基于GIS和分形理论的城市蔓延度研究——以马鞍山市为例

URBAN SPRAWL RESEARCH BASED ON GIS AND FRACTAL THEORY:A CASE STUDY OF MAANSHAN CITY,CHINA

在快速城市化过程中,城市不断扩张而产生的蔓延现象与土地可持续发展紧密相关,合理控制城市蔓延度可以节约资源,促进城市内涵式发展。根据蔓延度内部机理和分形理论构建蔓延测度指标体系,采用GIS方法,通过分维数、空间稳定性等指数,以马鞍山市为例分析研究区城市蔓延度特征和时空差异。研究表明:(1)分形理论适用于城市蔓延度的定量研究;(2)从时间维度看,研究区内部不同区域间的蔓延趋势总体相似,但蔓延程度有所差异;(3)从空间维度看,蔓延度与分维数、建设用地破碎度呈正相关,与空间稳定性指数呈负相关。马鞍山市城市蔓延的机制是土地导向,经济发展是抑制过度蔓延的动力。

Urban sprawl is a form in the process of rapid urbanization in recent China. The urban expansion has led to urban sprawl. The sprawl phenomenon is closely related to sustainable land development; it affects the social, economic and environmental development. If urban sprawl is controlled reasonably, it can conserve resources and promote the city connotation development. The internal mechanism of sprawl and fractal theory was used to construct sprawl measurement indicator system, GIS means was applied to calculate the index, and spatial and temporal difference was analyzed through the fractal dimension and spatial stability index. This paper took the urban expansion of Maanshan City during 2005--2010 as a study case, and indicated that urban sprawl could be measured through growth configuration, urban growth efficiency and its impacts of urban growth. This study described the urban growth configuration based on fractal theory, and established an urban sprawl evaluation system with AHP on the basis of western experiences and approaches from sprawl mechanism and the traditional perspective of spatial pattern for measuring sprawl in Maanshan City, covering eight factors of irregular of land patches, patch fragmentation, clustering, concentration, elasticity index, economy, commuter and urban life quality, a total of 12 indices in all. Specifically, patch fractal dimension（D）, patch shape index（LS）, stability index （SK）, fragmentation of built-up land （FC）, leapfrog index（LF）, compactness（C）, the rate of change of the central area population density（PD）, consumption of built-up land for construction per new population （PC）, twenty-three production input-output coefficient（IO）, built-up land and economic growth coefficient （CE）, crowding level（CL）and residential density（RD） were developed for measuring the degree of urban sprawl. ArcGIS 9.3 was selected to analyze land-use data in order to calculate by weight sum of these 12 indices. The results show as follows. （1） The fractal theory was applied to study the quantitative research of sprawl degree. （2） During the study period, the sprawl degree of three districts in the study area was different, but the overall sprawl trend was similar. （3） The sprawl degree, fractal dimension and built-up land fragmentation were being related. It was negatively correlated with spatial stability index. Based on the result, we discussed the regional spatial differences of urban sprawl and some proposals were put forward from many aspects. The study area was further divided into 86 smaller regions, which selected street or village as a unit to calculate built-up land stability coefficient, fragmentation, the compact degree and the shape index of urban space. The built-up land fractal dimension was closer to 1.5. It indicated that the overall stability of the plaque was low, and the expansion ring in the study area was from the city center to the periphery; if it was closer to the city center area, the built-up land fragmentation was smaller, and the concentration of compact was higher; if it was away from the city center area, the built-up land fragmentation was larger, and the concentration of compact was lower. The SK, FC, CI and LS in the spatial distribution were similar to urban sprawl morphological characteristics. The mechanism of urban sprawl in Maanshan City was land-oriented. Economic development was one drive to suppress the urban sprawl.