Experimental study of bed-load transport using particle motion tracking

A series of experiments were conducted in a flume to study bed-load transport.The motion of bed-load particles was captured by a series of images taken by a high-speed camera.A novelparticle motion tracking method was developed to automatically detect all the moving particles and calculate the instantaneous particle velocities.The instantaneous bed load transport rate was calculated based on particle velocity and the volume of moving particles.To verify this method,bed load transport rate based on the image processing technique was compared to the manually measured ones as well as data from other experiments.Results showed that the new technique made it possible to quantify the spatial and temporal variations of bed load transport rate at the individual particle scale.     

SEDIMENT TRANSPORT IN THE YANGTZE RIVER ESTUARY

SEDIMENT TRANSPORT IN TIIE YANGTZE RIVER ESTUARYSHEN Zhigang'ANSTa^CTThe hy~ntalc and the sedimen tranSport Patter'nS within the estUaIy of the YangtZe mver arecomPlex because of intemehon of fluvial and the hdal forCes, depending on freshwate discharge andhdal range. Based on the data measuIed in meent years, thes papo discusses the characterishcs of flowand sNnt movemen in the tw forer EstUaIy and their iIifluences on the evolution of theestuaryKey W: YangtZe mver…     

A MATHEMATICAL MODEL FOR UNSTEADY SEDIMENT TRANSPORT IN THE LOWER YELLOW RIVER

1 INTRODUCTIONMany mathematical models for sediment transport have been developed for solving practical Problemsin hydraulic engineering. HoweveT, most of them are not able to simulate the hyper-concentratd flows inthe Lower Yellow Xiver because of the extremely high load concentration of the flows. This paper isdevoted tO the simulation of unsteady sediment trallsport in the Lower Yellow mveLIn this paPer, the riverbed deformation equation is modified and the new expressions for sedi…     

BED-LOAD TRANSPORT IN THE SOUTH CHANNEL OF THE CHANGJIANG ESTUARY

1 INTRODUCTION The Changjiang River (Yangtze River) is bifurcated into North and South Branches by the Chongming Island (Fig. 1). The North branch is further divided into the North channel and South channel by the Changxing and Hengsha Islands, and the…     

Generalized algorithms for particle motion and collision with streambeds

Recent theoretical and numerical models for the motion of saltating particles close to stream beds are constituted of three sub-models: a) a set of equations describing the particle “free flight”, b) a sub-model to calculate the post-collision particle velocity, and c) a mathematical representation of the bed roughness. In this paper, a comprehensive three-dimensional (3-D), theoretical/numerical model for bedload motion at large Reynolds numbers is presented. By using geometric considerations and stochastic parameters to characterize collisions with the wall, five new sub-models for representation of bed roughness are, for the first time to the best of our knowledge, proposed and implemented. The emphasis of this paper is on the particle model, for which Basset, Magnus, drag, submerged weight, virtual mass, and lift forces are included. For the range of particle sizes (sands) analyzed herein, it is found that the stream-wise contribution of the Basset force, compared to other forces, may be as large as 60%. Whereas in the wall-normal direction, the Basset force is equally important as the drag force, and it is exceeded only by the submerged weight. It is also found that the best agreement between numerical and experimental results in terms of jump length, jump height, and stream-wise particle velocity is achieved for restitution and friction coefficients of 0.65 and 0.1, respectively. Important conclusions are obtained regarding the lack of realistic prediction with available “roughness” models with small ranges of angles.     

NUMERICAL SIMULATION OF SEDIMENT TRANSPORT IN ALLUVIAL RIVER WITH FLOODPLAINS

1 INTRODUCTION The transport of sediment in rivers with active floodplains is a two-dimensional process because the main channel and the floodplain can have very different transport capacities. Therefore, two-dimensional (2D) models are often used to simulate the streamwise and transverse variations of sediment erosion and deposition. Many 2D numerical models have been presented to simulate sediment transport in floodplains (James, 1985; Pizzuto, 1987; Howard, 1992; Nicholas and Walli…     

DEFORMATION OF RIVER BED AND THE CHARACTERISTICS OF SEDIMENT TRANSPORT DURING HYPER-CONCENTRATED FLOOD IN THE YELLOW RIVER

LINTRODUCTIONTheYellowforeriswellknownasaheavilysilt-caacingriverintheworld.Haaer-concentratedfloodsoftenoccurinitsmasterstemandaswellasthetriblltaries.ThecharacteristicsofdeformationandsedimellttranSportdifferfromreachtOreach.Duetohighsedimelltconcelltration,StrongfluvialactionandthenatUreofunSteadysedimenttranSPOrt,problemsandabnormalphenomenonareoflencreated.ThelaterbringinimpacttOnoodcontrolOfthelowerreach.Thus,itishelpfultoenhancetheunderstandingofthemotionlawsOfhaer-concentrat…     

RIVER BED DYNAMICS AND BED SEDIMENT TRANSPORTIN MOUNTAIN TORRENTS IN MOUNTAIN TORRENTS

LIN~DUCTIONTheinvenigationsofrivermorphologyandOfriverbeddebilityresultalwaysinidalsabouttheinterrelationshipbetweenthehydrauliccondihons,sc(hant~rtandbeddynndcs.ThedeCOuragingfactforsuchinveedgationsarethecomplexityoftheseSystemsandthehugenumberofimportantvariables.IfwefollowSimonsetal(1965)andall~eneeandtheconcentrationsofSUSPendedlOadandbedloadthefollowingparametersarethepnncapleVarialllesf-av~velocityofnow,diStributionofnowvelociticsacdeadofturbulence-meandepthacthedistributionofde…     

FREQUENCY AND MAGNITUDE OF BEDLOAD TRANSPORT IN A MOUNTAIN RIVER

Magnitude and frequency of bedload transport was examined in the Lainbach River, Bavaria, using magnetically tagged particles. During the study, 18 small to moderate events and one major event occurred. About 1 per cent of the flow period exceeded the entrainment threshold and at least once every year about 50 per cent of the tagged particles were mobile. Themajor event which occurred during the study period resulted in the deposition of a thick layer of sediment in parts of the channel and passive burial of most of the recovered particles. The step–pool pattern, which characterized the study site prior to the large event, was obliterated. However, the channel recovered quickly and has returned to a new step–pool pattern. The event changed the boundary conditions by increasing the availability of loose sediment and creating higher river-bed slopes in reaches between breached check dams. As a result, movement of individual particles measured for events of both the same magnitude and duration, occurring before and after the large event, yielded different values. For events which occurred after the large event, the range and the mean distance of movement were about ten times higher.     

THREE-DIMENSIONAL NUMERICAL MODELING OF COHESIVE SEDIMENT TRANSPORT BY TIDAL CURRENT IN PEARL RIVER ESTUARV

IINTRODUCTIONEstUariesareprominentcoastalfeatUres.Estuariesareofgreateconomicssignificancetomankind.Attheseareas,manyharborsandwaterchannelshavetobebuiltforeconomicpurposes.ThedesignandconstrUctionofcoastalstrUctUresinestUariesrequireknowledgeofhydrodynamicsaswellassedimenttransportinsuchregions.ThenatUreofestuariesiscontrolledbyvariouscoastalhydrodynamicprocesses.Undertheactionofhydrodynamics,sedimentdepositionsorerosionswilloccurinestuariesornearcoastalstrUCtures.Tomaintainnavigati…     

TRANSPORT OF GRAVELS WITH DIFFERENT RANGES OF GRAIN SIZES IN A STEEP CHANNEL

An understanding of the transport mechanism of gravel-bed rivers is very important for the river management and engineering works. The main objective of this study was to conduct a series of laboratory experiment in a steep flume to investigate the particle segregation and the transport rate of nonuniform gravel. Median sizes of 15 mm and 7.5 mm, and gradation coefficients of 1.5 and 2.0 were selected for the particle size distributions of nonuniform gravel. In addition to the 36 sets of data collected in this study, 635 sets of existing data for gravel with both nonuniform and nearly uniform sizes were analyzed. According to the results of the sieve analysis and the related theory, hiding functions for both particle size distributions of this study were derived. An attempt was made to develop an Einstein-type transport relationship for nonuniform gravel using dimensionless parameters with mean size as a representative particle size. A modified Schoklitsch-type sediment transport equation with a critical unit flow discharge was also developed to reasonably predict the transport rate of gravels. In addition, an artificial neural network (ANN) model with a back-propagation network (BPN) algorithm was also applied in this study.     

THREE DIMENSIONAL MATHEMATICAL MODEL OF SEDIMENT TRANSPORT IN ESTUARINE REGIONS -A CASE STUDY OF THE HAIHE RIVER MOUTH

1 INTRODUCTIONUnderstanding the flow characters in open channel or other water area, whether natufal water bodies(such as rivers and estuaries) or man-made strUctures (such as navigational channels, harbors), isimportant for addressing numerous hydraulic engineering problems. These include the selechons ofsuitable waste disposal sites, contndnant transport, sediment transport and other ecological problems.The major difficulty for solving these problems is that it often requires an optimal…     

INFLUENCES OF NATURE FRIENDLY RIVER TRAINING WORKS ON BED LOAD TRANSPORT

1INTRODUCTIONTheBedloadtransportofthealluvialriversisoneofthebasicproblemsinrivetdynamics.Itisbasisfortheplaninganddesignoftherivertrainingworks.Since1879DuBoyspresentedthefirstbedloadtransportformulaintermsofthebedshearstress,manyexperimentalorexperimental-theoreticalformulasfartheevaluationofbedloadtransporthavebeenwidelydevelopedthroughusingdifferentprinciplesandbasedondifferentmeasureddata.TheyusuallygiveresultsatvariancewithoneanotherInrecentyearspeoplebegintousen~-friendlymeasuresi…     

A laboratory investigation of bed-load transport of gravel sediments under dam break flow

Dam break flows and resulting river bed erosion can have disastrous impacts on human safety,infrastructure,and environmental quality.However,there is a lack of research on the mobility of non-uniform sediment mixtures resulting from dam break flows and how these differ from uniform sized sediment.In this paper,laboratory flume experiments revealed that coarse and fine fractions in non-uniform sediment had a higher and a lower bed-load parameter,respectively,than uniform sediments of the same size.Thus,the finer fractions were more stable and the coarser fractions were more erodible in a nonuniform bed compared to a uniform-grained bed.These differences can be explained by the hiding and protrusion of these fractions,respectively.By investigating changes in mobility of the mixed-size fractions with reservoir water levels,the results revealed that at low water levels,when the coarser fractions were only just mobile,the bed-load parameter of the finer fractions was higher than the coarser fractions.The opposite was observed at a higher water level,when a significant proportion of the coarsest fractions was mobilized.The higher protrusion of these grains had an important effect on their mobility relative to the finer grains.The transported sediment on these mixed-sized beds was coarser than the initial bed sediment,and became coarser with an increase in reservoir water level.     

A NUMERICAL MODEL OF SEDIMENT TRANSPORT IN HANDUN IRRIGATION DISTRICT

LABRIEFINTRODUCTIONOFRANDUNIRRIGATIONDISTRICTYellowRiverisoneofthemainWaterresourcesinNOrthChina.SincethefiftiesirrigationbydivertingwaterfromtheYellowforerdevelOPssteadily.AstheYdlowforerisaheavilysacmentsladenone,sedimentisdiVertedsimultaneouslywhenwaterisdiverted.HOwtoproperlytreatthedivertedsedimentboomesoneOfthekeyproblemsrestrichngthesustainingdevelOPmentofthCwaterresourcesinthatarea.LongchStanceconvopngsedimentisoneofthemainmeasuresfordealingwiththediVertedsedim…     

STREAM-SUBSURFACE EXCHANGE, SUSPENDED SEDIMENT TRANSPORT, AND THE COUPLED TRANSPORT OF COLLOIDS AND CONTAMINANTS IN SEDIMENT BEDS

1 INTRODUCTION Alluvial streams generally have permeable bed sediments that can admit significant pore water flows. Steady flow of surface water over bed roughness features such as sand waves or pools and riffles can then drive water flow into and out of the shallow subsurface. This is often termed hyporheic exchange, and the subsurface region where mixing between stream and ground waters occurs is the hyporheic zone (Hynes, 1983). The hyporheic zone has been shown to be a critical com…     

SEDIMENT TRANSPORT PROCESSES IN AGRICULTURAL WATERSHEDS

lINTR0DUCTI0NTheerosion,transportanddep0siti0nofsedimentinawatershedarepallofthenaturalsystemofwatershedprocesses.InanundistUrbedwatershed,s0ilsinuplandareasaregraduallyeroded,transportCdforsomedistanceandeventuallydepositedatlowereIevations.WhenwatershedsaredistUrbedbyhumanactivitiessuchasclearingofvegetation,urbaniZati0n,orotherchangesthataffectthelandscaPe,unstablechannelswithlocallyhighratesoferosion,transport,0rdepositionofsedimentoftenaretheresult.Theimpact0fer0sionisespeciallyhigh…     

FLOW MECHANISMS AND SEDIMENT TRANSPORT IN COMPOUND CHANNELS

IINTRODUCTIONCompoundortWo-stagechannelshavereceivedconsiderableattentioninrecentyearsduetotheirrelevancetofloodstudiesinnaturalrivers,theirsignificanceinunderstandingrivermol'phology,andtheiruseinsomefloodalleviationschemeswherethefloodplainshavebeenartificiallyloweredtoproduceengineeredchannels.ThispaperreviewsworkwhichhasbeenundertakenintheUKFloodChannelFacility(FCF)overthepastdecade.TheACewasbuiltatHRWallingfordin1986,asalargescalenationalfacilityforhydraulicengineeringstUdies.T…     

CHARACTERISTICS OF SEDIMENT TRANSPORT ALONG A RIVER REACH WITH A RESERVOIR

Based on long-term measurements at three gauging stations, Toudaoguai, Fugu and Hequ, and one meteorological station, this article discusses the features of discharge (Q) and sediment concentration (Cs) of a river reach of the Yellow River with a reservoir located in the Loess Plateau. The impacts of the local sub-watershed between Toudaoguai and Fugu gauging stations on sediment budget to the Yellow River have been analyzed. In addition, the deposition processes in the Tianqiao Reservoir have been investigated. Results show over 80% of the precipitation that falls in the local subwatershed is unable to contribute to the Yellow River runoff process. It is found that the annualmaximum sediment concentration is usually less than 30 kg/m^3 during flood seasons at Toudaoguai Gauging Station, but the sediment concentration varies dramatically at Fugu Gauging Station. About 35% of the sediment eroded in the sub-watersheds between Toudaoguai and Fugu gauging stationswas produced from the Huangfuchuan sub-watershed which has a drainage area accounting only for 10% of the drainage area between Toudaoguai and Fugu gauging stations. The Tianqiao Reservoir generally has deposition during the summer flood season, and scouring during the non-flood season.On average, over 85% of deposited sediment in the reservoir occurs in the 12 km long lower reservoir reach. The volume of annual deposition in the reservoir mainly depends on the volume of water from the local region between Hequ and Fugu gauging stations.     

EXPERIMENTAL STUDY OF BEDLOAD TRANSPORT IN UNSTEADY OPEN-CHANNEL FLOW

I.INTRODUCTIONBedloadtransportinsteadyuniformopenchannelflowhasbeenextensiVelystudied.Manyoftheformulasdevelopedforthepredictionofbedloadtransportinuniformopen-channelflowcanbebroughtinthefollowingform(ChienandWan,1983);ac=f(O)(l)xvhereacisthedimensionlessparameterofbedloadtranSPortandOisthedimensionlessparameterofflowintensity.TheseparametersaredefinedasfwheregsisthebedloadtranspoftratePerunitwidthindryweight;disthesedimentdiameter,Sisthebedslopeofthechannel;Rbisthehydraulicradiusdue…