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珠江三角洲冲积平原河网密布,河道及河流的形态和演变影响着人们生活习性与经济发展水平,由于经济社会高速发展下的剧烈人类活动,以及气候、降水等自然环境的变化,导致河床演变加剧。对近60年的水文监测成果分析,发现自1990年代中期以来的河床演变,导致多种水文要素发生调整,给堤围险段、供水安全和水资源管理带来安全隐患,变化环境下的河流情势改变,是对当下水文工作的新挑战。 相似文献
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近岸河床的变化对于险工段河势稳定、护岸及堤防的安全产生影响。1990年代以来,尤其三峡水库蓄水运行后,上游来沙大幅减少,荆江河床普遍发生了冲刷,近岸河床发生了相应调整。主要结合荆江河段近岸河床监测资料及已有分析成果,从三个方面分析近岸河床演变对水沙条件变化的响应,一是近岸河床冲刷坑特征值与水沙条件的关系;二是近岸岸坡稳定性对水位变幅的响应程度;三是近岸河床平滩河道形态尺度对水沙过程的响应程度。通过计算分析得出近岸河床特征值与水沙定性及定量的关系。 相似文献
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选取对潜流交换具有重要影响的河床地形作为主要研究内容,采用数值模拟(MODFLOW程序)的方法研究在河床横剖面地形不均匀的条件下,潜流交换量的空间分布以及地下水流场的演变机制。结果表明:在河床地形起伏不均的情况下,潜流交换量更易发生在河道的深水区域;地下水流向受河床地形影响较小;近河床界面处的地下水流速受地形起伏影响剧烈,深水区域的地下水流速远大于浅水区地下水流速;通过与现场试验结果对比分析,得出河床地形起伏是引起潜流带渗透系数非均质现象的重要原因之一。 相似文献
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珠江三角洲水系属于典型的潮汐河网,水流同时受到地表径流及沿海潮位的双重影响。自20世纪80年代以来,该水系大规模的人工挖沙导致了水文条件、河床演变自然进程的较大变化。根据潮汐河网的水力特性,建立了用于模拟水位、流量时空变化的一维河网水动力数学模型,并根据由灰色模型预测的因挖沙引起的未来年份的河床演变情况,分别预测分析了不同水平年在丰水期、枯水期两种代表水情下的水系水位、流量变化情况。并对由此可能产生的对环境的影响进行了初步分析。 相似文献
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针对三峡工程蓄水后下游河道河床表面形态的变化,采用分形维数对河床表面形态进行量化,并分析河道冲淤调整特点,对河床表面分形维数(BSD)的变化特点及物理意义进行探讨。结果表明,BSD与河床各个剖面形态之间的关系是整体与部分的关系,BSD能全面地反映床面形态的复杂程度。三峡蓄水后,宜昌-虎牙滩和宜都河段BSD明显增大,关洲河段增大幅度较小,而芦家河河段BSD值略有减小,同时,各河段BSD的变化可在一定程度上表征三峡蓄水后下游河道河床综合阻力的调整结果。可通过对各河段演变趋势的分析,来预测其BSD的变化,进而为分析其阻力和水位的变化趋势提供依据。 相似文献
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本文针对石头河流域内河床多变的问题，并通过鹦鸽水文站多年的测验断面河床演变分析，提出在多变河床进行防洪、减灾不能简单地依照传统的水位－流量关系决定对策，而应充分考虑水流与河床冲淤变化情况。为防洪决策提出了一个不容忽视的问题。 相似文献
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通过地表实地踏勘和浅层探槽解释，结合卫星照片解译，参考第四纪和历史地理研究结果，对准噶尔盆地西北缘黄羊泉扇的沉积特征及其第四纪以来的演变进行了分析.黄羊泉扇是一个发育在内陆干旱地区、以河流沉积为主的河流扇，扇体平面上呈上细下粗的“葫芦型”，可以划分为上扇、中扇和扇缘3个相带，沉积物具有由上扇向扇缘变细的趋势.扇上沉积动力以河流为主，缺乏泥石流沉积，但扇面活动水道不发育，大多数河道为偶尔才有径流通过的暂时性河道，风对扇表面的沉积物有明显的改造作用.黄羊泉扇扇缘发育4种不同的终止方式，一部分进入艾里克湖，一部分终止在沼泽地带，一部分在小型湖泊边缘消失，一部分受地形阻挡终止，与经典冲积扇和扇三角洲都不完全相同.结合前人历史地理研究成果认为第四纪以来黄羊泉扇所在的古玛纳斯湖出现过6次高湖平面，在30 ka以前，黄羊泉扇体一直处于古玛纳斯湖包围中，形成黄羊泉扇三角洲.直到30~10 ka期间才由于湖泊水位下降，扇体逐步出露形成河流扇.研究建立了黄羊泉扇随着湖平面升降从河流扇三角洲不断演化为河流扇的沉积模式，表明黄羊泉扇目前正处于河流扇三角洲沉积体系向河流扇沉积体系演变的过渡阶段. 相似文献
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据新的地层划分方案及大量钻井、露头和岩心资料,详细研究了鄂尔多斯盆地华池地区延安组延9油层组（Y9）沉积体系特征及演化,认为延9油层组主要为河流沉积,是延10油层组的继承与发展,发育有辫状河、辫状型曲流河和网状河3种类型的河流。Y39油层是辫状河发育的油层,Y29油层在继承Y39油层河流的基础上发育辫状型曲流河,Y19油层则是在前两期逐渐填平补齐之后,在准平原条件下发育的网状河沉积。华池地区延9油层组发育辫状河-辫状型曲流河和网状河两种河流沉积模式。 相似文献
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全球范围内干旱区河流正日益受到高强度人类活动的扰动,但较少研究报道这种扰动对河流地貌过程的影响。采用历史文献、水文数据和遥感影像相结合的方式,详细分析了人类活动影响下中国最大内陆河塔里木河（简称塔河）的河流地貌变化过程。结果表明:塔河流域人类活动的规模和强度日趋上升,对河流水沙过程和地貌形态等影响显著。近50年来,塔河干流低流量过程发生频率呈显著上升趋势,而中、高流量过程则呈降低趋势,河道径流和输沙量减少显著。塔河干流上游现为游荡河道,冲淤变化剧烈且总体处于淤积抬升状态, 但河道平均河宽呈减小趋势,可能是因为塔河两岸冲积平原的开垦和河岸加固。塔河中游弯曲河道蜿蜒系数在近几十年呈缓慢上升趋势,但明显低于废弃古河道。 相似文献
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Recognition criteria,characteristics and implications of the fluvial to marine transition zone in ancient deltaic deposits (Lajas Formation,Argentina) 总被引：1，自引：0，他引：1 
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下载免费PDF全文 Marcello Gugliotta Stephen S. Flint David M. Hodgson Gonzalo D. Veiga 《Sedimentology》2016,63(7):1971-2001
The seaward end of modern rivers is characterized by the interactions of marine and fluvial processes, a tract known as the fluvial to marine transition zone, which varies between systems due to the relative strength of these processes. To understand how fluvial and tidal process interactions and the fluvial to marine transition zone are preserved in the rock record, large‐scale outcrops of deltaic deposits of the Middle Jurassic Lajas Formation (Neuquén Basin, Argentina) have been investigated. Fluvial–tidal indicators consist of cyclically distributed carbonaceous drapes in unidirectional, seaward‐oriented cross‐stratifications, which are interpreted as the result of tidal modulation of the fluvial current in the inner part of the fluvial to marine transition zone. Heterolithic deposits with decimetre‐scale interbedding of coarser‐grained and finer‐grained facies with mixed fluvial and tidal affinities are interpreted to indicate fluvial discharge fluctuations (seasonality) and subordinate tidal influence. Many other potential tidal indicators are argued to be the result of fluvial–tidal interactions with overall fluvial dominance or of purely fluvial processes. No purely tidal or tide‐dominated facies were recognized in the studied deposits. Moreover, fluvial–tidal features are found mainly in deposits interpreted as interflood (forming during low river stage) in distal (delta front) or off‐axis (interdistributary) parts of the system. Along major channel axes, the interpreted fluvial to marine transition zone is mainly represented by the fluvial‐dominated section, whereas little or no tide‐dominated section is identified. The system is interpreted to have been hyposynchronous with a poorly developed turbidity maximum. These conditions and the architectural elements described, including major and minor distributary channels, terminal distributary channels, mouth bars and crevasse mouth bars, are consistent with an interpretation of a fluvial‐dominated, tide‐influenced delta system and with an estimated short backwater length and inferred microtidal conditions. The improved identification of process interactions, and their preservation in ancient fluvial to marine transition zones, is fundamental to refining interpretations of ancient deltaic successions. 相似文献
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J. Vandenberghe S. Cordier 《Proceedings of the Geologists' Association. Geologists' Association》2010,121(2):107-112
This paper introduces a special issue arising from the biennial meeting of the Fluvial Archives Group (FLAG) that took place in September 2008 in Budapest, Hungary. Combining a two-day conference and three-day field excursion, this meeting provided an excellent opportunity for presentation and discussion of recent advances in research on fluvial evolution from the Plio-Pleistocene to the historical period. This editorial seeks to place these advances within the contexts both of long-term geomorphological research and the achievements of FLAG. It thus highlights progress towards a better understanding of fluvial responses to internal and external (including anthropogenic) forcing. It also points out some of the main obstacles, which can be targeted as goals for further research. Typically these relate to observed discrepancies in fluvial system responses, such as in patterns of lateral erosion and the timing of terrace incision, despite apparently similar fluvial parameters. Possible explanations for these discrepancies are mentioned, and the potential of new methods (especially in geochronology and modelling) to clarify such discrepancies is underlined. Finally the editorial provides brief reviews of the ten papers in this special issue (many of them developed from presentations in Budapest), which cover various areas in Europe (Hungary, England, Germany, Portugal, Russia), Asia (India) and South America (Bolivian Andes), placing them, in turn, within the context of this wider review of fluvial research. 相似文献
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The Rhine catchment experienced strong changes in upstream allogenic forcing during the last 20,000 years. Climatic changes of the glacial–interglacial transition and steadily growing human impact during the second half of the Holocene forced the Rhine to adapt, resulting in changes in the fluvial morphology. The lower Rhine left two late Weichselian terraces and many Holocene palaeo-meanders in the Lower Rhine Valley (western Germany). This well-preserved terrace sequence is used to investigate the exact course of events of the lower Rhine response to changes in allogenic forcing. Five detailed cross-sections that integrate new and existing borehole data were constructed, and the deposits were analysed with regards to abandonment of terraces, changes in number of active channels, fluvial style, terrace gradients, and overbank sedimentation during the Lateglacial and Holocene. We improved and expanded the chronology of the Lower Rhine Valley deposits by dating new samples (14C, OSL), and integrated these with existing dating evidence (archaeological and historical data, cross-cutting relationships). Twice during the glacial–interglacial transition, the lower Rhine changed from braided to meandering fluvial style. During both transitional episodes (meandering) secondary channels existed alongside the main channel, with a life span up to 2500 years. The findings imply that the lower Rhine was inherently slow to complete the full morphological transition to a single thread meandering system. On specific aspects of response, the morphological response (point bar/terrace formation, contraction to a single thread) extended over relatively long periods of time, whereas discharge-related response (e.g. fluvial style change, abandonment of braidplains, channel bed lowering/incision) seems to have been near instantaneous. Reach-specific conditions determine the degree to which the geomorphic response is delayed and the complexity of the resultant morphology. Increased human-induced sediment delivery (last 2000–3000 years) is expressed as relative thicker and coarser overbank deposits in the entire study area. In the downstream part of the Lower Rhine Valley it accelerated high-stand deltaic backfilling and decreased incision. The response to human activities occurred relatively quickly in contrast to the long-term fluvial response to the glacial–interglacial transition, because the human impact mainly involved change in delivery of the suspended load. 相似文献
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选择青海共和盆地多石在沟河道中6道新月形沙丘链作为研究对象,采用Trimble4700DGPS与常规测量手段,结合野外风沙观测与自动气象站数据,初步观测分析了2006年多石在沟河道沙丘在不同季节的形态变化过程,计算出2006年风季前比雨季后多石在沟河道沙丘体积减小了548.3m3,风积量为2351m3,流水的蚀平量为2899m3,2006年风水两相营力对河道沙丘的侵蚀贡献率约为45%∶55%,流水的搬运作用强于风力的堆积作用。但从较长的时间尺度来看,研究区的风力侵蚀作用强于流水侵蚀作用,河道沙丘不断增大。多石在沟河道沙丘是一个典型的风水交互作用系统,河道成为风力与流水交互作用的"中转站",在风水的交替作用下,沉积物由风积环境进入流水环境中。 相似文献
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主要通过岩心观察、粒度分析、参数计算、录井及测井分析等手段,充分吸收国内外河流研究成果,结合研究区区域地质背景,总结出渤海湾盆地垦东凸起北坡新近系馆陶组上段沉积相模式。研究认为：馆上段为河流相沉积,从沉积物特征和平面形态角度可以将研究区馆上段河流理解为介于辫状河与曲流河之间的过渡河型。其平均河道弯曲度大于1.7,垂向层序表现为泥多砂少,具有曲流河的特征;但沉积层序顶部常直接覆盖河漫/洪泛平原沉积,特别是河道内砂坝发育造成河道分汊河,砂坝沉积物粒度特征反映的受洪水控制的震荡性特点而与曲流河有重要差别。作者借用在水利学界和地貌学界广为使用的分汊河概念,建立了馆上段沉积相模式,包括河床、堤岸、河漫/洪泛平原和废弃河道等4个亚相,其沉积物组成下粗上细的正韵律。其中,河道砂坝是其主要砂体,顶部常被洪泛平原直接覆盖;决口扇是仅次于河道砂坝的次要砂体。 相似文献
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福建龙永煤田顶峰山井田童子岩组沉积环境及其演化 总被引：1，自引：1，他引：0
运用沉积学、古生物地层学、层序地层学等方法对福建龙永煤田童子岩组地层及其内主要煤层的沉积特征进行了详细的研究。结果表明童子岩组是一套海陆交互相的沉积,其沉积序列共分为三个沉积旋回,每个旋回都是以海侵开始,以海退结束,每一旋回缓慢海退背景都是由一系列的次级快速海进或海退事件构成。由于不断受到海陆两方面的影响,形成童子岩组中煤层的泥炭沼泽发育呈现出波动式特征,由此导致泥炭沼泽类型呈跳跃式演化,构成了包括碎屑滨岸、障壁岛—潟湖、泥炭坪、潮坪、潮汐三角洲和河控三角洲等沉积相在内的复杂沉积体系。 相似文献