Latest revision as of 20:19, 29 November 2021

Chennai, The floods of December 2015 (statistics as on 3 Dec 2015); Graphic courtesy: The Times of India, December 4, 2015

NASA map showing rain intensity between November 28 and December 4, 2015; Graphic courtesy: The Hindu, December 14, 2015

[edit] December 2015

[edit] December 2, 2015: Heaviest rain ever

The Times of India, Dec 03 2015  345mm In A Day Smashes 114-Yr Record

Chennai on 2 Dec 2015 recorded the heaviest-ever rainfall of 294mm and 345mm in the Met office's two observatories here in 24 hours, breaking the previous record of 261mm set in 1901. Level of 2 Dec 2015 was more than half the average rainfall for the entire northeast monsoon and pummelled an already stricken city into submission. Large swathes of Tamil Nadu remained marooned, leaving over 200 people dead over the past month, with the Met department predicting further downpour over the next 48 hours.

The last time a natural calamity struck the state with such vehemence was the 2004 Asian tsunami. While the death toll was much higher at nearly 8,000, the damage and disruption this time is feared to be on a similar scale.

“The entire southern part of the city is disconnected.There is no public transport running there. Two main bridges there have also been closed and water current is too high for our boats to reach there,“ National Disaster Response Force director-general O P Singh said.

Weather chief meteorologist Mahesh Palawat attributed the heavy rainfall primarily to the El Nino phenomenon.

“Many typhoons were formed in the Pacific Ocean this year due to the warming of the ocean. But the Indian Ocean is cool compared to the Pacific, and the wind carried more moisture, bringing in extreme rainfall,“ said Palawat.

“Not many countries get rainfall in December. It is biting winter or summer, depending upon the continent in which you live. But TN receives most of its rain at this time of the year,“ he added.

Beyond Chennai, the American state of California and the Caribbean islands are the ones which receive rainfall in December, but the intensity is lower than what the Tamil Nadu capital has experienced since the start of December in 2015.

[edit] Runoff water management

The Times of India, Dec 04 2015

Runoff water management new mantra for planners

 The increasing frequency of intense rainfall as witnessed in Chennai is changing traditional approaches to drainage with “retention and detention“ strategies that reduce peak flows and encourage local storage finding increasing favour with urban planners. Though the 347 mm rain -in contrast to the more usual 53 mm -that inundated Chennai in the past six days can challenge most sewage and drainage systems, mapping the urban needs of an area can help reduce pressure on the drainage system during normal rainfall and well as during surges. The traditional approach to drainage aims to remove water as quickly as possible from the point of collection but this can prove counter-productive during intense rainfall and in areas that might get wetter due to the effects of climate change.

Countries such as Singapore that have geared their water collection to harvest as much of the runoff as possible are moving to reduce peak flows by as much as 55% by using detention tanks. The city state's active, beautiful, clean (ABC) waters programme looks to both store and treat water near locations such as residential areas and parks. Newer constructions are encouraged to harvest water for local use such as cleaning, gardening and air cooling.

Storm water is channeled through parks that use natural media to filter water on its way to collection tanks and eventually reservoirs. This process is, of course, dependent on strong separation of sewage and drainage which is absent in most Indian cities. But the Chennai experience can give a major push to such solutions that find mention in the smart cities and the Atal mission for urban rejuvenation and urban transformation (AMRUT) programmes.

[edit] Corruption-free relief disbursal

The Times of India Jan 10 2016

Disbursal ofrelief after the 2015 floods in Chennai

Sivakumar B

Relief disbursal after a disaster is usually a bigger disaster. But TN may have shown the way with what is probably India's fastest and most transparent distribution of compensation

A little over a month after her makeshift house on the banks of the Adyarriver in Chennai was washed away on De cember 2, 2015, Sahaya Mary was puzzled by an SMS from her bank informing her that Rs 5,000 had been credited to her account.

The 30-year-old had no clue where the money had come from and headed to her bank on January 5 to check. She was told that her account had a balance of Rs 5,700 -the additional Rs 5,000 was flood relief from the government. Mary's family were also victims of the 2004 tsunami and her fisherman father lost his boat to the giant waves, but they'd waited months for the relief money then.

“In 2004, the compensation was distributed by party cadres and we did not get the full relief money sanctioned by the government,“ says Mary , a homemaker with a school-going son.“The other option was going to the tahsildar's office and standing in long queues for three days to get the money . This time, it was a surprise to get Rs 5,000 so quickly ,“ said Mary .

It's not just the beneficiaries who are surprised by the quick and hassle-free disbursement of cash --though it is a tad slower than the pace at which AIADMK cadre printed and distributed Amma stickers when relief material was sent out. Even the opposition parties -who criticized the mismanagement of water release from the Chembarambakkam reservoir, which caused the flash floods -were impressed by the government's decision to credit the relief directly into victims' bank accounts. The move cut out middlemen and erased the corruption that was rampant during tsunami relief work a little over a decade ago. In the first week of December 2015, water from the swelling rivers entered homes in several parts of south Chennai, including Nandambakkam, Saidapet, Mudichur, Nandanam and Kotturpuram. On January 4, 2016, the government transferred Rs 700 crore into bank accounts of 14 lakh families in Chennai, Kancheepuram, Tiruvallur and Cuddalore districts. This is perhaps the speediest disbursal of compensation in the country . Around 25.5 lakh households in four districts in Tamil Nadu were affected by the floods. The other households are likely to get the money on January 11.

Tamil Nadu's high banking penetration has helped the government transact with ease -87% of households in Tamil Nadu have bank accounts, and in urban areas like Chennai all families have one or more bank accounts in public or private banks. “Nearly 80% of the affected households in the four districts had bank accounts. We opened accounts for the remaining 5.1 lakh households under the Pradhan Mantri Jan DhanYojana,“ said a senior government official.

It's a model that other states that are affected by natural calamities could emulate. In Odisha, for example, which has been hit by floods or drought every year, victims get relief only through taluk offices. “We send a cheque to the district collector and then money is sent to each and every taluk. The victims have to go to the taluk offices and collect relief,“ said an official of Odisha Disaster Management Authority . All donations to the chief minister's relief fund in Odisha are done through banks.“We ask all donors to deposit the money into the chief minister's relief fund account and then disburse the money via cheques to the collectors,“ explained the official.

The AIADMK government has moved fast and its relief efforts as well as its work to check the outbreak of epidemics have come in for praise from Central teams, but whether the victims were really soothed will only be known after the elections later in the year.

[edit] 2021

[edit] November

Arun Janardhanan, Nov 9, 2021: The Indian Express

The heavy rain that lashed Chennai led to flooding in at least 40 busy residential and commercial neighbourhoods in the city. The overnight rain, which was reportedly the heaviest since 2015, was part of a formation of a low pressure over the Bay of Bengal.

Overnight Impact

The rains caused flooding in several city neighbourhoods including T Nagar, Vyasarpadi, Adyar, Velachery, Royapettah and Mylapore. Jawaharlal Nehru Nagar, Madhavram, Tondiarpet High Road, Northern Trunk Road, Royapuram, Teynampet, Khader Nawaz Khan Road, interior areas of Velachery, several stretches of Sholinganallur in the city suburb were among those areas reported flooding or water inundation early morning on Sunday.

According to a government release, 500 Cusecs of water from Puzhal reservoir will be released around 11 am and the local authorities issued alerts to people living in low-lying habitations on the banks of the surplus canal. The government has also announced that the water from the Chembarambakkam reservoir will be released.

Heaviest rain after 2015

Data from two rain recorders – Nungambakkam in Chennai city and Meenambakkam in the city suburb – shows that the city and suburbs received 21.5 cm and 11.3 cm rains respectively.

In one of the heaviest episodes of rain witnessed in 2015, on November 15 to 16, Chennai recorded 24.6 cm rainfall in 24 hours, which was breaking the previous record of 14.2 cm from November 2005.

But the maximum rainfall recorded in 24 hours time may be from November 1976, when Chennai had recieved 45.2cm of rainfall. Another record rainfall, in two days, was registered in 1985 – which was November 12 (25cm) and November 13 (33cm). The 14.2 cm rainfall in 2005 was the next.

North East monsoon bring rains to Chennai

Chennai’s monsoon is largely about the Northeast Monsoon, rains during October to December, with easterly winds starting from mid-October, precisely the usual onset that begins between October 10 to 20. It is the Northeast Monsoon, also known as the ‘primary monsoon of Tamil Nadu,’ that brings sufficient rains to the state when all other states depend on the South West monsoon for rains that sets in from May, June and July. The South West monsoon, after a prolonged summer, helps Tamil Nadu to maintain the ground water tables, 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.

Low pressure formation

The meteorological department 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.

“An upper air cyclonic circulation lies over southeast Bay of Bengal and adjoining equatorial Indian Ocean extending up to 3.1 km above mean sea level. Under its influence, a low-pressure area is likely to form over southeast Bay of Bengal and neighbourhood around November 9. It is likely to become more marked during subsequent 48 hours and move towards the north Tamil Nadu coast,” said a statement from the Regional Specialised Meteorological Centre – Tropical Cyclones. It also predicts chances of squally winds of 40 kmph to 50 kmph gusting to 60 kmph might prevail over the sea from November 9, and along and off the Tamil Nadu coast and south Andhra Pradesh coast from November 11 and 12.

A heavy rainfall warning also has been issued for November 10 as a thunderstorm with heavy to very heavy rain is likely to occur at isolated places over Chennai, Tiruvallur, Kancheepuram, Chengalpet, Villupuram, Cuddalore, Mayiladuthurai, Nagapattinam, Tiruvarur, Thanjavur and Pudukottai districts of TN, Puducherry and Karaikal.

[edit] As on Nov 11

Komal Gautham, Nov 12, 2021: The Times of India

Rainfall from October 1 to November 11, 2021
From: Komal Gautham, Nov 12, 2021: The Times of India

Chennai shows how not to manage monsoon

CHENNAI: Soon after the December 2015 floods, the blame for the devastation caused was placed on encroachments in water bodies, blocks in major canals, lack of storm water drains in many places and the absence of data on critical areas.

Nearly six years later, after heavy rain has caused almost similar destruction, the question is whether Greater Chennai Corporation was better prepared to deal with the crisis. Experts say the city administration did better, but residents, who had to bear the brunt of nature’s fury, feel otherwise.

They say the corporation built drains over 900km since 2018, but when it mattered, some were blocked and some connected to those on elevated roads such as near Inner Ring Road in North Chennai didn’t work. In the central region, the dumping of debris for the Mambalam canal improvement work just ahead of the monsoon led to a disaster, while in the south lakes filled during the southwest monsoon overflowed, flooding homes and entire localities.

Since May, a senior corporation official told TOI, a lot of garbage and debris was removed from road sides and slum. The civic body de-silted 900km of the 2,500km of drains, de-silted 30,000 catchpits. New drains were constructed in Velachery, Nandanam and other areas and a response system was also put in place. This, he claimed, helped keep water away from major most bus route roads.

KK Nagar, pockets of Alwarpet, Velachery, Ashok Nagar, Kilpauk, Subramania Puram and Aziz Nagar in Kodambakkam, Pulianthope, Broadway, Choolai and Madipakkam were all declared high risk in 2019 and details of how the drains didn’t have enough carrying capacity was submitted to the civic body by experts. Yet, it was in these areas that drain work didn’t take place in the last five years. “We had submitted the proposals. It will be completed in a year,” said an official.

Another reason for the flooding, officials said, was that the November 7 rain had already inundated major areas. This week’s rain only caused more havoc.

M V Ramanamoorthy, director of National Centre for Coastal Research, said there was a lot of improvement in the system. “In 2015, we were not prepared for heavy rain. Earlier, we used to have distributed rainfall over two months. Now, the entire rainfall is received within a few days. It is difficult for any city to accommodate this much water. The administration has done a lot by clearing many bottlenecks. However, a comprehensive plan for the entire city is needed as in the future more such events are likely to take place often,” he said.

[edit] See also

Floods in India

Floods in Tamil Nadu

Floods in Chennai, December 2015