高度城镇化背景下水系演变及其响应

针对长江三角洲地区高度城镇化对水系剧烈影响的事实,以该区太湖平原苏州市为例,选取河网密度、水面率、分形维数和支流发育系数作为水系变化指标,运用GIS分析近50年来河网的时空变化规律,在此基础上,研究水系变化对于城镇化及降水变化的定量响应,分析高度城镇化下水系的发展趋势。结果表明:①近50年来研究区水系呈衰减趋势,河网密度、水面率、分形维数和支流发育系数分别下降5.6%、19%、1.2%和3%;区内水系禀赋差异大。②近50年来水系衰减的主要影响因素为城镇化,气候变化对其影响相对较弱;在水系变化中,城镇化的贡献率在67%以上。③随着城镇化率增加,研究区河网密度、分形维数、支流发育系数呈现先增长后衰减的"倒U型"曲线特征;苏州的高度城镇化与其水系表现出"先松弛,后紧密"的关系,二者的发展目前处于曲线右侧;未来将过渡到"高水平适应阶段"。本研究的结果丰富了城镇化与水系发展关系研究,可为其他地区水系系统的健康、绿色发展和保护提供参考。

Changes of river system and its response to highly urbanization,China

The purpose of the study is to analyze the response of river system to the climate change and rapid urbanization process in Suzhou,Taihu Lake plain area. The study selected the drainage density,water surface ratio,fractal dimension and tributaries development coefficient as representative parameters. Based on GIS technology,the spatial and temporal variation of river networks caused by urbanization and climate change in the study area in the past 50 years was analyzed. On this basis,the study focused on the quantitative response of river network changes to urbanization and precipitation change,and the development trend of river system under highly urbanization. The results showed that:① The river system in Suzhou presented a high spatial heterogeneity and rapid descending tend in the past 50 years. The drainage density,water surface ratio,fractal dimension and evolution coefficient of branch river were decreased by 5.6%,19%,1.2% and 3%,respectively. ② Compared with climate change,highly urbanization was recognized as the stronger driving factors of river system degrading in the past 50 years. Urbanization contributed over 67% to each unit of river network change.③ With the increase of urbanization,the drainage density,fractal dimension and evolution coefficient of branch river first showed growing trend and then started to decay,presenting a curve in "inverted U shape". The influence of high urbanization to river networks grew from weak to strong. Currently,the development of river network and urbanization rate was in the right of the curve. With the mutual adaption between the urbanization and the development of river network systems,they will evolve into a high-level development stage in the future. This research investigated the developing rule and relationship of urbanization and river network systems,providing support for the river network health and green development and protection in similar area.