基于演化树模型的长江三角洲城市紧凑度综合评价

紧凑城市是一种高效的城市空间组织模式，对实现城市可持续发展战略具有重要意义。通过密度、规模、结构和强度维度建立紧凑城市四维理论模型，并以此为基础构建由4个二级指标和12个三级指标组成的城市紧凑度综合评价演化树模型。通过对长江三角洲16个核心城市实证分析，评价结果显示：整体城市紧凑度下降，且影响紧凑度因素存在区际差异；在空间上，紧凑城市大致呈现沪杭甬沿线高于南北两翼的空间格局；从演化过程上分析，城市紧凑度与城市发展阶段发展水平具有一定的关联性，城市化率和产业结构与城市紧凑度呈现显著正相关。近年来开发区分散建设、城市建设用地面积扩张等因素是造成长三角城市紧凑度下降的重要原因，交通、医疗等公共服务设施投入不足、分布不均及政府有限的约束力也在一定程度上制约城市的紧凑发展模式。因此，需要在未来加强协调市场和政府两种力量以推动城市发展的高效高质

COMPREHENSIVE EVALUATION OF COMPACTNESS BASED ON THE CITIES EVOLUTION TREE MODEL

Since the prevailing adoption of sustainable objectives in the early 20th century, there has been increasing interest in compact city. Due to its significant advantages, compact city has been advocated by many scholars to resolve such problems as city sprawling, city decline as well as limited supply of land resources. In addition, the promotion of compact city also has enshrined in land use planning policy in many countries; however, the lack of tools measuring compactness leads to difficulties not only in investigating the impacts of the process but also in gauging progress towards sustainability objectives. Therefore, better measures of compactness are needed for use as planning tools, as well as to enable measurement of progress toward sustainability and to assist study on the impacts of compactness. Based on the related theories and background of meaning of compact city, this paper explains the implication of compact city in the first place, which means higher economic and population density, mixed uses, higher intensity development and limited sprawling rate. A theoretical model is also established to assess the compactness of cities, which consists of the following four dimensional parts: (1) density, which can be identified by high population density, high density of built form and public transport; (2) scale, which is mainly measured by the percentage of urban construction land and the number of private cars; (3) intensity, which can be defined as an increase in the density of population and the intensification of the built form as well as economic agglomeration; (4) structure, which means varied and plentiful supply of facilities and services, and mix of uses within urban construction land. With this theoretical model, an index system consisted of four primary indicators, twelve secondary indicators is set up to evaluate the compactness of cities. The results show that: the overall compactness of 16 cities in the Chang jiang River Delta is low, and that the spatial disequilibrium exists obviously. Moreover, the development process of compact cities to some extent correlates with the development level of city itself, which is further proved by the test of the correlation analysis showing that the factors of industrial structure and urbanization rate are positively correlated with the compactness index of cities in the Chang jiang River Delta. Finally, the paper draws the conclusion that factors including as the dispersion of development zones, expansion of urban construction land have affected the spatial efficacy of cities in the Chang jiang River Delta. The spatial structure of the public transport, education and health service should be improved rapidly. The work outlined in this paper has made a clear contribution to the task of measuring urban compactness and thus provides support for further empirical work