As Kochi transforms into a concrete jungle with increasing urbanisation, it also has its own ‘urban heat island’, a term used to denote the unusual heating up of urban areas owing to excessive built-up area and infrastructure.
In a recent study where scientists of the Indian Institute of Technology Kharagpur used satellite images to examine land use change in Kochi and nine other metropolitan cities in the country, it was found that the urban areas of Kochi had shown a “substantial increase and spread” between 2001 and 2013. While the built-up area assessed in Kochi was around 17% of the city’s total area in 2002, it rose to around 23% in 2013, according to the study published in the International Journal of Remote Sensing.
Less dry land
The scientists, led by Dr. A.N.V. Satyanarayana of IIT-Kharagpur, also noted that Kochi was one of the three cities (the others being Mumbai and Nagpur) where dry land (less vegetated areas) had been continuously decreasing due to the rise in the number of construction projects.
Such an expanding urbanisation comes at a cost. It triggers the formation of urban heat islands.
Surface air temperatures in such place are far higher than even nearby rural areas. The scientists observed that in Kochi, the urban heat island intensity appeared to have “increased remarkably” between 2001 and 2013.
Regions with extremely high temperatures (hotspots) also expanded during the said period. And, it is attributed to the increasing densely populated regions, industrial areas, and bare lands.
In an earlier, but shorter, study conducted between 2011 and 2013, a team, including Dr. George Thomas from the Centre for Earth Science Studies, Thiruvananthapuram, analysed the urban heat islands in Kochi.
It found that the urban heat intensity in the city was moderate-to-high during winter and summer, and it was most intense in ‘compact mid-rise zones’ which cover the central part of the city and comprising buildings between nine to 24 metres tall.
Planning cities
“We do not place emphasis on existing vegetation when we plan our cities,” said Dr. Satyanarayana. “If we retain or increase vegetation in our cities without disturbing the ecological balance, we can reduce urban heat islands to some extent,” he added.
Wetland conservation
For a place like Kochi, which is not a planned city, the ideal way to arrest the expansion of heat islands is to regulate construction projects and conserve existing wetlands, said Dr. Thomas, currently assistant professor in physics at Catholicate College, Pathanamthitta.
“Wetlands have the ability to store heat,” he said, adding: “Even maintaining vertical gardens on Kochi metro pillars can help reduce urban heat islands.”