP

It's a wet, wet November for Chennai and its adjoining districts in Tamil Nadu.

The India Meteorological Department has issued a red alert for Chennai and four neighbouring districts — Tiruvallur, Kancheepuram, Chengalpet, Cuddalore and Villupuram for Thursday. It has predicted extremely heavy rainfall.

So, as Chennai prepares for more rainfall, we examine why this southern state keeps getting flooded.

Flooded in

Wednesday's red alert for Chennai and its adjoining areas is just the tip of the iceberg.

Chennai has been a victim of repeated floods and the most recent one took place last week.

Between 6 to 11 November, as many as 14 people lost their lives due to heavy rains. Reports stated that the downpour had led to the water-logging of 13 subways and uprooted 260 trees. Operations at the Chennai airport were also affected for over more than four hours due to the downpour on 11 November.

According to the Weather Channel India, Chennai had registered 815 mm of rain from 1 October to 16 November — a whopping 67 percent excess compared to its average.

Floods have ravaged the city in the past too; no one can forget the November 2015 deluge in which approximately 500 people died and over 18 lakh people were displaced. Also, it was estimated that the floods had caused damages worth approximately Rs 200 billion. At the end of the disaster, the IMD reported that the city had received 399 millimetres of rainfall in five days.

Reasons for floods

A wide range of issues are responsible — from rapid urbanisation, destruction of wetlands, inadequate infrastructure to even the city's geography.

One of the biggest causes for flooding is the loss of water bodies owing to rapid urbanisation. If you dig through the history of Chennai, you will notice that many localities are named after the presence of a water body. However, a look at Chennai today shows that most of these lakes have shrunk and many are now construction sites, apartments and skyscrapers.

Similarly, urbanisation without proper planning and encroachment has sapped the Adyar river’s ability to carry away floodwater. Another key waterway, the Buckingham Canal, is also choked with silt and sewage. Wetlands such as Pallikaranai, which could act as buffer in case of heavy downpour, are also being converted into built up areas leaving the water nowhere to go.

In July last year, the Madras High Court had pulled up the Tamil Nadu government for its apathy towards encroachment of water bodies and said development cannot be permitted at the cost of nature.

"Chennai was once a city of lakes. Where are the lakes now? It is the primary duty of the state to preserve the life source. If a world war happens it would be only for water," a division bench of Justice M M Sundresh and Justice R Hemalatha had said.

Another reason for the flooding could be attributed to the faulty storm water drains.

In suburban areas such as Velachery, Madipakkam, the storm drainage system is either woefully inadequate or virtually non-existent.

Janakarajan, a retired professor from Madras Institute of Development Studies, in a NewsClick report, was quoted as saying: "The drains should be scientifically designed to carry water. I doubt if there were any elevation and gravity surveys done before construction. Poor maintenance of the drains also played a role in inundating the city."

A Times of India report dated 15 November highlighted how Chennai was existing without a proper drainage system. The report stated that the Greater Chennai Corporation maintains roads stretching over 5,902 km, but its drain network extended to just 2,058 km.

Worse, only about 800,000 of the 1.5 million homes in the city have sewage connections, which implies that the rest of the city is letting sewage into storm water drains.

A report published by the Tamil Nadu government in September also said that 32 irrigation tanks around the Pallikaranai marsh in south Chennai were choked with waste, slush and debris, obstructing the flow of flood water. This also reduced the water-absorbing and groundwater recharging capacity of the marsh.

Besides poor planning and corruption involved in the building of storm water drains, climate change and global warming are also responsible for the floods in the city.

Mahesh Palawat, vice president, meteorology and climate change, Skymet Weather, in a recent interview with India Today had attributed the heavy rains to climate change. "In November-December, cyclones tend to form over the Bay of Bengal. So, it is not unusual. But the amount of rainfall is. We can say it’s an impact of climate change. Extreme weather events are increasing by the year. This will continue unless we start reversing climate change," he was quoted as saying.

A study in 2020 done collaboratively by Pune-based Indian Institute of Tropical Meteorology along with National Institute of Technology, Rourkela and SRM Institute of Science and Technology, Chennai had also stated that Chennai-like floods could become common if rising global temperatures were not brought under check.

What can we do?

The state government needs to plan better and build more storm water drains and also put a curb on encroachments and development.

However, these conventional urban-flood management approaches may not be enough.

The state must look into building permeable roads, green roofs, rain gardens to improve disaster risk management.
Additionally, city municipalities should work with grassroot organisations to promote awareness on flood risk management.

With inputs from agencies

Updated Date:

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