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1.
对黄河内蒙古段河道大断面进行了连续4 a的测量,分析了断面泥沙冲淤与形态调整的变化过程;通过对河床形态指标变化与水沙条件的相关分析,揭示了河床调整主要的影响因素。结果显示：近4 a内不存在河槽萎缩的现象,整个河段河道存在总的冲刷降低的趋势,继承了自2004年以来该段河道以深度加大为主,河槽逐渐缓慢扩大的变化方向。整个河段平均从2011年汛后至2014年汛后,全断面冲刷了64 m2,河槽河底降低了0.16 m,河槽断面面积增加了4.4%,平均深度增加了4.9%,河槽宽度只增加了0.88%,河槽宽深比减小了4.8%。河槽冲刷和形态调整主要发生在2011年汛后至2012年汛后期间,与2012年较大的洪峰有关。分析河槽冲淤和断面形态变化与水沙条件的关系,结果显示滩唇高度、河槽过水面积、平均深度及宽深比变率与流量大小关系密切。滩唇高度、河槽过水面积、平均深度随着流量的增大而增加,宽深比随着流量的增大而减小。相反,河床断面面积和主槽宽度的变化与水沙条件的关系不显著。除了滩唇高度与平均含沙量有关外,平均含沙量和来沙系数与河床冲淤以及河槽形态变化之间关系都不显著。揭示出近年来内蒙河道主槽以垂向冲淤为主,并且流量变化控制着河槽冲淤与形态调整过程。 相似文献
2.
黄河内蒙古河段冲淤演变及其影响因素 总被引：6，自引：1，他引：5
冲淤平衡的河流具有调整河床变形使之趋向不变形的特性,这种特性必然反映在河床横断面冲淤演变的趋势之中。据此,采用横断面冲淤指标跟踪计算法生成黄河上游巴彦高勒、三湖河口站1976-2006 年的横断面冲淤演变时间序列,对该长期序列的趋势变化和突变特点进行分析后发现：内蒙古河床演变明显存在3 个阶段,即演变相对稳定阶段、河床快速萎缩变形阶段和新的相对稳定阶段,以及孔兑来沙大的年份是横断面冲淤面积趋势改变的时间。大型水库修建后,孔兑来沙对河道横断面冲淤趋势变化的影响更加显著,表明近年来大洪水缺失和孔兑来沙的共同作用是导致河床萎缩的重要根源。90 年代中后期横断面冲淤演变再次发生突变之后,内蒙河段进入到一个新的相对稳定期,河床边界条件已经和来水来沙条件相适应,因此在新的稳定条件下,如何治理内蒙河道的淤积萎缩值得探讨。 相似文献
3.
2002年开始的黄河调水调沙改变了进入黄河口的水沙条件,必然引起尾闾河道地貌的显著调整。根据黄河尾闾河道利津以下的断面实测高程数据,建立基于正交曲线网格的河道DEM,结合河床形态与水沙条件变化,综合研究黄河尾闾河道冲淤的时空演变及其影响因素。结果表明,调水调沙以来尾闾河道冲刷明显,2002—2017年累计冲刷6240万m 3,根据冲淤速率可以分为3个阶段：快速冲刷阶段（2002—2005年）冲刷速率为1443万m 3/a;冲刷减慢阶段（2006—2014年）冲刷速率为139万m 3/a;以及淤积阶段（2015—2017年）,淤积速率为263万m 3/a。其中,调水调沙初始4年尾闾河道的冲刷量占总冲刷量的80%,2006年以后冲刷强度逐渐减弱,甚至转为淤积。从季节上看,主要表现为汛期冲刷,非汛期淤积;从空间上看,越往口门方向,冲刷强度越小。调水调沙改变了入海水沙的年内分配,造成了尾闾河道的持续冲刷,入海流路也发生多次调整。但经过多年冲刷,河床整体下切,加上河口淤积延伸影响,调水调沙对尾闾河道的冲刷效率在持续降低。受河口海域淤积影响,近口门段在经历冲刷后转为淤积,河道纵比降减缓,增加了尾闾的不稳定性。 相似文献
4.
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
5.
宽变幅水沙两相流的冲淤双临界现象及其地貌学意义 总被引：3，自引：1，他引：3
通过黄土高原一些河流资料的分析，发现了宽变幅水沙两相流冲淤过程中的2个临界值，位于非高含水流区域中的临界点，可称之为冲淤下临界；位于高含沙水流区域中的临界点，可称之为冲淤上临界，水沙两相流冲淤的双临界现象，对珩多沙河流河道泥沙的输移有重要意义，随着含沙量的增大，排沙比先减小而后增大，2次与代表排沙比等于1的直线相交，这2个交点即分别对应于挟沙水流冲淤的下临界和上临界，运用所揭示的水沙两相流冲淤过程的双临界现象，可以对冲积河流河型的形成进行新的解释，以我国近百条冲积河流的资料为基础，点绘了年均悬移质输沙率与年均流量的关系，并以不同的符号来区分弯曲河型、游荡河型和高含沙曲流河型。结果表明，上述3种河型可以很好于被代表特征含沙量分别为C=60kg/m^3和C=3.3kg/m^3的2条直线所区分，这2个特征含沙量反映了河道水沙两相流冲淤的上、下临界值。 相似文献
6.
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
7.
不同流路时期黄河下游河道的冲淤变化过程 总被引：4，自引：2，他引：2
运用统计学方法对1950-2007年的水沙数据以及不同流路各水文站同流量(3000m3/s)水位变化进行了分析,结果表明:黄河下游河道表现出淤积-冲刷交替出现的变化过程,当进入下游的含沙量为18.6kg/m3时,河道冲淤表现为动态平衡。艾山以下河道的冲淤变化过程除受水沙条件控制外,还受到流路变迁的影响。流路变迁初期河道发生溯源冲刷作用,中后期河道发生溯源淤积作用。各站同流量水位变化,神仙沟流路主要为下降,河道以冲刷为主;刁口河流路主要为升高,河道以淤积为主;清水沟流路有升有降,河道冲淤互有,总体表现为淤积。流路变迁对河道横断面形态的影响主要在利津以下。 相似文献
8.
长江中游马口-田家镇河段40 年来河道演变 总被引：2，自引：0，他引：2
运用地理信息系统(GIS) 与数字高程模型(DEM) 分析了马口-田家镇河段1963 年、1972 年与2002 年河道地形数据, 较为系统地研究了该河段过去40 年冲淤时空变化。研究结 果认为, 1972 年与1963 相比冲刷量达到789.9 hm3, 冲刷面积为39.7×104 m2; 2002 年与1963 年相比冲刷量达到1196.5 hm3, 冲刷面积为59.4×104 m2; 2002 年与1972 年相比冲刷量 达到960 hm3, 冲刷面积为54.3×104 m2。由以上结果认为, 马口-田家镇河段近40 年来以冲刷为主; 河道冲淤变化以马口卡口与田家镇卡口等窄深河段最为剧烈, 宽浅河段与顺直河 段冲淤变化较为和缓, 冲淤变化幅度不大; 卡口上、下端以淤积过程为主, 而卡口顶冲水流的顶弯部位以冲刷过程为主。研究河段冲淤变化受上游来水来沙条件影响很大, 对未来三峡工程建成后, 三峡大坝下游来水来沙以及研究河段冲淤变化的影响研究提供借鉴。 相似文献
9.
黄河内蒙古不同河型段对洪水过程的响应特征 总被引：7，自引：0，他引：7
黄河内蒙古河段的河道淤积近年来有所加重,一些人寄望于人造洪峰冲沙来降低河床。本文根据典型年份的最大洪水的流量—水位过程线变化特征,揭示黄河内蒙古不同河型段对这些洪水的响应机制,得出黄河内蒙古河段洪水的流量—水位过程线类型有线形、顺时针环线、逆时针环线3类单一关系和线形+逆时针环线、逆时针环线+线形、"8"字形+线形、嵌套状逆时针环线以及交叉线形5类复合关系。这些关系总体上可以反映洪水过程中河床是侵蚀还是沉积、何时侵蚀何时沉积、以及冲淤是否具有反复性。黄河内蒙古冲积性河段的河道对同一次洪水过程的响应沿程表现出分化现象,其中辫状河段以河床侵蚀下降为特征,弯曲河段以河床明显沉积升高为特征,而顺直河段以少量沉积或冲淤平衡为特征。不同河型段的河道对洪水的响应趋势与洪水动能的沿程减小相适应,洪峰含沙量沿程减小是该趋势的具体体现。人造洪峰冲沙难以逆转上述淤积趋势,对防治洪灾帮助有限。 相似文献
10.
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
11.
12.
《地理学报(英文版)》2017,(10)
Elucidating the influence of dams on fluvial processes can inform river protection and basin management.However,relatively few studies have focused on how multiple factors interact to affect the morphological evolution of meandering reaches.Using hydrological and topographical data,we analyzed the factors that influence and regulate the meandering reaches downstream the Three Gorges Dam(TGD).Our conclusions are as follows.(1)The meandering reaches can be classified into two types based on their evolution during the pre-dam period:G1 reaches,characterized by convex point bar erosion and concave channel deposition(CECD),and G2 reaches,characterized by convex point bar deposition and concave channel erosion(CDCE).Both reach types exhibited CECD features during the post-dam period.(2)Flow processes and sediment transport are the factors that caused serious erosion of the low beaches located in the convex point bars.However,changes in the river regime,river boundaries and jacking of Dongting Lake do not act as primary controls on the morphological evolution of the meandering reaches.(3)Flood discharges ranging from 20,000 to 25,000 m3/s result in greater erosion of convex point bars.The point bars become scoured if the durations of these flows,which are close to bankfull discharge,exceed 20 days.In addition,the reduction in bedload causes the decreasing of point bar siltation in the water-falling period.(4)During the post-dam period,flood abatement,the increased duration of discharges ranging from 20,000 to 25,000 m3/s,and a significant reduction in sediment transport are the main factors that caused meandering reaches to show CECD features.Our results are relevant to other meandering reaches,where they can inform estimates of riverbed change,river management strategies and river protection. 相似文献
13.
Elucidating the influence of dams on fluvial processes can inform river protection and basin management. However, relatively few studies have focused on how multiple factors interact to affect the morphological evolution of meandering reaches. Using hydrological and topographical data, we analyzed the factors that influence and regulate the meandering reaches downstream the Three Gorges Dam (TGD). Our conclusions are as follows. (1) The meandering reaches can be classified into two types based on their evolution during the pre-dam period: G1 reaches, characterized by convex point bar erosion and concave channel deposition (CECD), and G2 reaches, characterized by convex point bar deposition and concave channel erosion (CDCE). Both reach types exhibited CECD features during the post-dam period. (2) Flow processes and sediment transport are the factors that caused serious erosion of the low beaches located in the convex point bars. However, changes in the river regime, river boundaries and jacking of Dongting Lake do not act as primary controls on the morphological evolution of the meandering reaches. (3) Flood discharges ranging from 20,000 to 25,000 m3/s result in greater erosion of convex point bars. The point bars become scoured if the durations of these flows, which are close to bankfull discharge, exceed 20 days. In addition, the reduction in bedload causes the decreasing of point bar siltation in the water-falling period. (4) During the post-dam period, flood abatement, the increased duration of discharges ranging from 20,000 to 25,000 m3/s, and a significant reduction in sediment transport are the main factors that caused meandering reaches to show CECD features. Our results are relevant to other meandering reaches, where they can inform estimates of riverbed change, river management strategies and river protection. 相似文献
14.
Xingying You Jinwu Tang Xiaofeng Zhang Weiguo Hou Yunping Yang Zhaohua Sun Zhaohui Weng 《地理学报(英文版)》2017,27(10):1249-1267
Alluvial channel has always adjusted itself to the equilibrium state of sediment transport after it was artificially or naturally disturbed. How to maintain the equilibrium state of sediment transport and keep the river regime stable has always been the concerns of fluvial geomorphologists. The channel in the middle and lower reaches of the Yangtze River is characterized by the staggered distribution of the bifurcated river and the single-thread river. The change of river regime is more violently in the bifurcated river than in the single-thread river. Whether the adjustment of the river regime in the bifurcated river can pass through the single-thread river and propagate to the downstream reaches affects the stabilities of the overall river regime. Studies show that the barrier river reach can block the upstream channel adjustment from propagating to the downstream reaches; therefore, it plays a key role in stabilizing the river regime. This study investigates 34 single-thread river reaches in the middle and lower reaches of the Yangtze River. On the basis of the systematic summarization of the fluvial process of the middle and lower reaches of the Yangtze River, the control factors of barrier river reach are summarized and extracted: the planar morphology of single-thread and meandering; with no flow deflecting node distributed in the upper or middle part of the river reach; the hydraulic geometric coefficient is less than 4; the longitudinal gradient is greater than 12‰, the clay content of the concave bank is greater than 9.5%, and the median diameter of the bed sediment is greater than 0.158 mm. From the Navier-Stokes equation, the calculation formula of the bending radius of flow dynamic axis is deduced, and then the roles of these control factors on restricting the migration of the flow dynamic axis and the formation of the barrier river reach are analyzed. The barrier river reach is considered as such when the ratio of the migration force of the flow dynamic axis to the constraint force of the channel boundary is less than 1 under different flow levels. The mechanism of the barrier river reach is such that even when the upstream river regime adjusts, the channel boundary of this reach can always constrain the migration amplitude of the flow dynamic axis and centralize the planar position of the main stream line under different upstream river regime conditions, providing a relatively stable incoming flow conditions for the downstream reaches, thereby blocking the upstream river regime adjustment from propagating to the downstream reaches. 相似文献
15.
Moshe Inbar 《自然地理学》2013,34(4):305-319
This study examines the adjustment of river systems in the Golan Heights to reservoir construction in small basaltic mountainous catchments where total water flow is impounded, and discusses comparisons with the effects of large dams on alluvial rivers. Annual rainfall ranges from 500 mm to 900 mm, and no major springs are found in the area. About 3/4 of total runoff is in the form of floods caused by rainstorms. The 11 dams receive drainage from about 20% of the total catchment, and a third of the total runoff. Changes in the river channels were studied at 28 field stations. Flood marks provided peak stage levels for largest season discharge, and 8 nearby hydrometric stations provided a continuous hydrological record. Bed material was sampled at each cross-section site. The main effect of river impoundment is a sharp decrease in flood peaks below the reservoirs to about one-third of their previous natural regime. The channel cross-sectional area decreased, but no temporal adjustment can be established, as most of the reservoirs were built in the last 5–8 years. Channel-flow hydraulics are competent enough to transport the suspended material, but evidence of aggradation was found in the channel reaches close to the dams. Bedload transport and the size of transported cobbles and boulders decreased downstream from the dams. Increased vegetation cover downstream from the dams was the most pronounced effect. Adjustment of the fluvial system to dam building in mountainous streams seems to be less sensitive than in alluvial channels. [Key words: fluvial geomorphology, dams, water reservoirs, environmental changes, Israel.] 相似文献
16.
Landscapes in southeastern Australia have changed dramatically since the spread of European colonisation in the 19th century. Due to widespread forest clearance for cultivation and grazing, erosion and sediment yields have increased by a factor of more than 150. In the 20th century, erosion and sediment yield were reduced again due to an increasing vegetative cover. Furthermore, during the last decades, thousands of small farm dams were constructed to provide drinking water for cattle. These dams trap a lot of sediment, thereby further reducing sediment delivery from hillslopes to river channels. Changes in sediment delivery since European colonisation are documented in sediment archives. Within this study, these changing rates in hillslope erosion and sediment delivery were modelled using a spatially distributed erosion and sediment delivery model (WATEM/SEDEM) that was calibrated for Australian ecosystems using sediment yield data derived from sedimentation rates in 26 small farm dams. The model was applied to the Murrumbidgee river basin (30,000 km2) under different land-use scenarios. First, the erosion and sediment yield under pre-European land-use was modelled. Secondly, recent land-use patterns were used in the model. Finally, recent land-use including the impact of farm dams and large reservoirs was simulated. The results show that the WATEM/SEDEM model is capable of predicting the intensity of the geomorphic response to changes in land-use through time. Changes in hillslope erosion and hillslope sediment delivery rates are not equal, illustrating the non-linear response of the catchment. Current hillslope sediment supply to the river channel network is predicted to be 370% higher compared to the pre-European settlement period, yet farm dams have reduced this back to 2.5 times the pre-19th century values. The role of larger reservoirs is even more important as they have reduced the current sediment supply downstream to their pre-European values, thus completely masking the increased hillslope erosion rates from land-use change. However, the model does so far not include valley widening and sediment storage in river systems. Therefore, modelled rates of sediment delivery are lower than observed values. 相似文献
17.
Channel incision is part of denudation, drainage-network development, and landscape evolution. Rejuvenation of fluvial networks by channel incision often leads to further network development and an increase in drainage density as gullies migrate into previously non-incised surfaces. Large, anthropogenic disturbances, similar to large or catastrophic “natural” events, greatly compress time scales for incision and related processes by creating enormous imbalances between upstream sediment delivery and available transporting power. Field examples of channel responses to antrhopogenic and “natural” disturbances are presented for fluvial systems in the mid continent and Pacific Northwest, USA, and central Italy. Responses to different types of disturbances are shown to result in similar spatial and temporal trends of incision for vastly different fluvial systems. Similar disturbances are shown to result in varying relative magnitudes of vertical and lateral (widening) processes, and different channel morphologies as a function of the type of boundary sediments comprising the bed and banks. This apparent contradiction is explained through an analysis of temporal adjustments to flow energy, shear stress, and stream power with time. Numerical simulations of sand-bed channels of varying bank resistance and disturbed by reducing the upstream sediment supply by half, show identical adjustments in flow energy and the rate of energy dissipation. The processes that dominate adjustment and the ultimate stable geometries, however, are vastly different, depending on the cohesion of the channel banks and the supply of hydraulically-controlled sediment (sand) provided by bank erosion.The non-linear asymptotic nature of fluvial adjustment to incision caused by channelization or other causes is borne out in similar temporal trends of sediment loads from disturbed systems. The sediments emanating from incised channels can represent a large proportion of the total sediment yield from a landscape, with erosion from the channel banks generally the dominant source. Disturbances that effect available force, stream power or flow energy, or change erosional resistance such that an excess of flow energy occurs can result in incision. Channel incision, therefore, can be considered a quintessential feature of dis-equilibrated fluvial systems. 相似文献
18.
黄河内蒙古头道拐断面河道变化及其对上游水库的响应(英文) 总被引：9，自引：3，他引：6
The application of dams built upstream will change the input conditions,including water and sediment,of downstream fluvial system,and destroy previous dynamic quasi-equilibrium reached by channel streamflow,so indispensable adjustments are necessary for downstream channel to adapt to the new water and sediment supply,leading the fluvial system to restore its previous equilibrium or reach a new equilibrium.Using about 50-year-long hydrological,sedimentary and cross-sectional data,temporal response processes ... 相似文献
19.
黄河流域产水产沙、输移和沉积系统的划分 总被引：4，自引：1，他引：4
根据Schumm提出的河流系统的理论对黄河流域地貌系统进行了划分。结果表明 ,整个黄河流域地貌系统可以很明确地分为产水产沙系统、输移系统和沉积系统 ,其模式与Schumm的理想流域模式非常吻合 ,同时又表现出其特殊性。以河口镇为界 ,黄河流域上游和中下游两部分分别具有对应的产水系统、产沙系统和河道输移系统 ,各子系统处于动态变化过程中 ,存在一种强耦合关系 ,这种特点主要是由黄河流域的历史发育过程决定的。 相似文献
20.
中国河流地貌研究进展——纪念沈玉昌先生100年诞辰 总被引：1，自引：0，他引：1
2016年是中国现代河流地貌研究的开拓者和奠基人沈玉昌先生100年诞辰,本文对中国河流地貌研究进展进行综述,以资纪念。研究涉及4个方面：① 水系发育与河谷地貌演变,包括大江大河水系历史发育和山区河流地貌;② 侵蚀与产沙过程,包括有物理成因基础的侵蚀产沙模型、侵蚀产沙过程的尺度效应、植被对侵蚀的影响及临界现象、坡面细沟发育过程模拟等;③ 河床过程与河型,包括河道冲淤过程、河床演变、河型成因与演变等;④ 河流地貌系统研究,包括流域系统不同子系统的耦合关系、河流地貌系统中的高含沙水流和多营力地貌过程、河流地貌系统对于自然因素变化和人类活动的响应、河流地貌系统中的泥沙灾害和河流地貌系统的实验研究等。50年前沈玉昌先生与钱宁先生提出在地貌学与河流动力学相结合的基础上发展中国河流学科。文中对此方面的进展进行了综述,并提出了需要深化和解决的问题。 相似文献