District-based urban expansion monitoring using multitemporal satellite data: application in two mega cities

Urban expansion is a process of urban development as a result of population growth. Urban sprawl, known as unplanned and unrestricted urban expansion, is among the most important topics in urban studies. In recent decades, many cities around the world in both developing and developed countries have experienced urban expansion. Istanbul and Sydney are two of those cities encountering the urban expansion. Thus, in this study, the spatial and temporal pattern of urban expansion of the most urbanized districts of Istanbul (Arnavutkoy) and Sydney (Hills Shire) was analyzed using multi-temporal remote sensing data. Initially, the Landsat images were classified to evaluate the land use/land cover (LULC) changes. The change detection analysis revealed that urban area of Arnavutkoy district has increased about 669% from 1997 to 2017 and urban area of Hills Shire Local Government Area (LGA) increased by 78% between 1996 and 2018. The relationship of land surface temperature (LST) and urban areas extracted by recoding the LULC maps was also evaluated in different buffer zones. The results showed that with the increase in urban area extent, the LST has also increased. Then, Shannon's entropy and spatial landscape metrics were used to analyze the district-based urban expansion. The results showed that both study areas expanded over the time but the main differences observed are that Arnavutkoy has more fragmented and Hills Shire has a more compact urban growth process.