Groaning under the weight of burgeoning population bursts, the antiquated drainage systems zig-zagging across the world’s mega cities have started crumbling. Destruction of natural lakes, unprecedented rainfall and improper maintainence of drains have increased the frequency of flash floods in cramped urban spaces.
As a result cities are moving beyond the usual civil engineering approaches of open ditches and groundwater pumping and experimenting with innovative landscaping techniques.
If Tokyo is digging infiltration pits to make its runoffs sink into the soil, then Lyon in France is building gravel filled filter drains that prevent sediments from reaching recycling pumps and Ontario in Canada is constructing detention ponds near its rivers to reduce downstream flooding.
Another good example is the ‘stream daylighting’ project in Zurich in which 16,000 metres of the city’s streams have been revitalised and 31 per cent of the city’s extra rainwater diverted into them to prevent flooding. Today the city is installing rot proof, impact resistant polyester silt traps that capture increasing quantities of silt from surface runoffs and keep the drainage system clean.
Ecologically engineered porous pavements that suck in road runoffs, drainblockers that seal manholes to prevent overflows, algorithms that predict surface run offs, computer simulations that calculate flooding patterns of cities and GIS technologies that map flood prone areas are all increasingly being used to enhance urban hydrology.
In India, where disorganised urbanisation has caused recurring floods in 10 major cities in 2005 and over 20 cities in 2006, we are finally taking our drains seriously, harnessing new technologies to give our drains a new and better life.
While Mumbai has installed 30 automatic weather stations comprising state-of-the-art tipping bucket rain gauges at 26 locations to know exact rain patterns in real time, the Bangalore Water Supply and Sewage Board (BWSSB) is using a GIS application called BISON (Bangalore Infosysytems on Network) to manage and maintain the city’s water/wastewater network.
And if Kolkata is using a mathematical 3D flood simulation model to help map various flood situations, then Calicut under MATURE (Mission for Application of Technology to Urban Renewal and Engineering) programme, has undertaken an integerated development plan that aims to regenerate the city’s ponds, and model its drainage and wastewater facilities.
At the national level, the Central Road Research Institute (CRRI) has cleared the 'eco-phalt' road technology that uses a special ingredient called Drain Asphalt Modified Additive that keeps roads dry by sucking in the surface water. In 2006 a trial road paved with this technology has already been laid at Dhaula Kuan on National Highway 8.
And this is just the beginning. As cities increasingly realise drainage is the foundation of sustainable urban development, they will have to factor in freak weather patterns, locational features of the city and the speed and magnitude of its growth while designing their drainage systems.