Research On The Spatial Distribution Of Construction Land Of Central Urban Area In General Land Use Planning

With the rapid growth of economy, industrialization and urbanization in China have been expanding continuously. One notable feature of modern society is the increasing demand for land, and the amount of construction land developed during the planning period always exceed the limited amount in planning. Land resources are scarce and non-renewable. Besides, there are more people and less land in China leading to the rising lack of construction land, which has become the main limitation for economic development. On the other hand, in the context of enhancing protection of farmland and ensuring national food security, governments need to implement various control targets and distribution requirements in land use planning to achieve the consistence of diagram and number. Therefore, how to put limited construction land resources into space, fulfill its rational distribution, achieve its maximum effectiveness, and ensure the development of social economy has become the most important task of land use planning. In addition, the land for construction in central urban area is the core as well as the carrier of regional economic development. Spatial distribution optimization is directly related to the regional socio-economic sustainable development and ecological protection of the environment, which is of great significance to guide and control future land use.Currently, city and the process of forming it are widely considered to be a complex system with characteristics of open, dynamic, self-organized and non-equilibrium. At the same time, city's development process is easily disturbed by humans so that we need to coordinate each subsystem and the contradiction between multi-target actors through planning to remedy city's defect of spontaneity, blindness, and hysteresis. Therefore, based on the perspective of city complex system, this paper does research on optimization of construction land distribution in central urban, trying to achieve balance develop between urban land use planning and city's self-organizing rules. The following conclusions have been made,(1) Through computer simulation, we find that when the planning coordinates with the city's self-organizing rules, economic and social benefits will both improve. Adventurous decision-making body prefers economic efficiency, while, prudent decision-making body prefers social and ecological benefits. Consequently,for adventurous decision-making body, only when planning is in consistence with city's self-organizing law will the land development better meet the planning avoiding pervasive or saltant development. For prudent decision-making body, only when the planning coordinates with city's self-organization law can improve the economic value of urban development. In addition, when the planning accords with city's self-organization law, enhancing planning enforcement does good to social and ecological benefits in city development.(2) Based on the suitability evaluation of the central urban, this distribution is useful to determine preponderant location for future urban development, control city's spread development along main roads, and guide city to the filling development. The mentioned method also has its weakness. It is difficult to reflect the space pattern which is caused by the dynamic impact of neighborhood and the interaction between partial rules. It is not efficient to distinguish heterogeneity in a small range leading to centralized distribution. However, the reality is that anyone has the motive to pursue economic interests in regional development. Any land which has the better location around the building city is possible to be developed so that central development is always accompanied by the distributed development. Therefore, top-down construction land distribution does not take into account city's bottom-up self-organization law, which easily leads to the deviation between distribution results and the actual city development.(3) Before 1996, the speed of urban development is relatively slow in Hangzhou and certain city development pattern with single subject is the main mode. The driving factor for urban development is relatively simple and roads as well as existing city are the main factors for urban expansion. Edge-growth is the main mode, which city spreads along roads and the existing built-up areas. After 1996, with the growing rate of urbanization in Hangzhou, certain city development mode with single body is gradually replaced by the accident development with multi-body which is the representative of "new city development mode". Urban development is becoming more complex and has more influencing factors so that it is urgent to consider the complexity of urban development in the land planning for central urban construction.(4)The method of cellular automata model has superiority in forecasting likely development areas in the suburb and preventing random land development. Compared with the method of land suitability assessment, construction land distribution is more dispersed, but accords with reality, and has guiding significance. It often connects the adjacent broken patches in suburban areas, which is helpful to raise the city's compactness. According to statistic, the number of construction land patches reduced to 998 and aggregation index increased to 92.57 in 2010. Moreover, the number of patches will decrease to 875 and aggregation index will increase to 93.80 in 2020 and it is more consistent with city actual development. By comparing with the range of urban planning, this distribution result lines up with the city planning in the control of the land use for central urban area and the goodness of fit is 82.35%. Using the theory of convex hull for center city's land layout is beneficial to control the shape of urban development as well as control the land development priority in the convex shell, which will effectively promote the city development to the compact direction.