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1.
依据三峡水库修建以前的资料,运用数理统计方法对含沙量和悬沙粒径变化对长江宜昌-汉口河段年冲淤量的影响进行研究,以期为三峡水库修建以后库下游河道冲淤特性的预测提供参考。建立了1980-1997年间宜昌-汉口#河段年冲淤量与宜昌站年均含沙量C宜昌之间的回归方程,据此估算出使宜昌-汉口#河段处于不冲不淤状态的宜昌站临界年均含沙量为0.734 kg/m3。以宜昌-汉口冲淤量作为因变量,以宜昌站的含沙量、悬沙中径D50、最大流量和三口分流比作为影响变量,建立了多元回归方程。基于1980-1997年资料的方程表明,宜昌站含沙量越高,悬沙中径越粗,宜昌站洪水流量越大,宜昌-汉口河段年淤积量越大;三口分流比越小,宜昌-汉口河段年淤积量越大。 相似文献
2.
In this study, non-equilibrium transport of suspended sediment from one equilibrium state to another is investigated. Based on a convective-diffusion equation, a numerical model for flow with suspended sediment is developed by considering the effect of concentration-dependent settling velocity. The numerical model is validated by comparing analytical solutions and experimental results. The concentration profiles, mean concentrations and distance necessary to reach a new equilibrium state are examined by comparing them with the results of constant settling velocity. For a high concentration flow, the results indicate that evident differences between the above three indicators can be determined with and without concentration-dependent settling velocity. Additionally, the effects of concentration-dependent settling velocity are sensitive to the sediment mobility parameter (or Rouse number), although they are nearly independent of the diffusion Reynolds number. 相似文献
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A three-dimensional (3-D) suspended sediment model was coupled with a 3-D hydrodynamic numerical model and used to examine the spatial and temporal distribution of suspended sediments in the Satilla River estuary of Georgia. The hydrodynamic model was a modified ECOM-si model with inclusion of the flooding-drying cycle over intertidal salt marshes. The suspended sediment model consisted of a simple passive tracer equation with inclusion of sinking, resuspension, and sedimentation processes. The coupled model was driven by tidal forcing at the open boundary over the inner shelf of the South Atlantic Bight and real-time river discharge at the upstream end of the estuary, with a uniform initial distribution of total suspended sediment (TSS). The initial conditions for salinity were specified using observations taken along the estuary. The coupled model provided a reasonable simulation of both the spatial and temporal distributions of observed TSS concentration. Model-predicted TSS concentrations varied over a tidal cycle; they were highest at maximum flood and ebb tidal phases and lowest at slack tides. Model-guided process studies suggest that the spatial distribution of TSS concentration in the Satilla River estuary is controlled by a complex nonlinear physical process associated with the convergence and divergence of residual flow, a non-uniform along-estuary distribution of bottom stress, and the inertial effects of a curved shoreline. 相似文献
5.
Distribution of suspended sediment concentration in wide sediment‐laden streams: A novel power‐law theory 
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下载免费PDF全文 Francisco Nicolás Cantero‐Chinchilla Oscar Castro‐Orgaz Subhasish Dey 《Sedimentology》2016,63(6):1620-1633
The diffusion equation of suspended sediment concentration in a wide sediment‐laden stream flow is dependent on the vertical gradient of streamwise velocity and the sediment diffusivity. This study aims at investigating the influence of the streamwise velocity laws on the suspended sediment concentration distributions, resulting from the solution of the diffusion equation. Firstly, the sediment concentration distributions are obtained numerically from the solution of the diffusion equation using different velocity laws and compared with the experimental data. It is found that the power‐law approximation produces good computational results for the concentration distributions. The accuracy of using a power‐law velocity model is comparable with the results obtained from other classical velocity laws, namely log‐law, log wake‐law and stratified log‐law. Secondly, a novel analytical solution is proposed for the determination of sediment concentration distribution, where a power‐law, wall‐concentration profile is coupled with a concentration wake function. The power‐law model (for velocity and concentration) is calibrated using the experimental data, and then a generalized wake function is obtained by choosing a suitable law. The developed power‐law model involving the wake function adjusted by an exponent predicts the sediment concentration distributions quite satisfactorily. Finally, a new explicit formula for the suspended‐load transport rate is derived from the proposed theory, where numerical computation of integrals, as needed in the Einstein theory, is avoided. 相似文献
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在前人研究成果的基础上,根据挟沙水流任一粒径组泥沙在输移过程中质量守恒原理,建立了一维非恒定挟沙水流悬移质泥沙和床沙交换基本方程;通过引入平衡冲淤物粒径的概念,建立了河床处于淤积与冲刷时冲淤物粒径的计算公式,并提出了一套完整的一维非恒定挟沙水流悬移质泥沙和床沙交换计算方法。将该成果引入黄河下游一维扩展泥沙数学模型中,采用黄河下游1977年高含沙洪水与1999年汛后至2002年汛前冲刷系列进行了验证。结果表明,该方法能较好地模拟悬沙与床沙的交换过程,克服分组挟沙力方法的缺陷,使得非均匀沙计算理论上更加完善,应用上更加方便。 相似文献
8.
Wen−Cheng Liu 《Environmental Geology》2005,47(4):535-546
Settling velocities of suspended cohesive sediment in estuaries vary over a range of several orders in magnitude. Variations in the suspended sediment concentration are often considered as the principal cause. Turbulence and the suspended sediment concentration, as well as other factors such as salinity, dissolved organic substances, flocculation ability, and the rate of floc growth affect setting velocities. A laterally–averaged finite difference model for hydrodynamics and cohesive sediment transport is developed and applied in the Tanshui River estuary, Taiwan. The model has been calibrated and verified with water surface elevation, longitudinal velocity, salinity, and cohesive sediment measured. The overall performance of the model is in qualitative agreement with the available data. The model is used to investigate the influence of settling velocity on cohesive sediment transport dynamics. The simulation indicates that the turbidity maximum zone is near Kuan–Du. When settling velocities increase the surface cohesive sediment concentration at Kuan–Du station trends to decrease and bottom cohesive sediment concentration increases. Both surface and bottom cohesive sediment concentrations decrease at Taipei Bridge and Pa–Ling Bridge. This implies that suspended sediment advected seaward and deposited. There is consequently a net seaward flux of suspended sediment near surface, and a net landward flux near the bed. 相似文献
9.
Prediction of daily suspended sediment load using wavelet and neurofuzzy combined model 总被引：1，自引：0，他引：1
T. Rajaee Ph.D. S. A. Mirbagheri Ph.D. V. Nourani Ph.D. A. Alikhani Ph.D. 《International Journal of Environmental Science and Technology》2010,7(1):93-110
This study investigated the prediction of suspended sediment load in a gauging station in the USA by neuro-fuzzy, conjunction of wavelet analysis and neuro-fuzzy as well as conventional sediment rating curve models. In the proposed wavelet analysis and neuro-fuzzy model, observed time series of river discharge and suspended sediment load were decomposed at different scales by wavelet analysis. Then, total effective time series of discharge and suspended sediment load were imposed as inputs to the neuro-fuzzy model for prediction of suspended sediment load in one day ahead. Results showed that the wavelet analysis and neuro-fuzzy model performance was better in prediction rather than the neuro-fuzzy and sediment rating curve models. The wavelet analysis and neuro-fuzzy model produced reasonable predictions for the extreme values. Furthermore, the cumulative suspended sediment load estimated by this technique was closer to the actual data than the others one. Also, the model could be employed to simulate hysteresis phenomenon, while sediment rating curve method is incapable in this event. 相似文献
10.
A hydrologic regression sediment-yield model was established to determine the relationship between water discharge and suspended sediment discharge at the Blue Nile and the Atbara River outlet stations during the flood season. The model consisted of two main submodels: (1) a suspended sediment discharge model, which was used to determine suspended sediment discharge for each basin outlet; and (2) a sediment rating model, which related water discharge and suspended sediment discharge for each outlet station. Due to the absence of suspended sediment concentration measurements at or near the outlet stations, a minimum norm solution, which is based on the minimization of the unknowns rather than the residuals, was used to determine the suspended sediment discharges at the stations. In addition, the sediment rating submodel was regressed by using an observation equations procedure. Verification analyses on the model were carried out and the mean percentage errors were found to be +12.59 and –12.39, respectively, for the Blue Nile and Atbara. The hydrologic regression model was found to be most sensitive to the relative weight matrix, moderately sensitive to the mean water discharge ratio, and slightly sensitive to the concentration variation along the River Nile's course. 相似文献
11.
国内外河口悬沙通量研究进展 总被引：6，自引：0，他引：6
系统地介绍了国内外河口悬沙通量研究的进展,目前对于河口悬沙通量主要采用模型研究、水文学方法、机制分解、仪器直接测量等方法从理论和实际相结合的角度来进行研究。目前物理模型的研究成果比较直观,但受到模型尺度和精度等的限制,数学模型研究具有快、准的优点,可以给出令人满意的定性结果,但未能达到定量预报的程度;传统的水文学方法可以用来研究河口地区悬移质泥沙在不同动力因子作用下的输移情况;机制分解法是比较成熟和可靠的方法,但该方法与河口动力机制和泥沙输移过程结合不够;使用先进仪器进行直接测量则受到仪器精度和取样点的布设等条件的限制。因此,关于河口悬沙通量的研究还有待于深入和细化。 相似文献
12.
小浪底水库运行后,坝下游分组悬沙输移特点发生改变,不同河段冲淤过程有所差别。基于1999—2018年坝下游实测水沙资料及固定淤积断面地形数据,分析汛期分组悬沙输移的沿程调整特点,建立分组悬沙输移及河床边界条件双重影响下不同河段河床累计冲淤量的计算关系。分析结果表明：(1)汛期各组沙输沙率远小于蓄水前,且中沙输沙率降幅最大,在各水文断面平均降幅为85%;沿程上细沙输沙率基本不恢复,而中沙和粗沙恢复距离分别到利津及艾山。(2)坝下游河床持续冲刷,各河段河床组成均发生不同程度的粗化;在拦沙后期(2007—2018年),游荡段和过渡段床沙中细沙和中沙占比不足5%,对悬沙几乎无补给作用,而弯曲段床沙对中沙仍有一定的补给能力。(3)下游各河段以冲刷下切为主,但调整幅度不同,故对水流的约束能力有所差异。建立了各河段累计冲淤量与前期河相系数及进口断面分组来沙系数的经验关系,并采用2019年下游水沙数据对公式进行了初步验证,公式能合理反映断面形态与分组悬沙输移对河床累计冲淤过程的影响。 相似文献
13.
三峡工程运行后,长江中游荆江河段含沙量大幅度降低,次饱和水流冲刷河床使含沙量在沿程逐渐恢复,但其恢复特点由于沿程床沙组成差异而有所不同。本文基于Markov随机过程及泥沙起动理论,推导非均匀悬沙的泥沙落距表达式;结合悬移质扩散理论,修正非均匀悬沙恢复饱和系数公式。在此基础上,基于荆江河段实测输沙过程,提出考虑床沙组成影响的分组悬沙恢复饱和系数计算方法;该方法主要与泥沙粒径、悬浮指标、床沙组成及止滚概率、止悬概率等因素有关,无需考虑非饱和调整系数的影响。计算结果表明:①不考虑床沙组成时,沙市、监利站恢复饱和系数计算值均在区间0.12~0.27内变化,而考虑床沙组成时分别为0.000 3~0.171 8和0.003 5~0.157 9。②不考虑床沙组成时,分组悬沙恢复饱和系数计算值细沙>中沙>粗沙;考虑床沙组成时细沙 < 中沙 < 粗沙;除落水期外,沙市站粗沙的恢复速度均大于监利站。③沙市、监利站恢复饱和系数在各计算时段的变化过程对悬沙分组具有敏感性,其中洪水期恢复饱和系数大于枯水期、涨水期和落水期。采用河床变形方程反算分组悬沙恢复饱和系数,并与本文计算结果进行对比;通过比较分析,本文公式能够用于描述荆江河段分组悬沙恢复特性,可为三峡工程下游非均匀悬沙沿程恢复过程研究提供参考。 相似文献
14.
A three-dimensional, time-dependent hydrodynamic and suspended sediment transport model was performed and applied to the Danshuei
River estuarine system and adjacent coastal sea in northern Taiwan. The model was validated with observed time-series salinity
in 2001, and with salinity and suspended sediment distributions in 2002. The predicted results quantitatively agreed with
the measured data. A local turbidity maximum was found in the bottom water of the Kuan-Du station. The validated model then
was conducted with no salinity gradient, no sediment supply from the sediment bed, wind stress, and different freshwater discharges
from upstream boundaries to comprehend the influences on suspended sediment dynamics in the Danshuei River estuarine system.
The results reveal that concentrations of the turbidity maximum simulated without salinity gradient are higher than those
of the turbidity maximum simulated with salinity gradient at the Kuan-Du station. Without bottom resuspension process, the
estuarine turbidity maximum zone at the Kuan-Du station vanishes. This suggests that bottom sediment resuspension is a very
important sediment source to the formation of estuarine turbidity maximum. The wind stress with northeast and southwest directions
may contribute to decrease the suspended sediment concentration. When the freshwater discharges increase at the upstream boundaries,
the limits of salt intrusion pushes downriver toward river mouth. Suspended sediment concentrations increase at the upriver
reaches in the Danshuei River to Tahan Stream, while decrease at Kuan-Du station. 相似文献
15.
S. Isik 《Earth Science Informatics》2013,6(2):87-98
Estimations of annual suspended sediment loads are required for various types of water resources studies. Often estimation of the sediment load is needed for ungauged watersheds. Regionalization methods provide a practical solution to solve such problems. The purpose of this study is to classify suspended sediment yields in watersheds into homogeneous regions in order to identify their regional sediment rating curves. This study has been carried out for suspended sediment stations on 26 main basins of Turkey. Long term-scale suspended sediment rating curves of 115 gauging stations in Turkey were classified using cluster analysis on the basis of hydrological homogeneity. An agglomerative hierarchical clustering algorithm is used so that stations from different geographical locations are considered in the same cluster independently of their geographical location. 115 gauging stations were clustered into 4 different homogenous regions and the regional suspended sediment rating curve was developed for each region. The performance efficiencies of the developed regional rating curves were evaluated for 8 test stations and compared to the performances of rating curves in test sites. A regionalization model is developed for estimating suspended sediment rating curves for ungauged sites in Turkey. The developed regional rating curve models result in very close performances to those of their corresponding site rating curves. 相似文献
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Suspended Sediment Transport in the Freshwater Reach of the Hudson River Estuary in Eastern New York
Deposition of Hudson River sediment into New York Harbor interferes with navigation lanes and requires continuous dredging.
Sediment dynamics at the Hudson estuary turbidity maximum (ETM) have received considerable study, but delivery of sediment
to the ETM through the freshwater reach of the estuary has received relatively little attention and few direct measurements.
An acoustic Doppler current profiler was positioned at the approximate limit of continuous freshwater to develop a 4-year
time series of water velocity, discharge, suspended sediment concentration, and suspended sediment discharge. This data set
was compared with suspended sediment discharge data collected during the same period at two sites just above the Hudson head-of-tide
(the Federal Dam at Troy) that together represent the single largest source of sediment entering the estuary. The mean annual
suspended sediment–discharge from the freshwater reach of the estuary was 737,000 metric tons. Unexpectedly, the total suspended
sediment discharge at the study site in November and December slightly exceeded that observed during March and April, the
months during which rain and snowmelt typically result in the largest sediment discharge to the estuary. Suspended sediment
discharge at the study site exceeded that from the Federal Dam, even though the intervening reach appears to store significant
amounts of sediment, suggesting that 30–40% of sediment discharge observed at the study site is derived from tributaries to
the estuary between the Federal Dam and study site. A simple model of sediment entering and passing through the freshwater
reach on a timescale of weeks appears reasonable during normal hydrologic conditions in adjoining watersheds; however, this
simple model may dramatically overestimate sediment delivery during extreme tributary high flows, especially those at the
end of, or after, the “flushing season” (October through April). Previous estimates of annual or seasonal sediment delivery
from tributaries and the Federal Dam to the ETM and harbor may be high for those years with extreme tributary high-flow events. 相似文献
17.
鄱阳湖是我国重要的湿地生态系统,对调节流域的水沙变化有着重要作用。由于鄱阳湖湖区面积广,内部差异大,单一的悬浮泥沙反演模型不足以准确反演出湖区的悬浮泥沙浓度。以实测的反射光谱数据、泥沙浓度数据为基础,提出一种基于分类后的反演模型,即根据实测数据的光谱形态特征分类出5种典型的水体类型。在此基础上,将分类后的各类水体分别建立各自合适的反演模型进行反演。结果表明基于水体分类的经验模型反演达到满意效果,平均绝对误差为0.00217g/L,平均相对误差为3.022%。基于分类后的经验反演模型适用于鄱阳湖悬沙浓度分布的监测研究,有助于更加宏观、准确的掌握鄱阳湖泥沙浓度的空间分布和变化,为保持鄱阳湖资源的可持续开发与利用提供决策依据。 相似文献
18.
为了对南海近岸海域海水悬浮泥沙与叶绿素a进行浓度估算,基于Landsat-8数据确定悬浮泥沙与叶绿素a的敏感波段并构建估算模型。结果表明,Landsat-8数据第一、二、四波段对悬浮泥沙浓度较为敏感,第一、二、三波段对叶绿素a浓度较为敏感,而以上单波段仍不能单独用于准确提取该区悬浮泥沙与叶绿素a,故建立多种形式的统计模型。由第一、二、四波段线性组合形成的悬浮泥沙浓度反演模型的相关系数达到0.904,平均相对误差为10.24%,反演精度为89.76%。由第一、二、三波段线性组合形成的叶绿素a浓度反演模型的相关系数达到0.886,平均相对误差为11.27%,反演精度为88.73%。 相似文献
19.
给出了正交曲线坐标系下平面二维非恒定动床紊流模型基本方程组,即水流运动方程及潮汐水流不平衡输沙方程。对计算中的有关问题提出了处理方法,如基本资料及代表潮过程选取、糙率的确定、悬沙粒径及沉速、挟沙能力恢复饱和系数及河床冲淤判别条件等。以甬江口为例,计算了镇海弯道至大游山口门约5km河段潮汐水流潮位及流速过程、丁坝作用下的回流域及疏浚与整治相结合的河床变形,计算结果与野外资料吻合良好。在此基础上,计算了宁波大桥桥墩作用下的水流结构变化及对镇海港航道的冲淤影响。 相似文献
20.
Özgür Kişi 《International Journal of Earth Sciences》2010,99(6):1471-1482
This paper proposes the application of neuro-wavelet technique for modeling daily suspended sediment–discharge relationship. The neuro-wavelet models are obtained by combining two methods, artificial neural networks (ANN) and discrete wavelet transform. The accuracy of the neuro-wavelet and the ANN models is compared with each other in suspended sediment load estimation. The daily streamflow and suspended sediment data from two stations on Tongue River in Montana are used as case studies. The comparison results reveal that the suggested model could increase the estimation accuracy. 相似文献