2-D SIMULATION OF CHANNEL FLOWS WITH MOVEABLE BED

1 INTRODUCTIONFor many hydraulic engineering problems, the analysis of flow and bed level variations in openchannels is a fundamental prerequisite. forcal methOds fOr alluvial rivers are well develoPednowadays as far as onediInensional descriPtions are concemed. A cOmPrhensive analysis of Ihe wellknown models is Presented by Habersack(l998). HOwever, for a number of Problems such as channelwidening, flow pattem close to sPuds and etc. a more deailed knowledge of the bed level behavio…     

WATER AND SEDIMENT INFLOW OF HYPERCONCENTRATED FLOODS AND THE ASSOCIATED CHANNEL AGGRADATION IN THE YELLOW RIVER

ＷＡＴＥＲＡＮＤＳＥＤＩＭＥＮＴＩＮＦＬＯＷＯＦＨＹＰＥＲＣＯＮＣＥＮＴＲＡＴＥＤＦＬＯＯＤＳＡＮＤＴＨＥＡＳＳＯＣＩＡＴＥＤＣＨＡＮＮＥＬＡＧＧＲＡＤＡＴＩＯＮＩＮＴＨＥＹＥＬＬＯＷＲＩＶＥＲＺＨＡＯＹｅ＇ａｎ；ＰＡＮＸｉａｎｄｉａｎｄＦＡＮＺｕｏ...     

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…     

MITIGATION OF SEDIMENTATION HAZARDS DOWNSTREAM FROM RESERVOIRS

1 INTRODUCTION Increasing attention is being given to sedimentation hazards downstream from reservoirs as dams built during the past century accumulate progressively greater volumes of sediment. The sediment storage both decreases reservoir capacity and operating efficiency of the dam, and creates a 搒ediment-shadow?downstream where sediment-starved flows commonly erode channel boundaries and create long-term channel instabilities. Numerous studies have documented downstream channel change…     

NUMERICAL SIMULATION OF INUNDATION IN SHENZHEN CITY BY FINTE DIFFERENCE MODEL MIXED WITH 1D AND 2D UNSTEADY FLOW

ＮＵＭＥＲＩＣＡＬＳＩＭＵＬＡＴＩＯＮＯＦＩＮＵＮＤＡＴＩＯＮＩＮＳＨＥＮＺＨＥＮＣＩＴＹＢＹＦＩＮＴＥＤＩＦＦＥＲＥＮＣＥＭＯＤＥＬＭＩＸＥＤＷＩＴＨ１ＤＡＮＤ２ＤＵＮＳＴＥＡＤＹＦＬＯＷ￥ＣＨＥＮＧＸｉａｏｔａｏ；ａｎｄＱＩＵＪｉｎｗｅｉ（Ｓｅｎ...     

INFLUENCE OF THE UPSTREAM RESERVOIRS ON THE ADJUSTMENT OF DOWNSTREAM ALLUVIAL CHANNEL

I. INTRODUCTIONThe Yellow River is a heavily sediment--laden river. The sediment load of the Yellow River ranks the first in the world while its annual runoff is only of medium size. Toharness the river, it is necessary to build reservoirs for regulating runoff to meet the demands of economic development. Since the founding of PRC in 1949, I S4 large and medium--sized reservoirs have been constructed on the main stem and the tributaries with atotal storage capacity of 84.5 billion m3.…     

VELOCITY FIELD AND RESISTANCE OF FLOW OVER ROUGH SURFACES WITH LARGE AND SMALL RELATIVE SUBMERGENCE

LINTRODUCTIONPreciseknowledgeofthevelocityfieldandthecorrespondingresistanceofflowoverrollghsurfacesareofgreatimportanceformanypracticalproblemssuchastheestimationofthestabilitVofbedmaterialinerosiveriversortheremovalofaccumulatedfinesedimentfromthechannelandthelooseningofgravelbedmaterialbycontrolledreleaseofreservoirwater.Thelatterprocedure,calledflushingflows,isfrequentlyspecifiedtorestoreortomaintainaquatichabitat(WILCOCKetal.,1996).Dependingonwaterdepthhandroughnessheightk.(=equiv…     

SOME APPROACHES FOR STUDYING THE INTENSITY OF SMALL RIVER AGGRADATION

ＳＯＭＥＡＰＰＲＯＡＣＨＥＳＦＯＲＳＴＵＤＹＩＮＧＴＨＥＩＮＴＥＮＳＩＴＹＯＦＳＭＡＬＬＲＩＶＥＲＡＧＧＲＡＤＡＴＩＯＮＶ．Ｎ．Ｇｏｌｏｓｏｖ（ＬａｂｏｒａｔｏｒｙｏｆＳｏｉｌａｎｄＦｌｕｖｉａｌＰｒｏｃｅｓｓｅｓ，ＦａｃｕｌｔｙｏｆＧｅｏｇｒａｐｈ...     

STRUCTURE AND COMPOSITION OF A WATERSHED-SCALE SEDIMENT INFORMATION NETWORK

A "Watershed-Scale Sediment Information Network" (WaSSIN), designed to complement UNESCO’s International Sedimentation Initiative, was endorsed as an initial project by the World Association for Sedimentation and Erosion Research. WaSSIN is to address global fluvial-sediment information needs through a network approach based on consistent protocols for the collection, analysis, and storage of fluvial-sediment and ancillary information at smaller spatial scales than those of the International Sedimentation Initiative. As a second step of implementation, it is proposed herein that the WaSSIN have a general structure of two components, (1) monitoring and data acquisition and (2) research. Monitoring is to be conducted in small watersheds, each of which has an established database for discharge of water and suspended sediment and possibly for bed load, bed material, and bed topography. Ideally, documented protocols have been used for collecting, analyzing, storing, and sharing the derivative data. The research component is to continue the collection and interpretation of data, to compare those data among candidate watersheds, and to determine gradients of fluxes and processes among the selected watersheds. To define gradients and evaluate processes, the initial watersheds will have several common attributes. Watersheds of the first group will be: (1) six to ten in number, (2) less than 1000 km2 in area, (3) generally in mid-latitudes of continents, and (4) of semiarid climate. Potential candidate watersheds presently include the Weany Creek Basin, northeastern Australia, the Zhi Fanggou catchment, northern China, the Eshtemoa Watershed, southern Israel, the Metsemotlhaba River Basin, Botswana, the Aiuaba Experimental Basin, Brazil, and the Walnut Gulch Experimental Watershed, southwestern United States.     

DEVELOPMENT AND EXPERIMENT OF A NEW MODEL SAND BZY

Ｏｎｔｈｅｂａｓｉｓｏｆｐｒｅｖｉｏｕｓｒｅｓｅａｒｃｈａｎｄｐｒａｃｔｉｃｅ，ａｎｅｗｍｏｄｅｌｓａｎｄＢＺＹｈａｓｂｅｅｎｓｕｃｃｅｓｓｆｕｌｌｙｄｅｖｅｌｏｐｅｄ．Ｅｘｐｅｒｉｍｅｎｔｓｈａｖｅｂｅｅｎｃａｒｒｉｅｄｏｕｔｏｎｉｔｓｐｒｏｐｅｒｔｉｅｓ，ｉｎｃｌｕｄｉｎｇｕｎｉｔｗｅｉｇｈｔ，ｉｎｉｔｉａｔｉｏｎｖｅｌｏｃｉｔｙ，ｓｅｔｔｌｉｎｇｖｅｌｏｃｉｔｙ，ｒｅｐｏｓｅａｎｇｌｅ，ｅｔｃ．ＴｈｅｅｘｐｅｒｉｍｅｎｔｓｓｈｏｗｔｈａｔｔｈｅＢＺＹｍｏｄｅｌｓａｎｄｈａｓｍａｎｙｍｅｒｉｔｓｏｖｅｒｏｔｈｅｒｓ，ｓｕｃｈａｓａｄｊｕｓｔａｂｌｅｕｎｉｔｗｅｉｇｈｔ，ｗｉｄｅｒａｎｇｅｏｆｐａｒｔｉｃｌｅｓｉｚｅ，ｐａｒｔｉｃｌｅｓｈａｐｅｓｉｍｉｌａｒｔｏｎａｔｕｒａｌｓａｎｄａｎｄｓｔａｂｌｅｐｈｙｓｉｃａｌａｎｄｃｈｅｍｉｃａｌｐｒｏｐｅｒｔｉｅｓ．Ｔｈｕｓｉｔｈａｓｈｉｇｈｖａｌｕｅｆｏｒｓｔｕｄｙ，ｄｅｖｅｌｏｐｍｅｎｔａｎｄｅｘｔｅｎｓｉｏｎｆｏｒａｐｐｌｉｃａｔｉｏｎ．Ｓｔｉｌｌｓｏｍｅｏｆｉｔｓｐｒｏｐｅｒｔｉｅｓｎｅｅｄｔｏｂｅｆｕｒｔｈｅｒｓｔｕｄｉｅｄ     

NUMERICAL SIMULATION OF TURBIDITY CURRENT IN RESERVOIR

I. INTRODUCTIONWhen a sediment--laden flow reaches the backwater zone of a reservoir, the suddenreduction of flow velocity causes sediment particles to settle toward the river bed. Undercertain circumstsnces, it will plunge and form a layer of sediment--water mixture flowingbeneath the water surface. This flowing layer is called the turbidity current. A turbiditycurrent is relatively stable and has important impacts on reservoir sedimentation.In the case of deep reservoirs, due to temper…     

ENERGY DISSIPATION AND CALCULATION OF RESISTANCE AND VELOCITY OF DEBRIS FLOW

I.I~rnoxTherearemanyproblemsfortheresearchondebrisflowmechanism.ThemostimPOrtantandmOSturgentoneisthecalculationofresistanceandvelocityOfdebrisflow.Inthisaspectmuchresearchhasbeencompletedfromtwoapproaches.Oneapproachisbasedonordinaryhydraulicsandmodifiedbyfieldobservationdata,andempiricalformulaeofdebrisflowresistanceandvelocitywereestablished.MOStoftheearlyresearch,suchascalculatingdebrisflowvelocitywiththemodifiedformOfMariningformula,belongedtothisscope.Theonlydifferenceisthattherough…     

NUMERICAL SIMULATIONS OF SCOUR AND DEPOSITION IN A CHANNEL NETWORK

1 INTRODUCTION Evolution of the river bed in alluvial channels has been studied by many researchers using analytical and numerical approaches. The use of analytical approach alone is insufficient for solving natural river engineering problems. With rapid growth in computer technology, numerical models have become a popular means for the study of mobile bed hydraulics. During the past decade, several numerical models have been developed. Most of the computer codes, such as HEC2SR (Si…     

DISCUSSION ON ＂NUMERICAL SIMULATION OF SEDIMENT RELEASE FROM RESERVOIRS＂ （No. 1, 2006） BY KHOSROWNEJAD A. AND NEISHABORI A.

Sedimentation processes in reservoirs can be studied by performing theoretical analysis, laboratory experimentation, numerical simulation, or a combination of these three methods. Available literature focused on reservoirs is abundant. For instance, the works conducted by Hotchkiss and Parker (1991), Morris and Fan (1997), and De Cesare et al.     

A LINEAR THEORY FOR DISTURBANCE OF COHERENT STRUCTURE AND MECHANISM OF SAND WAVES IN OPEN-CHANNEL FLOW

1 INTRODUCTIONT'he early theory for tUrbulent boundare layer assumed that the now adjacent to the wall is a lndnar innature and is named lndnar bottom layer Its thickness is about V/u*, Where V is the ldnehc viscosityand u* is the fuchon velocity. Towmsend (l956) first suggested the concePt of tUrbulent strUctUre andpointod out that there are isotroPic small scale nuctUation and quasi-periodic large scale strUcture in theshear flow Einstein and Li (l956) discovered by the flow moving…     

COMBINED EXPERIMENTAL AND NUMERICAL INVESTIGATION OF FORMULAE FOR EROSION AND DEPOSITION OF COHESIVE SEDIMENTS

1 mTsonvCTIoxTIansport of fine cOhesive sedinds inevitably leads to the develoPment of sediment deposits inreservoirs or zones with small flow velocihes in lowland rivers. Such sediment dePosits often conshtUte aconsiderable ecological danger, as cOhesive sediInnts have the ability to bind POllutants like heavymetals, polycyclic aromatic hydrocrtons or chlorinated hydrocaIbons (F6f8iner, l989). In the case of anextreme hydraUlic event like a flood or a reservoir dePlehon, erosion of cone…     

THE VARIATION WITH TIME OF GRAVITATIONAL FIELD OF KUNMING AREA

This paper deals with the work for obtaining the gravitational value G on the basis of gravitational observation for 5 years at Kunming Observatory using the Birchaiv method in which the zero drift is removed and the theoretical value of earth tides corrected.The gravitational daily mean value G obtained after corrections of zero drift and theoretical values of earth tides shows obvious variations with periods of 15 days and one month respectively and the maximum amplitude of variation reaches approximately to 8μgal.The obtained gravitational monthly mean value Gmonth,also after corrections of zero drift and theoretical value of earth tide shows variation with periods of 6 months and one year respectively.This value tends to be greater in spring and fall and smaller in winter and summer,the maximum variation amplitude of which is about 4 μgal.No clear mutations in the gravitational field in Kunming area have been detected.It is therefore believed that the gravitational field of Kunming area is compara     

PERMEABILITY AND CONSOLIDATION OF SEDIMENT MIXTURES AS FUNCTION OF SAND CONTENT AND CLAY MINERALOGY

The current study is the first step in a systematic experimental research on the erosion behaviour of sand-mud mixtures. It concerns the effect of a varying sand content and clay mineralogy on the porosity, structure, strength and permeability of artificially generated sediment mixtures. The permeability of a sediment mixture is an especially significant parameter concerning the type of erosion that occurs. It determines if the erosion of the bed is either a drained or an undrained process, respectively indicating surface erosion or mass erosion. Measurements on various mixtures concerning the consolidation coefficient and the permeability have been executed. Results show a distinct transition of behaviour between a sand-silt dominated network structure and a clay-water matrix. The occurrence of these two types of structures appears to depend on the porosity of the volume fraction of sand related to silt, which is, therefore, an important parameter concerning the type of erosion. Finally, the study provides a valuable data set that can be used as a reference for following stages of this research on the erosion behaviour of natural cohesive sediments.     

ON THE VARIETY AND COMPLEXITY OF THE SHORT-TERM AND URGENT PRECURSORS OF THE TANGSHAN EARTHQUAKE

The Tangshan earthquake(M=7.8)which occurred on July 28, 1976 is the greatest event among the modern catastrophes in China. It occurred in a region that was the most densely networked with seismic stations, a region that had the longest history in seismological work and had received     

PRINCIPLES OF RIVER TRAINING AND MANAGEMENT

River regulation and river training have been performed for various purposes and negative effects have been shown in numerous cases. In some cases the negative effects are so serious that humans have to consider to "renaturalize" the regulated rivers. Only by using the strategy of integrated river management the diverse river uses and natural fluvial processes and ecological systems may be harmonized. Based on analysis of case studies and data collected from literatures this paper presents the concept of integrated river management and four principles of river training. The integrated river management comprises: 1) taking the watershed, upper stream basin including the tributaries, middle and lower reaches and the estuary as an integrated entity in the planning, design and management; and 2) mitigating or controlling the negative impacts on hydrology, erosion and sedimentation, fluvial processes, land use and river use, environment and ecology while in achieving economic benefit from water resources development, flood safety management and hydropower exploitation. River training and management should be in accordance with the four principles: 1) extending the duration of river water flowing on the continent, which may be achieved by extending the river course or reducing the flow velocity; 2) controlling various patterns of erosions and reducing the sediment transportation in the rivers; 3) increasing the diversity of habitat and enhancing the connectivity between the river and riparian waters; and 4) restoring natural landscapes.