中国大城市蔓延的测度研究——以杭州市为例

Measuring Urban Sprawl in Large Chinese Cities: A Case Study of Hangzhou

从土地不连续利用和低人口密度这两个城市蔓延的核心特征出发，提出了城市土地扩张指标与人口密度指标相结合的蔓延测度方法，利用杭州市1978～2010年的遥感影像，实证测度中国大城市蔓延的时空动态变化。测度结果表明，城市土地扩张与人口密度指标相结合的方法测度效果良好，与实际情况吻合度高。杭州城市蔓延十分典型，主城区蛙跳式开发以及大部分的边缘增长发生在人口低密度区或较低密度区，城市发展不紧凑，蔓延迅速；阶段特性显著，在空间上表现为由单一中心向多核心发展的态势。将城市土地扩张与人口密度指标结合来测度城市蔓延是十分有益的尝试，为中国大城市蔓延的测度研究提供了一种简单、易于推广使用的可选方法。

With rapid urbanization and economic transition, large Chinese cities have increasingly experienced urban sprawl that has been prevalent in the western countries. Despite of a proliferating literature in the con- cept, impact, mechanism, measurement and control strategy of urban sprawl, scholars have not reached agree- ments on its definition and approaches of measuring the sprawl. Based on two commonly accepted core charac- teristics of sprawl, i.e., the discontinuity of land use and low density of population, we proposed to use land ex- pansion index and population density index to define and measure urban sprawl in large Chinese cities and use the main city area of Hangzhou as a case. Based on the socioeconomic data and land use data derived from four scenes of Landsat MSS/TM/ETM＋ images in 1978, 1991, 2000 and 2010, we characterized the urban sprawl of Hangzhou over three periods （1978-1991, 1991-2000, 2000-2010）. In particular, this study has em- ployed unsupervised and supervised classification methods to interpret the pattern of urban land, GIS spatial analysis to analyze land patches of ＂leapfrog＂ and edge-growth, which reflect the discontinuity of land use in urban sprawl, and statistical analysis to investigate population density on a street （or town） scale. The results re- veal that Hangzhou has experienced extensive urban sprawl, with the comprehensive sprawl area amounting to 6.923 km2 during 1978-1991 but dramatically increasing to 137.413 krn2 during 2000-2010. Further, population growth rate has lagged behind the land expansion rate in Hangzhou. Moreover, although urban sprawl in differ- ent phases displayed distinct characteristics, a polycentric urban development can be identified, with most new- ly developed urban land concentrated in Binjiang and Xiasha districts. The study indicate that the method of us- ing land expansion index and population density to measure urban sprawl is a simple yet appropriate approach that can be used to other cities in different regions or countries.