【作者】 李芳；

【导师】 刘曙光；

【作者基本信息】 同济大学 ， 港口、海岸及近海工程， 2008， 硕士

【摘要】 长江河口是河流因子占主导作用的典型河口,长江源源不断的来沙是河口地区健康发展的物质基础。三峡工程的修建在一定程度上改变了下游水文情势,引起河口地区来水来沙条件的变化,从而对河口地区冲淤演变产生了影响。这一问题引起人们普遍关注,成为学术界和工程界研究的热点。本文对三峡工程修建前后长江河口的冲淤演变情况进行了研究。本文将地理信息系统(GIS)和数字高程模型(DEM)引入到河口演变分析中,结合泥沙运动力学、工程水文学、海岸动力学方法对长江河口地区在三峡工程修建前后的冲淤演变进行研究。本文应用MapInfo地理信息系统软件对1981～2004年长江口地区30张海图进行数字化,在surfer8.0软件中分别建立长江口北支、南支以及南汇地区的数字高程模型。分别对北支、南支和南汇边滩的横向、纵向变化情况进行了分析,对各自的冲淤进行了定量的计算,获得地形冲淤变化的强度和空间分布,并探讨了长江口地区的冲淤演变对三峡工程引起的长江供沙量变化的响应情况。分析认为,三峡工程对长江口北支河道及滩涂的影响基本不存在,对减缓北支倒灌南支有利。北支总体呈现淤积态势,受上段圈围等因素影响,北支累积性淤积的趋势不会改变。南支是长江入海主要通道,对三峡工程的响应较敏感,随着三峡工程初期蓄水,南支整体冲刷强烈,这对维持航道水深、河床稳定有利。但流域来沙量持续减少会使拦门沙区域整体淤积速率下降,将对河口的滩涂资源开发利用产生不利影响。南汇边滩总体向外淤涨,南汇东滩和南滩冲淤交替变化。受三峡工程的影响,南汇边滩近期淤积有所减缓。综上,三峡工程对河口地区冲淤的影响不容忽视。更多还原

【Abstract】 The Yangtze estuary is a typical estuary where fluvial factors play dominant roles. Sediment from upstream is the basis of healthy development in estuary area. With the construction of the Three Gorges project, hydrological situation in lower reaches has changed in a certain degree, including the changes of the sediment condition in estuary, which leads to the influence of beach erosion and deposition. People are commonly attracted by this issue which becomes a hot spot within the academic and engineering realm. In this paper, the erosion and deposition condition before and after the Three Gorges Project is studied in order to make clear what the influence to Yangtze Rive estuary.With the methods of sediment transport mechanics, engineering hydrology, coastal dynamics, GIS and DEM are leading into this paper to analyze the evolutional processes of the estuary which may be influenced by the Three Gorges Project. Furthermore, several pieces of charts of Yangtze Estuary from 1981 to 2004 are digitized with the help of Maplnfo, one kind of GIS software, and the digital elevation model of the Yangtze Estuary is established which includes north and south branch of the Yangtze River as well as Nanhuizui area by the means of surfer8.0. By comparing different series of topography data, scouring and sedimentation are calculated in a more accurate way. By analyzing the shift of the isobath and shore line, the evolution of typical cross section, a preliminary study of the response to the changes of upstream runoff and sediment are carried out, due to the effect of the construction of the Three Gorges Project.According to the study, three Gorges project plays little effect on the north branch of the River, but may slowdown the down-draught from north branch to South Branch. Moreover, North Branch is presented in a depositing tendency and will keep on depositing by the enclosing sludge project. Meanwhile, South Branch is the main channel into the sea, which has a more sensitive response to the Three Gorges project. With the storage of the water in Three Gorges Project, the South Branch presents an overall erosion, which is benefit to maintain the stability of channel depth and riverbed. However, the decreasing of the sediment will slow down the deposition of the sediment in Yangtze estuary, which will cause an adverse effect to the development and utilization of the estuarine resources. Nanhui beach, on the whole, is silting up, and meantime erosion and deposition on east and south Nanhui tidal flat change alternately. Under the influenced of the Three Gorges Project, the deposition in Nanhui is slowing down. On the whole, the erosion and deposition in estuary district are greatly influenced by the Three Gorges Project and more researches are needed in the future.更多还原