Bangalore’s lake count dropped from 262 in 1961 to 81 in 1985, priming the city for the flooding it sees daily, finds Akhila Seetharaman.
It was 9pm on Tuesday August 26. The rainfall was relentless. On the Inner Ring Road, between Koramangala and Indira Nagar, drain water encroached upon the street. Soon, the water reached people’s calves. A few low-chassis cars began to float. Drivers waited for the showers to subside, bobbing like bathtub toys while trying to bail out water. When the rains finally stopped, many found the electronics in their cars fried. Abandoning their cars they began to flag down autos. The story was the same across the city – from Chord Road and Okalipuram to JP Nagar, Hebbal and Bommanahalli – stranded vehicles dotted the streets like jetsam.
That night, according to the meteorological department, Bangalore received 66mm of rainfall, twice the normal amount for the month. “The city has so far received 240mm. The normal rainfall for August is 137mm,” A Muthuchami, director of the department said at a news conference the next day.
Floods, now a regular feature during the monsoon, are an immediate consequence of unplanned urbanisation and a dramatic rise in the city’s built-up area according to town planners, ecologists and forest department officials. “Since 1949, Bangalore has grown ten times in terms of geographical area, and seven times in terms of population to seven million in 2007,” wrote TV Ramachandra and Uttam Kumar of Centre for Ecological Sciences, Indian Institute of Science, Bangalore in a research article on geoinformatics and urbanisation, set to appear as a chapter in a book on geoinformatics. “And since 1973, Bangalore’s built up area has increased by more than 450 per cent.”
The two scientists have been studying the effects of urbanisation for the last decade, and have found that flooding is one of the most devastating outcomes of unplanned construction. “As land is converted from fields or woodlands to roads and parking lots, it loses its ability to absorb rainfall,” said Ramachandra.
As a result, the run-off (of unabsorbed water) has increased by two to six times what it would normally be if the terrain in Bangalore remained natural, he said. For instance, according to the research paper, the total annual rainfall received by the Madivala-Varathur catchment area, which has 14 lakes within its boundaries, is 247 million cubic metres. These lakes, which are in close proximity to all the residential areas in west, south and east Bangalore, are Venkatapura, Yellakunte, Bandepalya, Begur Doddakere, Madivala, Hulimavu, Marenahalli, Govindanayaka, Dorenarasipalya, Gittigere and Vaddarapalya. According to the study, only 90 million cubic metres of the water they receive percolates into the ground. The remaining 150 million cubic metres is either stored in the lakes or washes away as overland flow. The scientists calculated that the 14 lakes hold 110 million cubic metres of the water, which means as much as 40 million cubic metres of water overflows into the city’s streets and homes – from just that one catchment area (there are four in Bangalore).
These are staggering numbers and can only be comprehended when put into perspective. Imagine a water tank measuring a metre in width, length and depth filled to the brim. Such a tank would contain 3,000 litres of water. Now imagine 40 million such water tanks. That’s 120,00,00,00,000 litres of water.
The city’s natural terrain has valleys and ridges, which made possible the elaborate tank system first established by Bangalore’s founder Kempegowda. The city’s tanks or kerays are fed by water flowing through the city’s four natural valleys – Hebbal, Koramangala, Challaghatta and Vrishabhavathi.
“The lake system of Bangalore was such that surplus water from one lake would flow into the next lake. Now if the channels are blocked, the water will spread,” said Sandeep Dash, Special Commissioner at the city’s municipality.
Not only has new construction cut off links between tanks, but development has even killed many of these lakes. According to Ramachandra, the city’s water tank count in 1961 was 262. “By 1985, the number of tanks had reduced to 81, many of them encroached upon by illegal builders,” he said. Although the 74th Constitutional Amendment Act, passed in 1993, calls for the planning function to be handled by elected local bodies instead of parastatal organisations, the city corporation still does not have enough powers to do so, said Ramachandra, writing along with HS Sudhira and MH Balasubrahmanya in another research article for the science and health journal publisher Elsevier.
For the BBMP, this means constantly finding temporary solutions to the problem. “For example, Puttenahalli, shaped like a saucer, has been built over,” said Special Commissioner Dash. “Obviously, there’s going to be continuous flooding.”
Voices from the Waters, the water film festival, is on September 13-18, and includes workshops on Water and Sanitation: The Utopia of an Odourless City, and City Rivers and Streams: the Future of the Waters. With inputs from Jaideep VG
Source : Time Out Bengaluru ISSUE 1 Friday, July 23, 2010
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