城市化进程对长江下游平原河网水系格局演变的影响

以长江下游典型平原河网地区苏州市为例,基于1970s、1990s、2010s的遥感影像以及1960s、1980s、2010s水系数据,构建水系结构参数指标,重点探讨不同城市扩张方式对不同等级水系的干扰程度,以揭示城市空间扩展与水系结构演变的关系。结果表明:(1)城市扩展具有阶段性、趋向性,且受到自然环境和社会经济的影响与制约。(2)河网水系的改造和演化在不同城市化进程下表现出区域差异:近年来快速城市化区域的河网密度、水面率等水系结构指标变幅较大;80年代城市化区域变幅次之;进入高度城市化阶段的老城区,变化最小且稍有增加,其中近50年来河网密度在上述3个区域总体变幅为-21.06%、-16.23%以及1.88%。(3)河流结构发育受城市化进程显著影响,自然状态下河流长度与面积之比较大,河流结构更为稳定,而进入城市化阶段后,河流结构稳定性随之降低。该研究为城市化地区河流水系保护、城市规划及防洪减灾提供参考与理论支撑。

Effect of Urbanization on the Plain River Network Structure in the Lower Reaches of the Yangtze River

Taking Suzhou City, a typical city characterized by plain river network area in the lower reaches of the Yangtze River Delta, as an example. Based on the remote sensing images of the 1970s, the 1990s and the 2010s and the river system data of the 1960s, the1980s and the 2010s, streams structure parameters were adopted to analyze the disturbance of different urban expansion modes on different levels of rivers. Meanwhile, the evolvement relationship between spatial expansion of the city and river system structure was revealed. Research shows that: (1) Urban sprawl has the characteristics of stage and trend, and is affected and restricted by natural environment and social economy; (2) The transformation and evolution of river system shows regional differences under different stages of urbanization. River density, water surface ratio and other streams structure parameters have changed greatly in raptly urbanized area in recent years; followed by areas urbanized in the 1980s; while old town in highly urbanized stage had the smallest change and increased slightly. In the 1960s-2010s, the change range of river network density in above three districts was -21.06%, -16.23% and 1.88%, respectively. (3) The development of the river structure is significantly affected by urbanization process. The structure of the river network in the natural state is relatively stable, and after entering the urbanization stage, the stability of river structure is reduced. This study can provide reference and theoretical support for river system protection, urban planning and flood prevention and mitigation in urbanized areas.