Feeling the heat: Poor urban planning ups the mercury

CHENNAI: A ride through the city, especially at night, from IIT Madras through T Nagar to Nungambakkam offers a variety of scenes — abundant green cover, smaller buildings giving way to multi-storey steel and glass structures and more traffic. As the urban environment changes it also affects the temperature that can climb up by nearly 2˚C in the heart of the city. The closely packed high-rises, congested roads and lack of trees, restrict movement of air and notches up the heat in areas such as T Nagar resulting in a phenomenon called urban warming or urban

heat island

(UHI) effect.

A recent study by the civil engineering department of IIT Madras showed change in land use due to

urbanisation

, combined with increase in vehicular emissions intensified the (UHI) effect in the city.

Worsening the situation are the material used for construction like concrete and glass. "The thermodynamics of surface material can accelerate the temperature profiles in a particular area. Such changes further deteriorate the air quality," said associate professor of civil engineering at IIT-M, S M Shiva Nagendra. The UHI effect also depends on other factors like wind speed, direction and solar flux.

For the study, the researchers identified different neighbourhoods for their distinct classification as a residential set-up with green cover — IIT-M campus, a commercial area, T Nagar, and a mix of the two, Royapuram. In each of these spots, a square kilometre area was taken up for observation. "It was found that the UHI intensity significantly affected the outdoor thermal comfort, energy usage and air quality. The impact of land use change is an important parameter for local air quality estimation," said Nagendra.

The present land use, building height and density, and vegetation were characterised for each area. The average building at both IIT-M and Royapuram was found to be a three-storey structure at a height of 6m-9m, whereas in T Nagar the average building was nearly 18m high and closer to its neighbours.

Explaining the effects of a situation such as the one recorded in T Nagar, IIT-M researcher Undi Gangadhar said excess heat would have a serious impact on people both in terms of money and health.

"The excess heat will consume more energy, as many people will be forced to use airconditioners for a longer period. Secondly, the UHI effect will trigger stress levels in humans, leading to other health risks." Talking about the need to be mindful, Gangadhar referred to a World Health Organisation report that showed nearly 1,200 people die every year of diseases related to heat-induced stress.

Stressing on how lifestyles are driving up the heat, Gangadhar said, "Apart from the natural heat, emissions from vehicles, indoor heating due to cooking, airconditioning and other household activities are all increasing the local temperature of a particular area." This spells bad news for a tropical city like Chennai, which has seen rapid urbanisation in the last two decades from 1995 to 2015, and the average ambient day temperature in summer increasing by nearly 2˚C in the last decade.