【作者】 王张峤；

【导师】 陈中原；

【作者基本信息】 华东师范大学 ， 自然地理学， 2006， 硕士

【摘要】 河流是连接陆地和海洋的枢纽，是全球变化在区域响应上最敏感的地理位置之一。随着社会的发展和需求，人们越来越重视河流环境的变化，不仅是因为河流培育了我们人类的文明，更重要的是河流的可持续利用关系到人类社会发展的千百年大计。河流沉积物作为河流地貌单元组成的核心，是探讨河流沉积地貌环境演化最基本的要素；发现和揭示沉积物在流域环境中的产生、搬运和沉积机理，特别是在不同条件下的沉积过程，是河流地貌学家一件十分有意义、而且十分艰巨的任务。 长江作为我国第一、世界第三大河，其流域地貌环境的变迁、季风降雨作用以及高强度人类活动对环境的影响已经引起国内外广大学者的高度兴趣和关注。三峡水库的建设和在2009年的最终封坝将对三峡以下流域地貌环境产生深刻的影响。这种影响的评估必须基于对封坝前长江流域进行的全面的调查与研究。本文通过研究组在三峡封坝之前所取得的长江中下游水文泥沙资料，建立了三峡封坝之前长江中下游干流床沙数据库，阐明了长江中下游干流在长期自然和社会影响下的水沙运动规律特征，结合同河段的水沙参数，利用各种泥沙运动力学模型，分析了中下游河床地貌的纵向和侧向的稳定性；并在大量历史数据的基础上，对长江中游河道随流量变化沉积物运移趋势进行模拟预测，为长江中下游洪水防治、河道整治以及三峡水库建成后的河道变迁比较研究提供科学的依据。 长江中下游沉积物颗粒分布基本呈现从向下游方向波动变细的趋势，从300μm下降到100μm；分选也相应变好(0.5-2.5)；偏度系数(SK)略向下游增大，分布一般在0-0.8之间；峭度系数(KG)波动性略强，分布在0-4之间。相对来说南部样品比北部样品略粗，而主航道的样品最粗，体现河流能量主要集中在主航道，而科氏力的作用使河道南部沉积物粒径有所增大。而两侧沉积物粒径波动性大于主航道，且趋势基本相反则表现了“凹岸侵蚀，凸岸堆积”河流运动特征。徐六泾以下河段沉积物明显变细，一般低于100μm，体现河口地区江面展宽，水流变弱，泥沙大量淤积。沉积物在鄂州—武穴河段和芜湖—徐六泾河段有粗化的趋势，平均值分别为203μm和178μm，推测其原因可能是受河道采沙影响。 有序聚类分析将长江中下游沉积物分布分成12段(Ⅰ—Ⅻ)，显示长江流域河流地貌更多还原

【Abstract】 As the linkage between land and sea, river system is one of the most sensitive locations in reflecting the global change. With the demands of social development, more attention has been paid to the change of river system than before, not only because human civilization is cultivated in the river basin, but also the sustainable exploration of fluvial resources relates to the social development. Sediment, the core of fluvial geomorphology, is also the fundamental component in discussing sedimentary facies evolution in river system. To deal with sediment yield, transport and deposit in river system is an exciting, but tough task for geomorphologist, especially considering the complexity of coupling hydrogeomorphology, climate and human activity, etc.As the longest river in China and the third longest one in the world, the Yangtze River geomorphology has been of the great interest for many earth scientists, including the effect of topographic change, monsoon precipitation and intensive human activity. The construction of Three Gorges Dam being closed in 2009 will impact largely the middle and lower Yangtze River morphology. The environmental evaluation and associated impact should be based on on-site investigation and research of the basin scale before the closure of dam construction. Through several field trips from 2000-2003, our research group has established the sedimentological and hydromorphological database, including >500 sediment samples along the middle and lower Yangtze river, and ADP-surveyed flow velocity, Sonar-surveyed water depth and river-bed topography. In addition, many historical maps has been incorporated in the present database, in which, useful information was retrieved, such as river width, water depth, water surface gradient, and curvature, etc. By using this database, hydrological simulation was done to obtain a series of parameters, i.e. Froude Number, Unit Stream Power, and Shields Stress, etc. These have been applied to study sediment transport processes, in relation to longitudinal and lateral stabilization of the middle and lower Yangtze River system. Furthermore, river channel stabilization condition was forcasted under the assumption of larger discharge of 60,000 m~3/s. The present study highlights flood prevention, river channel management and future planning, and moreover, post-dam study after the construction of Three Gorges Dam in the middle and lower Yangtze River.更多还原