中国大城市蔓延指数的开发

城市蔓延已成为具有普遍意义的现象,然而,城市蔓延内涵的争议性和模糊性问题一直没有得到很好的解决。本文将城市蔓延定义为一种低效、低密度、无序的城市空间开发模式,这种开发模式与中国城市高质量发展的目标和要求是相违背的。为实现对城市蔓延的宏观管理和精准调控,有效遏制城市蔓延带来的负面影响,本文开发了一套多维度、可比较的,并且与城镇化质量紧密关联的城市蔓延指数。基于卫星影像与人口、经济统计数据,选取代表城市蔓延核心特征的多个指标,采用主成分分析法计算了全国主要大城市2014年城市蔓延指数。结果发现,经济效率维主成分对综合蔓延指数贡献最大（41.30%）,人口密度维主成分次之（20.49%）,空间形态维主成分贡献率排第三（12.35%）。值得注意的是,许多经济发展较落后的城市因为经济效率维度的短板效应显著而被列入最蔓延的行列。此外,不同维度城市蔓延指数空间分布差异明显,并且综合蔓延指数与城市规模呈一定的负相关关系。

Developing an urban sprawl index for China's mega-cities

Urban sprawl has become a global phenomenon. There is, however, no consensus on the connotation of urban sprawl, which still remains subjective to controversy and ambiguity. In this paper, urban sprawl was defined as an inefficient, low-density and disordered mode of urban space development. The definition includes three of the most recognized characteristics of urban sprawl summarized from previous studies. Characterized by the features mentioned above, urban sprawl has been recognized as an important challenge to the high-quality development of cities in China. Therefore, to build an urban sprawl index that can reflect the quality of urbanization is of significance to macro-micro regulation of urban sprawl. Multiple metrics representing the core characteristics of urban sprawl were selected as measuring indexes, based on satellite images and socio-economic statistical data. Furthermore, in order to make the results more objective and comparable, the method of principal component analysis was applied to calculate the comprehensive sprawl index. Finally, 106 of China's mega-cities were chosen as cases, and the degree of urban sprawl of each city was measured for the year 2014. As shown from the results, the first principal component mainly reflected the dimension of economic efficiency, contributing 41.30% to the comprehensive sprawl index. The second principal component mainly represented the dimension of population density, followed by the third principal component that described morphological dimension. It is noteworthy that, because the short board effect of economic efficiency dimension was significant, many less-developed cities were ranked to a high sprawling level. In addition, the spatial distribution of different dimensions of urban sprawl index were distinct. Population density and land use efficiency were generally consistent with each other, while the distributing law of city form showed distinguishing features. Last but not least, the comprehensive sprawl index had a certain negative correlation with city scale, which reminds us to pay more attention to urban sprawl in medium-sized cities in the future.