Impact of Urban Heat Island on the sustainability of Bangalore and Hyderabad cities in India

In the last 2 centuries, the urban population of the world has drastically increased from 7% to 50% and is predicted to rise further. This drastic change has brought about unsustainable development in urban areas, causing various environmental issues. The Urban Heat Island (UHI) is a byproduct of this development, affecting the sustainability of cities. The present study analyses the impact of UHI on the rapidly growing tier-1 cities of Bangalore and Hyderabad in India. The study analyses the change in the built-up area and the land cover of the study at 3 distinct periods over the past 2 decades. The urban area has expanded 573 km(2) in Bangalore and 356 km(2) in Hyderabad since 2001. The increase in the mean temperature of the converted area during this period is 0.99 degrees C and 1.3 degrees C for Bangalore and Hyderabad, respectively. The magnitude of the rise in the Land Surface Temperature (LST) of urban areas compared to rural areas is 1.67 times for Bangalore city and 2 times for Hyderabad city. The study found that there is an intense UHI effect in both cities, with an annual maximum Surface Urban Heat Island (SUHI) magnitude of 5.76 degrees C for Bangalore and 6.29 degrees C for Hyderabad. The SUHI magnitude increases at a rate of 0.040 degrees C/year annually with a p-value of 0, 0.043 degrees C/year in the summer with a p-value of 0, and 0.047 degrees C/year in the winter with a p-value of 0.001 for Bangalore. For Hyderabad, it increases at a rate of 0.033 degrees C/year annually with a p-value of 0.001, 0.030 degrees C/year in the summer with a p-value of 0.022, and 0.044 degrees C/year in the winter with a p-value of 0. The study also maps the regions within the 2 cities where the inhabitants have a higher-than-average risk of exposure to heatrelated problems. The study indicates that UHI adversely affects the United Nations (UN) Sustainable Development Goals (SDGs) - "Good Health and Well-Being," "Clean Water and Sanitation," "Reduced Inequalities," "Sustainable Cities and Communities," "Climate Action," "Life below Water," and "Life on Land".