Assessing the Impact of Rapid Urbanization and Associated Land Use Land Cover Variability on the Micro Climatic Conditions of Busan Metropolitan Area : The Urban Heat Island Effect

Abstract

Urbanization has been the order of the day since the late 1800s; until the recent acceleration of urban population growth rate that has caught global attention. However, Busan is a case study situated in Asian continent which is predicted to accommodate alongside Africa the greatest quota of the over 68% urban population in 2050. This is a coastal city with a mountainous topography whose natural, economic and touristic endowment has attracted a lot of population since mid-20th century. The strategic location makes its ports a gateway to the Asian subregion and the world at large, thus stimulating industrialization, economic boom and unprecedented infrastructural development. Nonetheless, all these recent urbanization related-transformations equally impacted the micro climatic conditions of the area such as the urban heat island effect. Consequently, this study sought to perform 3-decade monitoring of the spatiotemporal distribution of the surface urban heat island relative to urbanization across Busan metropolitan area, using Landsat time series thermal data. The land use land cover variability associated to urbanization trend was assessed using maximum likelihood supervised classification; and it conformed to at least 93.60% overall accuracy and 0.92 Kappa coefficient for the three designated years 1989, 2009 and 2020. The results displayed five LULC classes among which the Built-environment and Bare land experienced 10.10% and 2.73% increment to the detriment of Forest, Water body and Agriculture/Vegetation with 9.90%, 1.67% and 1.21% reduction between 1989 and 2020. The UHI intensity was rigorously analyzed using spatial statistical tools like zonal statistics, hot spots analysis (Getis-Ord Gi*) and cluster and outlier analysis (Anselin Local Moran's I); in a quest to understand the spatial distribution and seasonal patterns within autonomous districts. Generally, the results displayed a huge disparity between summer and winter spatial and temporal trends of urban heat island, but with a net increment of over 1.65°C in intensity during these years. The progressive signatures of urbanization on UHI increase were evident all over and particularly in Gijang-gu, Dongnae-gu, Seo-gu and Yongdo-gu. There were equally districts that displayed extremely high urban heat island values all these years like Gangsoe-gu and Saha-gu. Otherwise, some districts like Buk-gu and Suyeong-gu experienced relatively low values of urban heat island all through, due to the cooling effect of rivers among others. However, Dongnae-gu demonstrated significant influence of other drivers of urban heat island than urbanization particularly in winter. During the study period, the maximum value observed in winter was 5.89°C, while the maximum value witnessed in summer was 4.72°C. Therefore, in order to ensure sustainable wellbeing in Busan, concerned stakeholders should improvise resilient and mitigation strategies considering the proportionate increase of urban heat island intensity with urbanization.