Revisiting Urban Heat Island Effects in Coastal Regions: Mitigation Strategies for the Megacity of Istanbul

Abstract

Throughout history, the city of Istanbul has been an important settlement for different civilizations with its geographical location connecting two continents. This metropolis with a population of over 16 million has more than 50% of total economic activity for Turkey. Especially in the last 50 years, the city has been under a catastrophic anthropogenic pressure because of its historical, geographical, and economic attractiveness. These pressures on the city caused some environmental problems due to planning. Some of these problems are intensive urbanization; increase in impervious surface, pollution, traffic, and Urban Heat Island (UHI). The impact of UHI, as a result of wrong urban planning activities causes several adversities in terms of human health, energy efficiency, and ecological sustainability. Factors such as land use/cover (LULC) changes, canyon effect, surface covering material selection, intensive energy usage are effective in the emergence of the UHI effect. In recent years, increasing environmental awareness, international regulations, and developments in landscape planning have led to the emergence of planning strategies to reduce UHI impact. The existence of the UHI effect in Istanbul has been demonstrated and modeled in previous studies. Accordingly, the presence of the UHI effect was identified in both the European and Asian study areas. In the statistical modeling studies, it has been shown that the UHI effect is mainly due to changes in land cover usage components, urban impervious surfaces, green cover, bare soil, and agricultural areas. In this study, various scenarios of land cover elements, which are stated to reduce the UHI effect in Asian and European study areas of Istanbul, have been created. For this purpose, green corridors that are designed in accordance with the urban texture of Istanbul are proposed. As a result of the analyses, UHI intensity mitigation was observed in the European and Asian study regions above 2.5 °C on average. As a result, in addition to land cover usage changes, increasing water surfaces, the use of effective wind corridors, avoiding high buildings, and preferring reflective coating surface materials in landscape design and planning activities are considered to be of utmost importance in terms of UHI reduction.