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1.
大型水库的兴建深刻改变了下游水沙输移特点,进而导致河床演变规律显著调整,水库下游弯曲河型对水沙过程改变响应敏感,是水库下游河床演变、航道整治、河势控制等方面研究的关键区域。本文基于1996-2016年的实测水文、地形资料,对长江三峡水库下游弯曲河型的演变规律及其驱动机制开展研究,结果表明：① 三峡水库蓄水前,下荆江存在“凸淤凹冲”、“凸冲凹淤”两类弯曲河型,而三峡水库蓄水后均表现为“凸冲凹淤”的一致性规律;② 在水库拦沙作用的影响下,下荆江河段平滩河槽存在累积性冲刷现象,冲刷部位集中于枯水河槽与基本河槽之间的低滩,冲淤部位调整主要由变化的流量过程所驱动,上游河势、河道边界以及支流入汇等因素均有一定驱动作用;③ 在三峡水库蓄水后缺乏大洪水的情况下,凸岸水流挟沙力随流量增加逐渐增强,水流对凸岸冲蚀力度在平滩流量级附近（20000~25000 m3/s）达到最强,平滩流量附近流量级的持续时间超过20天时,弯曲河道发生凸冲凹淤现象。而悬沙中造床粗沙的减少,增强了水流冲刷强度,加剧了凸岸的冲蚀程度。 相似文献
2.
三峡水库一、二期蓄水对下游悬沙通量影响的计算 总被引：2，自引：0，他引：2
水库对坝下游泥沙通量影响的定量估算是一个国际前沿的科学问题.本文利用长江干流上寸滩、宜昌、汉口、大通四站及其间的支流控制站的水沙监测数据,结合对于流两侧不在支流控制站监测范围的"未测区"水沙贡献的估算,建立了悬沙收支平衡和悬沙输运经验关系,从而定量分析了三峡水库一、二期蓄水对大坝下游(至河口)悬沙通量的影响.结果表明:(1)三峡水库一期(2003-2005年)和二期(2006-2007年)蓄水期间水库的悬沙淤积比分别为64%和83%.(2)受坝下游河床冲刷和支流来沙补给的影响,三峡水库一、二期蓄水分别导致宜昌站悬沙通量下降62%和82%,汉口站悬沙通量下降37%和54%,大通站悬沙通量下降28%和40%.(3)与蓄水前的5年(1998-2002年)相比,蓄水后的2003-2007年上述三站悬沙通量分别下降354×109、172×109和163×109kg/a,其中三峡水库蓄水的贡献分别占41%、55%和45%.以上认识对科学和客观的评价河流建坝的环境效应提供了启示. 相似文献
3.
三峡水库蓄水以来长江中下游干流河床沉积物粒度变化的初步研究 总被引：2，自引：1，他引：1
于2008年在宜昌至徐六径之间的1 600 km干流河道进行30个横断面取样和分析,与前人于三峡水库蓄水前的取样分析资料进行对比。结果表明:①三峡水库蓄水以来坝下游约400 km的干流河床(宜昌至城陵矶)沉积物出现全程粗化,越近大坝粗化越明显,这种沉积物粗化与水库蓄水后坝下游河床出现的强烈侵蚀密切相关;②蓄水前后城陵矶以下的1 200 km干流河床沉积物粒度的沿程趋势基本一致;③蓄水后河床沉积物仍保持沿程向下游变细且越近河口变化越缓慢的格局。 相似文献
4.
三峡大坝下游水位变化与河道形态调整关系研究 总被引：8，自引：2，他引：6
三峡水库蓄水利用已有13年,对坝下游洪、枯水位和河道形态调整的影响已初步显现,通过对1955-2016年长江中游水位、河道地形等资料的分析,结果表明：① 坝下游各水文站同流量枯水位下降、洪水位变化不大,最低水位上升,最高水位下降趋势;② 2002年10月-2015年10月枯水河槽冲刷量占平滩河槽冲刷量的95.5%,冲淤分布由蓄水前“冲槽淤滩”转为“滩槽均冲”,不同蓄水阶段存在差异;③ 河槽冲刷过程中,上荆江及以上河段枯水位下降趋势趋缓,下荆江及以下河段下降速率增加,应采取防控措施遏制河道水位下降趋势;④ 枯水河槽冲刷是长江中下游航道水深提升的基础,枯水位降幅小于深槽下切深度,在河道和航道整治工程综合作用下航道尺度提升,提前5年实现了2020年航道尺度规划目标;⑤ 平滩水位以上河槽形态调整不大,在河床粗化、岸滩植被、人类活动等综合作用下河道综合阻力增加,出现了中洪水流量—高水位现象,应引起足够重视。三峡水库汛期调蓄作用可有效提升中下游洪水防御能力,但不排除遭遇支流洪水叠加效应,中下游洪水压力仍然较大。 相似文献
5.
长江干流河道对流域输沙的调节作用 总被引：1，自引：0，他引：1
利用长江干流和主要支流上测站1956~2004年的输沙量资料,对干流未测区域的来沙进行了估计。根据泥沙平衡 (Sediment budget) 概念,对长江干流河道的冲淤对来水来沙的响应以及对入海泥沙的影响进行研究发现,长江干流屏山至大通河道平均淤积速率为88.58×106 t/a,河道淤积占总的来沙量及大通站输沙量比例分别为14%与21%。由于河道淤积,大通站输沙量减少了17.5%。总体来说上游淤积较轻,宜昌至汉口区间淤积严重,汉口至大通区间为微冲。长江干流的河道冲淤与流域总的来沙具有显著的相关关系,但各段河道的冲淤对流域来沙的响应各不一样。上游的冲淤与流域的径流量和来沙量均没有很好的相关性,宜昌-汉口段河道冲淤的变化与宜昌站的来沙具有显著的相关性;影响汉口-大通间河道的冲淤变化的主要因素是流域的来水量,河道的冲淤与大通站径流量的存在显著的负相关关系。三峡水库蓄水后整个长江干流的冲淤形势发生了根本的变化。三峡水库的蓄水运用有效地减轻了洞庭湖的泥沙淤积,同时也降低了洞庭湖的对长江干流泥沙的调节作用;长江上游干流河道淤积增强,中下游河道出现冲刷,但不同的河段表现不一;中下游河道冲刷量小于预测值,三峡水库的蓄水运用直接导致了长江入海泥沙的减少。 相似文献
6.
重庆主城区河段河道泥沙冲淤事关防洪、航运及码头作业等,是三峡水库泥沙问题的重点内容之一。本文依据原型观测资料,以三峡水库175 m试验性蓄水前后河段的泥沙冲淤规律为基础,结合河床组成分析和一维数学模型,计算提出河段悬移质泥沙走沙基本条件,并应用于减淤调度实践中。结果表明：① 三峡水库175 m试验性蓄水后至2012年重庆主城区河段河床冲刷强度下降,主走沙期推迟至汛前消落期,2013年后上游来沙减少使得河床冲刷强度再次增大;② 当寸滩站流量大于4000 m 3/s、坝前水位低于167 m时,河段开始走沙;当寸滩站流量增大至超过5000 m 3/s、坝前水位下降至163 m时,河段走沙能力增强;加大水库自163 m水位的消落速度,能够避免库尾河段产生累积性淤积。 相似文献
7.
随着黄河上游控制性水利枢纽相继投入运用,黄河内蒙古段河道冲淤演变格局得到重塑。利用水文站实测数据,系统分析了海勃湾水利枢纽建设运行前后坝后河道水沙变化特征。基于河道断面高程数据,从滩槽冲淤（横向）及沿程冲淤（纵向）两方面定性分析坝后河道形态变迁,采用断面地形法定量计算坝后河道冲淤变化量。结果表明：海勃湾水利枢纽蓄水运用后,坝后河道的水沙搭配条件显著改善,来沙系数、单位径流量的输沙量降幅较大,对坝后河道减淤冲刷作用明显。坝后河道横纵断面变迁以冲刷为主,冲淤演变过程经历了淤积（2004—2012年）、冲淤过渡（2012—2014年）、冲刷（2014—2020年）3个阶段。 相似文献
8.
三峡水库运行下洞庭湖盆冲淤过程响应与水沙调控阈值 总被引：4，自引：0，他引：4
以1951-2011 年洞庭湖区及荆江段干流主要控制站实测径流输沙量资料为依据,分析三峡水库不同蓄水阶段及不同调度方式下洞庭湖盆冲/淤响应,并提出上游来水来沙调控阈值。结果表明：① 荆南三（四）口流量与枝城站流量、荆南三（四）口输沙率存在极显著正相关（p < 0.0001）,决定系数r2分别为0.859 及0.895。② 与三峡水库蓄水运用前（1999-2002）相比,一、二期蓄水阶段及全面试验性蓄水阶段（2008.10-2011.12）洞庭湖盆年均冲淤量由+4796.4×104 t 依次递减为+684.1×104 t、+449.8×104 t 及-559.6×104 t,湖盆冲淤率由+70.25%分别降至+31.13%、+23.56%及-42.64%。③ 预泄调度及蓄水调度期,湖盆泥沙均由以淤积为主转变为以冲刷为主,防洪补偿调度期湖盆泥沙表现为淤积,而在补水调度运用期则表现为冲刷。④ 洞庭湖盆处于冲/淤临界平衡状态时的荆南三口平均流量、输沙率及含沙量分别为970.81 m3/s、466.82 kg/s 及0.481 kg/m3。并认为,为增强湖泊调蓄功能,必须进一步优化三峡水库调度方式,合理调控下泄水沙量。 相似文献
9.
黄河下游泥沙输移数值模拟 总被引：2，自引：0，他引：2
本文从数学模型入手,探讨黄河下游在多年平均来水来沙条件下,泥沙输移与泥沙淤积的特性,得出黄河下游泥沙沿程淤积分布不均匀主要是由于粗沙、中沙沿程淤积不均匀造成的,如果使来沙减少42.6%,黄河下游可望达到冲淤平衡. 相似文献
10.
水库运行改变了坝下游水沙输移条件,在河道冲刷的同时,引起水位过程出现适应性调整。本文以长江中游荆江河段为对象,采用多项式拟合法,对比分析1991—2016年间分级流量—水位变化特征,采用基于河流动力学原理的分离变量法,识别河道冲淤、下游控制水位及河床综合糙率等变化对分级流量—水位变化的影响程度。研究表明：1991—2016年间,长江中游荆江河段同流量—枯水位呈下降趋势,2009年以来降幅增大;河道冲刷是引起同流量—枯水位下降的主控因素,河床综合糙率增加抑制了同流量—枯水位下降起到积极作用。1991—2016年间,荆江河段同流量—洪水位经历了先减小后增大的“凹”线型变化,2003年以前洪水特征为“高洪水流量—高水位”,2009年以来逐渐演化为“中大洪水流量—高水位”,同流量—洪水位特性发生转变;河床综合糙率增大是同流量—洪水位抬升的主控因素,河道冲刷抑制了同流量—洪水位的抬升态势。在航道条件及防洪情势上,应重点防控近坝段沙质河段冲刷引起的水位下降溯源传递作用,其洪水流量—水位特性的转变,不利于减缓荆江河段的防洪压力。 相似文献
11.
Mechanisms of suspended sediment restoration and bed level compensation in downstream reaches of the Three Gorges Projects (TGP) 总被引：3，自引：2，他引：1
Wei Zhang Yunping Yang Mingjin Zhang Yitian Li Lingling Zhu Xingying You Dong Wang Junfeng Xu 《地理学报(英文版)》2017,27(4):463-480
River basin reservoir construction affects water and sediment transport processes in downstream reaches. The downstream impact of the Three Gorges Projects (TGP) has started to become apparent: (1) reduction in flood duration and discharge, and significant reduction in sediment load. Although there was some restoration in downstream sediment load, the total amount did not exceed the pre-impoundment annual average; (2) in 2003–2014, the d > 0.125 mm (coarse sand) load was restored to some degree, and to a maximum at Jianli Station, which was mainly at the pre-impoundment average. After restoration, erosion and deposition characteristics of the sediment was identical to that before impoundment. The degree of restoration during 2008–2014 was less than during 2003–2007; (3) after TGP impoundment, there was some restoration in d < 0.125 mm (fine sand) sediment load, however, it was lower than the pre-impoundment average; (4) due to riverbed compensation, the d > 0.125 mm sediment load recovered to a certain degree after impoundment, however, the total did not exceed 4400×104 t/y. This was mainly limited by flood duration and the average flow rate, and was less affected by upstream main stream, tributaries, or lakes. Restoration of d < 0.125 mm suspended sediment was largely controlled by upstream main stream, tributaries, and lakes, as well as by riverbed compensation. Due to bed armoring, riverbed fine suspended sediment compensation capability was weakened; (5) during 2003–2007 and 2008–2014, Yichang to Zhicheng and upper Jingjiang experienced coarse and fine erosion, lower Jingjiang experienced coarse deposition and fine erosion, Hankou to Datong had coarse deposition and fine erosion, and Chenglingji and Hankou was characterized by coarse deposition and fine sand erosion in 2003–2007, and coarse and fine erosion in 2008–2014. This difference was controlled by flood duration and number at Luoshan Station. 相似文献
12.
三峡水库蓄水后荆江洲滩变化特征 总被引：4，自引：0，他引：4
目前对三峡水库蓄水后荆江河段的洲滩演变还缺乏完整认识。基于三峡水库蓄水前后枯水期遥感影像,分析了荆江洲滩的冲淤变化与分布及形态演变。结果表明,蓄水后荆江洲滩总面积持续冲刷减小,累计冲刷4.56 km2,大部分发生在蓄水后前6年（冲刷速率0.55 km2/a）。上、下荆江洲滩的冲淤演变存在差异性。上荆江洲滩总面积一直处于冲刷萎缩中,且其强度明显大于下荆江,累计冲刷6.46 km2;下荆江前期（2002-2009年）冲刷、后期（2009-2015年）淤增,累计淤1.90 km2。在冲淤分布上,上荆江凸岸滩持续冲刷萎缩,凹岸滩前期冲刷、后期略有淤增,心滩（洲）前期淤积增长而后期冲刷萎缩;下荆江主要是凸岸滩冲刷,凹岸滩和心滩（洲）有所发展。根据滩体位置活动和冲淤动态性,荆江心滩（洲）演变被划分为8种典型类型。在形态演变上,上荆江以凸岸突出滩体和边滩发育的凹岸滩冲刷显著,形态变化不大。下荆江凸岸滩上游弯侧冲蚀后退、湾顶退缩、下游弯侧淤积伸长,形态趋向低弯扁平化,在高弯曲特定河湾平面形态格局下凸岸冲刷—淤积过程延伸到相邻河湾凹岸,成为下荆江凹岸滩和心滩淤积发展的重要因素,但淤积一般不越过凹岸湾顶。 相似文献
13.
黄河宁蒙段河道淤积严重,阐明近源粗泥沙和远源细泥沙分选沉积规律对于河道淤积治理有重要意义。本研究基于120根河道钻孔泥沙样品,通过粒径分布和元素矿物组成,分析了河道>0.05 mm、>0.08 mm和>0.1 mm粗泥沙沿河分选沉积变化特征,并定量评估了近源粗泥沙和远源细泥沙沉积对于河道泥沙淤积的贡献。结果表明：黄河宁蒙段河道淤积的主要是来源于近源沙漠及其下伏砒砂岩区>0.08 mm的粗泥沙,而来源于上游黄土区<0.05 mm的细泥沙主要沉积在河道滩地,对河道淤积的贡献小于30%。因此,风水复合侵蚀引起的沿黄沙漠和下伏砒砂岩粗泥沙入黄是黄河宁蒙沙漠河段河道淤积的根源,也是该河段“悬河”的治理重点。 相似文献
14.
《自然地理学》2013,34(3):252-268
We examined a large, Late Pleistocene delta in northern Lower Michigan, formed by the Black River in Glacial Lake Algonquin. Today, this sandy, arcuate, wave-influenced delta stands several meters above the lake floor. The Black River transported mainly well-sorted, medium, and fine sands to the delta—at remarkably rapid rates. Our subsurface data, taken at 153 sites across the delta, show subtle and consistent trends in sediment texture across the delta surface. Although found in low amounts, gravel and very coarse sands are concentrated near the shoreline, presumably eroded by waves from the till and bedrock that crop out there. Sediments of very fine sand size (and finer) exist in higher concentrations near the eastern shore, sourced from eroded tills and also carried there on longshore currents. A clear sediment plume of medium and finer sands also traverses the delta SE to NW, which we interpret as evidence of sand transport by longshore currents flowing east to west, driven by easterly winds. High, perched spits on the head of the delta also suggest westerly longshore drift. These paleoclimate proxy data support previous interpretations of strong easterly winds here during the Late Pleistocene, probably in association with a glacial anticyclone. 相似文献
15.
以水蚀风蚀区内蒙古河段重要入黄支流西柳沟为研究对象,通过对西柳沟流域产沙地层及河流水文站悬移质泥沙采样分析和激光粒度仪测定,对研究区河道纵向、横向断面沉积的泥沙级配特征进行了分析,揭示了流域沉积泥沙粒径分布变化规律。结果表明：西柳沟流域沉积泥沙的中数粒径从上游丘陵沟壑区到下游农田区逐渐减小;河流右岸泥沙粒径较大,左岸泥沙粒径相对较小,河床泥沙粒径介于二者之间;流域沉积泥沙粒径主要分布在0.125~0.5 mm,而流域出口水文站悬移质泥沙粒径72.5%在0.025 mm以下,说明西柳沟进入黄河干流的泥沙主要为细泥沙。 相似文献
16.
This study focuses on the importance of different stages of bed formation and transportation processes along the partly managed lowland section of Maros River (South Hungary). The role of different stages was determined, applying a series of cross-sectional data. Besides, major morphological zones of over-widened, braided sections were defined, along with their role and function in sediment storage and transport processes.During the rising stage of floods a great volume of sediment is eroded from and transported through the cross-sections. On the falling stage accumulation will be the dominant process. However, concerning the total amount of sediment deposited during falling stages, braids store overwhelmingly more, than straight, narrow reaches. During long-lasting, low-stage periods the cross-sectional area increases, which means net erosion and an increase in mean depth. Therefore, braids have a significant role in falling stage sediment storage and low-stage release.Nevertheless, the location of accumulation within braids is different, influenced by their structure. In braids which are characterised by islands, the sediment is deposited at their upstream end. Islands create a transportation zone towards the downstream end of the braid by increasing stream power. Over-widened sections without islands are more likely to experience deposition at their downstream end.Constant narrowing of the studied reach was also observed. Braids on unmanaged reaches proved to be the most prominent places in this sense. Changes in the regime of the river, and altered land-use help to explain this process, as the frequency of floods has decreased, while the length of extreme low stages has increased. Therefore, the need for the sediment storing and releasing function of braids is less necessary, which leads to their narrowing. 相似文献
17.
为了研究采煤塌陷对地表环境的粒度成分(机械组成)影响作用与过程,通过野外调查和取样,以神府煤田风沙区采煤塌陷1年、塌陷2年的塌陷区和非塌陷区(对照)为研究对象,采用对比法系统地分析了采煤塌陷区粒度变化特征。结果表明:塌陷1年、塌陷2年塌陷区粒度组成以粗沙和中沙为主,占整个组成的65%以上,非塌陷区以中沙和细沙为主,约占80%;多变量方差分析表明,塌陷1年、塌陷2年塌陷区粒径变化无明显差异存在,而与非塌陷区粒径变化有显著差异;塌陷区沙粒起动风速随着平均粒径的增大,以对数函数增加,而风蚀量与平均粒径的关系则随着起动风速的增大,以指数函数增大。塌陷1年、塌陷2年塌陷区粒度分布曲线均为双峰态,峰值出现在0.54 mm和0.125 mm处,众数组出现在0.63~0.45 mm和0.1~0.065 mm,而非塌陷区粒度分布曲线为单峰,其极值出现在0.125处。塌陷区地表(0~10 cm)范围内细粒和极细粒基本被风带走,地表颗粒呈现粗化现象,潜在的可风蚀性程度加强。 相似文献
18.
In this study, data measured from 1955-2016 were analysed to study the relationship between the water level and river channel geometry adjustment in the downstream of the Three Gorges Dam (TGD) after the impoundment of the dam. The results highlight the following facts: (1) for the same flow, the low water level decreased, flood water level changed little, lowest water level increased, and highest water level decreased at the hydrological stations in the downstream of the dam; (2) the distribution of erosion and deposition along the river channel changed from “erosion at channels and deposition at bankfulls” to “erosion at both channels and bankfulls;” the ratio of low-water channel erosion to bankfull channel erosion was 95.5% from October 2002 to October 2015, with variations between different impoundment stages; (3) the low water level decrease slowed down during the channel erosion in the Upper Jingjiang reach and reaches upstream but sped up in the Lower Jingjiang reach and reaches downstream; measures should be taken to prevent the decrease in the channel water level; (4) erosion was the basis for channel dimension upscaling in the middle reaches of the Yangtze River; the low water level decrease was smaller than the thalweg decline; both channel water depth and width increased under the combined effects of channel and waterway regulations; and (5) the geometry of the channels above bankfulls did not significantly change; however, the comprehensive channel resistance increased under the combined effects of riverbed coarsening, beach vegetation, and human activities; as a result, the flood water level increased markedly and moderate flood to high water level phenomena occurred, which should be considered. The Three Gorges Reservoir effectively enhances the flood defense capacity of the middle and lower reaches of the Yangtze River; however, the superposition effect of tributary floods cannot be ruled out. 相似文献