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1.
The areal distribution of stream sediment and source-rock heavy mineralogy was studied to determine the mineralogical relations between source and derived sediment in the Piney Creek drainage basin of Wyoming. Heavy-mineral distribution in the streams was characterized using factor analysis. The results of analyses show that for an actively degrading stream system, the heavy-mineral composition of stream sediment is controlled to a considerable extent by the composition of local sediment sources and by continuous addition of detritus from bank cutting. Only the most common minerals from upstream sources persist as statistically significant variables downstream. In some cases the heavy-mineral mineral composition of stream sediment can be controlled by comparatively few, or volumetrically rare source rocks, even though more abundant source rocks supply a wide range of heavy minerals. Specific drainage configurations such as lakes and proximity of streams to major sediment sources significantly modify sediment mineralogy immediately downstream. 相似文献
2.
为确定黄土缓坡片蚀过程中侵蚀限制条件的变化及水力参数的适宜性,采用模拟降雨试验,在60 mm/h雨强、3种坡度（7.5°、10°、15°）和2种坡长（5 m和10 m）条件下,验证含沙量作为表征参量判定片蚀过程侵蚀限制条件的可行性,提出检验水力参数与产沙量作用关系适宜性的评价方法。结果表明:①依据含沙量随径流的变化规律,片蚀过程依次经历输沙能力限制阶段、剥蚀能力限制阶段Ⅰ和剥蚀能力限制阶段Ⅱ共3个侵蚀阶段,其中剥蚀能力限制阶段Ⅰ的侵蚀量占绝对优势。②从水力参数的适宜性来看,径流功率和雷诺数均能很好地表征与产沙量的关系,径流剪切力和弗劳德数则不能有效反映与产沙量的关系。③在不同侵蚀限制阶段,径流功率和雷诺数与产沙量的作用关系是不同的。输沙能力限制阶段和剥蚀能力限制阶段Ⅱ时,径流功率和雷诺数与产沙量分别呈指数关系和线性正相关关系;剥蚀能力限制阶段Ⅰ时,该2种水力参数均与产沙量呈线性负相关关系,但作用关系不唯一,且存在雷诺数临界值,即在输沙能力限制阶段和剥蚀能力限制阶段Ⅱ,径流功率和雷诺数与产沙量的作用关系不受坡长效应影响;在剥蚀能力限制阶段Ⅰ,需要同时考虑坡长和雷诺数临界值的共同影响。该研究结果可为深入理解片蚀过程的复杂性提供参考依据。 相似文献
3.
为探明锥状工程堆积体坡面薄层水流剥蚀率与水力要素之间的关系, 室内模拟赣北红土区散乱锥状工程堆积体。通过人工降雨试验, 设计4种降雨强度(1.0~2.5mm/min)和3种砾石含量(10%~30%)完全组合。采用灰色关联度分析法, 评估坡面水力参数与土壤剥蚀率之间的关联度。结果表明:① 在试验条件下, 坡面水流功率与土壤剥蚀率呈幂函数关系;② 当堆积体砾石含量一定时, 以降雨强度为变量能反映堆积体坡面水力参数与土壤剥蚀率之间的关联度;③ 当降雨强度一定时, 大雨强下(≥1.5mm/min)堆积体砾石含量不宜作为灰色关联度分析的变量。综上所述, 水流功率是描述赣北红土区锥状工程堆积体侵蚀过程的最佳水力参数, 可用于建立堆积体侵蚀物理模型。 相似文献
4.
在弯道水槽中展开系列试验,研究水力冲刷过程中非粘性岸坡冲刷崩塌与河床冲淤交互作用过程及其影响因素,进一步分析塌岸淤床泥沙贡献率。试验成果表明,水流冲刷过程中岸坡破坏是水流淘刷岸坡坡脚、岸坡崩塌及崩塌体淤积坡脚并在河床上输移掺混的交互作用反复循环过程。塌岸淤床模式及掺混程度与近岸流速、主流贴岸程度、水位及河床边界条件等关系密切。近岸流速越大、水位越高,岸坡总冲刷坍塌量、河床总淤积量以及河床累计淤积率也越大,稳定后的岸坡越趋平缓;河床可动程度越大,岸坡总冲刷坍塌量及其在河床上的总淤积量也越大,但河床累计淤积率却越小;水位越高,在弯道段等横向输沙强度较大的地方,岸坡冲刷崩塌体与河床发生掺混的程度也越大。 相似文献
5.
A Comparison of Fluvial Sediment Phosphorus (P) Chemistry in Relation to Location and Potential to Influence Stream P Concentrations 总被引：3，自引：0，他引：3
Fluvial sediments are subject to cyclic submersion during changes in stream flow, which can affect their phosphorus (P) sorptive capacity. As fluvial sediments play a major role in determining P concentrations in stream flow, we compared the P chemistry of exposed stream bank and submerged bed sediments from an agricultural catchment in central Pennsylvania, USA. Total P concentration was greater in bank (417 mg kg-1) than bed sediments (281 mg kg-1), but because bed sediments contained more sand-sized material, they could release more P and support a higher solution P concentration (0.043 mg l-1) than bank sediments (0.020 mg l-1). Phosphorus release was a function of Mehlich-3 soluble Fe in stream sediments (r > 0.65), reflecting redox processes in the fluvial system. In contrast, P sorption maxima of bank and bed sediments were related to Mehlich-3 soluble Al (r > 0.78) and organic matter concentration (r > 0.79). Overall, our research suggested that erosion of bank sediments should contribute less P and may be a sink for P in the stream system compared with resuspension of bed sediment. However, bank sediments may have the potential to be a large source of P in downstream reservoirs or lakes, where increased microbial activity and reducing conditions may solubilise sediment-bound P. 相似文献
6.
Many lowland stream channels have dramatically widened over the last two centuries. There has been considerable debate about whether this widening was caused by an unusually large flood, by a series of large floods, or by decreased bank stability caused by clearing of riparian vegetation. The relative effects of floods and vegetation can be disentangled in southeastern Australia where streams have undergone both clearing of bank vegetation, and decadal sequences of relatively higher and lower flood magnitude and frequency. Archival aerial photographs of the Nepean River, in southeastern Australia, suggest that banks did not erode during periods of low flood magnitude (drought-dominated regime: from 1901–1949) whether they were cleared or not. However, during periods of flood-dominated regime (1950 to 1970s) only cleared stream banks eroded. Thus, on the upper Nepean River, clearing alone was insufficient to trigger erosion by small floods, and even large floods were unable to erode vegetated banks. The conclusion is that substantial channel widening in this river required both clearing of bank vegetation, and periods of unusually large and frequent floods. This conclusion is supported by geomechanical modelling that examine the reduction in bank shear strength arising from the loss of tree-root reinforcement. The modelling also suggests that bank instability arising from devegetation amplifies the potential for bank failure during the drawdown phase of a flood, leading to channel widening. 相似文献
7.
A case study of long-term field performance of check-dams in mitigation of soil erosion in Jiangjia stream,China 总被引：3，自引：0，他引：3
This paper examines the long-term field performance of the check-dams in mitigation of soil erosion in the Duozhao catchment
of Jiangjia stream, southwest China. Since their construction between 1979 and 1982, the check-dams have been functioning
effectively. The examination is made via comparisons between the environmental conditions of the Duozhao catchment with its
adjacent Menqian catchment in the stream, because no check dams were constructed in the Menqian catchment. The examination
is based on recent field investigations and aerial photograph analyses, and covers four aspects: (a) bed gradients of catchment
channels; (b) stability of bank slopes; (c) rates of land erosion; and (d) vegetations on bank slopes. The field data demonstrate
that the check-dams have had the following good functions for mitigation of soil erosion: (1) restricting the channel depth
and lateral erosions, (2) protecting the channel erosion base, (3) reducing the bed gradients of debris-flow channels, (4)
fixing the channel bed, (5) stabilizing the bank slopes, as well as (6) facilitating the growth of vegetations.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
8.
Semi-two-dimensional numerical model for river morphological change prediction: theory and concepts 总被引：2，自引：2，他引：0
Tew-Fik Mahdi 《Natural Hazards》2009,49(3):565-603
This paper presents a new numerical model for river morphological predictions. This tool predicts vertical and lateral cross-section
variations for alluvial rivers, which is an important task in predicting the associated hazard zone after a flood event. The
Model for the HYdraulics of SEdiments in Rivers, version 1.0 (MHYSER 1.0) is a semi-two-dimensional model using the stream
tubes concept to achieve lateral variations of velocity, flow stresses, and sediment transport rates. Each stream tube has
the same conveyance as the other ones. In MHYSER 1.0, the uncoupled approach is used to solve the set of conservation equations.
After the backwater calculation, the river is divided into a finite number of stream tubes of equal conveyances. The sediment
routing and bed adjustments calculations are accomplished separately along each stream tube taking into account lateral mass
exchanges. The determination of depth and width adjustments is based on the minimum stream power theory. Moreover, MHYSER
1.0 offers two options to treat riverbank stability. The first one is based on the angle of repose. The bank slope should
not be allowed to increase beyond a certain critical value supplied to MHYSER 1.0. The second one is based on the modified
Bishop’s method to determine a safety factor evaluating the potential risk of a landslide along the river bank. 相似文献
9.
Site assessment and monitoring data were analyzed for 26 stream restoration projects in North Carolina where the channel was
reconfigured. Post-project changes in channel capacity were highly variable from site to site, but more than 60% of the projects
underwent, on average at a given site, at least a 20% change in channel capacity. An analysis of site and basin geomorphology
revealed that large post-construction adjustments were associated with highly dynamic stream channels characterized by a combination
of high sediment transport capacity, large sediment supply, and/or easily eroded bank materials. In-stream structures along
dynamic, reconfigured channels also exhibited high incidences of damage. Thus, the design and construction of channels in
a state of equilibrium, which do not exhibit excessive erosion or deposition along highly dynamic rivers is currently problematic.
In light of these findings, a conceptual framework based on geomorphic parameters is put forth to assess the likelihood of
project success early in the design process to (1) eliminate high risk sites from consideration of channel reconfiguration
and (2) improve upon the implemented management strategies that are ultimately used. It is also argued that where space permits
an enhanced natural channel, adjustment approach is likely to be more effective than projects based on natural channel design. 相似文献
10.
This study assesses a simple sediment source tracing method using major- (Al, Ca, Fe, K, Mg, Mn, Na, P, Si, Ti) and trace-element (Ba, Be, Ce, Co, Cr, Mo, Nd, Pb, Sr, Th, V, Y, Zn) signatures of stream suspended particulate matter (SPM), bed sediments and soils in a small agricultural catchment in NE Scotland. Whilst most erosion studies characterise the large amounts of material mobilised at the highest flows, this study aimed to assess properties of sediments during moderate to low flow periods. These occur more frequent than intense storms and are important in linking stream sediments, near-channel sources and aquatic ecosystem impacts. Data were transformed by multivariate statistical methods to compare elemental signatures of SPM (ranging from 3 to 53 mg L−1 in the stream) and stream bed sediments with a limited number of near-channel source soils. Increased concentrations of Ce, Nd, Th and Y in subsoils contributed to the ability to discriminate between surface fieldslope and stream bank erosion sources. Stream bed sediments showed close matches with compositions of stream bank and arable surface soils, but signatures of SPM differed greatly from any of the sources. Large concentrations of Cr, Pb and Zn in SPM, particularly during summer (677, 177 and 661 mg kg−1, respectively) exceeded water quality standards and were linked to an accumulation of trace elements associated with biological material. The potential for within-stream alteration of SPM in relation to erosion sources was confirmed by changes in the nature of the SPM organic matter observed by IR spectroscopy. Thus the potential is shown for multi-element signatures to give information on catchment sediment sources to aid land management decisions, given careful consideration of the effects of in-stream alteration of eroded material. However, this combined information may be beneficial to process understanding linking land use and stream ecosystems at critical ecological periods. 相似文献
11.
In Scandinavia, most fluvial erosion takes place in the Quaternary glacial overburden at a restricted number of small source areas along individual drainage channels. As a consequence, a sample of active stream sediment is representative of only a very limited portion of the drainage area. This restriction makes stream sediment less reliable for regional exploration than generally expected. Overbank (levee or river-plain) sediment produced during large floods is an alternate more representative sampling medium. The sediment suspended during a flood has a much more widespread origin, and when the load is deposited upon the flood plain, nearly horizontal strata are formed and preserved at levels above the ordinary stream channel. A composite sample through a vertical section of such strata represents a great number of sediment sources that have been active at different times and forms an integrated sample of the entire catchment area. Because young sediments overlay older, the uppermost layers will be contaminated by pollutants in industrialized regions, but those at depth may remain pristine and will to a greater extent reflect the natural pre-industrial environment. In regional geochemical mapping, overbank sediment can be sampled at widely spaced sites, keeping costs per unit area low. Examples from Norway (1 sample station per 500 km2) show that overbank sediment produces broad geochemical patterns with high contrasts reflecting the bedrock geochemistry. Some patterns agree with known geological units and metallogenic provinces, but hitherto unknown major structures have also been indicated. A large Mo-deposit missed by a traditional stream survey is readily detected in the overbank sediment. It is concluded that overbank sediment is a promising alternate sample medium that should be tested in other physiographic regions. 相似文献
12.
Beach erosion has advanced in many countries of the world, especially in Japan, because of a decrease in sediment sources from rivers and a lack of longshore sediment transport from the adjacent coasts due to coastal structures. The former cause concerns the reduction of river deltas due to a decrease in sediment input from the river. Two timescales important in beach erosion, a longer timescale which concerns a change in the location of the river mouth, and a shorter one which is due to a decrease in longshore sediment transport, are discussed in the formation and reduction of the delta of the Kurobe River. Based on these timescales, beach erosion control is considered. 相似文献
13.
北支河槽容积变化是北支河道演变趋势在定量上的直接表现,河道边界条件和河床泥沙运动是影响河槽容积变化的主要因素。收集1986—2013年长江口北支河道年实测地形资料,利用GIS技术建立不同时期水下数字高程模型,进行北支河槽容积变化和河床冲淤变化特征分析。结果表明,北支岸线圈围和泥沙淤积导致了1986年以来河槽容积萎缩。北支河槽0m线以下容积共减少约7.110亿m3,岸线圈围引起河槽容积减少4.000亿m3,占比56.3%;泥沙淤积引起的河槽容积减少3.110亿m3,占比43.7%。具体而言,北支上段河槽容积萎缩主要是泥沙淤积所致,其航道开发综合利用应遵循上段的泥沙运动规律特点;中段则是边滩圈围和沙洲并岸引起,边界调整后束流作用加强,河床冲刷,断面形态调整后水深条件更加有利于中段的航道利用开发;下段是泥沙淤积和边滩圈围共同影响所致,泥沙淤积影响略大,但下段沿北岸-5m深槽始终存在且稳定,具备航道开发利用的河势基础,且南侧河道边界仍具有可圈围的余地。 相似文献
14.
Jinxi Song Weiwei Jiang Shaofeng Xu Guotao Zhang Liping Wang Min Wen Bo Zhang Yuanyuan Wang Yongqing Long 《Hydrogeology Journal》2016,24(8):2049-2062
Recognizing the heterogeneity of hydraulic conductivity and hyporheic flow is critical for understanding contaminant transfer and biogeochemical and hydrological processes involving streams and aquifers. In this study, the heterogeneity of hydraulic conductivity and Darcian flux in a submerged streambed and its adjacent exposed stream banks were investigated in the Beiluo River, northwest China. In the submerged streambed, Darcian flux was estimated by measurement of vertical hydraulic conductivity (K v) and vertical head gradient (VHG) using in-situ permeameter tests. On exposed stream banks, both horizontal hydraulic conductivity (K h) and K v were measured by on-site permeameter tests. In the submerged streambed, K v values gradually decreased with depth and the higher values were concentrated in the center and close to the erosional bank. Compared to the exposed stream banks, the K v values were higher in the streambed. From stream stage to the topmost layer of tested sediment, through increasing elevation, the K h values increased on the erosional bank, while they decreased on the depositional bank. The values of VHG along the thalweg illustrate that downwelling flux occurred in the deepest area while upwelling flux appeared in the other areas, which might result from the change of streambed elevation. The higher value of the Darcian flux in the submerged streambed existed near the erosional bank. 相似文献
15.
贵州西部龙场地区水系沉积物Pt、Pd异常源地球化学示踪的初步研究 总被引：8，自引：1，他引：8
以贵州龙场地区水系沉积物中的Pt、Pd异常为研究对象，选择相容性接近的7对元素比值Cr/Ni、Nb/Ta、Pd/Pt、Rb/Cs、Sr/Ba、Th/U和Zr/Hf以及CaO、TFe2O3作为地球化学示踪指标，对龙场地区水系沉积物的物质来源组成进行了示踪探讨。结果表明：（1）龙场地区水系沉积物的物质来源主要为玄武岩风化产物，其中的高含量Pt、Pd是对玄武岩层中Pt、Pd高背景的继承和进一步浓缩富集；（2）根据对分布在灰岩区的水系沉积物物质来源的地球化学示踪研究，推测部分样品的物质来源应为玄武岩和灰岩风化产物；（3）根据对红岩村的水系沉积物物质来源的示踪研究，推断有热液活动和基性－超基性侵入体的物质成分，预测该地区具有一定的找矿远景。 相似文献
16.
Liping Wang Weiwei Jiang Jinxi Song Xinyi Dou Hongtao Guo Shaofeng Xu Guotao Zhang Ming Wen Yongqing Long Qi Li 《Hydrogeology Journal》2017,25(5):1283-1299
Investigating the interaction of groundwater and surface water is key to understanding the hyporheic processes. The vertical water fluxes through a streambed were determined using Darcian flux calculations and vertical sediment temperature profiles to assess the pattern and magnitude of groundwater/surface-water interaction in Beiluo River, China. Field measurements were taken in January 2015 at three different stream morphologies including a meander bend, an anabranching channel and a straight stream channel. Despite the differences of flux direction and magnitude, flux directions based on vertical temperature profiles are in good agreement with results from Darcian flux calculations at the anabranching channel, and the Kruskal-Wallis tests show no significant differences between the estimated upward fluxes based on the two methods at each site. Also, the upward fluxes based on the two methods show similar spatial distributions on the streambed, indicating (1) that higher water fluxes at the meander bend occur from the center of the channel towards the erosional bank, (2) that water fluxes at the anabranching channel are higher near the erosional bank and in the center of the channel, and (3) that in the straight channel, higher water fluxes appear from the center of the channel towards the depositional bank. It is noted that higher fluxes generally occur at certain locations with higher streambed vertical hydraulic conductivity (K v) or where a higher vertical hydraulic gradient is observed. Moreover, differences of grain size, induced by stream morphology and contrasting erosional and depositional conditions, have significant effects on streambed K v and water fluxes. 相似文献
17.
非均质岸滩广泛分布于冲积河流中,其侧蚀过程沿垂向具有分层特点。基于全三维水沙模型及河岸侧蚀坍塌力学模式,提出动态网格跟踪技术,构建了非均质岸滩侧蚀沿垂向差异的三维动力学模拟方法。以连续弯道概化水槽为例,模拟分析了非均质河岸侧蚀过程中三维水流结构的响应特征。研究结果表明:坡脚冲刷后,底部主流向凹岸偏移,在已有弯道环流的基础上,于坡脚处出现一反向次生流;上部粘性土层坍塌后,崩塌土体堆积于坡脚处,上部主流明显左偏,下部次生流消失;随着坡脚堆积体的冲刷搬运,下部主流进一步向凹岸偏移;如此循环,主流不断向凹岸偏移,致使岸坡持续崩退、河道摆动。 相似文献
18.
山东莒县果庄地区位于华北陆块鲁西隆起汞丹山断隆(次级隆起)构造单元,区内构造复杂,岩浆活动强烈,区域成矿条件优越。为实现区内找矿突破,在区内进行了系统的1：5万水系沉积物测量和1：1万激电中梯测量。本次研究在成矿地质背景研究的基础上,对莒县果庄地区物化探异常特征进行综合分析,结果表明区内水系沉积物测量金异常富集中心明显,且异常高值出露位置与土壤剖面测量金异常高值出露位置基本吻合;激电异常总体分布与断裂构造和沂水岩群分布相一致;激电测深具有明显的高极化异常体;土壤剖面测量金异常与激电中梯异常位置基本对应。据此认为莒县果庄地区具有较好的找金矿潜力,岩体接触带及断裂构造发育带是下一步找矿重点方向。 相似文献
19.
利用水系沉积物地球化学数据判别浅覆盖区岩性与构造--欧氏距离法 总被引：3，自引：2，他引：3
针对浅覆盖区地质调查困难，缺少可对比已知资料的实际问题，这里以大兴安岭阿龙山地区1：250000水系沉积物资料为例，给出了浅覆盖区岩性和构造识别的一种方法。该方法依据水系沉积物对原岩的继承性，以不同岩性所对应的典型土壤为已知样品，采用欧氏距离作为分类指标，将研究区划分为不同的岩性类。得到的区域地球化学分类图反映了一定的岩性分布及构造特点，为区域地质调查提供了线索。 相似文献
20.
Sediment production and transport in a proglacial stream: Hilda Glacier, Alberta, Canada 总被引：2，自引：0，他引：2
KATHLEEN M. HAMMER NORMAN D. SMITH 《Boreas: An International Journal of Quaternary Research》1983,12(2):91-106
Hilda Glacier, a small cirque glacier in the Canadian Rocky Mountains, yields two principal types of sediment: ablation till, deficient in fine material and produced by rockfalls and avalanches falling on to the glacier surface, and basal lodgement till, rich in fines and formed mainly by subglacial erosion. Recent recession from its Neoglacial maximum has exposed large areas of basal till with thin veneers of ablation till which, when combined with present subglacial and supraglacial debris, provide abundant material for erosion and transport by the mcltwatcr stream. Sediment transport measurements over two summers (1977–1978) showed that bed load and suspended load occur in approximately equal proportions and that dissolved loads are minor. Local source variations, especially bank slumps, are a major cause of scatter in sediment rating curves. Suspended-sediment concentrations are greater early in the melt season due to availability of loose sediment produced by freezing and thawing. Other contributors to scatter in suspended-sediment rating curves include rain showers and diurnal hysteretic effects. Although the distinction between bed load and suspended load is never sharp, available data suggest that the sand/ gravel grain-size boundary (-1ø) approximates the suspendcd-load/bed-load division for characteristic Hilda flows transporting gravel. This approximation, combined with till grain-size analyses, suspended-sediment measurements, and spatial distributions of till types, leads to the following computations of fluvial sediment sources: for suspended load - 6% supraglacial, 47% subglacial, 47% channel banks; for bed load - 46% supraglacial, 27% each subglacial and channel banks. Supraglacial debris provides only about one-fourth of all fluvial sediment, but nearly half of the bed load. 相似文献