The spatiotemporal dynamics of rapid urban growth in the Nanjing metropolitan region of China

To better understand the spatio-temporal dynamics of the urban landscape of the Nanjing metropolitan region, China, we conducted a series of spatial analyses using remotely sensed data of 1979, 1988, 1998, 2000 and 2003. The results showed that the urban area as well as the growth rate increased significantly. Three urban growth types were distinguished: infilling, edge-expansion and spontaneous growth. The pattern of urban growth can be described as a 'diffusion-coalescence' phase transition. Although edge-expansion was the most common growth type, the spontaneous growth took a greater proportion in area and patch number than the infilling growth at the early stage, but its dominance decreased as urbanization proceeded from the diffusion phase to the coalescence phase. Hot-zones of urban growth and the distribution pattern of newly urbanized areas in different periods were studied with a buffering analysis. More than 80% of the growth area occurred within a zone of 1.4 km wide outwards from the pre-growth urban fringes. The spatial distribution of newly urbanized areas in each period showed a uniform negative exponential decline relative to the distance from the edge of the urban patches. There existed an outward wave-like shifting of urban growth hot-zones, but the distance-growth area curves varied at different stages of urban growth. While a double-peaked pattern usually occurred in the diffusion phase, a single-peaked pattern was common in the coalescence phase.