The heaviest rains in a century saw the Indian coastal city of Chennai brought to its knees by flooding at the tail end of last year.

The metropolis of 4.3 million people, formerly known as Madras, suffered the wettest November since 1918 followed by the highest daily rainfall in 100 years on 1 December.

Power supplies to 60 per cent of the city were suspended, there was widespread disruption to train services and the international airport closed for nearly a week. Some 57,000 homes were damaged and the estimated loss to the Indian economy is put at up to $3bn.

The unusually high rainfall has been attributed to the El Nino weather phenomenon, but experts say irresponsible urban planning – in particular encroachment on the water bodies that have historically served as the city’s natural drainage system – greatly exacerbated the flooding.

Records from the Water Resources Department for the state of Tamil Nadu show the area of 19 major lakes has shrunk from 1,130 hectares in the 1980s to around 645 hectares in the early 2000s, while documents submitted by city officials to the Madras High Court claim illegal developments have resulted in the disappearance of more than 300 water bodies as canals and lakes have been replaced with impermeable concrete.

It’s not only illegal development that is to blame, says Chennai-based environmental activist Nityanand Jayaraman. The Pallikaranai Marshlands, which drains a 250-square-kilometre catchment, has seen its area reduced from 50km2 to just 4.3km2 thanks to government-sanctioned developments like a huge IT corridor and several major roads.

Other examples include a Mass Rapid Transit system whose supporting pillars were built into the Buckingham Canal – one of the city’s main drainage channels – and the international airport built on the floodplains of the river Adyar.

“The first step in sound planning is site location, and if you go with a bad site expecting engineering to work magic, it shows a very poor understanding of how nature works,” says Jayaramand.

The city experienced bad flooding in 2005 too, but Jayaramand says solid recommendations from the city’s engineers to avoid a repeat were ignored in the name of political expediency.

Dr Kapil Gupta, a professor of civil engineering at the Indian Institute of Technology Bombay, agrees. “Because of local politics and the real estate market, engineering and planning have been given a back seat in preference to rapid development,” he says.

Poor urban design was exacerbated by poor management of the city’s flood defences. Despite warnings from the India Meteorological Department (IMD) in mid-October that rainfall would exceed the seasonal average by roughly 112 per cent (in other words, more than double), work to desilt and clear rubbish from the city’s waterways still hadn’t been approved by the state government by the month’s end.

But with urban populations continuing to rise worldwide, pressure to develop unsuitable low-lying land is unlikely to abate anytime soon, says Gupta.

Jayaramand agrees. “As the intensity of the shocks increases, I think people might be more receptive to safer ways of living. Until then, we will put our faith in good engineering and go about business as usual.”