【作者】 蔡娟；

【导师】 许有鹏；

【作者基本信息】 南京大学 ， 环境科学， 2012， 硕士

【摘要】 武澄锡虞区位于太湖流域腹部,河网密布,水系发达。自改革开放以来,城市化进程不断加快,为了争夺有限的土地资源,大量城市河流水面被侵占,低等级河道、小水体等被填埋,造成区域水面率不断下降,河网结构在人类活动的强烈干预下偏离了自然发育规律,逐渐趋于单一化、主干化,最终导致区域河网调蓄功能萎缩,防洪排涝压力加大,洪涝灾害频发。因此,从河流地貌学角度出发,结合土地利用变化,研究城市化背景下平原河网地区水系结构特征及其调蓄能力的变化,对探讨区域水面率及水系结构的恢复与保护,提高区域调蓄功能至关重要。论文依托水利公益专项科研项目“改善长江三角洲地区水系结构与河湖连通研究”(编号：201201074),基于3期土地利用数据、水系数据及代表性水位站的特征水位值,以武澄锡虞区为研究区,借助ArcGIS、SPSS软件,运用自然地理综合分析法,从多时相、多尺度及多指标角度对比分析了研究区近16年来的土地利用时空变化特征,近50年来的河网水系时空变化特征以及水系结构变化下的河网调蓄功能的变化特征,并结合研究区自身特点,分析了区域水系结构变化的驱动因素,提出了基于调蓄功能变化的水系保护对策,以便为研究区未来城市化发展过程中河网水系的保护与管理提供相关参考依据。论文基于1991、2001和2006年3期土地利用图,从土地利用变化幅度、变化速度、结构变化及转移方向变化等角度,对比分析该区域在1991-2006年间的土地利用变化过程和空间分布特征。结果表明：(1)研究区土地利用类型主要以水田、城镇用地为主,两者共占研究区总面积的90%以上；(2)近16年来城镇用地共增加126.9%,水域共减少79.8%；(3)研究区土地利用变化总量不断增加,城镇用地每年以6倍于转移速度的新增速度增长,水域则以10倍于新增速度的转移速度减少,城镇、水田是水域最主要的流向地类；(4)城镇用地主要集中于城市化水平较高的无锡、常州两市,不同城市化水平的城市均表现出城镇用地大幅增加,水田、水域不断减小,但变化幅度不尽相同,且无锡在各地类总量变化上最突出。论文采用4项河网水系结构表征指标,即河网密度、水面率、河网复杂度和水系分维,对比分析1960s、1980s和2009年3个不同时期的河网水系结构特征以及同一时期不同城市化水平下的水系空间变化特征。结果表明：(1)研究区河流总长度不断减少,近50年来总减幅达35.74%,且1980s后变化更为剧烈；(2)不同等级的河流总长度均不断减小,且等级越低,河流总长度的减幅越大；(3)研究区总体水面积变化趋势与河流总长度的变化趋势一致,即逐年代不断减少；(4)研究区河网密度、水面率、河网复杂度以及水系分维均不断下降,说明城市化水平越高,河网复杂度越小,河网结构就越简单,河网发育正趋于主干化、单一化；(5)研究区不同城市的水系结构参数均呈现出逐年代减少的趋势,这不仅与各市现有的城市化水平有关,还与其城市发展建设速率相关；(6)无锡、常州两市的非农业人口、国内生产总值等与河网水面率的相关性分析进一步证实了城市化对河网水系影响的显著性。论文选取研究区4个代表性水位站,采用河道槽蓄容量C、可调蓄容量AC、单位面积槽蓄容量SR和单位面积可调蓄容量ASR4个参数,对比分析不同等级河道容蓄能力和可调蓄能力的时空变化特征,揭示区域水面率与区域调蓄功能的内在联系。结果表明：(1)不同等级河道的SR和ASR均表现为逐年代不断减小,且河道等级越低,河道容蓄能力、可调蓄能力减小越多；(2)与高等级河道相反,三级河道ASR减小率大于SR减小率,说明其在河网水系中的调蓄、汇水作用更明显,高等级河道用于调蓄的那部分容积占河道总容积的比例相对较小；(3)不同城市的SR和ASR逐年代不断减小,其数值大小顺序与四市水面率大小顺序一致；(4)研究区水面率Wp-SR、Wp-ASR相关分析进一步证实了水系结构与调蓄功能密切相关,因此可以通过拓宽河道、沟通水体、增加人工水体等措施提高区域水面率,从而实现区域水系结构的保护和恢复。更多还原

【Abstract】 Located in the center of Tai Lake Basin, Wuchengxiyu region is densely covered with river networks. Since Reform and Opening in1978, the process of urbanization is accelerating continuously. For the limited land resources, a large number of water surface are occupied while low-grade river and some small water bodies are landfilled. These human activities result in the decline of water surface ratio and the stream structure is becoming much simpler in urbanized area. Finally, the regulating and storage function of river networks is weakened and the flood disaster happens frequently. Therefore, in the perspective of fluvial geomorphology, research on the variation characteristics of stream structure and its storage effect in urbanized area, combined with LUCC, is of great significance.This paper is supported by the public welfare project of ministry of water resources (No:201201074). Based on landuse、water system and water level data in three different periods, it analyzed the spatial and temporal changes in landuse, stream structure and its storage effect comparatively between different periods and scales with multiple indicators. Also, this paper analyzed the driving factors of the change in stream structure with ArcGIS and SPSS, and put forward some protection countermeasure of the stream structure based on the regulating and storage function. These countermeasures will provide relevant references for the protection and management of stream structure in the future.Based on remote sensing images of landuse in1991,2001and2006, this paper analyzed the spatial and temporal changes in landuse comparatively from the perspective of total change, structural change and the intensity change. The results showed that:(1) paddy field and urban construction land were the two main landuse types, which account for more than90%of the total area;(2) In the past16years, the urban construction land increased dramatically, and the increasing rate is126.9%; The decreasing rate of water was79.8%;(3) The total amount of landuse change is increasing year by year, and the increasing speed of urban construction land is six times of its transferring speed; Water land was mainly transferred into urban construction land and paddy field;(4) Four cities in Wuchengxiyu Region with different level of urbanization showed the same change trends in landuse, a substantial increase in urban construction land and continuously decreasing in water land; But the change ranges were different, and Wuxi city showed the most prominent changes in the total change.In order to analyze the spatial and temporal changes in stream structure comparatively, this paper calculated four characterization indicators, Rd, Wp, CR and D in1960s,1980s and2009. The results showed that:(1) the total length of rivers is continuously reducing in the past50years, and its reducing rate is35.74%; The reducing rate between1980s and2009was much larger than the last period;(2) The lower river grade is, the greater the reduction rate of river total length was;(3) Water areas in Wuchengxiyu Region showed the same change trends as the total length;(4) Since1960s, four indicators, Rd, Wp, CR and D declined year by year, which indicated that the higher the urbanization level is, the simpler the stream structure is;(5) Four indicators in different cities also reduced continuously, and the reducing rate is not only related to the urbanization level, but also to its development speed;(6) The significant impact of urbanization on stream structure was futher confirmed by the correlation analysis between non-agricultural population, GDP and the water surface rate.This paper choosed four representative water level stations to analyze the spatial and temporal changes in storage effect comparatively. Four parameters, C, AC, SR and ASR were analyzed in different periods and different river grades. The results showed that:(1) the value of SR and ASR in different grade rivers were declined continuously; The lower the river grade was, the greater the reduction of storage function was;(2) Affected by the same environment change, the third-grade river showed a positive function in regulating and storage, and the higher-grade rivers mainly showed water diversion and drainage functions;(3) The value of SR and ASR in different cities were reduced year by year, and the size order is consist with the water surface ratio;(4) Regulating and storage function closely related to stream structure is futhur confirmed by the correlation analysis between SR, ASR and Wp; Therefore, we can broaden the river channel, connect the rivers and increase the artificial water body to improve regional water surface ratio.更多还原