Abstract:

Since the 1980s, with demands from water conservancy projects, the rise of canal tourism, and the proposal of the national canal cultural development strategy, the China's Grand Canal has been reviving. At the same time, the size, expansion pattern, and spatial distribution of built-up areas along the Grand Canal have experienced significant changes, with far-reaching effects on city traffic, communication, production, daily life, and public facilities. There have been abundant studies on the key river sections or typical cities. However, there is a general lack of research on the overall expansion of cities along the Grand Canal. In this study, 35 cities along China's Grand Canal were selected as the research subjects. The research area covered two municipalities and six provinces from north to south. Statistical data and remote sensing data were combined in this study for analyzing urban expansion speed, urban expansion pattern, and regional differences of cities along the Grand Canal during 1984-2016. All statistical data were collected from statistical yearbooks. Landsat images were the main data source for urban land mapping. Dispersion index (DI) was applied in this study. The index is a new landscape metric, which was developed for describing the structures and distributions of geographic elements in a region. The results show that: 1) The cities can be classified into four types according to the characteristics of the speed of expansion. Class one contains Shandong, Anhui, Jiangsu, and Zhejiang Provinces, where urban land expansion speed increased dramatically after 2000 and decreased latter. Class two contains Hebei Province and Tianjin Municipality, where urban land expansion speed increased moderately but decreased dramatically latter. Class three contains Beijing, where the highest expansion speed appeared in 2000 and then changed dramatically. Class four contains Henan Province, where expansion speed of urban land changed moderately before and after 2000. 2) Urban built-up areas extracted from remote sensing images are generally larger than urban built-up areas collected from statistical yearbooks. The former is usually between 1-2 times of the latter, and urban expansion in northern China mainly extended around one center, but urban expansions in southern China gradually became polycentric. 3) The spatial distribution of built-up areas in most cities tends to become dispersed and discontinuous, and cities in Jiangsu and Zhejiang Provinces are more remarkable in this respect. The spatial distribution of built-up areas in Beijing was most integrated and compact. The growth of DI values of built-up areas in Hebei Province was the lowest and urban land expansion there was slow. With the successful application for World Heritage of the Grand Canal and the proposal of the Grand Canal cultural development strategy, the construction of the Grand Canal culture belt and the development of canal tourism will become an important measure for promoting the joint development of different regions.

Key words: urban expansion, dispersion index, spatial feature, regional difference, China's Grand Canal