Simulation Of Urban Land Expansion Based On Constrained Fuzzy Cellular Automata

As a valuable natural resource, land is the basic material base for human existence and development, especially in China where has 1/5 of the world's population. "Densely populated, land resources are very scarce" has become China's basic national conditions now and even for a long period of time in the future. It is a critical period for the development of society and economy in currently China, urbanization and industrialization require urban land continuously expanding, while the needs of food security for large population and ecological protection are also need to be ensured. Therefore, "Food, construction and ecosystem" has become the major problem in the land utilization and management in China. Currently, although China just own very scarce land resources, China's urbanization, processing with a mode of extensive growth of urban land, not only failed to ease the pressure on land protection in China, but also resulted in excessive reduction of arable land and pressure of food security. Meanwhile, the irrational use of urban land has made the economic, social and ecological benefits extremely low. Thus, how to guide the rational expansion of urban land correctly and improve the efficiency of urban land utilization, how to ensure the sustainable development of socio-economy and reduce the cost of land resource consumption on condition that food security and ecological security are ensured, have became the urgent issues to be solved in land use planning. Though the mesure of space control through establishing the boundaries of urban and rural construction land was proposed in the third round of land use planning, the guiding theories and methods is lacked in the planning work. Thus, it is of great theoretical and practical significance to guid the rational and orderly expansion of urban land through the study of dynamic simulation of urban expansion, which is capable of determining the reasonable scale and spatial distribution of urban land by using scientific and reasonable methods.Based on the previous studies and the related theories such as Complecxity Theory, Land Location Theory. Sustainable Development Theory and the Theory of Man-Land Relationship etc., this research, which aims at the reasonable expansion of urban land, adopts research normal forms such as normative & empirical analysis, qualitative & quantitative analysis etc., does a systematic study on the theory and method of simulation of urban expansion by using GIS technology, economics analysis, scenario analysis and cellular automata methods comprehensively. And then, this research does an empirical research of urban land expansion simulation take Taicang City as a case. Specifically, this paper concerns the mainly contents as following:(1) The analytical framework of dynamic simulation of urban land expansion. The paper builds up a logical analytical framework of dynamic simulation of urban expansion from the basis, constraints and method of urban expansion simulation separately. That is, it's necessary to analyze the mechanism of urban land expansion to grasp the evolution law of urban land use system in order to simulate the reasonable expansion of urban land. And then, we need to identify the issuses such as:what is the reasonable expansion form, how to determine the reasonable area of urban land and its location for expansion, and what is required on the simulation model of urban land expansion. Based on the analysis above, we need to construct a suitable model by selecting the appropriate method, and make it implemented. (2) The complexity of urban land use system and mechanism of urban land expansion. Based on a brief analysis of the complexity of urban land use systems and the inevitability of urban land sprawl, the paper analyzes the factors of urban land use expansion from the aspects of land area and spatial expansion systematicly, and explores characteristics of these factors' action in different stages of economic development. (3) Analysis of the constraints for urban land simulation. Based on the exploration of positive and negative effects of urban land expansion, the paper analyzes theoretically the connotation and characteristics of reasonable expansion of urban land, and puts forward that the simulation model of urban expansion should be constrained by land area and spatial factors. Then, it studies the methods to analyze the constraints of land area and spatial factors by the support of theories and methods such as Variable Weight Theory, Fuzzy Set Theory, Scenario Analysis and economic theory, etc. (4) Method and implementation of urban land expansion simulation. Considering the requirements of spatial control of urban land expansion in land use planning, the paper constructs a simulation model for urban land expansion based on Constrained Fuzzy Cellular Automata (CFCA), which takes land area and spatial factors as the main constraints of urban land expansion simulation. Then, the model of CFCA is implemented by using ModelBuider based on the ArcGIS platform. (5)Finally, this paper makes a case study in Taicang city based on the theories and methods above.From the research above, some conclusions are drawn out as following:First, as one kind of decision support tools for land use planning, the model of urban land expansion simulation should be constrained by additional constraints combining with land use planning and land use management, rather than predict the future only base on the previous expansion trend of urban land. Thus, it can provide a more comprehensive support system for urban land spatial control in land use planning by building a relatively complete theoretical system of urban land expansion simulation.Second, the basis and premise is laws and mechanism of the complex system in study of urban land use system simulation. There are some drivers for changes of urban land area, such as the urban population growth, the acceleration of urbanization, economic and industrial development, technological progress, urban transport development, comparative advantage of land, fixed assets investment and historical factors, etc. And there are also several braking forces, include eco-security, regional land resource endowment, food security and land-control policies, etc. And the factors to affect the spatial expansion of urban land include administrative divisions, ecological factors, natural environment, geographic location, relevant regulatory policies and self-regulations of urban land use system and so on. These factors have different influences at different stages of economic development, therefore, it is necessary to identify the stage of socio-economic developments, analysis the characteristics of urban land expansion and the main factors in the study area when doing the simulation study of urban land expansion. The result of the case study of Taicang city from 1989 to 2008 indicates that:the speed of urban land expansion is high and even accelerating, the economic return of urban land use is rising, and the waste of land has been eased. In term of spatial variation of urban land expansion, the focus of urban land are moving to northeast, and the compact degree of urban land is lower and lower, so that the large-scale land use benefits has been imitated. Besides, Taicang city is at the stage of overall industrialization, the factors of urban land expansion mainly including the second and third industrial added value and its proportion, the labor force of the second and third industry, urban population, investment in fixed assets, the city center, high-speed intersection, general roads, national highways and provincial roads, and so on.Third, generally speaking, to expand the urban land reasonably, the scale of urban land should be reasonable, so does the spatial distribution of additional urban land. So the area of urban land and spatial factors should be the constraints of the simulation model. Taking Taicang city as an example, result shows that the urban land scale of Taicang city is larger than corresponding reasonable scale except for 2006 and 2007 without considering the ecosystem services value of land, while considering the value of ecosystem services, the scale of urban land is also larger than corresponding reasonable scale during the period of study. Depending on whether to considere the land ecosystem services value and the speed of socio-economic development, the paper sets up 6 kinds of scenarios and calculated the reasonable urban land scale for each scenario. And then,3 scenario programs are selected as the area constraints of urban expansion simulation on the base of the socio-economic development stage in Taicang city.Forth, it is entirely feasible to introduce cellular automata model into the simulation of the urban land expansion in land use planning. By introducing the synthetic method of variable weight, fuzzy set theory, a model of fuzzy cellular automata (CFCA), which is mainly constrained by the ecological suitability, location suitability and reasonable urban land use scale, has been built in this paper, thus to handle the fuzzy decision-making problems in the process of urban expansion rationally. Simulation results of urban land expansion in Taicang city show that the model of CFCA can reflect the expansion law of urban land. And the simulation results of the three scenarios in 2015 and 2020 not only reflect the compact development mode, but also take the ecological benefits of urban expansion into account. So the results could help improving efficiency of urban land use. they are also agreement with the request of "Eleventh Five-Year Plan" in development of Taicang City. Therefore, the simulation results can be used to guide the urban expansion reasonably in land use planning.Some suggestions are proposed to control the urban land expansion from the aspects of urban land scale and spatial expansion based on the conclusions above:firstly, the ecosystem services value of land should be included in the urban land expansion cost, and the transfer mechanism between rural land and urban land should be further improved; Secondly, flexible land use planning should be made, and urban land scale should be determined under multiple scenarios in the planning; Thirdly, performance appraisal system of "Land use & Economic Development" should be established, and the annual plan management system for land use should be improved; Fourthly, the priority of urban expansion areas should be classfied, and the transfer system of urban land development rights could be tried out; Finally, the various types of urban land should be distributed rationally by scientific urban planning, and the concept of using land must be improve in local government.