Three-Dimensional Urban Morphology Transformation of Coal Mining Cities: Case Study of Tangshan

Coal mining cities in China are in a significant era of urban spatial transformation. However, most of the existing studies have ignored the three-dimensional built environment and the impact of subsidence areas on the whole city, which has made it difficult to grasp the spatial development process of coal mining cities. In this study, we defined the subsidence areas and seismic zones as unstable regions and the other areas as stable regions. On this basis, a framework of cognition and evaluation of the transformation of both regions was constructed, by using three-dimensional urban morphology types (3D-UMTs), a landscape expansion index (LEI), and an urban transformation evaluation system. Lunan District and Lubei District of Tangshan were selected as the study area, and the time range was set from 2000 to 2018. The results indicated that the whole study area had experienced inefficient urban spatial transformation during the time span. This study also proved that considering unstable regions made the evaluation of the spatial form transformation of coal mining cities more accurate. The urban transformation evaluation system is helpful to visualize and evaluate the implementation of existing policies and assist decision-makers with delineating key areas for future urban development.