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.