Remote Sensing Monitoring and Spatiotemporal Pattern of Land Use/Cover Change in Built-up Area of Tianjin in the Past 70 Years

Urban land use/cover changes have an important impact on urban ecosystem services functions and the environmental quality of human settlements. This study mapped urban expansion process using the historical data, remote sensing images and urban planning maps, and acquired the urban impervious surface and green space fraction based on big data platform. We analyzed the process of Tianjin urban expansion rate, intensity and urban land cover change since 1949, and revealed the driving factors in the process of urban expansion with social economic and policy factors. The results showed that the built-up area increased from 49.15 km² in 1949 to 663.39 km² in 2015. The expansion has undergone four stages of "acceleration – deceleration – acceleration - deceleration"; the urban expansion mode presents the filled with built-up area and along with the neighboring transportation trunk lines. The proportion of green space in the built-up area is increasing, indicating that the urban ecological greening in the main urban area of Tianjin has been improved.