中文摘要：

城市化对水系演化影响的研究国内目前多集中在快速、高速城市化地区,而对大流域、城市化发展较缓地区的研究比较薄弱.以南四湖流域为研究区,基于1987、2000和2014年3期遥感影像,分析了流域城市化进程中的下垫面变化特征;选取流域1980s、2003和2014年的地形图进行水系提取,从数量参数、结构参数和连通性参数3个角度分析近30年城市化进程中水系结构的时空变化特征.结果表明：（1）近30年来流域建设用地增加了1568.06 km~2,2000年以后城市建设用地扩张显著,2012年流域人口城市化率为32%;（2）1980s—2010s流域总河流长度、面积和河网密度均呈现出持续减少趋势,分别减少了135.46 km、2.75 km~2和0.49 km/km~2,各级河流表现出不同的变化特点,较低等级河流受到的影响较大;而流域水面率持续增加,近30年共增加了59.79%;（3）流域水系总体上还保持着自然状态下的空间格局,但结构特征发生了较大改变,河网结构稳定度减少了4.30%,连接率和实际结合度分别减少了21.82%和21.62%;子流域内部距湖区越远的空间城市扩展强度指数值越大,城市化对水系的影响越显著.该研究将补充对不同空间尺度、不同城市化水平地区河网水系演化影响的案例,并为研究区河网水系的保护提供支持与参考.

英文摘要：

Currently many studies have been conducted to analyze the impact of urbanization on the change of stream structure. However, most of them have concentrated on some developed areas, but the less developed urban areas have attracted few attentions. Taking Nansi Lake Basin as the investigation area, this study analyzed the change of stream structure during the urbanization process. The change of land surface was firstly extracted by using remote sensing images of 1987, 2000, and 2014. Based on the stream structure data derived from topographic maps in 1980s, 2003 and 2014, this study further analyzed the effect of urbanization on spatiotemporal change of stream structure in 30 years by adopting indicators of quantity, structure and connectivity, respectively. The results show that： （ 1 ） The construction land increased by 1568.06 km2 during the past 30 years. The area of urban construction land has grown significantly since 2000. The percentage of urban population was 32% in 2012. （2） The whole river length, area and fiver density percentage have decreased by 135.46 km, 2.75 km2 and 0.49 km/km2, respectively during the study period. In addition, the impact of urbanization on stream structure varied spatially across the study area. The rivers at the low level experienced more significant change, while the water surface rates increase by 59.79% continuously. （3） Although the spatial pattern of stream remained unchanged, the stream structure varied significantly during the study period. The stability value of river network decreased by 4.30%, and the connection rate and the combination degree fell by 21.82% and 21.62%, respectively. Moreover, the urban expansion intensity has strong-positively impacted on the stream. The study helps in better understanding the impact of urbanization on stream structure at different spatial scales and urbanization levels, as well as to provide a valuable support and reference for stream protection.