Natural Disasters

Rain reigns in Chennai

Shrinking lake area and blocked drains have reduced Chennai's capacity to drain rainfall runoff

By Shreeshan Venkatesh, Sushmita Sengupta
Last Updated: Thursday 03 December 2015
Taxi aggregator Ola launched free boat service in flood-hit areas of Chennai (Courtesy: OLA)
Taxi aggregator Ola launched free boat service in flood-hit areas of Chennai (Courtesy: OLA) Taxi aggregator Ola launched free boat service in flood-hit areas of Chennai (Courtesy: OLA)

The high-intensity rainfall that Chennai received in November brought it to a standstill. Between November 11 and 18, the capital of Tamil Nadu received 449.9 mm of rain—a 329 per cent rise against the normal rainfall of 104.9 mm, says the Chennai division of the India Meteorological Department.

The rainfall the country receives this time of the year is caused by the north-east monsoon. But its intensity this year was much more due to the presence of two separate and well-marked cyclonic depressions, which caused the heavy spells of rain between November 9 and 14 and between November 15 and 17. By the time the state government brought the flood-like situation under control, 79 people had died in the state. Unofficial estimates, however, put the number close to 200.

Though the government repeatedly pointed out that the situation was unprecedented, the downpour exposed the state’s inability to handle heavy rainfall. This should not have been the case because Chennai has been a pioneer of sorts among Indian cities as far as rainwater management is concerned. Having faced the severe drought of 1999-2000, the state government made rainwater harvesting (RWH) mandatory in all buildings in 2003. The Chennai Metropolitan Water Supply and Sewerage Board (CMWSSB) took a number of steps to popularise RWH at the household as well as the community levels. Stormwater drains were provided with percolation pits to recharge underground aquifers with the runoff. Efforts were made to keep the waterbodies in the city healthy to soak up the rainwater and recharge groundwater.

There are natural canals and drains that directly connect the city with wetlands, waterbodies and rivers such as the Cooum and the Adyar that run through Chennai. The Cooum is supposed to collect surplus water from 75 tanks in its catchment area within the Chennai Metropoliton Area, while the Adyar is supposed to carry the surplus water of about 450 tanks in its catchment area and also from the Chembarambakkam tank which is not in its catchment. It was estimated that the city would harvest almost 129 million cubic metres of rain and recharge through different methods. Physiographically, Chennai is flat and needs a very good drainage system. A combination of natural and artificial drainage is the only way to protect Chennai from drought as well as floods. However, it seems that the government’s efforts made have not been effective.

According to the Centre for Environmental and Water Resources Engineering, Chennai had more than 600 waterbodies in the 1980s but a master plan published in 2008 said that only a fraction of the lakes could be found in healthy condition. According to records of the state’s Water Resources Department, the area of 19 major lakes has shrunk from a total of 1,130 hectares (ha) in the 1980s to nearly 645 ha in early 2000s, reducing their storage capacity, explains architect K Lavanya of Crescent School of Architecture, B S Abdur Rahman University, Chennai. Anil Kumar Gupta of the National Institute of Disaster Management (NIDM), New Delhi, says that there are over 30,000 slums on the banks of waterbodies in these areas. The drains that carry surplus water from tanks to other wetlands are also encroached upon. A joint research paper by the department of physical geography, University of Freiburg, Germany, and Care Earth, India, shows that the Pallikaranai marsh, which is the major flood sink in the city, has been totally killed by buildings and roads that pass over it.

The human-made stormwater drains constructed to drain the flood water are clogged and require immediate desiltation. The recharge pits constructed by CMWSSB along the drains also require maintenance and repair at some places. According to a 2011 study by NIDM, Chennai has only 855 km of stormwater drains against 2,847 km of urban roads. Thus even a marginally heavy rainfall causes havoc in the city. Moreover, the population of the city has grown eight times in the last century, according to NIDM. This has increased the runoff which the city is unable to dispose of in the absence of an adequate drainage system.

Monumental waste

The loss of waterbodies, drainage systems and green areas show that the city has never given a serious thought to flood management. But the state government has spent huge amounts to clean up the rivers and rework its sewage infrastructure. A government-funded flood alleviation scheme was launched in 1998, at a cost of Rs 300 crore, focused mainly on structural measures. Cleaning of certain waterways and lakes was also undertaken under the scheme. The Chennai City River Conservation Project was launched in 2000 to improve the waterways, with an estimated outlay of Rs 1,700 crore. In 2009, the Union government allocated around Rs 633 crore under the Jawaharlal Nehru National Urban Renewal Mission for Chennai to get its drains in shape. By 2014, about Rs 394 crore were spent by Tamil Nadu. In 2014, the Comptroller and Auditor General of India noted that the state has not done enough to protect Chennai from floods and the plans made for flood control were flawed.

Citizens' efforts

Concerned citizens groups have moved the courts several times to save the wetlands. For example, in September 2015, the Madras High Court ordered all authorities concerned to remove encroachments from the marsh of the Pallikaranai lake. Laws, such as the Tamil Nadu Protection of Tanks and Eviction of Encroachment Act, 2007, have not been able to save the wetlands in the city, say experts. Even the court orders are waiting to be implemented.

Lavanya says that the city needs an integrated approach to flood control and management. This can be done under a nodal agency that can plan, coordinate and monitor authorities like the Chennai Corporation, the Slum Clearance Board and CMWSSB. L Elango, head of the geology department, Anna University, Chennai, says that the mapping of the flood-prone areas has already been done, but it is not clear why the state government has not initiated action on this.

Apart from these steps, the management of untreated sewage and solid waste should be done on a war footing to avoid choking of the drains, says Lavanya. Strong regulations to save the urban waterbodies should be implemented to stop encroachment of the wetlands and water channels. The existing rules and regulations are just not strong enough to protect the urban lakes, says Delhi-based advocate Sanjay Upadhyay.

Subscribe to Weekly Newsletter :

India Environment Portal Resources :

Comments are moderated and will be published only after the site moderator’s approval. Please use a genuine email ID and provide your name. Selected comments may also be used in the ‘Letters’ section of the Down To Earth print edition.

  • Lack of drainage, encroachment of irrigation canals and lack of proper planning while giving permission to new constructions by Municipal Corporation are essential factors that led to this devastating floods. Here we should look back to traditional planning of canals and water systems prevailed in Tamil Nadu(Tanjore Ayacut),water ways in Gujarat and Rajasthan. Centre of Science and Environment has done monumental work in identifying these structures besides rainwater harvesting. In the future construction of cities and towns some of the well proven traditional methods can be adopted blending with modern techniques.
    Lessons from the Grand Anaicut of Tamil Nadu
    The Cauvery River, as seen in the image above is split into two channels by the island of Srirangam. While the southern channel retains the name Cauvery, the northern channel is called as Kollidam or Coleroon River. These two channels come close again downstream and it is at this strategic meeting point that Karikala Cholan decided to build the Kallanai. Karikalan built the Kallanai for mainly two reasons: Flood control and Irrigation. Having witnessed the river causing great floods during the rainy season and also forcing droughts during the dry months, he and his advisors devised this grand project to maintain a steady flow of water throughout the year. The dam was constructed from unhewn stone and is 329 m (1,079 ft) long, 20 m (66 ft) wide and 5.4 m (18 ft) high. The dam has since been developed by the British who laid the grid separators and a bridge on top of the old dam.
    The story of the Kallanai imparts some very important lessons for the Design world. Foremost is the amazing vision that Karikalan possessed. When he decided to build a dam across the Cauvery River he could have easily just thought of something a little less grand and achievable based on the technical and monetary reservations of his time but Karikalan did not just think of the near future. When he stood on the mud banks and pictured his dam, he imagined it to stand for a very long time to come. And it is his extraordinary long term planning and foresight that is reflected in the fact that the Kallanai is still in excellent condition even after almost 2000 years.
    Karikalan’s story of an extraordinary long term vision, meticulous planning and astounding execution of an engineering marvel makes sense even today. A culture of long term thinking with the ability to look at the long term benefits becomes more vital in a world today that seems content with temporary solutions. The design field particularly can learn a lot from examples such as the Kallanai about the importance of vision in Design.
    • How relevant are the long term benefits of any product or service?
    • What solutions can a Design provide and how permanent is it?
    • Can our service or solution add more value than what is expected?
    • How much more effort do we need to put in to turn an ordinary solution into a more robust, long term and innovative one?
    • Is it all worth it?
    Dr.A.Jagadeesh Nellore(AP

    Posted by: Anumakonda Jagadeesh | 4 years ago | Reply
  • . This Vedic astrology writer had sought to convey , over a year past on 23rd October 2014 , two crucial spells of time for India in article - " Months of substantial concern for India in next year 2015" - published online at The second crucial spell of time identified to be November and December of 2015 was conveyed to be more grim , particularly for places nearby the sea. It was predicted : " Places nearby the sea may also need to take a cue. Massive floods , landslides , earthquake or epidemics or health hazards may visit. Prices of everyday essential use items are likely to shoot up to the level of high concern. Food and other crops may disappoint. Downside trend of economy may pinch one and all. Those at the helm of affairs , both in the Centre and States , may have a tougher time. Power , or dams or major accidents could be a cause of tension. There is a need to be particularly cautious on the borders because likelihood of conflict or intrusions or even war cannot be ruled out". It seems the alert implied so clearly for Chennai- Tamil Nadu and other coastal States of India may have possibly escaped attention of the concerned , being in online which is an ocean.
    Note :If winter comes, can spring be far behind. This astrology writer has, some days back , predicted that fury of rain may ease around 11th December to a satisfactory level while, there may be some relief in between.

    Posted by: Kushal Kumar | 4 years ago | Reply