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1.
三峡工程运用后,长江中游荆江河段持续冲刷,床沙与推移质、悬移质泥沙不断交换,从而造成该河段床沙发生不同程度的调整,对长江中下游河床演变及非平衡输沙机理的研究具有重要影响.在新水沙条件下,总结分析了沙波运动特性及床沙交换方式,引入Markov三态转移概率及非均匀沙隐暴系数,得到基于状态转移概率的沙质河段床沙级配调整的计算模型.研究结果表明:(1)20092014年,沙市站年内床沙中值粒径有先增大后减小的趋势,而监利站年内床沙中值粒径则先减小后增大,且荆江河段年际床沙中值粒径总体呈上升趋势,粗化程度约为6.9%~9.3%;(2)20092014年,沙市站床沙组成中粒径d<0.062 mm的泥沙所占比重不变,0.062 mm≤d<0.25 mm的泥沙所占比重逐年减少(累计减少11.4%),d≥0.25 mm的泥沙所占比重逐年增加(累计增加11.4%),而监利站床沙组成均存在波动性变化;(3)荆江河段床沙转换为推移质的概率随着泥沙粒径的增大而增大,床沙转换为悬移质的概率随着泥沙粒径的增大而减小,而推移质和悬移质转换为床沙的概率均随着泥沙粒径的增大而增大,河床发生冲刷粗化时泥沙输移的主要形式为悬移质(概率为81%~87%),而淤积细化时床沙补给主要来源于推移质(概率为8%~12%).通过验证,本文概率模型的计算结果与实测资料符合较好,能够应用于长江中游沙质河段年际床沙粗化及年内床沙级配调整过程预报,为进一步开展三峡工程下游非均匀悬移质泥沙沿程恢复机理的研究提供理论基础. 相似文献
2.
Sven HARTMANN Institute for Hydrosciences German Armed Forces University Munich Neubiberg Germany. 《国际泥沙研究》2001,16(2)
1 BASIC PROBLEMFlood protecton, sPreaing of settlements and occuPatin Of river valleys were maor reasons to damand lindt rivers throughout Europe in the ndd 19th century. Engineers of those days often knew very wellabout the effects of their plannings: shortening the river length would accelerat the now and thusencourage the erosion into the river's sedAnents. Two vital advanages could be obtalned from that kindof constrUction, landuse of the fOrmer flood plains on the one and increasin… 相似文献
3.
Field experiments were conducted on total load transport in the Chelichay River Basin,a mountainous catchment (1,400 km~2) located in north eastern of Iran,to evaluate total load formulas including four gravel bed rivers and a sand bed river(Qaresoo River).Gravel bed rivers in Chelichay River Basin can be grouped into two types;steep slope rivers with high shear values(Chehelchay River and Khormaloo River) and mild slope rivers with low shear values(Narmab River and Soosara River).Two depth integrating suspended load samplers(DH-48 and D-49),and two bed load samplers(Helley-Smith and BLSH) were used to measure total load.The performance is tested of 8 total load transport formulae including 4 macroscopic and 4 microscopic methods.A systematic and thorough analysis of 59 sets of data collected from sand bed river indicate that Yang and Engelund and Hansen reach to the better results, and from four gravel bed rivers confirmed that the methods of Karim and Kennedy and Engelund and Hansen yields the best results for steep slope rivers,and the methods of Einstein and Bijker are ranked highest in gradual slope rivers. 相似文献
4.
1 INTRODUCTION At present, most of the instruments used for sampling sediment loads at the canal intakes along the Yellow River in Shandong Province are horizontal samplers. These kinds of samplers cannot sample the suspended load 0.3 m from the riverbed. More recently use of bottle samplers has allowed sampling of the sediment load up to 0.1 m from the riverbed. However, bottle samplers are not able to measure suspended loads with high sediment concentrations and coarse sediment particl… 相似文献
5.
Extensive investigations of trace metals concentrations in water, suspended particulate matter (SPM) and bottom sediments of the whole Odra River system were carried out over the years 1997–2000. The vertical distribution of selected metals and their mobility were also studied in the sediment cores from upper and middle river sections. Significant levels of metal contamination were found. Median concentrations (Cd, Pb, Cu, Zn and As) in the SPM and sediments were (mg kg−1) 7.1 and 8.9 Cd, 128 and 146 Pb, 81 and 119 Cu, 1198 and 1204 Zn, 48 and 54 As, respectively. The highest metal pollution of the Odra River solids was found with cadmium, zinc, lead and arsenic, showing high similarity in their frequency distributions in both SPM and sediments. Cd, Zn and As appear to be of particular concern because of the high levels, that appear to be bioavailable, and their high mobility. The exchangeable and carbonate chemical forms of Cd and Zn reached up to 50% of their total amount. Besides the determination of total metal concentration, the metal chemical forms in river solids were investigated. The results of very wide studies of the Odra River system through 4 years suggest that metal pollution decreased, especially for Zn, Pb and Cu. Among all metals studied in the Odra River sediments, substantial reductions of Cd contamination were observed neither in the period after ’97 flood, nor if compared with the earlier results obtained before ’97. No essential differences of the metal contents were observed among the samples for the same river compartment, from the same locality, taken within the five sampling campaigns. The pattern of spatial and vertical metal distributions in the river solids indicates that a variety of sources might be responsible for the contamination; very intensive, historical and current mining and smelting activities probably are the most important ones. 相似文献
6.
Most rivers in Taiwan are intermittent rivers with relatively steep slopes and carry rapid sediment‐laden flows during typhoon or monsoon seasons. A series of field experiments was conducted to collect suspended load data at the Tzu‐Chiang Bridge hydrological station of the lower Cho‐Shui River, which is a major river with the highest sediment yield in Taiwan. The river reach was aggrading with a high aspect ratio during the 1980s. Because of sand mining and extreme floods, it was incised and has had a relatively narrow main channel in recent years. The experimental results indicated that typical sediment transport equations can correctly predict the bed material load for low or medium sediment transport rates (e.g. less than about 1000 tons/day‐m). However, these equations far underestimate the bed material load for high sediment transport rates. The effects of cross‐sectional geometry change (i.e. river incision) and earthquakes on the sediment load were investigated in this study. An empirical sediment transport equation with consideration of the aspect ratio was also derived using the field data collected before and after river incision. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
7.
Transport of moderately sorted gravel at low bed shear stresses: The role of fine sediment infiltration 
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下载免费PDF全文 Emeline Perret Céline Berni Benoît Camenen Albert Herrero Kamal El Kadi Abderrezzak 《地球表面变化过程与地形》2018,43(7):1416-1430
A reliable estimation of sediment transport in gravel‐bed streams is important for various practical engineering and biological studies (e.g., channel stability design, bed degradation/aggradation, restoration of spawning habitat). In the present work, we report original laboratory experiments investigating the transport of gravel particles at low bed shear stresses. The laboratory tests were conducted under unsteady flow conditions inducing low bed shear stresses, with detailed monitoring of the bed topography using a laser scanner. Effects of bed surface arrangements were documented by testing loose and packed bed configurations. Effects of fine sediments were examined by testing beds with sand, artificial fine sand or cohesive silt infiltrated in the gravel matrix. Analysis of the experimental data revealed that the transport of gravel particles depends upon the bed arrangement, the bed material properties (e.g., size and shape, consolidation index, permeability) and the concentration of fine sediments within the surface layer of moving grains. This concentration is directly related to the distribution of fine particles within the gravel matrix (i.e., bottom‐up infiltration or bridging) and their transport mode (i.e., bedload or suspended load). Compared to loose beds, the mobility of gravel is reduced for packed beds and for beds clogged from the bottom up with cohesive fine sediments; in both cases, the bed shear stress for gravel entrainment increases by about 12%. On the other hand, the mobility of gravel increases significantly (bed shear stress for particle motion decreasing up to 40%) for beds clogged at the surface by non‐cohesive sand particles. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
8.
Elaborate experiments were performed in a 30 m long, 0.5 m deep and 0.2 m wide laboratory flume to study the process of infiltration of fine sediment into the pores of coarse sediment forming the channel bed material. Different concentrations of suspended load of fine sediment of size 0.064 mm were passed over the channel bed made up of three different types of coarse sediments; two uniform and one nonuniform. The proportion of fine sediment infiltrated into the pores of bed material for each equilibrium concentration of suspended load of fine sediment in the flow was studied during several experimental runs. The proportion of fine sediment within the pores of bed material increased with an increase in the equilibrium concentration of suspended load of fine sediment in the flow. This process continued till the pores within the coarse sediment bed were filled up to the capacity with the fine sediment transported by the flow in suspension. The theoretical value was identified for limit for maximum proportion of fine sediment that can be present within the pores of bed material. On further increase in the concentration of suspended load of fine sediment in the flow, deposition of fine sediment occurs on the surface of the flume bed in the form of ripples of the fine sediment. This condition is defined as 'depositional condition'. Experimental observations on these and related aspects are presented herein. 相似文献
9.
The flood in the Odra river in 1997 has led to considerable additional pollution of the Stettin Lagoon and the Baltic Sea with contaminated suspended solids. For some priority substances, the pollutant entries via suspended solids during the flood period are estimated to be approximately 1/3 of the usual annual load. Among these priority pollutants there are total organic carbon (TOC), nitrogen, and the heavy metals Cu, Pb and Zn. For the concentrations of the priority pollutants in suspended solids accumulation factors from 2 to 4 in the comparison with normal conditions were observed. On the basis of the analysis of sediments sampled after the flood, main sources of the pollutants should be evaluated. As reference area with an industrial background as well as a typical pollutant pattern the region around Glogow/Legnica is proposed. 相似文献
10.
《国际泥沙研究》2016,(4):376-385
Twenty runs of experiments are carried out to investigate non-equilibrium transport of graded and uniform bed load sediment in a degrading channel. Well-sorted gravel and sand are employed to compose four kinds of sediment beds with different gravel/sand contents, i.e., uniform 100%gravel bed, uniform 100% sand bed, and two graded sediment beds respectively with 53% gravel and 47% sand as well as 22%gravel and 78%sand. For different sediment beds, the experiments are conducted under the same discharges, thereby allowing for the role of sediment composition in dictating the bed load transport rate to be identified. A new observed dataset is generated concerning the flow, sediment transport and evolution of bed elevation and composition, which can be exploited to underpin devel-opments of mathematical river models. The data shows that in a degrading channel, the sand greatly promotes the transport of gravel, whilst the gravel considerably hinders the transport of sand. The promoting and hindering effects are evaluated by means of impact factors defined based on sediment transport rates. The impact factors are shown to vary with flow discharge by orders of magnitude, being most pronounced at the lowest discharge. It is characterized that variations in sand or gravel inputs as a result of human activities and climate change may lead to severe morphological changes in degrading channels. 相似文献
11.
The river Odra is one of the biggest transboundary rivers in Central Europe. The basin is characterized by an area of 110 074 km?sk (upstream Krajnik Dolny) and a population of about 15.5 million inhabitants. Compared with the Westeuropean river basins the specific runoff of the Odra basin is low and amounts only 4.5 L km?sk s–1. The long term changes of the average annual nutrient transport of the Odra at Krajnik Dolny show for the period 1991 to 1994 a low reduction for phosphorus but no changes for nitrogen. For the period of 1991 to 1994 an inventory of the point sources produces emissions of 10.7 kt a–1 P and 54.4 kt a–1 N upstream of the station Krajnik Dolny/Schwedt. Emissions from agricultural land and urban areas represent the main diffuse sources. A range of 68 to 96 kt a–1 N and 3.3 to 3.9 kt a–1 P were estimated for the total diffuse emissions depending on the database and the method of modeling. The emission situation of the river is characterized by a high dominance of point sources in the case of phosphorus (about 73%). For nitrogen the diffuse emissions dominate the total emissions to an amount between 59 and 67%. Compared to the emissions the nutrient transport is low. An average load of 5.1 kt a–1 P and 70.1 kt a–1 N was observed at the station Krajnik Dolny for the period 1991 to 1994. The emission and load situation within the main tributaries of the river Odra is comparable to the whole basin. The big difference between the total emissions and the observed load refers to intensive retention and loss processes within the river system of the Odra. 相似文献
12.
YOSHIMASA KURASHIGE 《地球表面变化过程与地形》1996,21(12):1163-1173
Suspended sediment is supplied from river bed sediment in Hiyamizusawa Brook, Hokkaido, Japan, during the early snowmelt season. The stirring up of fine grains from the river bed is an important control of the time variation of suspended-sediment flux. In this stream, about 10 per cent of the river bed is covered with sand sediment, 80 per cent with cobbles and/or pebbles and the remaining 10 per cent is exposed bedrock. A model previously used to explain the stirring up of fine grains within a cobble and pebble bed is applied to a sand bed, with the modification that fine grains in a sand bed are assumed to be stirred up from the tractive layer formed on the surface, whereas those in a cobble and pebble bed are assumed to be stirred up from the gaps formed by the selective movement of pebbles on the river bed. The lift force acting at the river bed is estimated from the bed shear stress, and the maximum grain size capable of being stirred up was calculated from the lift force. Consequently, the amount of fine material stirred up from the river bed is estimated from the grain size distribution of river bed sediment, and the suspended-sediment flux is thus calculated. All stirred-up fines are assumed to become suspended sediment. The simulated time variation of suspended-sediment concentration was similar to that obtained in the field study. The calculated grain size of suspended sediment was also equivalent to the field data. 相似文献
13.
Peter Ergenzinger Carmen de Jong Berlin Environmental Research Group Institut fur Geographische Wissenschaften Freie Universitut Berlin Grunewaldstr. Berlin Germany 《国际泥沙研究》1997,(3)
LIN~DUCTIONTheinvenigationsofrivermorphologyandOfriverbeddebilityresultalwaysinidalsabouttheinterrelationshipbetweenthehydrauliccondihons,sc(hant~rtandbeddynndcs.ThedeCOuragingfactforsuchinveedgationsarethecomplexityoftheseSystemsandthehugenumberofimportantvariables.IfwefollowSimonsetal(1965)andall~eneeandtheconcentrationsofSUSPendedlOadandbedloadthefollowingparametersarethepnncapleVarialllesf-av~velocityofnow,diStributionofnowvelociticsacdeadofturbulence-meandepthacthedistributionofde… 相似文献
14.
SHEN Zhi-Gang 《国际泥沙研究》1999,(2)
IINTRODUCTIONRiversareanimportantcomponentofournatUralworld.ForthePurposeoffloodprotection,inlandshippingandlandutilization,manyrivershavebeenregulatedornarrowedinaschematic,monotonousmanner.Theriverbedandbanksaresmoothedinordertoreducetheflowresistanceandtoincreasetheflowcapacity.Thesetraditionalrivertrainingmeasures,whichcontradictnlderalevolutionlawofrivers,exertharmfuleffectsontheriverecosystemand"thealenvironmentalongtherivers.Theprimaryequilibriumofthebedloadtransportofriversaredam… 相似文献
15.
Hongwei FANG 《国际泥沙研究》2003,18(2)
1 INTRODUCTION With advances in computer technology and numerical methods, three-dimensional (3D) mathematical models for sediment transport are gradually applied more often and for more practical projects of hydraulic engineering. Three-dimensional mathematical river models can describe not only the secondary flow, but also the transport, deposition, and erosion of sediment in the river channel and the flood plain. However, at present the theories of sediment transport are not as well de… 相似文献
16.
J. Lehmann Th. Puff H. Damke J. Eidam K.-H. Henning W.-D. Jülich H. Roßberg 《洁净——土壤、空气、水》1999,27(5):321-324
The Odra river flood of 1997 was a rare hydrological as well as an interesting sedimentological event. At Hohenwutzen (Lower Odra River) we observed the suspended particulate matter transport and the temporal development of water and solidsπ pollution with heavy metals and As. While the suspended particulate matter concentration decreased the trace element concentrations increased during the flood by fractionation of particles and solution processes. Because of a successive flooding of differently contaminated sedimentary sources and polluted regions the contents of heavy metals developed irregularly. Their median particulate concentrations did not exceed the values of older samples taken under mean discharge conditions between 1989 and 1995. The dissolved amounts correspond to those of the Elbe river in 1990. During the flood the dissolved share of all analyzed total element contents increased. The total loads increased 4fold (Cr) to 17fold (Cd). 相似文献
17.
Zhi-Gang SHEN 《国际泥沙研究》1999,(2)
1INTRODUCTIONTheBedloadtransportofthealluvialriversisoneofthebasicproblemsinrivetdynamics.Itisbasisfortheplaninganddesignoftherivertrainingworks.Since1879DuBoyspresentedthefirstbedloadtransportformulaintermsofthebedshearstress,manyexperimentalorexperimental-theoreticalformulasfartheevaluationofbedloadtransporthavebeenwidelydevelopedthroughusingdifferentprinciplesandbasedondifferentmeasureddata.TheyusuallygiveresultsatvariancewithoneanotherInrecentyearspeoplebegintousen~-friendlymeasuresi… 相似文献
18.
Sediment production and yield from an alluvial gully in northern Queensland,Australia 总被引：1，自引：0，他引：1
Sediment production, transport and yield were quantified over various timescales in response to rainfall and runoff within an alluvial gully (7 · 8 ha), which erodes into dispersible sodic soils of a small floodplain catchment (33 ha) along the Mitchell River, northern Australia. Historical air photographs and recent global positioning system (GPS) surveys and LiDAR data documented linear increases in gully area and volume, indicating that sediment supply has been relatively consistent over the historic period. Daily time lapse photography of scarp retreat rates and internal erosion processes also demonstrated that erosion from rainfall and runoff consistently supplied fine washload (< 63 µm) sediment in addition to coarse lags of sand bed material. Empirical measurements of suspended sediment concentrations (10 000 to >100 000 mg/L) and sediment yields (89 to 363 t/ha/yr) were high for both Australian and world data. Total sediment yield estimated from empirical washload and theoretical bed material load was dominated by fine washload (< 63 µm). A lack of hysteresis in suspended sediment rating curves, scarp retreat and sediment yield correlated to rainfall input, and an equilibrium channel outlet slope supported the hypothesis that partially or fully transport‐limited conditions predominated along the alluvial gully outlet channel. This is in contrast to sediment supply‐limited conditions on uneroded floodplains above gully head scarps. While empirical data presented here can support future modelling efforts to predict suspended sediment concentration and yield under the transport limiting situations, additional field data will also be needed to better quantify sediment erosion and transport rates and processes in alluvial gullies at a variety of spatial and temporal scales. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
19.
Peter E. Ashmore 《地球表面变化过程与地形》1988,13(8):677-695
Bed load transport rate was measured in ten self-formed small-scale gravel braided streams developed in a laboratory flume at several different values of steady discharge and flume gradient. The streams are approximate Froude models of typical prototype braided streams but of no particular river. Slight viscous effects may be present in the models because particle Reynolds numbers are close to 70. Total bed load discharge was measured every fifteen minutes throughout each 60 hour run. In addition, 80 channel cross-sections were measured in each run to establish the average channel geometry. Total bed load transport rate correlates well with total discharge and total stream power, although at a given stream power bed load discharge is greater when braiding is less intense and the width/depth ratio is lower. Analysis using unit stream power and cross-section average bed shear stress reveals that the laboratory data conform to existing empirical bed load transport relationships. However, comparison with field data from gravel-bed rivers shows discrepancies that may be due to differences in bed material size gradation and bed sediment structure. At constant discharge, wide fluctuations in bed load discharge occur with some regularity. Periods range from 2 to 10 hours in the models, which is equivalent to several tens of hours in a prototype. The presence of these long-period fluctuations compounds the problems of field measurement of bed load in braided streams. 相似文献
20.
An experimental investigation on the initiation and development of bed forms on a bed of fine silica sand was conducted under alluvial flow conditions in a laboratory flume with a diverging channel. The main aims of the study were to assess： i） the steepness of bed forms in the transition stage of development; and ii） the threshold height of wavelets （ηt） that triggered the start of ripple development. Detailed bed profile measurements were carried out using an acoustic Doppler probe, traversed longitudinally over the sediment bed at various experimentation times. The bed form dimensions were extracted from such bed profile records and analysed for the wavelet, transition and equilibrium stages. It was found that the steepness of ripples in the transition and equilibrium stages were similar, confirming predictions of previous mathematical model simulations. A lognormal distribution fitted the wavelet length data. The wavelet threshold height was estimated as ηt ≈ 7 mm, or ηt≈ 80 in wall units. Such a height magnitude suggested that ripple development could be triggered by the wavelets reaching the outer flow zone of a turbulent boundary layer. The ηt value obtained corresponded generally to the intersection point between two predictive equations for bed form dimensions. A formulation was developed to predict ηt as a function of the sediment grain size, which was confirmed for the fine sand used in this study. 相似文献