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1.
通过黄河上游沙漠宽谷河段现场考察及实测资料分析,依据河岸物质来源及组成将黄河上游崩塌河岸划分为粘性河岸及非粘性风沙堆积河岸两大类,前者可分为平面崩塌、弧形滑动崩塌和复合式崩塌3种类型,后者表现出非粘性河岸的表层滑移及平面崩塌两种形式。进一步以磴口、乌海河段为例,分析粘性河岸和风沙堆积河岸的塌岸特征,并结合近10年的遥感影像解译分析河岸线崩退变化规律,揭示塌岸引起河道横向变化特征。结果表明粘性河段的塌岸后退距离大于风沙堆积河段,局部河段短期出现凹退凸淤的动态岸线变化特点,但全河段长期仍然处于总体淤积的态势。 相似文献
2.
The role of geomorphic processes in the transport and fate of mercury in the Carson River basin, west-central Nevada 总被引：1，自引：0，他引：1
The historic processing of precious metal ores mined from the Comstock Lode of west-central Nevada resulted in the release
of substantial, but unquantified amounts of mercury-contaminated mill tailings to the Carson River basin. Geomorphic and stratigraphic
studies indicate that the introduction of these waste materials led to a period of valley-floor aggradation that was accompanied
by lateral channel instability. The combined result of these geomorphic responses was the storage of large volumes of mercury-enriched
sediment within a complexly structured alluvial sequence located along the Carson River valley. Much of the contaminated sediment
is associated with filled paleochannels produced by the cutoff and abandonment of meander loops, and their subsequent infilling
with contaminated particles. Geochemically, these deposits are characterized by variations in mercury levels that exceed three
orders of magnitude. Continued lateral instability, coupled with an episode of channel-bed incision, followed the decline
of Comstock mining, and has reexposed contaminated debris within the banks of the river. Erosion of bank sediments reintroduces
mercury-enriched particles to the modern channel bed. It is suggested on the basis of geochemical and sedimentological data
that during the bank erosion process, much of the mercury associated with fine (<63 μ) valley-fill deposits are carried downstream
without being incorporated to any appreciable extent within the channel-bed sediments. In contrast, mercury associated with
larger and denser particles, particularly mercury-gold-silver amalgam grains, are accumulated in the channel-bed sediments
as the river traverses polluted reaches of the Carson River valley. Concentration patterns developed along the modern channel
indicate that the valley fill is the primary source of mercury to the river today. Thus, these data imply that efforts to
reduce the influx of mercury to the aquatic environment should examine methods for reducing bank erosion rates.
Received: 13 December 1996 · Accepted: 15 April 1997 相似文献
3.
板块俯冲碰撞拼合带是盆山相互作用最为强烈的地区,发育有弧前、弧间及弧后多种类型的盆地,沉积物的剥蚀搬运作用极为活跃。证据显示,沉积物搬运充填过程在构造—古地理控制型盆地中具有一定的演变规律,伴随盆地演化,沉积物轴向搬运与横向搬运呈此消彼长的互动关系。南海南北两侧均发育了大型板块俯冲拼合带及相关的沉积盆地,在盆地发育早期沉积物沿盆地长轴方向分别形成昆莺琼古河和巽他古河,以轴向搬运的方式分别把越南中部及马来半岛沉积物由西向东输送到南海,形成大型三角洲及前三角洲深水扇沉积,河流发育位置均在板块拼合转折地段。在盆地发育的成熟阶段,沉积物以横向搬运的方式进入盆地,与轴向搬运沉积物形成混合堆积。轴向搬运是洋陆碰撞拼合盆地中一种重要的沉积物搬运途径,主要受盆地形成时的构造古地理控制。 相似文献
4.
Aspects of riverbed evolution including bank erosion in the Ural River basin have been considered in this paper. The natural morphodynamic types of riverbeds have been described. The spatial features of their genesis have been characterized within the Ural River basin. To study the riverbed processes, decoding of remote sensing data of the water surface has been used. The risks for the infrastructure facilities and for the residential districts have been analyzed in terms of the bank erosion in the Ural River basin. The issues concerning the border between the Russian Federation and the Republic of Kazakhstan due to riverbed reconfiguration of the Ural River have been outlined. Maps of the development of bank erosion in the Ural River basin have been created. A way to solve the problem of riverbed evolution along the border area has been proposed by organizing an Intergovernmental Specially Protected Natural Zone.
相似文献5.
板块俯冲碰撞拼合带是盆山相互作用最为强烈的地区,发育有弧前、弧间及弧后多种类型的盆地,沉积物的剥蚀搬运作用极为活跃。证据显示,沉积物搬运充填过程在构造—古地理控制型盆地中具有一定的演变规律,伴随盆地演化,沉积物轴向搬运与横向搬运呈此消彼长的互动关系。南海南北两侧均发育了大型板块俯冲拼合带及相关的沉积盆地,在盆地发育早期沉积物沿盆地长轴方向分别形成昆莺琼古河和巽他古河,以轴向搬运的方式分别把越南中部及马来半岛沉积物由西向东输送到南海,形成大型三角洲及前三角洲深水扇沉积,河流发育位置均在板块拼合转折地段。在盆地发育的成熟阶段,沉积物以横向搬运的方式进入盆地,与轴向搬运沉积物形成混合堆积。轴向搬运是洋陆碰撞拼合盆地中一种重要的沉积物搬运途径,主要受盆地形成时的构造古地理控制。 相似文献
6.
中吉乌铁路是我国西北地区通往中亚、南欧国家的一条国际通路,对其方案线沿线的地质灾害的调查及预测可为其选线提供一定建议。本文基于Mamdani模糊推理系统(Mamdani FIS)对方案线北线AK53-AK130、南线AK61-AK131段研究区的滑坡易发性进行预测。通过区域地质背景资料和遥感影像人机交互解译获取了该区地质环境背景、地形因素以及生态环境3类9种滑坡影响因子,建立768条推理规则,通过Mamdani FIS模型得到区内滑坡敏感度文件,在GIS环境中制作研究区滑坡易发性等级图,将研究区划分为极低易发区、低易发区、中等易发区、高易发区和极高易发区。结果显示,滑坡极高易发区和高易发区分布在研究区东北部的费尔干纳山脉附近以及南部的亚瑟河流域。采用受试者工作特征曲线(Receiver Operating Characteristic Curve,ROC曲线)对结果进行验证,曲线下面积为0.859,表明预测结果精度较高。 相似文献
7.
Bank failure and erosion on the Ohio river 总被引：1，自引：0，他引：1
River bank erosion has benn the focus of recent concern surrounding construction and operation of navigation dams along the Ohio River. Such factors as navigation pool levels, pool fluctuations, and towboat traffic have been alleged to be the cause of severe erosion of Ohio River banks. In this paper available information on Ohio River bank erosion is examined from an historical perspective and from the perspective of recent comprehensive investigations. Historical illustrations, photographs, and published reports indicate a history of significant bank erosion for more than 150 years on the Ohio River. Results of field bank condition reconnaissance studies suggest that construction of navigation dams on the Ohio River has not significantly accelerated or intensified bank erosion. Analysis of erosional mechanisms indicates that bank failure and erosion on the Ohio River are complex and episodic phenomena; however, the principal erosional mechanisms appear to be bank material removal by current tractive forces during flood events and internal erosion of bank materials by bank discharge following floods. It is concluded that waves generated by tow and recreational vessels have little impact on bank stability, but land use changes may affect slope stability and bank erosion. 相似文献
8.
季节性冰冻河流（季冻区河流）受水动力-冻胀/冻融耦合作用,岸滩崩塌机理复杂,且对河道演变具有重要影响。通过建立水动力-冻胀/冻融耦合作用岸滩崩塌力学模式,以中国东北地区松花江干流大顶子山航电枢纽下游近坝段为例,开展季冻区河流岸滩崩塌及河道演变的三维数值模拟分析。研究结果表明:岸滩坡脚侧蚀主要由水力冲刷所控制,冻胀作用使岸滩开裂深度增加,冻融过程则会使岸坡土体力学强度降低,影响岸滩稳定;岸滩崩塌对季冻区天然河流演变具有显著影响,考虑岸滩崩塌的模拟结果与天然实测结果基本吻合,可较好地模拟河床冲淤、岸滩崩塌所引起的河道演变过程。研究成果可为季冻区河流岸滩崩塌及河道演变的深入研究提供技术支撑。 相似文献
9.
利用地理信息系统(GIS)与数字高程模型(DEM)技术,模拟了40年来长江九江段的冲淤过程,结果表明:1963-1972年,总体表现为淤积,淤积量为650.5万m3,平均淤积速率为65万m3/a。1972-2002年,总体表现为冲刷,冲刷量为2072万m3,平均年冲刷率为103.6万m3/a。1963-2002年,九江河床总体表现为冲刷,冲刷量为1497.7万m3。2003年与1963年比较,河床淤积区域主要在长江九江上段的近南岸区域、中下段的中间区域;冲刷区域主要在长江九江上段的中间及近北岸区域、中下段两岸的近岸区域。长江九江河段40年的演变是河床的边界条件、上下游来水来沙及人类活动耦合的结果。中下段南岸的不断刷深和南偏对九江的防洪带来更大的压力。 相似文献
10.
The USA Clean Water Act requires the development of a total maximum daily load (TMDL) when Minnesota’s water quality standard
for turbidity is exceeded; however, regions underlain with fine-grained lacustrine deposits yield large natural background
loads of suspended inorganic sediment. A review of hydrogeologic pathways was conducted along with the statistical analysis
of geomorphic metrics, collected at 15 sites with varying drainage areas in the upper Nemadji River basin, northeastern Minnesota.
Regression analysis indicated a strong linkage between bankfull cross-sectional area and drainage area. Dimensionless geomorphic
metric ratios were developed to predict channel evolution potential and associated channel erosion risk. Sites located in
drainage areas less than 2 km2 had low erosion risk and showed a correlation between channel slope and relative roughness (D
84/mean bankfull channel depth, 88%). A principal components analysis explained over 98% of the variance between sites and indicated
five important channel shape metrics to predict channel erosion: bankfull width, bankfull depth, maximum depth, cross-sectional
area, and valley beltwidth. Mass wasting of cohesive stream channel sediment was influenced by groundwater discharge and produced
turbid waters in the upper Nemadji River. 相似文献
11.
钱塘江南岸ＳＥ２孔晚第四纪以来沉积物粒度特征及环境演化 总被引：3，自引：0，他引：3
利用钱塘江南岸萧山地区SE2孔的粒度资料,分析了粒度参数、频率分布曲线和概率累积曲线的
特征,并结合沉积物的岩性、沉积构造和有孔虫的分布特点,探讨了该区自晚第四纪以来的沉积环境演化。结
果表明,晚第四纪以来,钱塘江南岸地区依次接受了河床相、河漫滩相、潮坪相、近岸浅海相和河口湾相5种
沉积。河床相沉积物以砂砾为主,粒度参数变化较大,概率分布曲线为3段式,频率分布曲线为不对称的双峰
式,主要发育块状层理,生物化石稀少。河漫滩相以细砂、粉砂级沉积物为主,频率分布曲线为单峰式,富含
生物壳体碎屑和植物根茎。潮坪相沉积物表现为粉砂和黏土互层沉积,粒度参数变化频繁,频率分布曲线多为
双峰式,韵律层理发育。近岸浅海相沉积物主要为淤泥质黏土,粒度参数稳定,概率分布曲线为2段式,以悬
浮组分为主,频率分布曲线为单峰式,有孔虫含量丰富。河口湾相沉积物以粉砂和细砂组成的韵律性沉积为主,
粒度参数富于变化,概率分布曲线为3段式,频率分布曲线为双峰式。 相似文献
12.
The present work deals with meandering and bank erosion of the River Nile of Egypt and its environmental impact between Sohag and El-Minia, Egypt. The study depends on using Landsat imagery acquired on 1987–2000 and field observations. Field observations, remote sensing, and GIS analysis and sinuosity index were used in this study to investigate river meandering and the associated processes of erosion of river bank and islands, deposition of sediments and formation of new islands. The analysis of Landsat imagery revealed the migration of river course with time and space. Some islands disappear completely in the study area whereas new islands appear in other places. The lateral erosion on the river banks led to a decrease in agricultural lands bordering the river banks and decrease in the areas of the river islands which in turn reduces the agricultural production. Depositional processes create new floodplains on the convex sides of the river course and new islands and sand bars. Protection methods are recommended to protect the river bank from further movement and erosion. The present conditions of river meandering and the associated processes of erosion and deposition accelerated with human activities have its impact on the environment. The most prominent hazard problem is reduction of agricultural lands and loss of property as well as navigation problems. River control is recommended to weaken the secondary currents created by the river bends. It is recommended to regularly monitor the river banks and islands and measure the rates of erosion and deposition. Sand bars and subsurface islands should be monitored and identified with flash lights to mitigate navigation problems. 相似文献
13.
Shirin Mohammadkhan Hasan Ahmadi Mohammad Jafari 《Arabian Journal of Geosciences》2011,4(1-2):331-338
Soil erosion is the dominating factor of damaging roads in Iran. Roads are a critical component of civilization. Developing and maintaining the economic activity that is vital for the quality of modern life would be difficult without roads. Accelerated erosion and increased sediment yields resulting from changes in land use are critical environmental problems, and one of the important changes is road construction. Construction and condition of roadways are associated with direct and indirect impacts on soil erosion. This paper presents the relationship between soil erosion and some characteristics such as distance to roadway, slope, and parent material in Latian Watershed, Tehran Province, Iran. Soil erosion map was interpreted using aerial photos and GIS technology. Buffer zones, subdivided into 12 strips, each 0.2 km wide, which were located alongside roadway. The distribution patterns of various types of erosion were also identified by GIS by overlaying road buffer strips and soil erosion map. The results show that soil erosion landform such as land slide, badland, bank erosion, channel erosion, etc. found in buffer zones along both sides of roads. 相似文献
14.
John P. Hoffmann Donald R. Pool A. D. Konieczki Michael C. Carpenter 《Hydrogeology Journal》1998,6(3):349-364
Land subsidence in the form of sinks has occurred on and near farmlands near Tucson, Pima County, Arizona, USA. The sinks
occur in alluvial deposits along the flood plain of the Santa Cruz River, and have made farmlands dangerous and unsuitable
for farming. More than 1700 sinks are confined to the flood plain of the Santa Cruz River and are grouped along two north-northwestward-trending
bands that are approximately parallel to the river and other flood-plain drainages. An estimated 17,000 m3 of sediment have been removed in the formation of the sinks. Thirteen trenches were dug to depths of 4–6 m to characterize
near-surface sediments in sink and nonsink areas. Sediments below about 2 m included a large percentage of dispersive clays
in sink areas. Sediments in nonsink areas contain a large component of medium- to coarse-grained, moderately to well sorted
sand that probably fills a paleochannel. Electromagnetic surveys support the association of silts and clays in sink areas
that are highly electrically conductive relative to sand in nonsink areas. Sinks probably are caused by the near-surface process
of subsurface erosion of dispersive sediments along pre-existing cracks in predominantly silt and clay sediments. The pre-existing
cracks probably result from desiccation or tension that developed during periods of water-table decline and channel incision
during the past 100 years or in earlier periods.
Submitted, April 1997 · Revised, November 1997 · Accepted, April 1998 相似文献
15.
本文主要采取历史水下地形和水位数据分析、干流河槽现场测量、室内测试和综合评价等方法对重大水利工程影响长江中下游干流河槽和岸线进行了分析和研究,取得如下新进展：（1）创新构建了一套多模态传感器系统,实现陆上和水下一体化水动力、沉积和地貌特征测量与数据采集。（2）调查研究发现,长江干流河槽冲刷强烈,岸线窝崩、条崩发育。（3）悬沙和床沙粗化,河床阻力下降,发育侵蚀型链珠状沙波,长江大桥主桥墩冲刷严重。（4）潮区界显著上移,潮区界变动河段地貌发生重要变化。在此基础上,研究认为应该加强长江中下游干流河槽、沿岸高陡岸坡、支流入汇干流河口、崩岸以及跨江大桥桥墩冲刷等调查、监测和成因机理分析。上述研究成果对长江岸滩防护和修复、航道整治、沿岸防洪、长江大桥桥墩维护等具有重要意义。 相似文献
16.
Hema Achyuthan Nagalakshmi Thirunavukarasu 《Journal of the Geological Society of India》2009,73(5):683-696
In this paper we present Quaternary stratigraphy of the area around Chennai based on archaeological findings on the ferricrete
surface, geomorphological observations supplemented by radiocarbon dating. The coastal landscape around Chennai, Tamil Nadu,
has preserved ferruginised boulder gravel deposits, ferricretes and fluvial deposits of varying thickness. The area studied
is approximately 150 km east to west and 180 km north to south with a broad continental shelf towards the seaward. Several
rivers enter the Bay of Bengal along its shores like the Koratallaiyar, Cooum and the Adyar. Precambrian charnockite and Upper
Gondwana sandstone and shale bedrock rim the shelf margin. For the most part, the Upper Pleistocene-Holocene fluvial sediments
overlie an erosion surface that has cut into older Pleistocene sediments and ferricrete surface. Incised valleys that cut
into this erosion surface are up to 5–6 km wide and have a relief of at least 30 m. The largest valley is that cut by the
Koratallaiyar River. Holocene sediments deposited in the incised valleys include fluvial gravels, early transgressive channel
sands and floodplain silts. Older Pleistocene sediments are deposited before and during the 120-ka high stand (Marine isotope
stage 5). They consist of ferricretes and ferricrete gravel formed in nearshore humid environments. Muddy and sandy clastic
sediments dated to the ca. 5 ka highstand suggest that the climate was semi arid at this time with less fluvial transport.
The coarsening up sequence indicates deposition by high intensity channel processes. Pedogenic mottled, clayey silt unit represents
an important tectonic event when the channel was temporarily drained and sediment were sub aerially exposed. Uplift of the
region has caused the local rivers to incise into the landscape, forming degradation terraces. 相似文献
17.
在弯道水槽中开展6组试验,分别用非黏性土及黏性土填筑河床,研究相同水力作用下近岸河床组成对黏性岸坡崩塌的影响规律。研究发现,在试验给定的岸坡及河床组成情况下,非黏性河床凹冲凸淤且总体表现为淤积,近岸河床及凹岸岸坡冲刷强度大,凸岸附近床面上泥沙掺混较明显;黏性河床及凹岸岸坡均被冲刷,河床主流区冲刷强度比近岸河床及凹岸岸坡大。相较于黏性河床,非黏性河床近凹岸处较易冲刷,水流结构重新调整,凹岸坡脚处水流流速及紊动能可增至2倍左右,环流强度可增至11倍,加速了岸坡崩塌及崩塌体的分解输移;非黏性河床近凹岸坡脚处变形以及凹岸岸坡崩塌量均相对较大,岸坡崩塌强度为河床淤积强度的2~4倍,崩塌物质可充分补给河床的泥沙来源;经水力冲刷后非黏性河床组成情况下形成的河道滩槽高差相对较小,河道横断面相对宽浅。 相似文献
18.
在弯道水槽中展开系列试验,研究水力冲刷过程中均质土岸坡冲刷崩塌输移与河床冲淤过程及其影响因素。该过程及变化特征可描述为:水下坡面侵蚀及坡脚淘刷导致岸坡失稳崩塌;暂时堆积在凹岸坡脚处的崩塌体加剧附近水流紊动程度利于其输运与分解;分解后较粗的颗粒随弯道螺旋流以推移质形式被输移至下游凸岸落淤,较细的颗粒大部分都随水流以悬移质形式被携带至下游出口;水流结构随岸坡及河床变形而调整;如此循环往复。试验成果进一步表明:冲刷状态下,试验材料黏性越小、近岸流速越大、作用时间越长,岸坡冲刷崩塌量及河床冲刷量都越大;同条件下岸坡冲刷崩塌总量大于河床冲刷总量,且河床相对冲刷率随岸坡冲刷崩塌量的增大而减小,数值范围为0.40~0.92。 相似文献
19.
黄河下游具有辫状河流、弯曲河流和微弯顺直河流3种河型，从横断面上可见，辫状河段的河道变化最频繁且最不稳定，微弯顺直河段最稳定；而弯曲河段明显向上游延伸，随着输沙量在各河段的阶段性变化，冲淤 状况在各河段也表现出阶段性，但加积升高是各河段发展的总趋势，从河相关系可见，弯曲河段和微弯顺直河段基本相似，但和辫状河段有着本质的区别。辫状河段的演变主要受到中上游来水来沙等自然因素的综合影响，但其更大范围的摆动仍然受到人为作用的影响；弯曲河段是河流自动调整的必然结果，两岸河堤对它的形成及向上游的延伸具有促进作用，但对它侧向迁移的特性具有较大的限制作用；而微弯顺直河段是人力强迫下河流局部调整的产物。 相似文献
20.
长江沉积物环境地球化学特征及生态风险评价 总被引：1，自引：0，他引：1
为了进行长江流域沉积物生态风险评价,对长江流域干流以及主要支流的沉积物统一进行采样分析。首先对其元素的组成特征及重金属元素的富集特征进行分析。常量元素含量在流域空间上的变化主要受其携带矿物含量变化的影响;Cu、Pb、Cd、As、Hg 5种微量元素富集程度较大,存在异常。同时采用潜在生态风险指数法对长江沉积物Cr、Mn、Co、Ni、Cu、Zn、Pb、Cd、As、Hg 10种元素进行了评价研究。结果表明,潜在生态风险指数较大的地区分布在湖南湘江、安徽铜陵等地区,中等的地区分布在四川、重庆及江西等地区,这些潜在污染指数与矿产的开采冶炼以及工业的布局有一定的关系,很大程度上是由人为因素造成的。从元素的潜在污染程度看,长江流域Cd、As、Hg污染程度较重,Cu、Zn、Pb次之,而Cr、Mn、Co、Ni基本没有污染。本研究为探讨长江流域沉积地球化学过程和环境保护提供了科学依据。 相似文献