【作者】 吴华林；

【导师】 沈焕庭；

【作者基本信息】 华东师范大学 ， 自然地理学， 2001， 博士

【摘要】 河口泥沙通量不仅是全球变化的研究内容，而且是与河口工程、环境等有密切联系的实际课题。本文以长江口为背景，以入海泥沙通量为目标，采用GIS技术与泥沙动力学、水文统计学相结合的方法对长江中下游水沙通量、长江口海图深度基准面、长江河口冲淤演变、长江口泥沙收支平衡、长江口泥沙通量及其相关问题进行了系统研究。 长江水通量由中游向下游逐渐递增，大通站多年平均径流量为9.03×10¹¹m³（1951-1999），比上游宜昌站增加近一倍。悬沙通量由中游向下游略有减少，大通站多年平均输沙量为4.36亿吨（1953-1999）；与悬沙数量相比，长江干流推移质输沙量极少，且有从中游向下游沿程递减趋势。大通站来水年通量无明显增大或减小的趋势；悬沙通量则呈明显减少趋势，20世纪70年代以来尤甚。水量年内变化由降雨量在年内的分布决定，下游大通站径流一般集中在5-10月，占全年径流的71％。大通站洪季（5-10月）输沙量占全年总输沙量的85％，其洪季集中程度显然比水量更甚。 用Matlab语言实现了对海图理论深度基准面的人机交互式计算，基于1977年实测潮位资料计算获得的调和常数，研究了长江口10个验潮站的深度基准面，探讨了不同深度基准面之间的换算关系，为冲淤量的精确计算打下了基础。 在总结GIS和DEM的定义、特点、应用及发展趋势的基础上，提出应用GIS和DEM技术计算河槽冲淤量和进行河床演变分析的思路和方法，基于这一手段，首次将整个长江口和杭州湾作为研究对象，对其各组成区域在同一时间背景下的冲淤量进行了全面系统的分析，力求提供有关长江口及杭州湾百余年来平均冲淤状况全貌的认识。 分别对南支、南北港、拦门沙、口外及杭州湾多个区域百余年来的泥沙冲淤量进行了计算，并对各区域在不同水文条件下表现出的演变特点进行了剖析和归纳。南支河槽暗沙众多，频繁移动，造成局部演变剧烈，但总的河槽容积变化不大，来沙基本属过境性质，南港和北港河槽容积的变化呈此消彼长之态势，与分汊口的河势演变有密切关系，但两汊总的河槽容积基本保持稳定，变幅较小。拦门沙地区呈累积性淤积趋势，平均每年约有6.8％的来沙在此落淤。口外水下三角洲及杭州湾是长江来沙的主要淤积地，过大通断面的泥沙约有70％左右进入此区域沉积。 在冲淤量定量计算的基础上，首次构建了较精确的长江口泥沙收支平衡模式。长江来沙10％左右淤积在大通至徐六泾河道，6.5％左右淤积在北支，徐六 华东师范大学2001届博土学位论文 内容提要 u 径至口门的南支汉道略有冲刷，约 31％淤积在口门以外的水下三角洲，40％淤 积在杭州湾及其近海，4％左右泥沙用来塑造陆地和岸线，其它的泥沙，主要沉 ’”积在浙闽沿海近岸区域，极少量扩散至深海。通量与断面位置密切相关，考虑 一 不同的时间尺度可分为年通量、月通量、日通量等。若以口门作为河流与海洋 的作用界面，那么长江人海年均泥沙通量为3．70亿吨，同时还计算了长江口其 他若干重要断面的泥沙年通量，其中大通断面为 4．sl亿吨，徐六注断面为屯刀6 亿吨，长江口与杭州湾界面为2．30亿吨。更多还原

【Abstract】 Estuarine sediment flux is not only one of contents of Global Change Research, but also is a practical problem nearly related to estuarine engineering and estuarine environment. Aiming at sediment flux into ocean and taking Changjiang Estuary as background, several key problems are systematically studied with combined methods of GIS technique, sediment transport dynamics and hydrologic statistics. Mainly the problems are water and sediment fluxes of mid- to lower Changjiang River, nautical chart Depth Datum Levels of Changjiang Estuary, evolution process of Changjiang Estuary, sediment budget of Changjiang Estuary, sediment fluxes of Changjiang estuary, and so on.The runoff of Changjiang River increases from middle reach to lower reach. The yearly averaged runoff is 9.03 xlO’V in Datong Station (1951-1999), which isabout twice the amount in middle reach. Suspended sediment discharge decreases a little from middle reach to lower reach. The yearly averaged sediment discharge is 436 million tons in Datong (1953-1999). Comparing to suspended sediment, the amount of bedload is much small, which decreases form middle reach to lower reach. There aren’t apparent trends of either decrease or increase for runoff flux hi Datong, but there is apparent decrease trend for sediment flux, especially since 1970s. Runoff changes monthly are closely related with the precipitation in the basin. Runoff in Datong Station mainly concentrates on the period from May to December and amounts to 71% of annual total runoff. The sediment discharge on flood seasons (from May to December) amounts to 85% in Datong Station.Calculations of theoretical depth datum (TDD) level are carried out with Matlab program language. The datum levels of 10 tidal stations in Changjiang Estuary are calculated with harmonic constants calculated with tidal level data in 1977 and the relationships among datum levels are discussed.Based on summarizing the definition, characters, application and development trend of GIS and DEM, the thought and method of calculating channel volumes and channel evolution analyses with GIS and DEM technique are brought forward. Withthis technique, silt-deposit amounts of several regions for over one hundred years are calculated, which separately are South Branch, South and North Channel, mouth bar area, offshore and Hangzhou Bay, etc. Moreover, the evolution regularities for different area under different hydrology conditions are discussed.There are so many frequently moving sandbars hi South Branch that local evolution often is very violent, but its total channel volume changes little. So the sediments from upper reach essentially pass through the region without detention.Channel volume of South Channel and North Channel usually change with reverse trends, which is closely related to the situation of bifurcation mouth. But the total volume of the two channels keeps equilibrium and changes little. Cumulative deposition trend is clearly showed in mouth bar area, and 6.8% of coming sediment is deposited here. Coming sediment mainly deposit in the submerged delta and Hangzhou Bay, and there is about 70% of sediment that go through Datong section into this region.Based on calculation of silt-deposit sediment, the mode of sediment budget of Changjiang Estuary is established for the first time. 10% of coming sediment is deposited in the channel from Datong to Xuliujing; 6.5% of it is deposited in North Branch; a little is eroded hi South Branch from Xuliujing to the mouth; 31% of it is deposited in the submerged delta; 40% of it is deposited hi Hangzhou Bay and its near sea; 4% of it is accreted to land; other sediment is mainly transported to the nearshore of Zhejiang and Fujian coast and thimbleful sediment is diffused into the blue water. Fluxes are nearly related with locations of sections. Sediment fluxes for some important sections hi Changjiang Estuary are calculated, thereinto that of Xuliujing is 406 million tons each year and that of the mouth is 370million tons each year.更多还原