opinion

Updated: Aug 05, 2019 15:13 IST

For a city that suffers water-logging after every shower even as its water table sinks to new lows, it is criminal that Delhi makes little effort to tap the rain.

Each time it rains, stormwater inundates the roads, sinking vehicles, crippling pedestrian movement, causing traffic jams and damaging roads. Sewage back-flows are reported from everywhere — from working-class neighbourhoods to plush homes.

However, unlike the monsoon, the reasons for the civic collapse it triggers are not seasonal. Apart from inadequate drainage and poor maintenance of the stormwater network, our mindless tendency to overbuild is responsible for the mess.

At 98%, Delhi has the highest level of urbanisation anywhere in India. This means heavy concretisation and little open space that can absorb the rain and replenish the precious aquifers.

Excessive concretisation is also making Delhi hotter. Roads, pavements and rooftops absorb heat during the day, forming a dome of warm air. This trapped heat does not get released after sundown, keeping night-time temperatures high. A 2011 study by IIT-Delhi’s Centre for Atmospheric Sciences had found that between 1968 and 1985, Safdarjung had higher night temperature than Palam because it was more built-up. But after 2000, as Palam saw excessive urbanisation, the two stations had almost the same annual mean minimum temperatures.

In fact, now, temperatures at Palam are usually higher than most parts of the city. On June 10 this year, for instance, when Palam recorded day temperature of 48°C, an all-time high for Delhi, Safdarjung had a maximum of 45.6°C. The night temperature at Palam was 33.3°C while it was 30.4°C at Safdarjung.

Plummeting water tables and urban heat islanding are serious health warnings for any city. It is a no-brainer that we need to free stormwater drains and natural channels, which traditionally carried rainwater to the Yamuna, from garbage, sewage and encroachments. More importantly, we need to minimise the use of asphalt and concrete. Pavements are a good place to start with.

According to the United States Environmental Protection Agency, conventional paving materials can reach peak summertime temperatures of 48–65°C, transferring excess heat to the air. While the use of coating and reflective material is prescribed by experts to minimise heating, there are simpler solutions such as permeable pavements, which absorb run-offs and also have a cooling effect.

The union ministry of housing and urban affairs’s greening guidelines also ask Indian cities to tile only those pavements that see heavy pedestrian traffic and recommends perforated tiles and grass cover for the rest. Ideally, footpaths and other open spaces should remain unpaved for the grass and trees to grow freely. This allows stormwater to enter the ground more effectively instead of just flowing into sewers. Cities across the world -- Chicago with its Green Alleys, New York with its Greenstreets, and the Chinese “sponge” cities projects – are using these methods to prevent urban flooding.

South Delhi’s Sarvodaya Enclave has made a beginning, and over the years replaced concrete tiles with grass pavers -- tiles with cavities that allow percolation of water and growth of grass -- on most of its pavements.

Green activist Padmavati Dwivedi, who started the initiative by persuading residents, and worked with the municipality, said that these pavers are low maintenance and durable. “One does not have to break tiles for underground repairs. Just dig out the pavers, repair and put them back in their place. Also, there is no debris. Residents like them because they give a uniform look and are aesthetic,” she said.

Dwivedi said that these pavers are also good for parking areas as they get tightly lodged into the ground under the cars’ weight, giving a hard surface, and allows water from the carwash to percolate into the ground. Residents are proud of this initiative and would want it replicated in other neighbourhoods, the resident welfare association’s general secretary Shefali Mittal said.

As the next step, they said, the residents and authorities must now focus on unclogging stormwater drains, removing concrete surfaces and rejuvenating the soil to get a good grass cover and make percolation easy.

The humble grass is also the best dust trap. Authorities in Delhi, who spend huge funds in buying vacuum-cleaners for roads, should use every bit of open space to grow its green defence against air pollution, water scarcity, flooding and rising temperatures. Let grass be greener on our side.