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…     

TWO-DIMENSIONAL SEDIMENT MATHEMATICAL MODEL FOR UNSTEADY FLOW IN THE LOWER YELLOW RIVER

IINTRODUCTIONTheYellowRiverisfamousforitsheaVysedimentloadandcompledpluvialprocessesobviousadvanceshavebeenmadeinthetwo-dimensionalsedimentmathematicalmodel.Amongtile1llodelscreatedbeforethemechanismofsedimenttransportandrelatedphysicalparametel's,suchassedimentvelocity,sedimentcan'yingcapacityandriverfi.ictionetc.arenotyetundel.stoodvery\veil.Thesynchronousobserveddataoftheflowwithsediment,especiallyathyperconcentration,arenotenougllforthemodelcalibration.Thereforethedevelopmentoftwo-di…     

DEVELOPMENT OF LONGITUDINAL PROFILE OF THE LOWER YELLOW RIVER

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GEOMORPHIC THRESHOLDS FOR CHANNEL EVOLUTION IN THE LOWER YELLOW RIVER

Channel evolution refers to boundary changes of rivers affected by fluvial actions. This paper provides an analysis of the development and formation of stream patterns in the lower Yellow River and presents intensive studies of several critical problems relating to channel evolution, including thresholds of channel gradient and longitudinal profile adjustment, channel surface morphology, response of channel pattern to boundary conditions, critical discrimination of cross sections and the discrimination of channel pattern changes using hydrologic parameters.     

DIVERTING SEAWATER TO SCOUR THE LOWER YELLOW RIVER

1 INTRODUCTION The Lower Yellow River starts from Huayuanko and runs on a plain for about 800 km before emptying into the Bohai Sea. The river is notorious for its extremely heavy sediment load, 1.6 billion tons annually with a relatively small runoff of only 41 km3 at the river mouth. Such a huge volume of sediment is partly deposited in the channel and partly discharged through the estuary into the Bohai Sea. As the tide nearby is weak, a bulk of the sediment cannot be brought to th…     

TWO－DIMENSIONAL MATHEMATICAL MODEL FOR STUDYING EROSION AND SEDIMENTATION OF A WANDERING STRETCH IN THE LOWER YELLOW RIVER

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LOCAL SCOUR DEPTH AROUND SPURS IN THE LOWER YELLOW RIVER

1 INTRODUCTION The Lower Yellow River is a suspended river channel bed much higher than the adjacent ground behind the dikes, well known all over the world. The floods flow east into the sea under the constraints of dikes. The safety of the dikes or embankments mainly relies on the protection provided by the river training works that have been constructed and maintained for several thousand years. There are three types of river training works and they are spurs, guide banks, and reve…     

RANGE SURVEY OF DEPOSITION IN THE LOWER YELLOW RIVER

1 GENERAL DESCRIPTION The Yellow River, running out of the gorges below the Sanmenxia (SMX) and Xiaolangdi (XLD) reservoirs, flows through the vast North China alluvial plain, and finally empties into the Bohai Sea (Fig. 1). The upper part of the Lower Yellow River (LYR), nearly 400 km in length, is confined by levees along both banks. The river wanders with a shallow main channel and broad flood plains. The lower part has a relatively narrow and deep main channel and less b…     

FLUVIAL PROCESS OF THE DREDGING TEST REACH IN THE LOWER YELLOW RIVER

1THETESTREACHANDDREDGINGIN1997~1998TheYellowRiverhasextended38kmfartherintotheseaeversincethechangeoftherivercourseattheestuarytotheQingshuigouflowpathin1976.InMay1996therivercoursewaschangedtoabranchatthepointof950mabovetheCSQSandtheriverlengthwas16kmshorterthanbefore.Conditionsofincomingwaterandsedimentduringthefloodseasonof1996werefavorablesuchthat3].6milliontonsofsedimentwerescouredbelowLain.Amongthem,11.6milliontonswerescouredbetweenakinandXihekou(47.5km)and2040milliontonswe…     

SEDIMENT HAZARDS IN THE LOWER YELLOW RIVER

1DEFINITIONOFSEDIMENTHAZARDHazardsaredefinedasthenaturaleventsthatcauselossesofhumanlifeandproperty.Reasonably,thesedimenthazardsarethehazardsoccasionedbythenatUralphenomenonandprocessesthatarerelatedwithsedimenterosion,transport,andaccumulation.Thelandslideandsoilerosionarethedirectresultsofsedimentmovement.Theoccurrenceofsomeotherhazardsisnotthedirectresultofbutrelatedtosedimentmovement.Forexample,inadditiontometeorolog.icalconditions,somekindsoflandformsarefavorabletoformationoff…     

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…     

ONE D AND TWO D COMBINED MODEL FOR ESTUARY SEDIMENTATION

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A STUDY ON THE WARPING NEAR IRRIGATION HEADWORK OF THE LOWER REACH OF YELLOW RIVER

IINTRODUCTIONTheYellowRiverisfamousforitsttemendousamountofsedimenttransport.Basedonastatisticaldataanalysis,along-timeaverageannualof1.6billiontonsofsedimententerstheLowerYellowRiver,inwhich400milliontonsaredepositedintherivercharmel.Thesedimentdepositioncausesavapidriseofthebedelevation.Withahistoricalevollltionoftheriverchanges,aso-called"suspendedriver"graduallyformed.UPtonow,thegroundleveloftheareaolltsidetheriverleveesismuchlowerthanthewaterlevelintheriver.Thissituationbringsanex…     

DIVERTING SEAWATER TO SCOUR THE ESTUARY-A QUEST FOR NEW APPROACH TO REGULATETHE LOWER YELLOW RIVER-

1GENERALTraditionally,theLowerYellowRiverstartsatHuayuankouandrunsonaplainforabout800km,beforeemptyingintotheBohaiSea.Theriverisfedwithextremelyheavysedimentload(1.6billiontonsannuallyuptotheeighties)andrelativelysmallrunoff(46billionm3uptotheeighties)fromitsdrainagebasinupstream.Thisloadofsedimentispartlydepositedinthechannelresultinginaggradationorincreaseinthebedslope.TheremainderisdischargedtotheBobalSea.AsthetidesoftheBohaiSeaareweak,thedepositionintheareaaroundtherivermouthisusual…     

REGULATION OF FLOW AND SEDIMENT LOAD IN THE YELLOW RIVER

Small runoff, large sediment load, and incompatible relationship of flow and sediment load are very important characteristics of the Yellow River. They are also the crux of the most prominent problems of the Yellow River. To solve these problems, the regimes of flow and sediment load have to be improved by increasing water, reducing sediment load, and by using reservoirs to regulate flow and sediment load. The results of experiments for regulating the flow and sediment load in the last three years by the Xiaolangdi Reservoir have indicated that this measure is a realistic and effective way to mitigate the prominent problems in flood control of the Lower Yellow River at present and in the near future. However, the regulation system is still imperfect. It is advisable to speed up the pace of research and construction of the system for regulating flow and sediment load.     

VERIFICATION OF MATHEMATICL MODEL FOR SEDIMENT TRANSPORT BY UNSTEADY FLOW IN THE LOWER YELLOW RIVER

Field data from the Lower Yellow River (LYR) covering a period often consecutive years are used to test a mathematical model for one dimensional sediment transport by unsteady flow developed previously by the writers. Data of the first year of the said period, i.e., 1976, are used to calibrate the model and those of the remaining years to verify it. Items investigated include discharge, water stage, rate of transport of suspended sediment and riverbed erosion/deposition. Comparisons between computed and observed data indicate that the proposed model may well simulate sediment transport in the LYR under conditions of unsteady flow with sufficient accuracy.     

ANALYSIS ON PECULIARITIES OF "92.8"FLOOD EVENT IN THE LOWER YELLOW RIVER

lCOMPOSITIONOFTHE"92.8"FLOODThreerainstormsoccurredfrom7ththrough13,,,August,1992inShaanxiProvince,diStributingfromnorthtosouthinsequence.Therainfallareacoveredtheregionsofintensivesoilerosion,'wheretheaveragerateoferosionis10,000-15',000ton/kmZ'year.Fig.IshowsisohyetsofrainfallintensityinthecatchmentoftheMiddleYellowRiVerdepictingthedistributionoftherainstormsfrom7thto13,,,August,1992(thehydrologicalBureauYRCC,1992).ThecenterofthefirstrainstormwaslocatedattheYikezhaomengPrefec…     

2D NUMERICAL SIMULATION OF FLOOD AND FLUVIAL PROCESS IN THE MEANDERING AND ISLAND-BRAIDED MIDDLE YANGTZE RIVER

The characteristics of water flow and sediment transport in a typical meandering and island-braided reach of the middle Yangtze River is investigated using a two-dimensional （2D） mathematical model. The major problems studied in the paper include the carrying capacity for suspended load, the incipient velocity and transport formula of non-uniform sediment, the thickness of the mixed layer on the riverbed, and the partitioning of bed load and suspended load. The model parameters are calibrated using extensive field data. Water surface profiles, distribution of flow velocities, riverbed deformation are verified with site measurements. The model is applied to a meandering and island-braided section of the Wakouzi-Majiazui reach in the middle Yangtze River, which is about 200 km downstream from the Three Gorges Dam, to study the training scheme of the navigation channels. The model predicts the processes of sediment deposition and fiver bed erosion, changes of flow stage and navigation conditions for the first 20 years of impoundment of the Three Gorges Project.     

1800年以来长江中下游地震区中强地震集丛分布和迁移特征

本文对长江中下游地震区1800年以来中强地震活动进行了分区讨论,总结其活动规律,类比外推对该区M≥5.5级地震活动趋势作了估计。     

大地电磁测深二维正演中辅助场的新算法

文中提出一种计算大地电磁二维正演辅助场的新方法。在主场满足线性插值基函数的前提下,通过构建二次插值基函数来提高辅助场计算中数值求导的精度。通过与线性插值函数法的计算结果进行对比,证明该算法在基本不增加计算量的同时可以大幅度提高大地电磁二维正演精度。文中还研究了网格对辅助场计算的影响,结果表明二次插值法较线性插值法对网格的要求更为宽松。此外还以均匀半空间模型为例讨论了地表网格纵向间距与模型之间的关系,这对正演计算中的网格设计有参考意义