Policy and planning go together
Over the years, the rain-holding capacity of the cities was reduced putting a strain on the age-old stormwater drainage system, writes Saikat Neogi.Updated: Jul 16, 2007 00:08 IST
The year 2005 came as a grim reminder of one of urban India’s biggest crises. Within a short span, heavy rains brought three major metros – Mumbai, Bangalore and Chennai – under neck deep water. The crisis of poor drainage immobilised these cities for weeks, causing deaths, diseases and economic ruin.
At all three metros the natural flow of rainwater was hindered by encroachments on flood plains, constructions on open grounds meant for absorption of excess rainwater, and clogging of drains. Over the years, the rain-holding capacity of the cities was reduced putting a strain on the age-old stormwater drainage system.
A large part of land along Mumbai’s Mithi river, the lifeline for the city’s drainage system, has been encroached upon. In a case study of Mumbai floods, H J Shiva of G B Pant University of Agriculture and Technology says that the city’s builders have illegally encroached on about 40 per cent mangroves along the Mithi river and Mahin Creek, causing seawater incursion into the city during high tides.
Post Mumbai floods, a National Institute of Disaster Management study found the city had the lowest ratio of open ground per head of population in any Indian metropolis. The study recommended delinking of the sewer and stormwater drainage systems and a complete ban on riverside constructions. In Delhi, according to MCD estimates, builders have illegally covered about 60 per cent drains in residential colonies. As a result, stormwater drains are either filled up with mud or covered with concrete slabs. In most metros drains have simply disappeared from many colonies due to extension of roads.
Lack of coordination
Professor S.K. Gupta of Central Soil Salinity Research Institute says that road engineering and stormwater drainage system should complement each other through coordination between engineering and sanitation departments. "Unfortunately, such a coordination does not exist in any Indian city," he says.
Poor maintenance of drains and inadequate desilting before monsoon means our city roads get waterlogged within a few minutes of rain. In Delhi the MCD has consistently failed to meet the deadline to desilt its over 1,200 stormwater drains. And with multiple departments involved in the cleaning process, it is easy to pass the buck. In most cities desilting is still done manually, which is not only slow but also ineffective. Use of machines like high pressure jetting pumps can do complete desilting cost effectively and reduce the human drudgery.
The success of any drainage system depends on the efficacy of its design. For the water to run off properly, storm water drains need to have the correct incline. An Asian Development Bank study found that in many cities residential colony drains were not even joined with the main stormwater drains. It said the gradient of the internal drains is faulty which results in water logging leading to vector-borne diseases.
Many studies have shown that the basic framework of drainage needs effective planning, use of appropriate technologies, accountable administration, community participation and, above all, unequivocal political will. A good beginning could be made by reducing the generation of waste and introducing some basic recycling at the level of residential colonies followed by treatment of industrial waste before discharging it in water bodies.