Decent Urban drainage is synonymous with civilised living. The human settlement dates back to over 3,000 years but the earliest evidence of urban drainage is found around 2,500 BC in Harappa and Mohenjo Daro, the cities of the first recognised civilisation. The Harappan man was also adept at economics, geometry and astronomy but the hallmark of his civilisation was his skillful town planning.
The Indus Valley cities were built on rectangular grids with drains flowing along brick-layered streets, according to the chronicles of archeologist Rakhal Das Banerjee and historian Mortimer Wheeler. Five thousand years down the line, the philosophy of civilised living hasn’t changed fundamentally. Cities and countries that made early investments in managing their environment were the ones that advanced the most in every field of human endeavor.
European cities changed decisively in the 1830s once John Snow, the father of modern epidemiology, established the link between drainage and cholera, one of history's most virulent killers. This was followed by the formation of public health agencies and enactment of laws to separate sewage lines from stormwater drains and drinking water sources. No wonder, the advent of innovative drainage coincided with the conquest of plagues and epidemics.
Urban drainage is more about town planning and water management, rather than just a sanitation issue. It involves environmentally sound systems of collecting, reusing and disposing of all forms of unwanted water from the cities. No single formula works for all, but the best global models integrate systems of public health and water management with local hydrology, broadly the process in which an area’s water is depleted and replenished.
India’s backward march
The great Indian cities are clearly slipping on the index of civilisation. In Mumbai, Kolkata, Hyderabad and Delhi, 70-year-old storm water drainage systems are fighting pressures of urbanisation. Except Surat, where some improvement followed an outbreak of plague in 1994-5, most large cities in India are prone to flash floods (see box, right). Mumbai alone has over a hundred flood prone areas. Even in the country’s driest district, Jaisalmer, and in adjoining Barmer, last year’s freak floods killed over 150 people because haphazard construction had choked natural runoffs.
The story is the same everywhere: Urbanisation disrupts traditional watercourses and sewage and solid waste are dumped in natural drains, already burdened by erosion and silting. The biggest challenge for urban planners everywhere is to factor a constant migration of rural folks. (By 2020, over 550 million people or 42 per cent of India’s population would migrate mostly to city slums, according to ADB estimates.) Typically, the flash floods kill and displace slum dwellers, disrupting livelihoods of the poorest.
<b1>Only the health impact of India’s annual environmental degradation, according to a World Bank report, is nearly $10 billion or about 4.5 per cent of the GDP. Almost 60 per cent of this is due to drainage-linked issues like water pollution and inadequate sanitation. The figure is enough to justify big spending (like the Prime Minister’s Rs 1,200 crore grant for Mumbai) on improving drainage infrastructure in the country’s other metros and 24 odd cities with over one million population.
Sewage as sunshine
The UN Environment Programme’s Integrated Wetland System uses examples from Kerala and West Bengal to prove that biochemical reaction can utilise the sun’s energy for recycling. It routes treated wastewater through wetlands for aquaculture and irrigation, generating food and employment. As a country heading for a huge water crisis, India also needs to learn from global best practices of integrated water management. But UNESCO’s Institute of Water management cautions that the success of all such systems would hinge on the quality of urban governance—A reminder that our big investments to pare down the humongous environmental costs of poor drainage will come to naught unless we rescue our municipalities from administrative and financial ruin.