共查询到16条相似文献，搜索用时 125 毫秒
1.
长江中下游阻隔性河段作用机理 总被引：1，自引：0，他引：1
阻隔性河段能够阻隔上游河势调整向下游的传递,对稳定河势起到关键性作用。本文以长江中下游34个单一河段为研究对象,在系统总结长江中下游河道演变规律的基础上,归纳出阻隔性河段控制要素包括：单一微弯的河道平面形态、河段中上部无挑流节点;河相系数小于4;河道纵比降大于1.2?;凹岸黏粒含量高于9.5%;床沙中值粒径大于0.158 mm等。从Navier-Stokes方程出发,推导出河湾水流动力轴线弯曲半径的表达式,进而分析了各控制要素对水流动力轴线摆动及阻隔性河段形成的作用。阻隔性河段的判别条件为：不同流量级下水流动力轴线摆动力与河道边界条件约束力的比值始终小于1;阻隔性河段作用机理在于：即便上游河势发生调整,本河段的河道边界始终能约束主流摆动幅度,归顺上游不同河势条件下的主流平面位置,为下游河道提供了相对稳定的入流条件,从而阻隔上游河势调整向下游传递。 相似文献
2.
河型转化是河流演化由量变到质变的综合反映,具有科学研究和服务生产的双重价值。以嫩江干流上游（以下简称嫩江上游）为研究区,利用遥感影像和地貌、气候等资料描绘了1985—2020年嫩江上游的河流形态特征,分析了河流类型、河型转化控制因素及河型转化模式。研究表明：(1)嫩江上游整体为稳定的河流且稳定性先增后减,顺河流方向发育三种河型——低坡度高弯度稳定的曲流河（河段Ⅰ）、高坡度高弯度稳定的曲流河（河段Ⅱ）、低坡度较稳定的网状河（河段Ⅲ）;(2)构造活动微弱是河流稳定的前提,气温和降水变化量是稳定性变化的控制因素,且气温变化量的贡献率更大;(3)河段Ⅰ转化为河段Ⅱ的控制因素为断层和冻土,土壤起协同作用,河段Ⅱ转化为河段Ⅲ的控制因素为地形和河流边界岩性,土壤、植被起协同作用;(4)嫩江上游的河型转化是一种流域尺度内构造运动限制的中纬度半湿润-湿润区山地曲流河向平原网状河转化的模式,这一模式常见于东北亚。 相似文献
3.
近50年黄河乌兰布和沙漠段辫状河道演变 总被引：4，自引：3，他引：1
依据水沙资料和断面资料,对黄河乌兰布和沙漠段辫状河道形态近50年演变特征及趋势进行探讨分析。结果表明：在大流量条件下（1966-1993年）,河流横向侵蚀、搬运堆积过程强烈,风沙入黄（河）量大,河道横向摆动频繁,辫状河道发育强烈。当黄河流量减小时（1993-2013年）,河流横向摆动能力减弱,黄河主河槽远离左岸乌兰布和沙漠沙丘,河流输沙能力减弱,汊道泥沙淤积导致心滩边滩相连,河流分汊数量明显减少,辫状河道萎缩,黄河乌兰布和沙漠段辫状河型有向弯曲型河道转变的趋势。 相似文献
4.
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
5.
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
6.
游荡性河道在中国广泛分布,其中以黄河下游上段最为典型,但关于游荡性河型的归属问题尚存在很大争议,国际上多将游荡性河流归属为辫状河型。本文以黄河下游游荡性河道为典型案例,系统总结了游荡性河流的演变特征、主要影响因素和形成机理,并从定义、成因、特征及河道形成过程方面,将游荡与辫状河型的异同点进行对比分析。得到以下启示：游荡性河型是一种重要的河道型态,与辫状河型在许多方面存在较明显差异。特别是游荡河型主要发育于能量小于输沙需求的环境,因而形态呈现不稳定特性,但辫状河型不仅出现在能量较多的环境,而且也常在能量较小的环境中出现,因而一部分具有稳定形态,另一部分则表现出不稳定的特性,因此,有必要对游荡性河道和辫状河道给予区分。最后对未来研究进行了展望,提出应重视河型形成的内在机理,对能量理论进行发展及深化,进一步系统性评价游荡性河道与辫状河道的异同性,以解决游荡性河道的河型归属问题。 相似文献
7.
黄河下游河道断面形态参数变化及其水沙过程响应 总被引：1，自引：0，他引：1
基于1965—2015年黄河下游花园口、高村、泺口站的逐年水文和汛前河道断面的实测资料，分析了河道断面形态参数（河道断面面积，河道宽深比等）的变化，以及对河道断面形态与来水来沙间的关系做出定量化分析。结果表明：主槽断面形态参数与水沙搭配以及前期断面形态密切相关，沿程3个断面形态参数调整方式存在显著差异。河宽调整幅度沿程减小，辫状河段变幅最大，尤其在1986—1999年，辫状河段萎缩程度最为严重，其次为弯曲河段，顺直河段横向调整幅度最小。受到前期断面形态的影响，辫状河段河道断面调整方式既有横向展宽（萎缩）又有垂直加深（淤积）；弯曲河段河道宽深比与流量呈较弱的正相关关系，具有横向和垂向的调整方式；而顺直河段的宽深比与流量呈负相关关系，与来沙系数呈正相关关系，河道以垂直加深（淤积）为主。 相似文献
8.
前人对北川湔江袭夺湾位置的争议引发了对古湔江流向演化模式的争议。通过对断裂构造的水系响应方式的研究并辅以河流地貌证据,表明湔江的流向演化经历了银屏口分水岭迁移的主动袭夺过程和新构造运动造成湔江改道的被动袭夺过程,都坝河与通口河近似直角的交汇端应为袭夺湾的准确位置。具体来说,沿断裂发育的古都坝河在曲山镇附近首先注入古湔江,通口河溯源侵蚀切穿银屏口分水岭,古都坝河上游河段被通口河袭夺后改道注入通口河,古都坝河下游河段成为断头河。随后,因构造隆升而南流受阻的古湔江在曲山镇附近改道,水流沿已成断头河的古都坝河下段河道注入通口河。计算表明,北川湔江由古流向向现代流向转变的时期大致为距今970 ka的早更新世晚期。 相似文献
9.
以分析青海巴音河流域地表水与地下水转化关系为目标,2016年8月,沿巴音河采集了23组地表水样、13组地下水样和9组泉水样,室内分析得到了其对应的主要水化学离子和氘氧稳定同位素数据,运用统计分析、Piper三线图、Gibbs图分析了流域水化学特征;以溶解性总固体（TDS）、氯离子（Cl-）和氧同位素（δ18O）作为示踪剂,定性分析了巴音河沿程地表水与地下水的转化关系;基于质量平衡法,运用δ18O定量计算了巴音河沿程地表水和地下水之间的转化量。研究结果表明：TDS、Cl-、δ18O可用于定性分析巴音河流域不同河段地表水与地下水之间的转化关系,定量评估其转换强度;巴音河流域地表水和地下水的水化学类型主要为HCO3·Cl-Ca·Mg,地下水水化学类型更为多样,地表水受控于岩石风化作用,地下水与泉水受到岩石风化与蒸发作用的影响;地表水与地下水水力联系密切,沿巴音河流向,二者相互转化频繁,上游河段,地下水主要接受地表水渗漏和沿途侧向径流补给,补给比例分别为65.33%、34.67%,至黑石山水库上游,地表水接受上游地下水和溢出泉水的补给,补给比例分别为49.54%、50.46%;中游河段,地下水接受地表水和北部山区侧向径流补给,补给比例分别为65%、35%;下游河段,地表水接受地下水和泉水补给,补给比例分别为53.12%、46.88%。研究结果有助于建立流域水循环模式、揭示水资源形成机制,可以为巴音河流域水资源可持续开发利用和生态环境保护提供理论和技术支持。 相似文献
10.
长江中下游河床沉积物分布特征 总被引：10，自引：0，他引：10
对长江中下游武汉至河口段304处河床沉积物样品进行了粒度测量与分析,通过各参数间的模拟、统计及对比,探讨了沉积物粒度、水动力因素及河床地貌三者间的关系。研究结果表明：本区河床沉积物以中、细砂为主,床底搬运十分微弱,河道相对稳定;从上至下沿程有明显的“粗-细-粗-细”粒径变化,主要反映河流动力地貌、动力沉积特征;粒径在河床的沿程分布总体为北粗南细,说明北岸侵蚀,南岸淤积的特点。研究同时也表明,颗粒因河型不同而迥异;颗粒偏态度-峭度在不同河型中表现各异,对区分顺直微弯分汊和鹅头形分汊河道尤为显著。 相似文献
11.
The Milk River, the northernmost tributary to the Missouri–Mississippi River system, exhibits an anomalous sand-bed braiding reach in an otherwise meandering system. Shortly after leaving Alberta and entering Montana the river suddenly changes to braiding and maintains this pattern for 47 km before entering Fresno Reservoir. Measured stream gradient and bankfull discharge in the braiding reach severely fail the Leopold and Wolman [U.S. Geol. Surv. Prof. Pap. 282B (1957) 39] slope–discharge test for differentiating channel patterns. While channel slope has long been regarded as one of the primary variables associated with braiding, our data from the sand-bed Milk River do not support this relationship. Instead, the data show that the braiding reach has a lower channel slope (0.00047) than the meandering reach (0.00055). Coupled with a constant discharge the unit length stream power is comparable between the two reaches. At the morphologic transition between meandering and braiding, a dramatic reduction in channel bank strength occurs where the sampled silt–clay content declines from 65% in the meandering reach to 18% in the braiding. This enables channel widening which is reflected in a 60% reduction in unit area stream power in the braiding reach. Thus, sediment transport capacity declines and channel bars are deposited. During waning flows, these bars are dissected, producing a braiding morphology. We suggest that for sand-bed braiding rivers the silt–clay percentage in the channel banks may be more important than slope. A review of the original Leopold and Wolman [U.S. Geol. Surv. Prof. Pap. 282B (1957) 39] dataset, and many subsequent analyses, reveals that most braided rivers studied were gravel-bed. As a result, causal variables associated with braiding in sand-bed environments may need a thorough evaluation. 相似文献
12.
Analysis of controls upon channel planform at the First Great Bend of the Upper Yellow River, Qinghai-Tibet Plateau 总被引：3，自引：3，他引：0
Zhiwei Li Zhaoyin Wang Baozhu Pan Jun Du Gary Brierley Guo-an Yu Brendon Blue 《地理学报(英文版)》2013,23(5):833-848
The 270 km long section of the Upper Yellow River at the First Great Bend is comprised of single channel and multiple channel systems that alternate among anastomosing, anabranching, meandering and braided reaches. The sequence of downstream pattern changes is characterized as： anastomosing-anabranching, anabranching-meandering, meandering-braided and braided-meandering. Remote sensing images, DEM data and field investigations are used to assess ahd interpret controls on these reach transitions. Channel slope and bed sediment size are key determinants of transitions in channel planform. Anas- tomosing reaches have a relatively high bed slope （0.86‰） and coarser sediment bed material （d50 = 3.5 mm）. In contrast, meandering reaches have a low slope （0.30‰） and fine sediment bed material （d50 = 0.036 mm）. The transition from a meandering to braided pattern is characterized by an increase in channel width-depth ratio, indicating the important role of bank strength （i.e. cohesive versus non-cohesive versus channel boundaries）. Interestingly, the braided-meandering and meandering-braided transitions are coincident with variable flow inputs from tributary rivers （Baihe and Heihe rivers respectively）. Theoretical analysis of the meandering-braided transition highlights the key control of channel width-depth ratio as a determinant of channel planform. 相似文献
13.
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
14.
黄河下游清水冲刷阶段河床的调整及其对基准面变化的反应 总被引：1，自引：1，他引：0
本文采用黄河下游的实测资料,分析了三门峡水库下洩清水阶段,河床的调整及其对基准面的反应。认为在来水来沙条件变化的情况下,河床纵剖面以近于平行的方式调整;横断面形态向窄深式发展;河型的转化主要取决于地貌临界值和粉沙—粘土含量。从长时间看,下游的淤积特性不会发生根本性的变化。 相似文献
15.
在全新世时间尺度内,沉积记录主要受控于沉积物供给、输运和堆积过程等因素。对废黄河沉积记录的深入分析可以反演黄河南流夺淮过程中沉积物的“源”-“汇”关系。基于废黄河故道沉积记录中重矿物和地球化学元素特征,并结合与现代黄河沉积物的对比,揭示废黄河沉积记录中物质来源的信息。结果表明,废黄河故道沉积物中重矿物平均含量为0.19%,种类多达15余种,以稳定矿物为主,不同矿物的时空变化差异较大。废黄河故道泥质和砂质沉积物中,地球化学元素表现出明显的时空变化规律,随深度递增元素含量可分为降低、稳定和增加趋势。对比现代黄河沉积物,发现废黄河故道沉积物中稳定和极稳定矿物相对含量较高,泥质沉积物中更多地富集Zn,Ni,Al,Ba,Cu,Li,K等元素。这一差异性反映出其它不同河流物质补给而产生的影响,淮河沉积物中重矿物和地球化学元素的研究为该论断提供了佐证。 相似文献
16.
Fluvial diversity in relation to valley setting in the source region of the Yangtze and Yellow Rivers 总被引：3，自引：3，他引：0
Guo-an Yu Le Liu Zhiwei Li Yanfu Li Heqing Huang Gary Brierley Brendon Blue Zhaoyin Wang Baozhu Pan 《地理学报(英文版)》2013,23(5):817-832
The spatial distribution of valley setting （laterally-unconfined, partly-confined, or confined） and fluvial morphology in the source region of the Yangtze and Yellow Rivers is contrasted and analyzed. The source region of the Yangtze River is divided into 3 broad sections （I, II and III） based on valley setting and channel gradient, with the upstream and downstream sections being characterized by confined （some reaches partly-confined） valleys while the middle section is characterized with wide and shallow, laterally-unconfined valleys. Gorges are prominent in sections I and III, while braided channel patterns dominate section II. By contrast, the source region of the Yellow River is divided into 5 broad sections （sections I-V） based on valley characteristics and channel gradient. Sections I, II and IV are alluvial reaches with mainly laterally-unconfined （some short reaches partly-confined） valleys. Sections III and V are mainly confined or partly-confined. Greater morphological diversity is evident in the source region of the Yellow River relative to the upper Yangtze River. This includes braided, anabranching, anastomosing, meandering and straight alluvial patterns, with gorges in confined reaches. The macro-relief （elevation, gradient, aspect, valley alignment and confinement） of the region, linked directly to tectonic movement of the Qinghai-Tibet Plateau, tied to climatic, hydrologic and biotic considerations, are primary controls upon the patterns of river diversity in the region. 相似文献