Chennai’s storm water drains suffer from faulty construction and lack of planning, as a result of which many of them are of inadequate size and do not flow into natural water bodies, the Comptroller and Auditor General of India has said in a report that throws light on the city’s struggles with flooding. These design flaws necessitated the reconstruction of 51 drains in 2014 at an additional expense of Rs 54.3 crores, the Local Bodies Audit Report, which was tabled in the Tamil Nadu Assembly on July 19, added.
No hydrological, meteorological or topographical study was conducted and thus, the storm water drains were built with little understanding of the course of water flow, rainfall patterns and surface terrain, according to the document.
These findings, city planners say, is yet more proof that urban infrastructure is rarely based on detailed and concerted studies and does little to improve the resilience of cities in the face of extreme weather conditions. Such as the deluge of December 2015, when what was termed the heaviest rainfall in 100 years left Chennai reeling for days – while 347 flood-related deaths were reported across Tamil Nadu since the onset of the North-East Monsoon in October that year. Then too, urban planners and activists had blamed the flooding of Chennai on poorly designed city infrastructure along with rampant conversion of wetlands for other uses.
This is the case with many Indian cities, not just Chennai.
Experts pointed out that in Mumbai too, the storm water drainage system was not integrated effectively with roadways and waterways, even after deadly floods in 2005. And to the north, in Haryana’s Gurgaon, a real estate boom with no real planning means the city gets waterlogged at the slightest hint of rain.
Down the drain
The Tamil Nadu capital’s storm water drains were constructed under the Chennai Mega City Development Mission, which was aimed at improving sanitation, water supply, road and sewerage in an integrated manner, especially in the 42 areas that were merged with the Chennai Corporation after the municipality expanded in 2011.
The reconstruction of the 51 poorly designed drains was undertaken under another programme, the Integrated Storm Water Drain System, which was launched in March 2014. This system sought to efficiently discharge storm water by linking the drains to the city’s four river basins – Adyar, Cooum, Kosasthalaiyar and Kovalam. The project yielded more efficient drains as they were built after hydrological and topographical studies were conducted.
“The Chennai municipal corporation does not have a strong planning department that undertakes these studies,” said Satyarupa Shekhar of the non-profit Citizen Consumer and Civic Action Group. She remarked that even in 2014, the corporation was using an extremely outdated map on storm water drains in the city, adding, “They did not have any life cycle information about when the map was prepared and how long it would last.”
Scroll.in called the office of the superintending engineer in the corporation’s storm water drain department, L Nandakumar, for comment but the official was not available.
Apart from poorly built drains, Chennai’s infrastructure also contributed to the flooding in 2015, according to the Citizen Consumer and Civic Action Group. During its investigation, it said it found that the drains of older buildings were not connected to newly laid roads. Also, since many of the newer buildings had a higher plinth (base), the drains were also built at a higher level, which affected their ability to effectively channel the floodwater to the nearby water bodies.
“Because of poor planning, everyday stresses erode the city’s resilience to storm surges and high precipitation,” said Shekhar.
The same is true for the other cities. Like Chennai, Mumbai is prone to flooding. As Maharashtra witnessed deadly floods in 2005 in which over 1,000 people died, the city, too, came to a standstill after heavy rain on July 26 that left thousands stranded on roads and in offices, unable to get home.
After these devastating floods, efforts were made to develop an efficient storm water drain system for Mumbai. But despite this, the city still goes under every monsoon. Even areas that were not earlier affected have started flooding during the rains, said Rishi Agarwal, an urban activist who has worked extensively for the protection of Mumbai’s wetlands. “A lot of these drains have been designed in a very wrong manner,” he said. For instance, he explained, concrete embankments have been built over what were previously natural drains, thereby reducing their capacity and causing water to flow out on the roads.
If the problem in Mumbai is poorly developed drains, it is large-scale unplanned construction in Gurgaon.
“Gurgaon is a planning disaster,” said Pravin Kushwaha of the Transdisciplinary Research Cluster on Sustainability Studies, Jawaharlal Nehru University. He said lack of city-level planning makes Gurgaon immensely prone to flooding even when it rains heavily for just half an hour.
“The city is increasingly seeing real estate-driven urban development where private firms develop infrastructure only within the boundary wall of the complex,” Kushwaha added. “Such unmindful planning is going to result in several man-made disasters.”
In June 2016, as monsoon rain lashed Gurgaon – an industrial and financial hub that houses the offices of some of the world’s biggest companies – overflowing drains sent the storm water right back out on the roads, flooding them and creating mile-long traffic snarls that took hours to clear.
Apart from flood mitigation, there are other benefits to efficient storm water management: it ensures a healthy drinking water supply, for one. “There is an urgent need to collect storm water and recharge our groundwater,” said Kushwaha. “We are already facing a massive water crisis.”
However, the lack of urban planning in Gurgaon means the storm water often mixes in with the sewage lines.
At the mercy of the climate
Extreme weather, such as erratic and intense spells of rainfall, is a major reason for flooding in our cities. And the incidence of such phenomena is increasing.
Chennai, for instance, receives around 60% of its annual rainfall during the North-East Monsoon, which is spread over the months of October, November and December. But in November 2015, it received almost 50% of the year’s rainfall in just 26 days.
According to K Palanivelu, director of the Centre for Climate Change and Adaptation Research in Chennai, the city is increasingly seeing short spells of intense rainfall. Receiving more than 250 mm of rainfall on a given day can be called an extreme event, he explained. “Such events have begun occurring more often, both in terms of rain and heat,” he said. Last year, though, Chennai received barely 18 mm of rainfall over nine days in November, but witnessed record showers over nine days in May that year.
Other cities with different weather patterns are also seeing changes in rainfall. Mumbai receives an average 2,142 mm of rain in a year, 96% of it during the South-West (June to September) Monsoon. According to a study in the Journal of Hydrology: Regional Studies, the city often records 250 mm of rain in a day during the rainy season. But this study on the impact of climate change on rainfall in Mumbai also finds a clear seasonal shift and delayed onset of the monsoon season, with the amount of rainfall increasing in September and decreasing in June.
For efficient urban planning, these changes in rainfall pattern should be taken into account, as this study in Current Science says. According to it, “An understanding of the spatial and temporal distribution and changing patterns in rainfall is a basic and important requirement for the planning and management of water resources.”
However, experts said extreme weather has made urban planning even more difficult for city planners, who, they say, struggle even under normal weather conditions.
“Climate change is actually throwing into disarray how we go about planning,” said Rishi Agarwal of the Observer Research Foundation. “Cities and towns in Saurashtra and Rajasthan are not equipped to handle the high levels of precipitation they are receiving. Historically, our cities have not been prepared for flooding even during normal rains.”
He added, “Climate change is going to be a huge challenge for Indian cities.”
According to Vishwanath Srikantaiah, a water activist in Bengaluru, the most effective way of tackling floods in a growing city is to reduce the surface run-off (rain water that flows over the land surface). On an unbuilt plot of land, he said, the run-off is 15% of the rainfall received. But on a built-up site, the run-off goes up to 95% of the rainwater. “No storm water drain can deal with this amount of run-off,” he said.
One way of decreasing run-off on a plot, Srikantaiah said, is by building rainwater harvesting systems. “Resilience starts from the individual building,” he said. “We have to change our urban planning techniques drastically in order to tackle climate change.”