The trajectory of urbanization process in the Yangtze River delta during 1990 to 2005

Rapid economic development, combined with tremendous population growth and migration from rural areas, has resulted in a dramatic urbanization in the Yangtze River Delta over the last three decades. In order to develop a more quantitative understanding of urbanization trajectory in the Yangtze Delta from the late 1980s to 2005, the time-series national land cover / land-use database (NLCD), interpreted from remote sensing imagery (including Landsat TM, ETM+ and CBERS), was examined from the aspects of spatial pattern and temporal process. The results showed that the urban land in the Yangtze River Delta has increased from 2.29times10³ km² in the late 1980s to 4.19times10³ km² in 2005. The percentages of total land area in the Yangtze Delta occupied by urban environments in the late 1980s, 1995, 2000 and 2005 were 2.09%, 3.03%, 3.28%, and 3.82% respectively. During the late 1980s - 2005, the total urban expansion in this region was 1.92times10³ km², resulting in an annual urban expansion area (UX_a) of about 118.72 km² per year, with an urban expansion intensity (UX_r) of 83.03%. There were significant spatial trends and differences in urbanization level and urban expansion. Most urban land and urban expansion have occurred along the Huning Railway (Shanghai-Nanjing) and the Hanzhou Bay. This study also revealed substantial temporal differences in the rate at which urban areas have expanded. There was a great deal of urban growth in the late 1980s - 1995, and also in 2000 - 2005. The 1995 - 2000 period saw a slow expansion speed due to government initiatives designed to halt the loss of agricultural land. In this study, both patterns and dynamics of urban distribution and urban expansion were examined on temporal and spatial scales, and integrated to produce a comprehensive evaluation of recent urbanization trajectory in the Yangtze River Delta.