The Research On Demarcation Of Development Boundary Of Small And Medium-sized Cities In Hilly Area

The boundary of urban development is a technical solution and a spatial policy response to the reflection of urban sprawl.Under the background of the reform of China's spatial planning system,as one of the means of spatial control(three districts and three lines),urban development boundaries need to continuously explore targeted delineation methods to form a boundary delineation technical system that adapts to the actual situation of the city,so that it has both local characteristics and promotional significance.In this paper,small and medium-sized cities in hilly areas are taken as the research object.As hilly areas have great ecological constraints on urban development,and small and medium-sized cities also generally have expansion needs,how to balance the relationship between development and protection in spatial expansion and explore the development boundary method suitable for small and medium-sized cities in hilly areas are the research objectives of this paper.Firstly,the concept definition and research summary of hills,small and medium-sized cities and urban development boundaries are given.On the basis of summarizing the previous research results,the basic attributes,functional objectives and composition contents of urban development boundaries are proposed.The composition and control measures of urban development boundary system are mainly elaborated.The delimitation of urban development boundaries in different regional types of cities such as hills,mountains and plain cities and in different development stages of large cities and small and medium-sized cities are analyzed respectively.Secondly,it studies the influencing factors of urban development boundary delimitation from two aspects of constraint and drive,and combining with the natural characteristics and development characteristics of small and medium-sized cities in hilly areas,it proposes that disaster prevention and control,ecological network,landscape pattern,spatial growth and natural boundary should be taken into account in the delimitation of the development boundary of small and medium-sized cities in hilly areas,and sums up the eight steps of boundary delimitation with corresponding analysis methods.In general,a development boundary system is formed,which is dominated by "rigid constraint boundary" to prevent and control disasters and protect the integrity of ecological space,and assisted by "limit scale boundary+elastic stage boundary" to expand land due to population and economic growth.Finally,taking Luxi County planning area in western Hunan as an example,taking ArcGIS software as the core technical support,the ecological security pattern,suitability of land development and carrying capacity of resources and environment are comprehensively evaluated.On the basis of determining the development direction,scale and spatial layout of Luxi central urban area,the development boundary delimitation scheme of Luxi County planning area is proposed and compared with the original urban development boundary.The conclusions drawn in this paper are as follows:(1)There are differences in the emphasis of demarcation of urban development boundaries in different regional types of cities such as hills,mountains and plain cities,as well as in different development stages of large cities and small and medium-sized cities;(2)The demarcation process of the development boundary of small and mediumsized cities in hilly areas can be divided into eight steps: preparation of working technology,rigid constraint boundary,evaluation of resources and environment carrying capacity,evaluation of suitability of land development,direction of city development,prediction of city scale,layout of city space and demarcation of flexible boundary.(3)Four development boundary lines will be formed in Luxi planning area to jointly form Luxi county development boundary system.Comparing the delimitation result with the original Luxi County urban development boundary,it shows that the delimitation method proposed in this paper further considers the carrying capacity of local resources and environment than the existing technical methods for delimiting the urban development boundary,which can effectively protect the ecological security pattern and guide the orderly development of the city.