长江流域城市蔓延特征识别及演化趋势模拟——基于城市蔓延多维度指标的测度

Spatio-temporal characteristics and evolutionary trends of urban sprawl based on measuring the multi-dimensional indicators in the Yangtze River Basin,China

城市蔓延是一种低密度、非连续的城市化现象,严重威胁城市的可持续发展。本文基于夜间灯光数据识别2005—2020年长江流域建成区范围,从密度维、形态维、结构维、效率维和品质维五个维度,结合流域、城市群和不同类型城市三个空间尺度,构建多维度城市蔓延测度指标体系和城市蔓延特征识别模型对长江流域城市蔓延时空特征进行识别分析,结合城市蔓延速度、地形地貌、生态屏障和生态阻力约束因素建立城市蔓延情景分析模型,对长江流域城市蔓延演化趋势进行模拟。研究表明:①2005—2020年,长江流域城市蔓延速度整体呈下降的趋势。其中,密度维和形态维的城市蔓延速度呈上升趋势,结构维、效率维和品质维的蔓延速度呈下降趋势。②2005—2020年,长江流域城市蔓延效率以波动减少和持续下降为主,波动增加和持续上升次之。③2005—2020年,长江流域Ⅰ型小城市、Ⅱ型小城市和成渝城市群发展均衡性逐渐下降,其余类型城市发展均衡性均呈上升趋势。④2005—2020年,长江流域城市蔓延模式主要以边缘蔓延为主。飞地式蔓延斑块数量占比逐年降低,边缘式蔓延、填充式蔓延斑块数量占比逐年增加。⑤2025—2040年,长江流域不同尺度城市蔓延模拟面积均将呈持续增长的趋势。长江上游流域城市、Ⅱ型大城市、中等城市、Ⅰ型小城市、Ⅱ型小城市蔓延面积占比呈上升趋势,其余类型城市的蔓延面积占比呈下降趋势。本文为长江流域高质量发展和国土空间规划提供了科学依据与参考。

Urban sprawl is a low-density,discontinuous urban spatial development pattern that threatens the urban sustainable development seriously.In this paper,the Yangtze River Basin(YRB)was picked up as a case to elucidate the characteristics of urban sprawl.First,we identified the built-up area boundary of the YRB in the year nodes of 2005,2010,2015 and 2020 by using NPP-VIIRS-like nighttime light data.Then,we analyzed the spatio-temporal characteristics of urban sprawl in the YRB from 2005 to 2020 by using constructed multidimensional urban sprawl indicator system and urban sprawl feature recognition model.Finally,we simulated the evolutionary trends of urban sprawl on the three scales of city,urban agglomeration and watershed from 2025 to 2040 by using urban sprawl scenario analysis model.The results indicate that from 2005 to 2020,the urban sprawl speed in density dimension and morphological dimension showed an increasing trend,while that in structure dimension,efficiency dimension and quality dimension showed a decreasing trend.Meanwhile,from 2005 to 2020,the efficiency of urban sprawl was dominated by fluctuating decreases and sustained decreases,followed by fluctuating increases and sustained increases.And regarding the developing balance,the Type I small cities,Type II small cities and the Chengdu-Chongqing urban agglomeration in the YRB showed a decreasing trend,while that of the remaining types of cities showed an increasing trend.In addition,from 2005 to 2020,the pattern of urban sprawl in the YRB was dominated by edge sprawl.The number of leapfrog sprawl patterns was decreasing year by year,while the number of edge sprawl and infilling sprawl patterns was increasing year by year.Furthermore,the urban sprawl at different scales in the YRB will continue to grow during 2025-2040.The percentage of sprawling area of cities,Type II large cities,medium cities,Type I small cities,and Type II small cities in the upper Yangtze River Basin shows an increasing trend,and the percentage of sprawling area of the remaining types of cities shows a decreasing trend.Our findings may provide a scientific basis and reference for high-quality development and territorial spatial planning in the YRB.