| Severe urban uncontrolled expansion and urban spread have already occupied a large amount of natural resources, which have caused water and land resources to become an important bottleneck restricting the development of city. Facd with the urban space expansion accompanied by future urbanization, it is emergent to take actions to bring urban growth under control, and to optimize the spatial pattern of urban development in order to avoid the negative effects on ecological environment and social economy brought by rapid urbanization from the root. Under this background, delimiting urban growth boundaries in a scientific way has been explicitly required in the Central Urban Work Conference held in December 2015, and in the subsequent released document "CPC Central Committee and State Council on further strengthening urban planning and construction management". Taking this into consideration, it is necessary to adopt differentiated land use and urban management policy and to solve the contradictions among economic development, land resources and environment protection by means of delimiting the urban development boundaries. Wuxi as a central city in Yangtze River Delta and adjacent to the Taihu Lake, the economic development of Wuxi is under transition from late stage of industrialization to post-industrial stage. At the same time, with high ecological sensitivity, and under a severe pressure to protect water environment, Wuxi is a typical area for studying the delimitation of urban development boundaries.This thesis used Wuxi City as the study object, in which the land use change, the pattern of urban sprawl and its impact on water environment were analyzed. Under the premise of protecting important ecological targets and water environment quality, the strict development boundaries and the urban development boundary in 2020 of Wuxi City were delimited, through optimizing the allocation of land use quantity and structure, and considering the factors of social, economy, and policies. In addition, suggestions and recommendations were proposed to ensure the effective implementation of the urban development boundaries. The main results are as follows:(1) The land use in Wuxi City changed tremendously during 1985-2010. The accelerative growth of land use for urban construction has made it the dominant land use type gradually replacing agricultural land use. The quantity of land use for forest, garden and water, however, scarcely changed during the same period. The urban growth of Wuxi City was guided by the planning and management of local government, and there were mainly three patterns of urban spatial growth:first is the extensions along the major city meridians including the Grand Canal and Hu-ning highway; second is the circled expansions around the central city and the surrounding townships;third is the explosive growth propelled by industrial parks and development zones.(2) Land use quantity and structure were optimized based on the quality targets of water environment using multi-objective linear programming model. Area of urban construction land use of Wuxi City in 2020 was forecasted to be 524.00 km2.(3) Based on the ecological red-line areas, the strict urban development boundary was delimited using the methodology of anti-planning, integrating factors including basic farmland, geological disasters, elevation and slopes. Result shows that the area analyzed inside the boundary was 991.63 km2. The existing urban construction land was partly overlapping with the area outside the strict boundary.(4) The regionalization of water environmental constraints was introduced into Wuxi’s urban development boundary delimitation system considering the characteristics as a lakeside city with huge pressure on water environment protection, transforming the protection requirements of water environment into restriction of land exploitation and urban spatial growth. Result shows that the overall water environmental constraints were in low or moderate levels, and that the highly constrained areas were mainly distributed along the bank of the Taihu Lake and river basin of Zhihugang River and Wangyu River.(5) The impacts of location condition and radiation effect on urban spatial growth were evaluated quantitatively. The result showed that nearly 60% of the non-urban construction lands have high potential of urbanization. Considering the factors such as guiding policies and development strategy, the main directions of urban growth were predicted to be in the urban core areas including Liangxi District and Taihu Lake New City, and in the townships including Donggang and Ehu in Xishan District, Luoshe and Yangshan in Huishan District and Hudai in Binhu District. The suitability of urban spatial growth was evaluated by integrating water environmental constraints and urbanization potential. The urban development boundary of Wuxi City in 2020 was delimited by combining the development directions of the city and the predicted scale of urban construction land, through which the results turnde out to be linking up well with the major function oriented zones. |
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