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Sample records for bed-load sediment transportation

  1. Influence of turbulence on bed load sediment transport

    DEFF Research Database (Denmark)

    Sumer, B. Mutlu; Chua, L.; Cheng, N. S.;

    2003-01-01

    This paper summarizes the results of an experimental study on the influence of an external turbulence field on the bedload sediment transport in an open channel. The external turbulence was generated by: (1) with a horizontal pipe placed halfway through the depth, h; (2) with a series of grids...... correlated with the sediment transport rate. The sediment transport increases markedly with increasing turbulence level.......-bed experiments and the ripple-covered-bed experiments. In the former case, the flow in the presence of the turbulence generator was adjusted so that the mean bed shear stress was the same as in the case without the turbulence generator in order to single out the effect of the external turbulence on the sediment...

  2. Study on bed load transport for uniform sediment in laminar flow

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Previous studies focused on the bed load transport rate for the condition of turbulent flow,while the knowledge of sediment transport in laminar flow is very limited.As an extreme case to reflect the viscous effect on sediment transport,sediment transport in laminar flow is considered in this paper.There are at least two factors affecting the transport rate of sediment under laminar flow conditions: (1) fluid forces;(2) particle to particle interactions.Together,these two factors represent the physical transport system.First,an exposure degree Probability Density Function (PDF) is developed to explore how the transport rate can be associated with characteristics of laminar flow and this factor reflects the particle to particle interactions,and the pickup probability equation in the absence of turbulence is developed based on the stochastic approach which reflects the exposure degree influence.Then,the formulas to calculate the critical shear stress of incipient motion and the bed load transport rate of fine uniform sediment are established.The derivation is made mainly based on Einstein’s bed load theory;we choose Einstein’s equation to model this system because we believe that the probabilistic approach taken is an appropriate way to account for the spatial and temporal variations in the forces causing sediment transport.These formulas have been tested against a wide range of existing laboratory data and compared with other existing empirical or semiempirical methods.The predictions by these newly proposed formulas are very good.

  3. Experimental study on bed-load sediment transport under irregular wave and current combined flow

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Using an irregularly oscillating tray and flume, a series of experiments are completed to evaluate bed-load sediment transport rate under irregular wave- current coexistent fild. Testing conditions include three interaction angles 0°, 45°, 90° and two kinds of median sizes (0.38 and 1.10 mm).The results of transport rate show that the net sediment transport rate can be expressed approximately as the function of the maximum bottom shear stress of waves, mean shear stress of current and the grain size.

  4. Modeling bed-load transport of coarse sediments in the Great Bay Estuary, New Hampshire

    Science.gov (United States)

    Bilgili, A.; Swift, M. R.; Lynch, D. R.; Ip, J. T. C.

    2003-12-01

    Current, sea level and bed-load transport are investigated in the Lower Piscataqua River section of the Great Bay Estuary, New Hampshire, USA—a well-mixed and geometrically complex system with low freshwater input, having main channel tidal currents ranging between 0.5 and 2 m s -1. Current and sea level forced by the M 2M 4M 6 tides at the estuarine mouth are simulated by a vertically averaged, non-linear, time-stepping finite element model. The hydrodynamic model uses a fixed boundary computational domain and accounts for flooding-drying of tidal flats by making use of a groundwater component. Inertia terms are neglected in comparison with pressure gradient and bottom friction terms, which is consistent with the observed principal dynamic balance for this section of the system. The accuracy of hydrodynamic predictions in the study area is demonstrated by comparison with four tidal elevation stations and two cross-section averaged current measurements. Simulated current is then used to model bed-load transport in the vicinity of a rapidly growing shoal located in the main channel of the lower system. Consisting of coarse sand and gravel, the shoal must be dredged every five to eight years. Two approaches are taken—an Eulerian parametric method in which nodal bed-load flux vectors are averaged over the tidal cycle and a Lagrangian particle tracking approach in which a finite number of sediment particles are released and tracked. Both methods yield pathways and accumulations in agreement with the observed shoal formation and the long-term rate of sediment accumulation in the shoal area.

  5. EXPERIMENTAL STUDY ON BED-LOAD SEDIMENT TRANSPORT IN IRREGULAR WAVE-CURRENT COEXISTENT FIELD

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    In order to evaluate bed-load sediment transport in an irregular wave-current coexistent field, a series of experiments were completed in laboratory with an irregularly oscillating tray, which was specially designed to simulate the irregular wave-current coexistent field. Experimental results are presented on the initial motion of sediment and the rates of transport over flat horizontal bed. Testing conditions included three interaction angles, 0°, 45°, 90° and six kinds of grain sizes. Four kinds (0.2mm, 0.46mm, 0.85mm and 1.3mm) were used for the tests of initial motion, while the other two kinds (0.38mm and 1.1mm) for the tests of transport rate. Comparisons between experimental results of initial motion and modified Shields curve indicate that the Shields curve is still valid for the case of irregular wave-current coexistent field. Analysis of flow regime shows that initial conditions fall within smooth-turbulent transitional region. The results of transport rate show us that net sediment transport rate can be expressed approximately as the function of the maximum bottom shear stress and mean shear stress. A dimensionless formula is proposed on the basis of mechanism "Waves erode sediments, tides transport sediments".

  6. Bed load proppant transport during slickwater hydraulic fracturing: insights from comparisons between published laboratory data and correlations for sediment and pipeline slurry transport

    CERN Document Server

    McClure, Mark W

    2016-01-01

    Bed load transport is the movement of particles along the top of a bed through rolling, saltation, and suspension created by turbulent lift above the bed surface. In recent years, there has been a resurgence of interest in the idea that bed load transport is significant for proppant transport during hydraulic fracturing. However, scaling arguments suggest that bed load transport is only dominant in the laboratory and is negligible at the field scale. I review laboratory experiments that have been used to develop concepts of bed load transport in hydraulic fracturing. I also review the scaling arguments and laboratory results that have been used to argue that viscous drag, not bed load transport, is dominant at the field scale. I compare literature correlations for fluvial sediment transport and for pipeline slurry transport with published laboratory data on proppant transport in slot flow. The comparisons indicate that fluvial transport correlations are suitable for predicting the rate of sediment erosion due...

  7. Bed-Load Transport Rate Based on the Entrainment Probabilities of Sediment Grains by Rolling and Lifting

    CERN Document Server

    Li, Jun-De; Lin, Binliang

    2016-01-01

    A function for the bed-load sediment transport rate is derived. This is achieved from the first principle by using the entrainment probabilities of the sediment grains by rolling and lifting, and by introducing two travel lengths, respectively, for the first time. The predictions from the new bed-load function agree well with the experimental results over the entire experimental range and show significant improvement over the commonly used formula for bed-load transport rate. The new function shows that, in terms of contributing to the bed-load transport rate, the total entrainment probability of the sediment grains is a weighted summation of those by the lifted and rolling grains, rather than a simple addition of the two. The function has also been used to predict the total entrainment probability, saltation length and the bed layer thickness at high bed-load transport rate. These predictions all agree well with the experimental results. It is found that, on average, the travel length for the rolling sand gr...

  8. Nonlinear Mechanism of Bed Load Transport

    Institute of Scientific and Technical Information of China (English)

    XU Haijue; BAI Yuchuan; NG Chiu-On

    2009-01-01

    From the group movement of the bed load within the bottom layer, details of the nonlinear dynamic characteristics of bed load movement are discussed in this paper. Whether the sediment is initiated into motion cor-responds to whether the constant term in the equation is equal to zero. If constant term is zero and no dispersive force is considered, the equation represents the traditional Shields initiation curve, and if constant term is zero with-out the dispersive force being considered, then a new Shields curve which is much lower than the traditional one is got, The fixed point of the equation corresponds to the equilibrium sediment transport of bed load. In the mutation analysis, we have found that the inflection point is the demarcation point of breaking. In theory, the breaking point corresponds to the dividing boundary line, across which the bed form changes from flat bed to sand ripple or sand dune. Compared with the experimental data of Chatou Hydraulic Lab in France, the conclusions are verified.

  9. CONCENTRATION DISTRIBUTION OF SEDIMENT IN BED LOAD LAYER

    Institute of Scientific and Technical Information of China (English)

    ZHONG De-yu; ZHANG Hong-wu

    2004-01-01

    In this paper the concentration profile in bed load layer is derived based on kinetic theory. According to observations, particles moving in near wall region behave differently during ejection and sweeping of turbulence burst, as indicates that they are subject to different influences from turbulence, and therefore, the forces acting on particles are not the same. Consequently, particles moving in bed load layer are classified into two groups, one lifted upward by ejections, the other carried back to bed by sweepings, and the forces corresponding to upward and downward motions are proposed. By solving the basic transport equation of kinetic theory, the velocity distribution functions, upward and downward fluxes of particles in bed load layer are derived. Upon assumption of equilibrium sediment transport, concentration profile in bed load layer is obtained. Verification is also presented in this paper, which shows that the concentration profile produced by the relation proposed in this paper agrees with observations well.

  10. TRANSPORTATION CHARACTERISTIC OF BED LOAD FOR NON-UNIFORM SEDIMENT WITH EQUIVALENT GRAIN

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The incipient velocity of sediment is one of themost important basic theory problems of hydraulic engineers.The initial motion of sediment is a random process. Based on the combination methods of classical mechanics with statisticstheory the formula to calculate the incipient motion of sedi-ment was established. According to the standard of incipientmotion, motion status, relative degree of expose for sedimentand equivalent grain was defined in this paper. The coefficientin the formula included the flow fluctuation and relative degreeof exposition. The value of the coefficient was calculated by u-sing some parameters value. The results show that the valueof dimensionless shear stress coefficient is not a constant, butlocating in a range from 0. 022 to 0. 063 to weak and middlemotion status, and varying with the relative degree of sedi-ment expose. The value of dimensionless Shields numbers thatput forward in the text can explain the reason that why the co-efficients in difference formulas have wide scatter. The theo-retical formula has been verified with amount of data collectedfrom both natural rivers and flumes. The results can reflectthe motion characteristic of the sediment.

  11. Experiments with non-uniform sediment in case of bed-load transport

    NARCIS (Netherlands)

    Ribberink, J.S.

    1983-01-01

    An experimental study was carried out in the framework of a research project concerning the development of a mathematical model for morphological computations in rivers in case of non-uniform sediment. The study consists of a series of laboratory experiments in a straight flume under steady, uniform

  12. Sediment and Fecal Indicator Bacteria Loading in a Mixed Land Use Watershed: Contributions from Suspended and Bed Load Transport

    Science.gov (United States)

    Water quality studies that quantify sediment and fecal bacteria loading commonly focus on suspended contaminants transported during high flows. Fecal contaminants in bed sediments are typically ignored and need to be considered because of their potential to increase pathogen load...

  13. On different regime relations between bed load transport and bed topography

    Science.gov (United States)

    Zhang, L.; Ma, H.; Fu, X.; Duan, J. G.

    2016-12-01

    Bed load transport is determined by the effective part of the total shear stress subtracting the form drag that arises from bed topography. Wang et al. (2004) quantified the overall topographic roughness of the channel bed with the parameter Sp and claimed that the increasing Sp corresponds with increasing flow resistance and decreasing bed load transport rate due to increasing form drag and decreasing skin friction. However, the flume experiments for non-uniform sediment transport on steep slope at the University of Arizona show opposite results that bed load transport increases with Sp. We investigate the physical reason of the contrasting results for the full understanding of the different regimes between bed load transport and bed topography. We develop the energy conveyance equation for water flow and bed load transport and apply it to the development of the equilibrium relation between bed load transport and energy dissipation due to the form drag. The energy theory for bed load transport shows that since our flume experiments achieved the equilibrium transport state with water and sediment circulating supplying, the bed topography Sp is determined by the flow and sediment grain size, and the bed load transport is positively related to the energy dissipation rate which is thus positively related to Sp. However, in the field experiment of Wang et al. (2004), at first, the referenced Sp is determined by the most recent significant flood whereas the bed load transport is always below the transport capacity with insufficient sediment supply. After one-time sediment feed, the bed load transport rapidly varies from ephemeral full capacity state to sediment starving state. In this process, the removal of relative fine sediment results in the rapid increment of Sp from the instant equilibrium state to the referenced Sp whereas the coarsen bed leads to decrement of bed load transport. Eventually, the sediment starving state results in the increasing Sp and decreasing

  14. Bed load transport in a proglacial river (Fagge, Gepatschferner, Tyrol)

    Science.gov (United States)

    Morche, David; Baewert, Henning; Bryk, Alexander

    2014-05-01

    Large amounts of solid load are transported in proglacial streams. This material originates mainly from bedrock eroding glaciers (supra-, en- and subglacial stores). While suspended sediment dynamics in glacier-fed streams are quite well investigated, data on the bed load component of the total load are still rare. Due to the ongoing glacier melt down in high mountain areas it is highly debated whether more solid load (higher sediment availability) or less solid load (trapping effect of proglacial lakes) is transported in the near future. We present measurements of fine to medium sized bed load and discharge recordings from a proglacial river responding to the dramatic glacier retreat in the last years. The measurements have been carried out in cross sections close to the glacier snout of the Gepatschferner in Tyrol (Austria). First results show the more or less continuous transport of coarse sand and fine to medium sized gravel even during low flows in the ablation period. The investigations are part of the DFG/FWF joint project "PROSA" (http://www.ku.de/mgf/geographie/prosa).

  15. Evaluation of Bed Load Transport Formulas Using Flume Experiments

    Science.gov (United States)

    Cashman, E. M.; Smith, B.; Sorenson, C.; Gayheart, J.

    2002-12-01

    The ability to model sediment transport is a critical assessment tool for forest management of water quality, endangered fisheries and downstream communities. The analysis of sediment transport is especially relevant on the North Coast of California. The economy of the region is heavily dependent upon the production of wood products and the extensive ownership and activity of forest product companies has led to substantial controversy over the effects of forest management on other resources. In this research, an experimental flume has been used to evaluate bed load transport formulas based on sediment size distributions appropriate to Coastal watersheds in Northern California. The intended outcome of this research project is to verify the total sediment transport equation used in mathematical modeling of sediments in this particular model (KINEROS2) to ensure that the most appropriate equation is being used for modeling sediment load in the North Coast Region. This analysis is critical to improve the physical and numerical models of sediment transport and extend this type of analysis to other Northern California watersheds. The flume experiments are being conducted in a research quality sediment transport flume at the College of Natural Resources and Sciences at Humboldt State University. The open channel flow laboratory flume is capable of simulation of open channel flows, sediment transport, flow through floodplains and unsteady flow over in-stream structures such as sediment traps and weirs. The flume is 40 feet long and 2.5 feet wide, with two-foot high sidewalls. There is a storage tank for water that runs under the flume, and water is recirculated through the tank and down the flume by several pumps. A headworks tank with baffling allows the water to enter at the top of the flume. At maximum output the flow is approximately 550 gpm and about 6 inches high. The slope on the flume can be adjusted from 0 to 6%. Instrumentation on the flume includes flow meters

  16. VERIFICATION AND COMPARISON OF FORMULAS FOR BED LOAD TRANSPORT

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Several typical formulas for bed load transport are examinedbased on field data in this paper. It is concluded that, the Einstein formula provides good estimates for the bed load transport rate while other ones predict much lower transport rates. The main reason for the under-prediction is that Dp, the effective diameter of particles, is too large as a representative diameter of the bed material for gravel streams with partially movable bed. Performance of these formulas can be significantly improved if D35 is adopted instead of Dp.

  17. Can bed load transport drive varying depositional behaviour in river delta environments?

    Science.gov (United States)

    van der Vegt, H.; Storms, J. E. A.; Walstra, D. J. R.; Howes, N. C.

    2016-11-01

    Understanding the processes and conditions at the time of deposition is key to the development of robust geological models which adequately approximate the heterogeneous delta morphology and stratigraphy they represent. We show how the mechanism of sediment transport (the proportion of the sediment supply transported as bed load vs. suspended load) impacts channel kinematics, delta morphology and stratigraphy, to at least the same extent as the proportion of cohesive sediment supply. This finding is derived from 15 synthetic delta analogues generated by processes-based simulations in Delft3D. The model parameter space varies sediment transport mechanism against proportions of cohesive sediment whilst keeping the total sediment mass input constant. Proximal morphology and kinematics previously associated with sediment cohesivity are also produced by decreasing the proportion of bed load sediment transport. However, distal depositional patterns are different for changes in sediment transport and sediment load cohesivity. Changes in sediment transport mechanisms are also shown to impact clinoform geometry as well as the spatiotemporal scale of autogenic reorganisation through channel avulsions. We conclude that improving insight into the ratio of bed load to suspended load is crucial to predicting the geometric evolution of a delta.

  18. Modeling of spatial lag in bed-load transport processes and its effect on dune morphology

    NARCIS (Netherlands)

    Duin, van O.J.M.; Hulscher, S.J.M.H.; Ribberink, J.S.; Dohmen-Janssen, C.M.

    2016-01-01

    In the present study, two bed-load transport models are introduced in an existing idealized dune model. These allow for the modeling of the spatial lag between the sediment transport rate and bed shear stress along dune surfaces. This lag is an important factor in determining transitions between bed

  19. Bed load transport in a very steep mountain stream (Riedbach, Switzerland): Measurement and prediction

    Science.gov (United States)

    Schneider, Johannes M.; Rickenmann, Dieter; Turowski, Jens M.; Schmid, Bastian; Kirchner, James W.

    2016-12-01

    Compared to lower-gradient channels, steep mountain streams typically have rougher beds and shallower flow depths, making macro-scale flow resistance (due to, e.g., immobile boulders and irregular bedforms) more important as controls on sediment transport. The marked differences in hydraulics, flow resistance, and grain mobility between steep and lower-gradient streams raise the question of whether the same equations can predict bed load transport rates across wide ranges of channel gradients. We studied a steep, glacier-fed mountain stream (Riedbach, Ct. Valais, Switzerland) that provides a natural experiment for exploring how stream gradients affect bed load transport rates. The streambed gradient increases over a 1 km stream reach by roughly one order of magnitude (from 3% to 38%), while flow discharge and width remain approximately constant. Sediment transport rates were determined in the 3% reach using Bunte bed load traps and in the 38% reach using the Swiss plate geophone system. Despite a ten-fold increase in bed gradient, bed load transport rates did not increase substantially. Observed transport rates for these two very different bed gradients could be predicted reasonably well by using a flow resistance partitioning approach to account for increasing bed roughness (D84 changes from 0.17 m to 0.91 m) within a fractional bed load transport equation. This suggests that sediment transport behavior across this large range of steep slopes agrees with patterns established in previous studies for both lower-gradient and steep reaches, and confirms the applicability of the flow resistance and bed load transport equations at very steep slopes.

  20. Predicting bed load transport of sand and gravel on Goodwin Creek

    Science.gov (United States)

    Bed load transport rates are difficult to predict in channels with bed material composed of sand and gravel mixtures. The transport of bed load was measured on Goodwin Creek, and in a laboratory flume channel with a similar bed material size distribution. The range of bed load transport rates meas...

  1. Spatial correlations in bed load transport: evidence, importance, and modelling

    CERN Document Server

    Heyman, J; Mettra, F; Ancey, C

    2016-01-01

    This article examines the spatial {dynamics of bed load particles} in water. We focus particularly on the fluctuations of particle activity, which is defined as the number of moving particles per unit bed {length}. Based on a stochastic model recently proposed by \\citet{Ancey2013}, we derive the second moment of particle activity analytically; that is the spatial correlation functions of particle activity. From these expressions, we show that large moving particle clusters can develop spatially. Also, we provide evidence that fluctuations of particle activity are scale-dependent. Two characteristic lengths emerge from the model: a saturation length $\\ell_{sat}$ describing the length needed for a perturbation in particle activity to relax to the homogeneous solution, and a correlation length $\\ell_c$ describing the typical size of moving particle clusters. A dimensionless P\\'eclet number can also be defined according to the transport model. Three different experimental data sets are used to test the theoretica...

  2. Propagation of hydrological modeling uncertainties on bed load transport simulations in steep mountain streams

    Science.gov (United States)

    Eichner, Bernhard; Koller, Julian; Kammerlander, Johannes; Schöber, Johannes; Achleitner, Stefan

    2017-04-01

    As mountain streams are sources of both, water and sediment, they are strongly influencing the whole downstream river network. Besides large flood flow events, the continuous transport of sediments during the year is in the focus of this work. Since small mountain streams are usually not measured, spatial distributed hydrological models are used to assess the internal discharges triggering the sediment transport. In general model calibration will never be perfect and is focused on specific criteria such as mass balance or peak flow, etc. The remaining uncertainties influence the subsequent applications, where the simulation results are used. The presented work focuses on the question, how modelling uncertainties in hydrological modelling impact the subsequent simulation of sediment transport. The applied auto calibration by means of MonteCarlo Simulation optimizes the model parameters for different aspects (efficiency criteria) of the runoff time series. In this case, we investigated the impacts of different hydrological criteria on a subsequent bed load transport simulation in catchment of the Längentaler Bach, a small catchment in the Stubai Alps. The used hydrologic model HQSim is a physically based semi-distributed water balance model. Different hydrologic response units (HRU), which are characterized by elevation, orientation, vegetation, soil type and depth, drain with various delay into specified river reaches. The runoff results of the Monte-Carlo simulation are evaluated in comparison to runoff gauge, where water is collected by the Tiroler Wasserkraft AG (TIWAG). Using the Nash-Sutcliffe efficiency (NSE) on events and main runoff period (summer), the weighted root mean squared error (RMSE) on duration curve and a combination of different criteria, a set of best fit parametrization with varying runoff series was received as input for the bed load transport simulation. These simulations are performed with sedFlow, a tool especially developed for bed load

  3. Fluctuations and time scales for bed-load sediment motion over a smooth bed

    Institute of Scientific and Technical Information of China (English)

    Francesco Ballio n; Alessio Radice

    2015-01-01

    Results are presented for experiments of bed-load sediment transport over a plane, smooth bed. The smooth-bed configuration, though not adequate for mimicking natural streams, enables the effects of bed roughness to be filtered out, thus, highlighting the role of flow turbulence for particle dynamics. Sediments were individually tracked along their paths, measuring position and velocity of the individual grains. A number of analyses were then applied to the data: probability density function, auto-correla-tion, and spectra of the grain velocity. Several Lagrangian time scales of particle motion were obtained and compared to available data for the turbulent flow field to determine a phenomenological inter-pretation of the process.

  4. Experimental modelling of marginal bed-load transport in an alpine mountain river

    Science.gov (United States)

    Kammerlander, Johannes; Gems, Bernhard; Koessler, Daniel; Aufleger, Markus

    2014-05-01

    The presented work deals with experimental transport modelling of bed-load over a self-stabilized channel bed, as it is often observed in alpine mountain streams. A reach of the Gurgler Ache, a mountain river situated in the Oetztal valley in Tyrol (Austria), was reproduced within a physical scale model (1:20) in the hydraulic engineering laboratory at the University of Innsbruck. The investigated river reach features a length of 280 m, a mean channel slope of 0.03 m/m, a bankful channel width of roughly 14 m, and a channel bed surface with a d84 of approximately 0.3 m. Experimental modelling was based on Froude's similarity law. At the lower end of the flume the bed was artificially fixed. Further, the lower boundary condition featured supercritical flow conditions as the water dropped into a tank, which was mounted on load cells. Ensuring an invariable relation of water level and volume in the tank the increase of weight is thus attributable to the bed-load leaving the flume. To ensure similar conditions as observed in the field, a bulk sediment mixture, corresponding to the sub-surface material of the Gurgler Ache, was set to a certain bed-level and a discharge (about one third of the mean annual peak flow) was applied until the bed-load transport decreased to virtually zero. With it, the observed mean bed slope as well as the characteristics of the bed surface could be configured. This was the initial condition of each experimental series. A series itself consisted of several experimental runs, each at a steady discharge, where 50 kg of sediment was added manually at the upper boundary of the flume. The sediment feeding was best possibly tried to be done at a constant rate. Once the 50 kg were fully added, the experimental run was continued for one third of the feeding duration. While for each experimental series a different grain size were added, the runs within one series differed in the discharges applied and were done successively, starting with the lowest

  5. How do macro-roughness elements affect bed-load sediment motion?

    Science.gov (United States)

    Radice, Alessio; Campagnol, Jenny

    2015-04-01

    Experimental results are here presented for bed-load particle motion in the presence of macro-roughness elements (MREs). Experiments were performed at the Hydraulics Laboratory of the Politecnico di Milano using plastic particles (size of 3 mm) as bed-load sediment that was fed into a rectangular-section, pressurized duct. The bottom of the duct was covered with a number of MREs, represented by concrete semi-spheres (diameter of 35 mm) that were not mobilized by the hydrodynamic conditions used. The experiments thus mimicked the transport of fine sediment in the presence of immobile boulders, that is one possible idealized representation of the granulometric variability found in natural water courses. The work is part of a project devoted to the characterization of particle kinematics for different roughness of the bed, undertaken within a long-term cooperation with the Environmental and Industrial Fluid Mechanics group at the University of Aberdeen (UK). Different flow conditions were tested. For each, MREs were placed in two different arrangements, corresponding to triangular grids with variable side length (130 mm and 100 mm). Colour of sediment was appropriately chosen (white grains over black background) to enable bed-load particles to be tracked by an image processing software (Streams, developed by the University of Canterbury, New Zealand). Particle kinematics was described using typical quantities: path length and tortuosity, path-averaged and instantaneous velocity components in the stream-wise and transverse directions, duration of motion events. The collected database was considerably wide, in terms of both measured particle paths and instantaneous velocity values. Results are discussed in terms of the measured kinematic properties and also comparing the sediment motion to that obtained for the same hydrodynamic conditions and in the absence of MREs. A discussion is made about comparability of the different scenarios, as the presence/absence of the MREs

  6. Peering inside the granular bed: illuminating feedbacks between bed-load transport and bed-structure evolution

    Science.gov (United States)

    Houssais, M.; Jerolmack, D. J.; Martin, R. L.

    2013-12-01

    The threshold of motion is perhaps the most important quantity to determine for understanding rates of bed load transport, however it is a moving target. Decades of research show that it changes in space and in time within a river, and is highly variable among different systems; however, these differences are not mechanistically understood. Recent researchers have proposed that the critical Shields stress is strongly dependent on the local configuration of the sediment bed [Frey and Church, 2011]. Critical Shields stress has been observed to change following sediment-transporting flood events in natural rivers [e.g., Turowski et al., 2011], while small-scale laboratory experiments have produced declining bed load transport rates associated with slow bed compaction [Charru et al., 2004]. However, no direct measurements have been made of the evolving bed structure under bed load transport, so the connection between granular controls and the threshold of motion remains uncertain. A perspective we adopt is that granular effects determine the critical Shields stress, while the fluid supplies a distribution of driving stresses. In order to isolate the granular effect, we undertake laminar bed load transport experiments using plastic beads sheared by a viscous oil in a small, annular flume. The fluid and beads are refractive index matched, and the fluid impregnated with a fluorescing powder. When illuminated with a planar laser sheet, we are able to image slices of the granular bed while also tracking the overlying sediment transport. We present the first results showing how bed load transport influences granular packing, and how changes in packing influence the threshold of motion to feed back on bed load transport rates. This effect may account for much of the variability observed in the threshold of motion in natural streams, and by extension offers a plausible explanation for hysteresis in bed load transport rates observed during floods. Charru, F., H. Mouilleron, and

  7. ON THE PHYSICS OF FLOW-DRIVEN SEDIMENTS (BED-LOAD)

    Institute of Scientific and Technical Information of China (English)

    Ulrich C. E. ZANKE

    2001-01-01

    More than three dozen significant formulae for bed-load transport have been developed over a period of more than 100 years with varying degrees of success. Major problems have been the use of completely or partly empirical approaches and too few data for fitting. This paper presents an analytical formulation for bed-load transport. It is based on a balance of forces for the determination of the thickness of the moving bed-load layer and on the determination of the velocity of this layer. The formula derived is compared to a set of approx. 2000 data published by 32 authors. It is demonstrated that the basic form of the MPM-formula is a special case of the analytical solution. The derivation also includes the effect of bed features such as ripples and dunes on quantitative transport.

  8. Comparison of genetic algorithm and imperialist competitive algorithms in predicting bed load transport in clean pipe.

    Science.gov (United States)

    Ebtehaj, Isa; Bonakdari, Hossein

    2014-01-01

    The existence of sediments in wastewater greatly affects the performance of the sewer and wastewater transmission systems. Increased sedimentation in wastewater collection systems causes problems such as reduced transmission capacity and early combined sewer overflow. The article reviews the performance of the genetic algorithm (GA) and imperialist competitive algorithm (ICA) in minimizing the target function (mean square error of observed and predicted Froude number). To study the impact of bed load transport parameters, using four non-dimensional groups, six different models have been presented. Moreover, the roulette wheel selection method is used to select the parents. The ICA with root mean square error (RMSE) = 0.007, mean absolute percentage error (MAPE) = 3.5% show better results than GA (RMSE = 0.007, MAPE = 5.6%) for the selected model. All six models return better results than the GA. Also, the results of these two algorithms were compared with multi-layer perceptron and existing equations.

  9. Effects of check dams on bed-load transport and steep-slope stream morphodynamics

    Science.gov (United States)

    Piton, Guillaume; Recking, Alain

    2017-08-01

    Check dams are transversal structures built across morphologically-active streams in mountainous regions. These structures have been used widely in torrent-hazard mitigation for over 150 years. Thousands of them are regularly maintained by stream managers and torrent-control services. The stabilization role of these structures is well known, i.e. they durably constrain the stream-bed through the creation of vertical and planar fixed points. What is not yet clear is to what extent check dams influence bed-load transport: How do peak solid discharge or flood-transported volume change when check dams are added to a reach? To address these questions, long-lasting small-scale experiments were conducted in a 4.8-m-long flume with either one, three or no structures. The results show that the addition of structures creates independent compartments in the bed level, which have a strong influence on bed surface armouring and stream morphodynamics: the consequence is that instantaneous transport intensities are unchanged, but peak solid discharge occur more often and for shorter duration. This results in the same total transported volume over the long term, but reduced volume for a single transport event. It reaffirms the observation of pioneering authors of the mid-19th and early 20th century who conceptualized the possible sediment transport regulation function of check dams: in addition to stabilizing the stream-bed, check dams influence bed-load transport through a buffering effect, releasing frequently and in small doses what, in their absence, would be transported abruptly en masse during rare extreme events.

  10. Petrology and Bulk Chemistry of Modern Bed Load Sediments From Rivers Draining the Eastern Tibetan Plateau

    Science.gov (United States)

    Borges, J. B.

    2003-12-01

    We studied river bed load petrology and bulk sediment chemistry of the headwaters of the Changjiang, Huang He and Red rivers in China and Vietnam. These rivers drain the eastern and southeastern parts of the Tibetan Plateau which includes part of the Indian-Eurasian suture zone. The eastern Tibetan Plateau is dominated by marine sedimentary rocks with a few scattered intrusive igneous outcrops, while the suture zone is characterized by a mixture of high-grade metamorphic, ultramafic, granitic, volcanic arc and marine sedimentary rocks. The arithmetic average for Qt: Ft: Rft along the suture zone varies from 56:2:42 along the Red River Fault (RRF) zone to 38:6:56 in the interior of the continent, while sands from rivers draining the plateau average 32:8:60. The sands analyzed in this study are relatively immature compared to most data available from most rivers in the tropics. The average Chemical Index of Alteration (CIA) for samples from the RRF suture zone (0.62) is similar to that of rivers draining other tropical regions like the Niger, Chao Phraya, Mekong, Ganges, Amazon and Brahmaputra. The CIA values from the RRF zone are also significantly different from the rest of the suture zone (0.36) and the plateau area (0.38). The difference can be attributed to the combined effect of relief and precipitation. The RRF lies in the Red River drainage and receives ˜1820 mm of precipitation annually, while the plateau area averages ˜620 mm annually. In the case of the Red River drainage, the relief combined with higher humidity can increase physical weathering and reduce the residence time of sediment in the river drainage, therefore, continuously replacing the sediment transported out of the drainage by freshly weathered immature materials. In the plateau area, lower precipitation and runoff may limit sediment transport and chemical weathering leading to sediment immaturity.

  11. Prediction of the bed-load transport by gas-liquid stratified flows in horizontal ducts

    CERN Document Server

    Franklin, Erick de Moraes

    2016-01-01

    Solid particles can be transported as a mobile granular bed, known as bed-load, by pressure-driven flows. A common case in industry is the presence of bed-load in stratified gas-liquid flows in horizontal ducts. In this case, an initially flat granular bed may be unstable, generating ripples and dunes. This three-phase flow, although complex, can be modeled under some simplifying assumptions. This paper presents a model for the estimation of some bed-load characteristics. Based on parameters easily measurable in industry, the model can predict the local bed-load flow rates and the celerity and the wavelength of instabilities appearing on the granular bed.

  12. The impact of benthic fauna on fluvial bed load transport: Challenges of upscaling laboratory experiments to river and landscape scales.

    Science.gov (United States)

    Rice, S. P.

    2012-04-01

    The impact on sediment transport processes and channel morphology of several relatively large, iconic animals including beaver and salmon is increasingly well understood. However, many other aquatic fauna are important zoogeomorphic agents and ecosystem engineers. These somewhat overlooked "Cinderella" species include benthic aquatic insect larvae, freshwater crustaceans and many species of fish. Despite relatively modest individual effects, the ubiquity, abundance and cumulative impact of these organisms makes them a potentially significant agency, with as yet undiscovered and unquantified impacts on channel morphology and sediment fluxes. Their actions (digging, foraging, moving, burrowing), constructions and secretions modify bed sediment characteristics (grain size distribution, interlock, imbrication, protrusion), alter bed topography (thence hydraulic roughness) and contribute to biogenic restraints on grain movement. In turn, they can affect the distribution of surface particle entrainment thresholds and bed shear stresses, with implications for bed load transport. Flume experiments have measured some of these impacts and provided direct observations of the mechanisms involved, but many of the most interesting research questions pertain to the impact of these animals at reach, catchment and even landscape scales: Not least, what is the impact of small aquatic animals on bed load flux and yield? This presentation will consider some of the challenges involved in answering this question; that is, of scaling up experimental understanding of how aquatic animals affect bed load transport processes to river scales. Pertinent themes include: (1) the potential impacts of experimental arrangements on the behaviours and activities that affect hydraulic or geomorphological processes; (2) field coincidence of the spatial and temporal distributions of (a) the animals and their behaviours with (b) the physical conditions (substrates, flows) under which those animals are

  13. Evaluation of a gravel transport sensor for bed load measurements in natural flows

    Institute of Scientific and Technical Information of China (English)

    Athanasios N.(Thanos) PAPANICOLAOU; Mohamed ELHAKEEM; Doug KNAPP

    2009-01-01

    A recent acoustic instrument (Gravel Transport Sensor,GTS) was tested for predicting sediment transport rate (bed load rate) in gravel bed streams.The GTS operation is based on the particle collision theory of submerged obstacles in fluids.When particles collide with the GTS cylinder their momentum is recorded in the form of ping rates.The GTS is attractive for further consideration here because of its potential to provide continuous unattended local bed load measurements,especially in areas found in streams that access may be difficult under extreme conditions.Laboratory experiments coupled with numerical simulations for the same flow conditions were performed in order to determine the conditions under which particles of different size will hit the GTS cylinder and be able to register a ping rate.The GTS was able to detect the number of particles with diameter in the range of 15.9 to 25.4 mm,with reasonable accuracy,if the applied Shields effective stress τ*e =τ*-τ*cr was in the range of 0.006 to 0.015.A drawback of the tested prototype GTS,however,was that it exerted increased resistance on the incoming particles.The added drag effects increased the overall resistance that was exerted by the flow on particles and thus increased the likelihood that particles will rest in the ambient region of the cylinder instead of hitting it.Numerical simulation of the flow around the GTS cylinder revealed that changing the prototype geometry from cylindrical to ellipsoid or rhomboid will increase the likelihood of the particles hitting the instrumet under the same flow conditions failed by the original tested GTS cylinder.

  14. An experimental analysis of bed load transport in gravel-bed braided rivers with high grain Reynolds numbers

    Science.gov (United States)

    De Vincenzo, Annamaria; Brancati, Francesco; Pannone, Marilena

    2016-08-01

    Laboratory experiments were performed with nearly uniform fluvial gravel (D50=9 mm, D10=5 mm and D90=13 mm) to analyse the relationship between stream power and bed load transport rate in gravel-bed braided rivers at high grain Reynolds numbers. The values of the unit-width dimensionless bed-load rate qb* and unit-width dimensionless stream power ω* were evaluated in equilibrium conditions based on ten different experimental runs. Then, they were plotted along with values obtained during particularly representative field studies documented in the literature, and a regression law was derived. For comparison, a regression analysis was performed using the data obtained from laboratory experiments characterized by smaller grain sizes and, therefore, referring to relatively low grain Reynolds numbers. A numerical integration of Exner's equation was performed to reconstruct the local and time-dependent functional dependence of qb* and ω*. The results led to the following conclusions: 1) At equilibrium, the reach-averaged bed load transport rate is related to the reach-averaged stream power by different regression laws at high and low grain Reynolds numbers. Additionally, the transition from bed to suspended load transport is accelerated by low Re*, with the corresponding bed load discharge increasing with stream power at a lower, linear rate. 2) When tested against the gravel laboratory measurements, the high Re* power law derived in the present study performs considerably better than do previous formulas. 3) The longitudinal variability of the section-averaged equilibrium stream power is much more pronounced than that characterizing the bed load rate, at least for high Re*. Thus, the stream power and its local-scale heterogeneity seem to be directly responsible for transverse sediment re-distribution and, ultimately, for the determination of the spatial and temporal scales that characterize the gravel bedforms. 4) Finally, the stochastic interpretation of the wetted

  15. Measurements and theory for transport layer structure in intense bed-load

    Science.gov (United States)

    Fraccarollo, L.; Capart, H.

    2012-04-01

    We focus on sediment laden flows driven by turbulent open-channel flows where the bed surface is fully mobilized and nonetheless the thickness of the bedload layer is conveniently smaller than the flow depth. This regime presents dynamic and kinematic features which persist in the range of applied Shields stress between about 0.3 and 3. Below the lower limit the moving grains do not develop significant stresses compared to the applied ones; above the upper limit, debris-flow type frictional contacts develop in a non negligible portion of the bedload layer. We report laboratory experiments in which, using high-speed cameras and a laser light sheet, detailed profiles of granular velocity and concentration have been measured. We checked that the transversal bed profile is flat and that the sidewall measurements are representative of the interior domain. The profiles provide new information on transport layer structure and its relation to the applied Shields stress. Contrary to expectations, we find that intense bed-load layers respond to changes in flow conditions by adjusting their granular concentration at the base. Two mechanisms account for the resulting behavior: stresses generated by immersed granular collisions, and equilibration by density stratification. Without parameter adjustment, the deduced constitutive relations capture the responses of velocity, concentration, and layer thickness in the above reported ten-fold increase Shields-stress range. Away from this intermediate range, in both directions, we show how the flow features rapidly change and the theoretical inferences decay.

  16. Linking the spatial distribution of bed load transport to morphological change during high-flow events in a shallow braided river

    Science.gov (United States)

    Williams, R. D.; Rennie, C. D.; Brasington, J.; Hicks, D. M.; Vericat, D.

    2015-03-01

    This paper provides novel observations linking the connections between spatially distributed bed load transport pathways, hydraulic patterns, and morphological change in a shallow, gravel bed braided river. These observations shed light on the mechanics of braiding processes and illustrate the potential to quantify coupled material fluxes using remotely sensed methods. The paper focuses upon a 300 m long segment of the Rees River, New Zealand, and utilizes spatially dense observations from a mobile acoustic Doppler current profiler (aDcp) to map depth, velocity, and channel topography through a sequence of high-flow events. Apparent bed load velocity is estimated from the bias in aDcp bottom tracking and mapped to indicate bed load transport pathways. Terrestrial laser scanning (TLS) of exposed bar surfaces is fused with the aDcp surveys to generate spatially continuous digital elevation models, which quantify morphological change through the sequence of events. Results map spatially distributed bed load pathways that were likely to link zones of erosion and deposition. The coherence between the channel thalweg, zone of maximum hydraulic forcing, and maximum apparent bed load pathways varied. This suggests that, in places, local sediment supply sources exerted a strong control on the distribution of bed load, distinct from hydraulic forcing. The principal braiding mechanisms observed were channel choking, leading to subsequent bifurcation. Results show the connection between sediment sources, pathways, and sinks and their influence on channel morphology and flow path directions. The methodology of coupling spatially dense aDcp surveys with TLS has considerable potential to understand connections between processes and morphological change in dynamic fluvial settings.

  17. Predicting fractional bed load transport rates: Application of the Wilcock-Crowe equations to a regulated gravel bed river

    Science.gov (United States)

    Gaeuman, D.; Andrews, E.D.; Kraus, A.; Smith, W.

    2009-01-01

    Bed load samples from four locations in the Trinity River of northern California are analyzed to evaluate the performance of the Wilcock-Crowe bed load transport equations for predicting fractional bed load transport rates. Bed surface particles become smaller and the fraction of sand on the bed increases with distance downstream from Lewiston Dam. The dimensionless reference shear stress for the mean bed particle size (t*rm) is largest near the dam, but varies relatively little between the more downstream locations. The relation between t*rm and the reference shear stresses for other size fractions is constant across all locations. Total bed load transport rates predicted with the Wilcock-Crowe equations are within a factor of 2 of sampled transport rates for 68% of all samples. The Wilcock-Crowe equations nonetheless consistently under-predict the transport of particles larger than 128 mm, frequently by more than an order of magnitude. Accurate prediction of the transport rates of the largest particles is important for models in which the evolution of the surface grain size distribution determines subsequent bed load transport rates. Values of term estimated from bed load samples are up to 50% larger than those predicted with the Wilcock-Crowe equations, and sampled bed load transport approximates equal mobility across a wider range of grain sizes than is implied by the equations. Modifications to theWilcock-Crowe equation for determining t*rm and the hiding function used to scale term to other grain size fractions are proposed to achieve the best fit to observed bed load transport in the Trinity River. Copyright 2009 by the American eophysical Union.

  18. Modification of the Engelund bed-load formula

    Institute of Scientific and Technical Information of China (English)

    Zhen Meng; Danxun Li; Xingkui Wang

    2016-01-01

    The classic Engelund bed-load formula involves four oversimplified assumptions concerning the quantity of particles per unit bed area that can be potentially entrained into motion, the probability of sediment being entrained into motion at a given instant, the mean velocity of bed-load motion, and the dimen-sionless incipient shear stress. These four aspects are reexamined in the light of new findings in hydrodynamics, and a modified bed-load formula is then proposed. The modified formula shows promise as being reliable in predicting bed-load transport rates in a wide range of flow intensities.

  19. LONG TERM EFFECTS OF REHABILITATION MEASURES ON BED LOAD TRANSPORT AT THE SALZACH RIVER

    Institute of Scientific and Technical Information of China (English)

    Sven HARTMANN

    2001-01-01

    The river Salzach and its tributary Saalach as part of the border line between Germany and Austria represents a permanent water management problem since centuries. While in former times threats for the people mainly arose from severe flood events the present situation is characterized by significant ecological deficits. These were caused by a rectification of the river resulting in a concentration of the flow followed by erosion of the river bed. The situation got worse in the late 60s after construction of hydropower plants started upstream holding back nearly all bed load material. The degradation of the river bed in the downstream section of the Salzach is stated critical by the authorities in respect of the lack of sufficient gravel remaining on top of fine material. As erosion processes of fine sand and silt cannot be predicted accurately but will be probably much faster than those of the gravel bed measures are necessary to stabilize the river bottom to avoid major damages of the embankments and further degradation of the groundwater table. Different alternatives were investigated in a framework of a wide range of studies over the past years. One of the major tasks was to estimate the long term effects on bed load transport.

  20. Nonlinear dynamical characteristics of bed load motion

    Institute of Scientific and Technical Information of China (English)

    BAI; Yuchuan; XU; Haijue; XU; Dong

    2006-01-01

    Bed forms of various kinds that evolve naturally on the bottom of sandy coasts and rivers are a result of the kinematics of bed load transport. Based on the group motion of particles in the bed load within the bottom layer, a study on the nonlinear dynamics of bed load transport is presented in this paper. It is found that some development stages, such as the initiation, the equilibrium sediment transport, and the transition from a smooth bed to sand dunes, can be accounted for by different states in the nonlinear system of the bed load transport. It is verified by comparison with experimental data reported by Laboratoire Nationae D'Hydraulique, Chatou, France, that the evolution from a smooth bed to sand dunes is determined by mutation in the bed load transport. This paper presents results that may offer theoretical explanations to the experimental observations. It is also an attempt to apply the state-of-the-art nonlinear science to the classical sediment transport mechanics.

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

    Institute of Scientific and Technical Information of China (English)

    Cailan GONG; Caixing YUN; Jianjun JIN

    2002-01-01

    The bed-load movement and the evolution of the Changjiang (Yangtze) Estuary are studied by using the geographic information system and the remote sensing image processing software Analysis on the erosion and siltation of the river mouth is performed for the period 1988-2000. The possible location and thickness of the future deposition areas in the estuarine channels are predicted.

  2. Erosion and transport of bed-load sediment

    NARCIS (Netherlands)

    Fernandez Luque, R.

    1974-01-01

    In this thesis first a general derivation is given of the 'macro'-equations of mass- and linear-momentum balance that govern the mo'mentum transfer from a Newtonian fluid to rigid particles in a fluid-solid mixture. In particular, attention is paid to a) the attenuation of viscous-momentum transfer

  3. Innovative Bed Load Measurement System for Large Alpine Gravel-Bed Rivers

    Science.gov (United States)

    Seitz, H.; Habersack, H. M.

    2009-04-01

    Samplers, Birckbeck-type bed load traps, etc.- in this regard used as a calibration technique but in general independent and throughout accepted bed load measurement methods) could be obtained. Finally in 2006, the measurement equipment was enlarged to an integrative and innovative bed load measurement system by installing Geophones. In addition hydrological, geological, meteorological and other related data are collected. For further investigations there is a chance to test new measurement techniques under well known boundary conditions at the fully equipped gauging stations. The instrumentation will allow observing transport processes in detail within the study reach. Calibration Measurements take place during the rainfall and snow melting season from May to August, furthermore in November due to Genoa depressions causing heavy rainfall in the catchment area of the Drau River. Especially the initiation of motion, the bed load transport rate and bed load transport processes (cross sectional variation, periodicity in bed load movement) are analysed. Moreover, for understanding bed load transport processes the initiation of motion is of central importance. As a result it could be shown that the counted number of geophone impulses per unit time is proportional to the transported sediment volume, calculated out of direct bed load measurements and the associated flow discharge. The scatter between geophone impulses, caused by bed load transport fluctuations, and flow discharge can be reduced if the sum of geophone impulses is averaged over longer time intervals (time lag between moving gravel sheet maximums is about 25 minutes). Furthermore, the assumed spatial and temporal variability of the bed load movement could now be proven. In addition it could be proven, that commonly used bed load predictors underestimate the measured bed load transport. In conclusion the results of the investigation are showing new aspects for understanding bed load transport processes. The installed

  4. 推移质输沙率公式比较与分析%The Comparison and Analysis for bed load transport rate formula

    Institute of Scientific and Technical Information of China (English)

    王承; 杨克君

    2013-01-01

      Load transport rate is a very important issue in the dynamics of the river.This article summarizes the six typical bed load transport rate which is calculated base onthe previous studies of bed load transport rate;the Single-wide sediment transport rates are unified into the form of bed load transport density,and a large number of theflume data validation is compared.The comparison shows that the largest relative errorcreated by Enge Long formula,up 118.6 percent;the lower relative error by Peterformula,39.1%;descending order of ac-curacy is Meyer-Peter formula,Douguorenformula,Ackers and White formula,Yalin formula,Sharmov formula, Engelund formula.The study can provide references for engineers to selection formulas.%  推移质输沙率是河流动力学中一个十分重要的问题。本文在前人研究推移质输沙率的基础上,总结了6个典型的推移质输沙率计算公式。把单宽输沙率都统一转化成推移质输移浓度的形式,并运用大量的试验水槽资料验证比较。比较结果表明,相对误差最大的是恩格隆公式,高达118.6%;相对误差最低的为梅叶-彼德公式,为39.1%;精度由高到低依次为 Meyer-Peter 公式,窦国仁公式, Ackers and White 公式, Yalin 公式, Sharmov公式, Engelund公式。该研究可为工程人员选择公式提供参考。

  5. STUDY ON TOTAL SEDIMENT TRANSPORT BY FLOW

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Total sediment transport under the action of flow includes generally three forms of sediment transport, suspended load, density current and bed load. How to realize simultaneously these three forms of sediment movement in an identical physical model was studied in this paper. For the suspended load, fall and pickup similarities were used to design sediment gradation, and similarities of sediment-carrying capacity and scouring and depositing time were be insured. For the density current its occurrence condition should be similar, and similarities of sediment concentration and depositing time were insured. For the bed load, sediment gradation was designed by the similarity of incipient motion, and similarities of sediment discharge and scouring and depositing time were satisfied. And a physical model test was conducted.

  6. Modelling transport of graded sediment under partial transport conditions

    NARCIS (Netherlands)

    Tuijnder, Arjan; Ribberink, Jan S.; Hulscher, Suzanne J.M.H.; Weerts, H.J.T.; Ritsema, I.L; van Os, A.G.

    2006-01-01

    Tentative plans are presented for research on the modelling of i) selective sediment transport in suspension and as bed-load, and ii) large-scale morphology in mixed sand-gravel bed rivers. Since the planning of the research is still in its early stages, the plans are flexible. Please feel free to

  7. Using RFID and accelerometer-embedded tracers to measure probabilities of bed load transport, step lengths, and rest times in a mountain stream

    Science.gov (United States)

    Olinde, Lindsay; Johnson, Joel P. L.

    2015-09-01

    We present new measurements of bed load tracer transport in a mountain stream over several snowmelt seasons. Cumulative displacements were measured using passive tracers, which consisted of gravel and cobbles embedded with radio frequency identification tags. The timing of bed load motion during 11 transporting events was quantified with active tracers, i.e., accelerometer-embedded cobbles. Probabilities of cobble transport increased with discharge above a threshold, and exhibited slight to moderate hysteresis during snowmelt hydrographs. Dividing cumulative displacements by the number of movements recorded by each active tracer constrained average step lengths. Average step lengths increased with discharge, and distributions of average step lengths and cumulative displacements were thin tailed. Distributions of rest times followed heavy-tailed power law scaling. Rest time scaling varied somewhat with discharge and with the degree to which tracers were incorporated into the streambed. The combination of thin-tailed displacement distributions and heavy-tailed rest time distributions predict superdiffusive dispersion.

  8. Sediment Transport

    DEFF Research Database (Denmark)

    Liu, Zhou

    Flow and sediment transport are important in relation to several engineering topics, e.g. erosion around structures, backfilling of dredged channels and nearshore morphological change. The purpose of the present book is to describe both the basic hydrodynamics and the basic sediment transport...... mechanics. Chapter 1 deals with fundamentals in fluid mechanics with emphasis on bed shear stress by currents, while chapter 3 discusses wave boundary layer theory. They are both written with a view to sediment transport. Sediment transport in rivers, cross-shore and longshore are dealt with in chapters 2......, 4 and 5, respectively. It is not the intention of the book to give a broad review of the literature on this very wide topic. The book tries to pick up information which is of engineering importance. An obstacle to the study of sedimentation is the scale effect in model tests. Whenever small...

  9. Universal shape evolution of particles by bed-load

    Science.gov (United States)

    Jerolmack, D. J.; Domokos, G.; Shaw, S.; Sipos, A.; Szabo, T.

    2016-12-01

    River currents, wind and waves drive bed-load transport, in which sediment particles collide with each other and the Earth's surface. A generic consequence is erosion and rounding of particles as a result of chipping, often referred to in geological literature as abrasion. Recent studies have shown that the erosion of river pebbles can be modeled as diffusion of surface curvature, indicating that geometric aspects of chipping erosion are insensitive to details of collisions and material properties. Here we present data from fluvial, aeolian and coastal environments that suggest a universal relation between particle circularity and mass lost due to bed-load chipping. Simulations and experiments support the diffusion model and demonstrate that three constraints are required to produce this universal curve: (i) initial particles are fragments; (ii) erosion is dominated by collisions among like-sized particles; and (iii) collision energy is small enough that chipping dominates over fragmentation. We show that the mechanics of bedrock weathering and bed-load transport select these constraints, providing the foundation to estimate a particle's erosion rate from its shape alone in most sedimentary environments. These findings may be used to determine the contribution of chipping to downstream fining in rivers and deserts, and to infer transport conditions using only images of sediment grains.

  10. The nature and role of advection in advection-diffusion equations used for modelling bed load transport

    Science.gov (United States)

    Ancey, Christophe; Bohorquez, Patricio; Heyman, Joris

    2016-04-01

    The advection-diffusion equation arises quite often in the context of sediment transport, e.g., for describing time and space variations in the particle activity (the solid volume of particles in motion per unit streambed area). Stochastic models can also be used to derive this equation, with the significant advantage that they provide information on the statistical properties of particle activity. Stochastic models are quite useful when sediment transport exhibits large fluctuations (typically at low transport rates), making the measurement of mean values difficult. We develop an approach based on birth-death Markov processes, which involves monitoring the evolution of the number of particles moving within an array of cells of finite length. While the topic has been explored in detail for diffusion-reaction systems, the treatment of advection has received little attention. We show that particle advection produces nonlocal effects, which are more or less significant depending on the cell size and particle velocity. Albeit nonlocal, these effects look like (local) diffusion and add to the intrinsic particle diffusion (dispersal due to velocity fluctuations), with the important consequence that local measurements depend on both the intrinsic properties of particle displacement and the dimensions of the measurement system.

  11. CASE STUDIES OF THREE-DIMENSIONAL NUMERICAL SIMULATION FOR TOTAL SEDIMENT TRANSPORT

    Institute of Scientific and Technical Information of China (English)

    Hongwei FANG

    2003-01-01

    The calculation of flow and sediment transport is one of the most important tasks in river engineering. The task is particularly difficult because of the many complex and interacting physical phenomena that need to be accounted for realistically in a model that has predictive power. This paper presents two study cases of three-dimensional calculation, respectively, of suspended sediment transport for the Three Gorges Project on the Yangtze River, China, and of bed load transport on the Elbe River, Germany. The suspended sediment transport calculation and bed load transport calculation are compared with experimental data whenever possible.

  12. Experimental investigations of graded sediment transport under unsteady flow hydrographs

    Institute of Scientific and Technical Information of China (English)

    Le Wang; Alan J.S. Cuthbertson; Gareth Pender; Zhixian Cao

    2015-01-01

    Natural fluvial channels can experience significant variations in sediment transport rates under unsteady flow conditions, especially during flood hydrograph events. At present, however, there is a distinct lack of understanding of the interaction between unsteady hydrograph flow properties and temporal variability in graded sediment transport rates. In the current study, a series of parametric experiments were conducted to investigate the response of two-graded sediment beds to a range of different unsteady hydrograph flow conditions. Investigations of the total and fractional bed-load sediment transport rates revealed strong temporal variations in transport over the hydrographs, with size-dependent temporal lag effects observed between peak flow conditions and peak bed-load transport rates. Specifically, coarse gravels had increased mobility during the rising limb of the hydrographs, attaining their peak bed-load transport rate either prior to, or near, peak flow conditions. By contrast, the finer grades tended to have enhanced mobility during the receding limb of the hydrographs, with peak transport rates measured after peak flow conditions had passed. Grain size distributions measured from the collected bed-load samples also indicated material coarsening over the rising limb and fining during the receding limb, while corresponding image analysis measurements of bed surface composition showed only marginal variation over the hydrographs. Computation of total and fractional sediment yields revealed that the bimodal sediment mixture tested was transported at significantly higher rates than the uni-modal mixture over all hydrograph conditions tested. This finding indicated that the uni-modal sediment bed was inherently more stable than the bimodal bed due to the increased abundance of medium-sized gravels present in the uni-modal sediment grade. The parametric dependences established in the study have clear implications for improved understanding of fractional

  13. Sediment transport in ice-covered channels

    Institute of Scientific and Technical Information of China (English)

    Ian KNACK; Hung-tao SHEN

    2015-01-01

    The existence of ice cover has important effects on sediment transport and channel morphology for rivers in areas with an annual occurrence of an ice season. The interaction of sediment transport and surface ice is poorly understood. In this paper, data from existing flume experiments, each with a limited range of flow and sediment transport conditions, are analyzed. The analysis showed that the bed load transport in ice-covered channels can be described by conventional relationships for the equivalent free-surface flow if the flow strength is expressed in terms of the bed shear stress. A modified Rouse formulation considering the effect of the ice cover on velocity and turbulent diffusion is shown to be applicable for calculating the suspended sediment transport discharge.

  14. Dynamics and mechanics of bed-load tracer particles

    Directory of Open Access Journals (Sweden)

    C. B. Phillips

    2014-12-01

    Full Text Available Understanding the mechanics of bed load at the flood scale is necessary to link hydrology to landscape evolution. Here we report on observations of the transport of coarse sediment tracer particles in a cobble-bedded alluvial river and a step-pool bedrock tributary, at the individual flood and multi-annual timescales. Tracer particle data for each survey are composed of measured displacement lengths for individual particles, and the number of tagged particles mobilized. For single floods we find that measured tracer particle displacement lengths are exponentially distributed; the number of mobile particles increases linearly with peak flood Shields stress, indicating partial bed load transport for all observed floods; and modal displacement distances scale linearly with excess shear velocity. These findings provide quantitative field support for a recently proposed modeling framework based on momentum conservation at the grain scale. Tracer displacement is weakly negatively correlated with particle size at the individual flood scale; however cumulative travel distance begins to show a stronger inverse relation to grain size when measured over many transport events. The observed spatial sorting of tracers approaches that of the river bed, and is consistent with size-selective deposition models and laboratory experiments. Tracer displacement data for the bedrock and alluvial channels collapse onto a single curve – despite more than an order of magnitude difference in channel slope – when variations of critical Shields stress and flow resistance between the two are accounted for. Results show how bed load dynamics may be predicted from a record of river stage, providing a direct link between climate and sediment transport.

  15. Sediment transport measurements: Chapter 5

    Science.gov (United States)

    Diplas, P.; Kuhnle, R.; Gray, J.; Glysson, D.; Edwards, T.; García, Marcelo H.

    2008-01-01

    Sediment erosion, transport, and deposition in fluvial systems are complex processes that are treated in detail in other sections of this book. Development of methods suitable for the collection of data that contribute to understanding these processes is a still-evolving science. Sediment and ancillary data are fundamental requirements for the proper management of river systems, including the design of structures, the determination of aspects of stream behavior, ascertaining the probable effect of removing an existing structure, estimation of bulk erosion, transport, and sediment delivery to the oceans, ascertaining the long-term usefulness of reservoirs and other public works, tracking movement of solid-phase contaminants, restoration of degraded or otherwise modified streams, and assistance in the calibration and validation of numerical models. This chapter presents techniques for measuring bed-material properties and suspended and bed-load discharges. Well-established and relatively recent, yet adequately tested, sampling equipment and methodologies, with designs that are guided by sound physical and statistical principles, are described. Where appropriate, the theory behind the development of the equipment and guidelines for its use are presented.

  16. A mechanistic-stochastic formulation of bed load particle motions: From individual particle forces to the Fokker-Planck equation under low transport rates

    Science.gov (United States)

    Fan, Niannian; Zhong, Deyu; Wu, Baosheng; Foufoula-Georgiou, Efi; Guala, Michele

    2014-03-01

    Bed load transport is a highly complex process. The probability density function (PDF) of particle velocities results from the local particle momentum variability in response to fluid drag and interactions with the bed. Starting from the forces exerted on a single particle under low transport rates (i.e., rolling and sliding regimes), we derive here the nonlinear stochastic Langevin equation (LE) to describe the dynamics of a single particle, accounting for both the deterministic and the stochastic components of such forces. Then, the Fokker-Planck equation (FPE), which describes the evolution of the PDF of the ensemble particle velocities, is derived from the LE. We show that the theoretical PDFs of both streamwise and cross-stream velocities obtained by solving the FPE under equilibrium conditions have exponential form (PDFs of both positive and negative velocities decay exponentially), consistent with the experimental data by Roseberry et al. Moreover, we theoretically show how the exponential-like PDF of an ensemble of particle velocities results from the forces exerted on a single particle. We also show that the simulated particle motions using the proposed Langevin model exhibit an emergent nonlinear relationship between hop distances and travel times (power law with exponent 5/3), in agreement with the experimental data, providing a statistical description of the particles' random motion in the context of a stochastic transport process. Finally, our study emphasizes that the motion of individual particles, described by the LE, and the behavior of the ensemble, described by the FPE, are connected within a statistical mechanics framework.

  17. A New Method for Tracking Individual Particles During Bed Load Transport in a Gravel-Bed River

    Science.gov (United States)

    Tremblay, M.; Marquis, G. A.; Roy, A. G.; Chaire de Recherche Du Canada En Dynamique Fluviale

    2010-12-01

    Many particle tracers (passive or active) have been developed to study gravel movement in rivers. It remains difficult, however, to document resting and moving periods and to know how particles travel from one deposition site to another. Our new tracking method uses the Hobo Pendant G acceleration Data Logger to quantitatively describe the motion of individual particles from the initiation of movement, through the displacement and to the rest, in a natural gravel river. The Hobo measures the acceleration in three dimensions at a chosen temporal frequency. The Hobo was inserted into 11 artificial rocks. The rocks were seeded in Ruisseau Béard, a small gravel-bed river in the Yamaska drainage basin (Québec) where the hydraulics, particle sizes and bed characteristics are well known. The signals recorded during eight floods (Summer and Fall 2008-2009) allowed us to develop an algorithm which classifies the periods of rest and motion. We can differentiate two types of motion: sliding and rolling. The particles can also vibrate while remaining in the same position. The examination of the movement and vibration periods with respect to the hydraulic conditions (discharge, shear stress, stream power) showed that vibration occurred mostly before the rise of hydrograph and allowed us to establish movement threshold and response times. In all cases, particle movements occurred during floods but not always in direct response to increased bed shear stress and stream power. This method offers great potential to track individual particles and to establish a spatiotemporal sequence of the intermittent transport of the particle during a flood and to test theories concerning the resting periods of particles on a gravel bed.

  18. Sediment transport during the snow melt period in a Mediterranean high mountain catchment

    Energy Technology Data Exchange (ETDEWEB)

    Alvera, B.; Lana-Renault, N.; Garcia-Ruiz, J. M.

    2009-07-01

    Transport of suspended sediment and solutes during the snow melt period (May-June, 2004) in the Izas catchment (Central Pyrenees) was studied to obtain a sediment balance and to assess the annual importance of sediment transport. The results showed that most sediment was exported in the form of solutes (75,6% of the total); 24.4% was exported as suspended sediment and no bed load was recorded. Sediment transport during the snow melt period represented 42.7% of the annual sediment yield. (Author) 7 refs.

  19. The nature of the bed load transport in the mouth of the river to the non-tidal sea (the Vistula River, Poland)

    Science.gov (United States)

    Lisimenka, Aliaksandr; Zwoliński, Zbigniew; Rudowski, Stanisław

    2015-04-01

    layer thickness exceeds 3 m. In addition to, granulometry analysis indicates dominating of medium-grained sands, in average well sorted, with the small add mixture of coarsed-grained sand (mainly on the crest of dunes) and sandy muds (mainly in the hollows). Field and computer analyzes indicated on the hydrodynamic conditions of water discharge in the mouth of the Vistula River in the longitudinal and transverse profiles, variations of bed load facies and variations of morphodynamic zones in the river channel. Despite the large internal dynamics of the river channel, analyzes show the relative spatial stability of that channel, independent of seasonal variations. This demonstrates the inertial character (stable) of depositional environment in estuary section of the Vistula River.

  20. Temporal variability and memory in sediment transport in an experimental step-pool channel

    Science.gov (United States)

    Saletti, Matteo; Molnar, Peter; Zimmermann, André; Hassan, Marwan A.; Church, Michael

    2015-11-01

    Temporal dynamics of sediment transport in steep channels using two experiments performed in a steep flume (8%) with natural sediment composed of 12 grain sizes are studied. High-resolution (1 s) time series of sediment transport were measured for individual grain-size classes at the outlet of the flume for different combinations of sediment input rates and flow discharges. Our aim in this paper is to quantify (a) the relation of discharge and sediment transport and (b) the nature and strength of memory in grain-size-dependent transport. None of the simple statistical descriptors of sediment transport (mean, extreme values, and quantiles) display a clear relation with water discharge, in fact a large variability between discharge and sediment transport is observed. Instantaneous transport rates have probability density functions with heavy tails. Bed load bursts have a coarser grain-size distribution than that of the entire experiment. We quantify the strength and nature of memory in sediment transport rates by estimating the Hurst exponent and the autocorrelation coefficient of the time series for different grain sizes. Our results show the presence of the Hurst phenomenon in transport rates, indicating long-term memory which is grain-size dependent. The short-term memory in coarse grain transport increases with temporal aggregation and this reveals the importance of the sampling duration of bed load transport rates in natural streams, especially for large fractions.

  1. Modeling on Flash Flood Disaster Induced by Bed Load

    Institute of Scientific and Technical Information of China (English)

    CAO Shuyou; LIU Xingnian; HUANG Er; YANG Keiun

    2008-01-01

    Flash floods result from a complex interaction among hydro-meteorological, hydrologi-cal, and hydraulic processes across various spatial and temporal scales. Sichuan Province suffers flash floods frequently owing to mountain weather and topography. A flash flood and gravel bed load transport are two key relative problems in mountain river engineering. Bed materials are often encountered in alternate scouring and deposition in mountain fluvial processes during a flash flood.In this circumstance, CRS-1 bed load numerical model jointly with scale physical model is em-ployed to predict water level and gravel bed scour and deposition for design of flood control dykes and flash flood disaster mitigation. A case study on the mechanism of a flash flood disaster in-duced by bed load transport for a hydropower station in Sichuan Province is conducted. Finally,suggestions to protect the hydropower station are proposed.

  2. Modelling sediment transport processes in macro-tidal estuary

    Institute of Scientific and Technical Information of China (English)

    Rauen; William; B.

    2009-01-01

    This paper outlines a numerical modeling study to predict the sediment transport processes in a macro-tidal estuary, namely the Mersey Estuary, UK. An integrated numerical model study is conducted to investigate the interaction between the hydrodynamic, morphological and sediment transport processes occurring in the estuary. The numerical model widely used in environmental sediment transport studies worldwide, namely ECOMSED is used to simulate flow and sediment transport in estuary. A wetting and drying scheme is proposed and applied to the model, which defines "dry" cells as regions with a thin film of fluid O (cm). The primitive equations are solved in the thin film as well as in other regular wet cells. A model for the bed load transport is included in the code to account for the dynamics of the mobile bed boundary. The bed evolution due to bed load transport which is calculated according to van Rijn (1984a) is obtained by solving the sediment mass-balance equation. An estuary-related laboratory flume experiment is used to verify the model. Six sets of field measured hydrodynamic data are used to verify the corresponding predictions of the model, with the model-predicted water elevations and salinity levels generally agreeing well with the field measurements. The numerical model results show that in the Mersey Estuary both the tidal level and river discharge affect significantly the sediment transport. Reasonable agreement between the model results and field data has been obtained, indicating that the model can be used as computer-based tool for the environment management of estuarine system.

  3. Evaluation of ADCP apparent bed load velocity in a large sand-bed river: Moving versus stationary boat conditions

    Science.gov (United States)

    Jamieson, E.C.; Rennie, C.D.; Jacobson, R.B.; Townsend, R.D.

    2011-01-01

    Detailed mapping of bathymetry and apparent bed load velocity using a boat-mounted acoustic Doppler current profiler (ADCP) was carried out along a 388-m section of the lower Missouri River near Columbia, Missouri. Sampling transects (moving boat) were completed at 5- and 20-m spacing along the study section. Stationary (fixed-boat) measurements were made by maintaining constant boat position over a target point where the position of the boat did not deviate more than 3 m in any direction. For each transect and stationary measurement, apparent bed load velocity (vb) was estimated using ADCP bottom tracking data and high precision real-time kinematic (RTK) global positioning system (GPS). The principal objectives of this research are to (1) determine whether boat motion introduces a bias in apparent bed load velocity measurements; and (2) evaluate the reliability of ADCP bed velocity measurements for a range of sediment transport environments. Results indicate that both high transport (vb>0.6 m/s) and moving-boat conditions (for both high and low transport environments) increase the relative variability in estimates of mean bed velocity. Despite this, the spatially dense single-transect measurements were capable of producing detailed bed velocity maps that correspond closely with the expected pattern of sediment transport over large dunes. ?? 2011 American Society of Civil Engineers.

  4. Advances in sediment transport under combined action of waves and currents

    Institute of Scientific and Technical Information of China (English)

    Yongjun Lu; Shouqian Li; Liqin Zuo; Huaixiang Liu; J.A. Roelvink

    2015-01-01

    The coastal zone continuously changes due to natural processes and human activities. In order to understand and predict these morphological changes, an accurate description of sediment transport, caused by waves and currents (tidal or wave-induced), is important. This paper presents a review of the state-of-the-art knowledge in this field, including sediment incipient motion, bed forms, bed roughness, bed-load transport, suspended-load transport, equilibrium sediment concentration, and sheet flow. Some possible research fields and topics for future study also are proposed.

  5. Formation and development of a breaker bar under regular waves. Part 2: Sediment transport and morphology

    DEFF Research Database (Denmark)

    Jacobsen, Niels Gjøl; Fredsøe, Jørgen

    2014-01-01

    condition is a profile of constant slope. One reference simulation is discussed in detail and the morphological development due to changes in the hydrodynamic forcing (wave period, wave height, wave irregularity and a net cross-shore current) and in other properties (sediment size and beach slope......In Part 2 of this work, the hydrodynamic model described in Part 1 is applied for the simulation of sediment transport and the associated morphological development of breaker bars. The sediment description is split into bed load and suspended load, and like the hydrodynamics the sediment transport...... is phase-resolved in order to get on- and offshore directed contributions to the sediment transport from phase lags between the suspended sediment and the hydrodynamics.First, the sediment transport over a morphologically fixed bed of a constant slope is considered, and the transport rates are discussed...

  6. Diffusion of bed load particles subject to different flow conditions

    Science.gov (United States)

    Cecchetto, Martina; Cotterle, Luca; Tregnaghi, Matteo; Tait, Simon; Marion, Andrea

    2015-04-01

    An in-depth understanding of sediment motion in rivers has acquired increasing importance lately in order to plan restoration activities that provide ecological benefit. River beds constitute the interfacial environment where several species live and mass exchange of sediments/nutrients/pollutants can take place. Moving grains interacting with the bed deposit and can locally change the bed surface topography they can also act as carriers for contaminants associated with the grains. Study the motion of grains on the bed, in particular the extent and variability of their travel distance with regards to the flow conditions can provide information on the transport of grain associated contaminants. The results of a series of experimental tests, in which increasing levels of boundary shear stress were applied over a bed deposit of natural river gravel, are reported. Image databases consisted of a series of bed images acquired at a frequency of 45 Hz were collected. Analysis of the images has provided time and position data to plot the trajectories of more than 200 moving grains for each test. This data enables the derivation of the statistics of the un-truncated probability distribution of the detected particles' step length, which is consider as the distance moved by a particle from the moment it is entrained to the instant it stops on the bed. In recent studies the movement of bed load material has been indicated as diffusive, but little is known about the spatial and temporal scales of this diffusion. The analysis of the longitudinal and transverse trajectories for the tracked particles has here revealed three regimes of diffusion: a ballistic diffusion which takes place at the very beginning of particles motion, an anomalous intermediate regime, and a normal subdiffusion which occurs for larger times. Characteristic time scales separate these three diffusive regimes. Results show that in experiments with higher shear stresses the time scale separating the ballistic

  7. Numerical simulation of sediment transport in coastal waves and wave-induced currents

    Institute of Scientific and Technical Information of China (English)

    TANG Jun; LYU Yigang; SHEN Yongming

    2016-01-01

    Prediction of coastal sediment transport is of particularly importance for analyzing coast erosion accurately and solving the corresponding coast protection engineering problems. The present study provided a numerical scheme for sediment transport in coastal waves and wave-induced currents. In the scheme, the sand transport model was implemented with wave refraction-diffraction model and near-shore current model. Coastal water wave was simulated by using the parabolic mild-slope equation in which wave refraction, diffraction and breaking effects are considered. Wave-induced current was simulated by using the nonlinear shallow water equations in which wave provides radiation stresses for driving current. Then, sediment transport in waves and wave-induced currents was simulated by using the two-dimensional suspended sediment transport equations for suspended sediment and the bed-load transport equation for bed load. The numerical scheme was validated by experiment results from the Large-scale Sediment Transport Facility at the US Army Corps of Engineer Research and Development Center in Vicksburg. The numerical results showed that the present scheme is an effective tool for modeling coastal sediment transport in waves and near-shore currents.

  8. DEPTH-AVERAGE ANALYSIS OF HYSTERESIS BETWEEN FLOW AND SEDIMENT TRANSPORT UNDER UNSTEADY CONDITIONS

    Institute of Scientific and Technical Information of China (English)

    Weiming WU; Mustafa ALTINAKAR; Sam S.Y.WANG

    2006-01-01

    A depth-averaged two-dimensional model has been established to simulate unsteady flow and sediment transport in streams. The difference in flow and sediment velocities is considered. It has been found that the depth-averaged suspended-sediment velocity and the bed-load velocity are smaller than the depth-averaged flow velocity, inducing a time lag between water and sediment transport. The significance of this time lag increases as the sediment size increases. The exchange between the moving sediment and the bed material, which may induce a spatial lag, is modeled by a non-equilibrium transport approach. Tests using laboratory and field measurements have shown that the established model is capable of capturing the hysteresis between flow and sediment transport under unsteady conditions. It is demonstrated that the hysteresis is larger when the hydrograph has steeper rising and falling limbs, and the time delay increases downstream.

  9. Literature Review for Texas Department of Transportation Research Project 0-4695: Guidance for Design in Areas of Extreme Bed-Load Mobility, Edwards Plateau, Texas

    Science.gov (United States)

    2005-01-01

    Uvalde County Kerr County Gillespie County Bandera County Mason County Menard County 100°30’W 100°0’W 99°30’W 29°30’N 30°0’N 30°30’N TEXAS So uth Llan o R...semiarid area, New Mexico : U.S. Geological Survey Professional Paper 352–G, p. 193–253. • The authors investigate sediment supply mechanisms to a...Jr., 1963, A preliminary study of sediment trans- port parameters, Rio Puerco near Bernardo, New Mexico : U.S. Geological Survey Professional Paper

  10. Velocity fields of a bed-load layer under a turbulent liquid flow

    CERN Document Server

    Penteado, Marcos Roberto Mendes

    2016-01-01

    The transport of sediments by a fluid flow is commonly found in nature and in industry. In nature, it is found in rivers, oceans, deserts, and other environments. In industry, it is found in petroleum pipelines conveying grains, in sewer systems, and in dredging lines, for example. This study investigates experimentally the transport of the grains of a granular bed sheared by a turbulent liquid flow. In our experiments, fully developed turbulent water flows were imposed over a flat granular bed of known granulometry. Under the tested conditions, the grains were transported as bed load, i.e., they became entrained by rolling and sliding over each other, forming a moving granular layer. The present experiments were performed close to incipient bed load, a case for which experimental data on grains velocities are scarce. Distinct from previous experiments, an entrance length assured that the water stream over the loose bed was fully developed. At different water flow rates, the moving layer was filmed using a hi...

  11. Effects of bed-load movement on flow resistance over bed forms

    Indian Academy of Sciences (India)

    Mohammad Hossein Omid; Masoud Karbasi; Javad Farhoudi

    2010-12-01

    The effect of bed-load transport on flow resistance of alluvial channels with undulated bed was experimentally investigated. The experiments were carried out in a tilting flume 250 mm wide and 12·5 m long with glass-sides of rectangular cross-section and artificial dune shaped floor that was made from Plexi-glass. Steady flow of clear as against sediment-laden water with different flow depths and velocities were studied in the experiments with a fine sand ($d_{50} =$ 0·5 mm). The results indicate that the transport of fine particles ($d_{50} =$ 0·5 mm) can decrease the friction factor by 22% and 24% respectively for smooth and rough beds. Increasing the bed-load size ($d_{50} =$ 2·84 mm) can decrease the friction factor by 32% and 39% respectively for smooth and rough beds. The decrease in flow resistance is due to filling up of the troughs of dunes. This separation zone is responsible for increasing the flow resistance. On the upstream side of dunes condition is similar to plane bed. Presence of bed-load causes to increase the shear velocity and hence increasing flow resistance. But decreasing in flow resistance is more and it causes to decrease the total flow resistance. Grains saturated the troughs in the bed topography, effectively helping in smoothening of bed irregularities.

  12. Sediment transport during flushing flows in the lower River Ebro

    Science.gov (United States)

    Batalla, R. J.; Vericat, D.; Palau, A.

    2009-04-01

    This study describes the sediment transport which occurred during several flushing flows between 2002 and 2008 in the impounded lower River Ebro (Northeast Spain). The experimental releases were designed and undertaken to control the excess of aquatic vegetation and enhance sediment-related processes in the river channel downstream the lowermost dams in the basin. Macrophytes cause problems to water users, especially to the hydroelectric and the nuclear power plants located in the vicinity of the river. Sediment transport results from flushing flows are compared with those observed during natural floods. Observations show distinct patterns of sediment transport owing to the particular channel conditions (i.e. exhaustion of fine sediment and removal of the surface layer). Flushing flows depict notably higher suspended sediment concentrations in relation to natural floods. Bed load rates during flushing flows are typically low and, because the flood duration is short, no incision is observed in the river bed. In spite of that, large quantities of macrophytes were removed. The combination of hydraulic and sedimentary parameters during the designed floods maximizes the ecological and management benefits of the experimental releases without significant adverse geomorphological impacts on the river channel.

  13. 1-D coupled non-equilibrium sediment transport modeling for unsteady flows in the discontinuous Galerkin framework

    Institute of Scientific and Technical Information of China (English)

    Farzam Safarzadeh MALEKI; Abdul A KHAN

    2016-01-01

    A high-resolution, 1-D numerical model has been developed in the discontinuous Galerkin framework to simulate 1-D flow behavior, sediment transport, and morphological evaluation under unsteady flow conditions. The flow and sediment concentration variables are computed based on the one-dimensional shallow water flow equations, while empirical equations are used for entrainment and deposition processes. The sediment transport model includes the bed load and suspended load components. New formulations for Harten-Lax-van Leer (HLL) and Harten-Lax-van Contact (HLLC) are presented for shallow water flow equations that include the bed load and suspended load fluxes. The computational results for the flow and morphological changes after two dam break events are compared with the physical model tests. Results show that the modified HLL and HLLC formulations are robust and can accurately predict morphological changes in highly unsteady flows.

  14. Community Sediment Transport Model

    Science.gov (United States)

    2007-01-01

    are used to determine that model results are consistent across compilers, platforms, and computer architectures , and to ensure that changes in code do...Mississippi State University: Bhate During the early months of this project, the focus was on understanding ROMS-CSTM model, architecture , and...Marchesiello, J.C. McWilliams, & K.D. Stolzenbach, 2007: Sediment transport modeling on Southern Californian shelves: A ROMS case study. Continental

  15. Tracing cohesive sediment transportation at river mouths around Tokyo, Japan by Cesium originated from Fukushima Daiichi Power Plant

    Science.gov (United States)

    koibuchi, Y.

    2012-12-01

    Sediment transport at river mouths, which consists of suspended-load and bed-load, has not been fully understood, since bed-load transport of cohesive sand is difficult to observe. Especially, the impact of sediment transport on the total amount of fine-grained cohesive sediment has not been elucidated. Cesium-134 and cesium-137 were spread from the Fukushima Daiichi Nuclear Power Plant (FDNPP) after the earthquake of March 11 of 2011, and attached to the fine-grained sand on the land. The contaminated sand flowed into the river mouths through the rivers possibly due to the complex physical processes in estuarine areas. To evaluate the fine-grained sediment transport around Tokyo and Tokyo Bay, field observations were carried out utilizing radionuclide originated from FDNPP as an effective tracer. The cohesive sediment transport at three different river mouths around Tokyo was successfully quantified. The cohesive sediment transport deposited in the estuary was found to be greatly dependent on the land use, geometry, river discharge and salinity. In addition,the transport driven by the rainfall was minute, and its behavior was quite different from suspended solids. Although further field observations of radionuclide are necessary, it is clear that fine-grained sediment in the bay from rivers already settled on the river mouth by aggregation. The settled sand will not move even in rainfall events. Consequently, the transport of radionuclide to the Pacific Ocean may not occur.; Cesium distribution around Tokyo Bay ; Cesium Concentration in Edogawa river

  16. A curved flume bed-load experiment

    NARCIS (Netherlands)

    Talmon, A.M.; Marsman, E.R.A.

    1988-01-01

    In this report the results of a bed-load experiment in a curved flume are presented. The experiments have been carried out in the Laboratory of Fluid Mechanics (L.F.M.) at the Delft University of Technology. The main object of the experiments is to develop and to test data-acquisition procedures for

  17. Passive acoustic monitoring of bed load discharge in a large gravel bed river

    Science.gov (United States)

    Geay, T.; Belleudy, P.; Gervaise, C.; Habersack, H.; Aigner, J.; Kreisler, A.; Seitz, H.; Laronne, J. B.

    2017-02-01

    Surrogate technologies to monitor bed load discharge have been developed to supplement and ultimately take over traditional direct methods. Our research deals with passive acoustic monitoring of bed load flux using a hydrophone continuously deployed near a river bed. This passive acoustic technology senses any acoustic waves propagated in the river environment and particularly the sound due to interparticle collisions emitted during bed load movement. A data set has been acquired in the large Alpine gravel-bedded Drau River. Analysis of the short-term frequency response of acoustic signals allows us to determine the origin of recorded noises and to consider their frequency variations. Results are compared with ancillary field data of water depth and bed load transport inferred from the signals of a geophone array. Hydrophone and geophone signals are well correlated. Thanks to the large network of deployed geophones, analysis of the spatial resolution of hydrophone measurements shows that the sensor is sensitive to bed load motion not only locally but over distances of 5-10 m (10-20% of river width). Our results are promising in terms of the potential use of hydrophones for monitoring bed load transport in large gravel bed rivers: acoustic signals represent a large river bed area, rather than being local; hydrophones can be installed in large floods; they can be deployed at a low cost and provide continuous monitoring at high temporal resolution.

  18. Bed-Load Dispersion: A Literature Review

    Science.gov (United States)

    2016-12-01

    However, the work of Phillips et al. (2013) suggested that the asymptotic limit of bed-load dispersion is super- dispersive. Fischer et al. (1979...Olinde and Johnson 2015, Phillips et al. 2013, Martin et al. 2012 and 2014). Campagnol et al. (2015) showed that if the particles are exhibiting...vertical dispersion. Journal of Geophysical Research: Earth Surface 119(9): 1818–1832. Phillips , C. B., R. L. Martin, and D. J. Jerolmack. 2013

  19. Onset of sediment transport is a continuous transition driven by fluid shear and granular creep.

    Science.gov (United States)

    Houssais, Morgane; Ortiz, Carlos P; Durian, Douglas J; Jerolmack, Douglas J

    2015-03-09

    Fluid-sheared granular transport sculpts landscapes and undermines infrastructure, yet predicting the onset of sediment transport remains notoriously unreliable. For almost a century, this onset has been treated as a discontinuous transition at which hydrodynamic forces overcome gravity-loaded grain-grain friction. Using a custom laminar-shear flume to image slow granular dynamics deep into the bed, here we find that the onset is instead a continuous transition from creeping to granular flow. This transition occurs inside the dense granular bed at a critical viscous number, similar to granular flows and colloidal suspensions and inconsistent with hydrodynamic frameworks. We propose a new phase diagram for sediment transport, where 'bed load' is a dense granular flow bounded by creep below and suspension above. Creep is characteristic of disordered solids and reminiscent of soil diffusion on hillslopes. Results provide new predictions for the onset and dynamics of sediment transport that challenge existing models.

  20. THE NONLINEAR CUSP-CATASTROPHE MODEL OF THE SEDIMENT TRANSPORT RATE

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    In the catastrophe theory of nonlinear science,the intensity of water-flow and the coefficient of non-uniformsediment m are regarded as two bound variables, and the in-tensity of bed-load transport Φ as the state variable in the mo-tion of non-uniform sediment in cusp-catastrophe model.Based on the standard equation of the cusp-catastrophe theo-ry, the relation equation between the intensity of bed-loadtransport Φ and the intensity of water-flow has been derivedby used coordinate transform and topology transform. The e-quation of bed load transport rate was built on the cusp-catas-trophe theory of nonlinear science. The others are applied toverify this equation, that the results calculated by the cusp-ca-tastrophe equation agree well with the other equations. Thisindicates that the cusp-catastrophe equation is reasonable, and the results fully reflect the characteristics of threshold motionand transport of non-uniform sediment. The purpose of thispaper is to explore the incipient motion and transport laws ofnon-uniform sediment from the viewpoint of nonlinear science.

  1. Modes of sediment transport in channelized water flows with ramifications to the erosion of the Martian outflow channels

    Science.gov (United States)

    Komar, P. D.

    1980-01-01

    The paper discusses application to Martian water flows of the criteria that determine which grain-size ranges are transported as bed load, suspension, and wash load. The results show nearly all sand-sized material and finer would have been transported as wash load and that basalt pebbles and even cobbles could have been transported at rapid rates of suspension. An analysis of the threshold of sediment motion on Mars further indicates that the flows would have been highly competent, the larger flows having been able to transport boulder-sized material. Comparisons with terrestrial rivers which transport hyperconcentration levels of sediments suggest that the Martian water flows could have achieved sediment concentrations up to 70% in weight. Although it is possible that flows could have picked up enough sediment to convert to pseudolaminar mud flows, they probably remained at hyperconcentration levels and fully turbulent in flow character.

  2. The feedback effect caused by bed load on a turbulent liquid flow

    CERN Document Server

    Franklin, Erick de Moraes; Rosa, Eugênio Spanó

    2016-01-01

    Experiments on the effects due solely to a mobile granular layer on a liquid flow are presented (feedback effect). Nonintrusive measurements were performed in a closed conduit channel of rectangular cross section where grains were transported as bed load by a turbulent water flow. The water velocity profiles were measured over fixed and mobile granular beds of same granulometry by Particle Image Velocimetry. The spatial resolution of the measurements allowed the experimental quantification of the feedback effect. The present findings are of importance for predicting the bed-load transport rate and the pressure drop in activities related to the conveyance of grains.

  3. Development of an integrated sediment transport model and application at a large gravel bed river

    Science.gov (United States)

    Tritthart, M.; Schober, B.; Liedermann, M.; Habersack, H.

    2009-04-01

    This paper presents the development, validation and application of iSed, an integrated numerical sediment transport and morphology model. The model was specifically designed to suit the needs of large gravel bed rivers, such as the Danube East of Vienna. It is coupled with external 2-D or 3-D hydrodynamic codes to obtain the flow field and bed shear stress patterns driving sediment transport processes. This approach is of particular advantage for an investigation into sediment dynamics based on hydrodynamics of different dimensionality. The model is capable of calculating both suspended and bed load transport. It solves a convection-diffusion equation to account for suspended load; in addition, four different transport formulae - the relations of Meyer-Peter/Müller, Hunziker, van Rijn and Egiazaroff - are implemented for the computation of bed load. The well-known Exner equation is solved for deriving resulting bed level differences for every node of the computation mesh based on the sediment balance. All equations are evaluated for an unlimited number of sediment size fractions, allowing for the investigation of sorting processes. The river bed is organized into an active layer, where sorting takes place, and an unlimited number of bed layers below the active layer. The sediment transport model was validated using results from three different laboratory experiments: (i) morphodynamics of a 180 degree channel bend, based on hydraulics of a 3-D numerical model; (ii) erosion and deposition patterns due to a channel contraction, using a 2-D model to provide the flow field; (iii) incipient motion and erosion processes due to different sediment materials in a straight laboratory channel, coupled with a 3-D numerical model. The results of the numerical code were in satisfactory agreement with the experimental measurements, demonstrating the general validity of the sediment transport model. After successful validation, the model was applied to a 4 kilometre reach of the

  4. APPLICABILITY OF SEDIMENT TRANSPORT FORMULAS

    Institute of Scientific and Technical Information of China (English)

    Chih Ted YANG; Caian HUANG

    2001-01-01

    The paper provides a comprehensive testing of the applicability of 13 sediment transport formulas under different flow and sediment conditions. The dimensionless parameters used for testing the reliability and sensitivity of formulas are dimensionless particle diameter, relative depth, Froude number, relative shear velocity, dimensionless unit stream power, and sediment concentration. A total of 3,391 sets of laboratory and river data are used in the tests. Engineers may find the test results useful to their selection of formulas under different flow and sediment conditions.

  5. THREE DIMENSIONAL NUMERICAL MODELLING OF FLOW AND SEDIMENT TRANSPORT IN RIVERS

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The 3D numerical model, ECOMSED (open source code), was used to simulate flow and sediment transport in rivers. The model has a long history of successful applications to oceanic, coastal and estuarine waters. Improvements in the advection scheme, treatment of river roughness parameterization and shear stress partitioning were necessary to reproduce realistic and comparable results in a river application. To account for the dynamics of the mobile bed boundary, a model for the bed load transport was included in the code. The model reproduced observed secondary currents,bed shear stress distribution and erosion-deposition patterns on a curved channel. The model also successfully predicted the general flow patterns and sediment transport characteristics ora l-km long reach of the River Klar(a)lven, located in the north of the county of V(a)rmland, Sweden.

  6. Fluvial sediment transport in a glacier-fed high-mountain river (Riffler Bach, Austrian Alps)

    Science.gov (United States)

    Morche, David; Weber, Martin; Faust, Matthias; Schuchardt, Anne; Baewert, Henning

    2017-04-01

    High-alpine environments are strongly affected by glacier retreat since the Little Ice Age (LIA). Due to ongoing climate change the hydrology of proglacial rivers is also influenced. It is expected that the growing proportions of snow melt and rainfall events will change runoff characteristics of proglacial rivers. Additionally, the importance of paraglacial sediment sources in recently deglaciating glacier forefields is increasing, while the role of glacial erosion is declining. Thus complex environmental conditions leading to a complex pattern of fluvial sediment transport in partly glaciated catchments of the European Alps. Under the umbrella of the joint PROSA-project the fluvial sediment transport of the river Riffler Bach (Kaunertal, Tyrol, Austria) was studied in 3 consecutive ablation seasons in order to quantify sediment yields. In June 2012 a probe for water level and an automatic water sampler (AWS) were installed at the outlet of the catchment (20km2). In order to calculate annual stage-discharge-relations by the rating-curve approach, discharge (Q) was repeatedly measured with current meters and by salt dilution. Concurrent to the discharge measurements bed load was collected using a portable Helley-Smith sampler. Bed load samples were weighted and sieved in the laboratory to gain annual bed load rating curves and grain size distributions. In total 564 (2012: 154, 2013: 209, 2014: 201) water samples were collected and subsequently filtered to quantify suspended sediment concentrations (SSC). Q-SSC-relations were calculated for single flood events due to the high variability of suspended sediment transport. The results show a high inter- and intra-annual variability of solid fluvial sediment transport, which can be explained by the characteristics of suspended sediment transport. Only 13 of 22 event-based Q-SSC-relations show causal dependency. In 2012, during a period with multiple pluvial-induced peak discharges most sediment was transported. On the

  7. Gradation effects in sediment transport

    NARCIS (Netherlands)

    de Meijer, RJ; Bosboom, J; Cloin, B; Katopodi, [No Value; Kitou, N; Koomans, RL; Manso, F

    2002-01-01

    To determine the effects of grain size and density gradation in oscillatory sheet-flow, experiments are conducted in an oscillating water tunnel. A formal derivation of a schematised transport model shows that the transport rates per sediment fraction can be determined with and without the assumptio

  8. Particle velocity and sediment transport at the limit of deposition in sewers.

    Science.gov (United States)

    Ota, J J; Perrusquía, G S

    2013-01-01

    This paper focuses on the sediment particle while it is transported at the limit of deposition in storm sewers, i.e. as bed load at the limit of concentration that leads to sediment deposition. Although many empirical sediment transport equations are known in the literature, there is only limited knowledge concerning particle velocity. Sediment particle and sphere velocity measurements were carried out in two pipe channels and these results led to the development of a semi-theoretical equation for sediment transport at the limit of deposition in sewers. Even in the transport process without deposition, sediment movement is slower than water velocity and depends on the angle of repose of sediment with a diameter d on the roughness k of the pipe channel. Instead of classical dimensionless bed shear stress ψ, a modified dimensionless bed shear stress ψ (d/k)(2/3) was suggested, based on the angle of repose and this parameter was proved to be significant for quantifying the transport capacity. The main purpose of this article is to emphasize the importance of careful observation of experiments. Not only number of tests, but physical understanding are essential for better empirical equations.

  9. Two-dimensional sediment transport modeling for reservoir sediment management: Reventazón River, Costa Rica

    Science.gov (United States)

    Dubinski, I. M.

    2012-12-01

    Sedimentation is an ongoing concern for reservoirs that may be addressed using a variety of sediment management options. Sedimentation in reservoirs reduces reservoir storage and alters the sediment supply downstream. The objective of this study is to estimate the spatial and temporal distribution of deposited sediment in a proposed reservoir in the Reventazón River, Costa Rica over long-term operation (40 years) under different sediment management scenarios. The two-dimensional sediment transport model MIKE 21C by DHI is used to simulate sediment deposition for the base case (i.e., no sediment management) and assess the anticipated effectiveness of two sediment management strategies (i.e., full drawdown flushing and partial drawdown flushing). Incoming total sediment load is estimated using measured and estimated suspended sediment load combined with bed load estimated using the BAGS model with the Wilcock and Crowe (2003) equation. The base case simulation indicates that the anticipated storage loss in the absence of sediment management would amount to about 35% of the total and 33% of the active storage volume over a 40-year period. The predicted storage losses are significantly less when the performance of full drawdown flushing and partial drawdown flushing was simulated. In the case of full drawdown flushing the total anticipated storage loss is about 22%, while the loss in active storage is only 7%. In the case of partial drawdown flushing the predicted loss in total storage is 26%, while the anticipated loss in active storage is 8% after 40 years of operation. The simulations indicate that flushing is a viable and sustainable sediment management option for maintaining active storage in the proposed reservoir and passing through sediment.

  10. SEDIMENT TRANSPORT EXPERIMENTSIN UNSTEADY FLOWS

    Institute of Scientific and Technical Information of China (English)

    DE SUTTER R.; HUYGENS M.; VERHOEVEN R.

    2001-01-01

    By means of a test flume with semi-circular cross-section, bedload and suspended-sediment transport of non-cohesive material have been studied in transient flow. The experimental facility enables us to investigate the time evolution of friction and transport parameters. Preliminary measurements with a fixed bottom instead of a sediment bed yield a reliable assessment of flow and friction characteristics. Time sequence in unsteady flow of the relevant parameters is revealed. The influence of turbulence variation and shear stress variation on the transport is investigated. As existing transport equations are found to be in poor agreement with experimental data, a new "engineering" concept is constructed which relates friction velocity to transport.

  11. On the effect of segregation on intense bimodal bed load

    Directory of Open Access Journals (Sweden)

    Zrostlík Štěpán

    2017-01-01

    Full Text Available Open-channel two-phase flow above a granular mobile bed is studied experimentally and theoretically. In the two-phase flow, water serves as a carrying liquid for plastic grains transported as collisional contact load in the upper-stage plane bed regime. The investigation evaluates friction- and transport characteristics of the flow under the condition of intense collisional transport of grains and links them with the internal structure of the two-phase flow. The paper focusses on the effect of bimodal solids (mixed two fractions of grains of similar density and different size and shape on the flow characteristics and internal structure. Hence, experimental results obtained for the bimodal mixture are compared with results for individual grain fractions. The experiments show that the bimodal character of the transported solids affects the layered internal structure of the flow as a result of fraction segregation due primarily to gravity (kinetic sieving during transport. The segregation also affects the friction- and transport characteristics of intense bed load. In the paper, the effects are described and quantified.

  12. Urban Sediment Transport through an Established Vegetated Swale: Long Term Treatment Efficiencies and Deposition

    Directory of Open Access Journals (Sweden)

    Deonie Allen

    2015-03-01

    Full Text Available Vegetated swales are an accepted and commonly implemented sustainable urban drainage system in the built urban environment. Laboratory and field research has defined the effectiveness of a vegetated swale in sediment detention during a single rainfall-runoff event. Event mean concentrations of suspended and bed load sediment have been calculated using current best analytical practice, providing single runoff event specific sediment conveyance volumes through the swale. However, mass and volume of sediment build up within a swale over time is not yet well defined. This paper presents an effective field sediment tracing methodology and analysis that determines the quantity of sediment deposited within a swale during initial and successive runoff events. The use of the first order decay rate constant, k, as an effective pollutant treatment parameter is considered in detail. Through monitoring tagged sediment deposition within the swale, the quantity of sediment that is re-suspended, conveyed, re-deposited or transported out of the swale as a result of multiple runoff events is illustrated. Sediment is found to continue moving through the vegetated swale after initial deposition, with ongoing discharge resulting from resuspension and conveyance during subsequent runoff events. The majority of sediment initially deposited within a swale is not detained long term or throughout its design life of the swale.

  13. A reduced-complexity model for sediment transport and step-pool morphology

    Science.gov (United States)

    Saletti, Matteo; Molnar, Peter; Hassan, Marwan A.; Burlando, Paolo

    2016-07-01

    A new particle-based reduced-complexity model to simulate sediment transport and channel morphology in steep streams in presented. The model CAST (Cellular Automaton Sediment Transport) contains phenomenological parameterizations, deterministic or stochastic, of sediment supply, bed load transport, and particle entrainment and deposition in a cellular-automaton space with uniform grain size. The model reproduces a realistic bed morphology and typical fluctuations in transport rates observed in steep channels. Particle hop distances, from entrainment to deposition, are well fitted by exponential distributions, in agreement with field data. The effect of stochasticity in both the entrainment and the input rate is shown. A stochastic parameterization of the entrainment is essential to create and maintain a realistic channel morphology, while the intermittent transport of grains in CAST shreds the input signal and its stochastic variability. A jamming routine has been added to CAST to simulate the grain-grain and grain-bed interactions that lead to particle jamming and step formation in a step-pool stream. The results show that jamming is effective in generating steps in unsteady conditions. Steps are created during high-flow periods and they survive during low flows only in sediment-starved conditions, in agreement with the jammed-state hypothesis of Church and Zimmermann (2007). Reduced-complexity models like CAST give new insights into the dynamics of complex phenomena such as sediment transport and bedform stability and are a useful complement to fully physically based models to test research hypotheses.

  14. Bed load tracer mobility in a mixed bedrock/alluvial channel

    Science.gov (United States)

    Ferguson, R. I.; Sharma, B. P.; Hodge, R. A.; Hardy, R. J.; Warburton, J.

    2017-04-01

    The presence of bare or partially covered rock in an otherwise alluvial river implies a downstream change in transport capacity relative to supply. Field investigations of this change and what causes it are lacking. We used two sets of magnet-tagged tracer clasts to investigate bed load transport during the same sequence of floods in fully alluvial, bare rock, and partial-cover reaches of an upland stream. High-flow shear stresses in different reaches were calculated by using stage loggers. Tracers seeded in the upstream alluvial channel moved more slowly than elsewhere until the frontrunners reached bare rock and sped up. Tracers seeded on bare rock moved rapidly off it and accumulated just upstream from, and later in, a partial-cover zone with many boulders. The backwater effect of the boulder-rich zone is significant in reducing tracer mobility. Tracer movement over full or partial sediment cover was size selective but dispersion over bare rock was not. Along-channel changes in tracer mobility are interpreted in terms of measured differences in shear stress and estimated differences in threshold stress.

  15. Sediment transport under breaking waves

    DEFF Research Database (Denmark)

    Christensen, Erik Damgaard; Hjelmager Jensen, Jacob; Mayer, Stefan

    2000-01-01

    generated at the surface where the wave breaks as well as the turbulence generated near the bed due to the wave-motion and the undertow. In general, the levels of turbulent kinetic energy are found to be higher than experiments show. This results in an over prediction of the sediment transport. Nevertheless...

  16. SEDIMENT TRANSPORT AND STREAM POWER

    Institute of Scientific and Technical Information of China (English)

    Chih Ted YANG

    2002-01-01

    This paper provides a step-by-step derivation of the sediment transport functions by Engelund and Hansen (1967) and by Ackers and White (1973). The theoretical derivations demonstrate that these two functions are closely related to Bagnold's (1966) stream power and efficiency concepts.

  17. Dynamics of bed load particles in supercritical flows close to the onset of motion

    CERN Document Server

    Heyman, J; Ancey, C

    2016-01-01

    The fair understanding of bed load dynamics in established transport conditions contrasts with the relatively poor knowledge and the rich variety of phenomena occurring close to the initiation of transport. Steep streams are also known to resist most of the existing predictive theories. In order to gain knowledge of the principal mechanisms involved in such transport cases, it seems necessary to refine our vision of the transport process down to the individual grain dynamics. Here, we present 10 experiments carried out in a steep, shallow water flume made of an erodible bed of natural, uniform gravel at low transport conditions. We simultaneously recorded bed load particle motions and bed and water elevations using two high-speed cameras. 8~km of particle trajectories were reconstructed with the help of a robust and original tracking algorithm. We propose a statistical analysis of this data in order to estimate how dependent particle velocity, particle acceleration, particle diffusivity, particle entrainment,...

  18. Longshore sediment transport along the Indian coast

    Digital Repository Service at National Institute of Oceanography (India)

    Chandramohan, P.; Nayak, B.U.

    An empirical sediment transport model has been developed based on longshore energy flux equation. Ship reported waves, published in Indian Daily Weather Reports, are compiled for 19 y and used for estimation of sediment transport. Annual gross...

  19. DEPTH-AVERAGED 2-D CALCULATION OF FLOW AND SEDIMENT TRANSPORT IN CURVED CHANNELS

    Institute of Scientific and Technical Information of China (English)

    Weiming WU; Sam S. Y. WANG

    2004-01-01

    The helical flow significantly affects the flow, sediment transport and morphological evolution in curved channels. A semi-empirical formula is proposed to determine the cross-stream distribution of the helical flow intensity in the developed regions of a channel bend. It is then used to evaluate the dispersion terms in the depth-averaged 2-D momentum equations and suspended-load transport equation as well as the bed-load transport angle, thus enhancing the depth-averaged 2-D model to account for the effect of helical flow. The tests in several experimental and field cases show that the enhanced depth-averaged 2-D model can much more reasonably predict the shifting of main flow from inner bank to outer bank, the erosion along outer bank and deposition along inner bank than the depth-averaged 2-D model without considering this effect.

  20. ASSESSMENT OF BED-LOAD PREDICTORS BASED ON SAMPLING IN A GRAVEL BED RIVER

    Institute of Scientific and Technical Information of China (English)

    HADDADCHI Arman; OMID Mohammad H.; DEHGHANI Amir A.

    2012-01-01

    Bedload transport in alluvial channels has been extensively studied and different equations based on field and/or experimental data have been proposed.Prediction of bed-load transport rate using different equations results in wide ranges which are not always reliable.In this study,some of the universal bedload predictors were evaluated with measured load by a Helley-Smith sampler in the Node River,a gravel bed fiver in the northeast part of Iran.From 19 sets of data,14 series of data were used to evaluate the bed-load transport equations.The results show that the equations presented by Van Rijn,Meyer-Peter and Mueller,and Ackers and White may adequately predict bedload transport in the range of field data.

  1. FRACTIONAL TRANSPORT OF SEDIMENT MIXTURES

    Institute of Scientific and Technical Information of China (English)

    Baosheng WU; Albert MOLINAS; Anping SHU

    2003-01-01

    A new method based on the Transport Capacity Fraction (TCF) concept is proposed to compute the fractional transport rates for nonuniform sediment mixtures in sand-bed channels. The TCF concept is derived from the understanding that the measurements and predictions of bed-material load are more accurate and reliable than the measurements and predictions of fractional loads. First the bed-material load is computed using an appropriate equation, then the fractional transport rates are determined by distributing the bed-material load into size groups through a transport capacity distribution function. For the computation of bed-material loads, the Aekers and White, Engelund and Hansen, and Yang equations are used in this study. Two new transport capacity distribution functions are developed for flows in sand-bed channels. The new expressions presented in this paper account for the sheltering and exposure effects that exist in mixtures. Comparisons with measured data show that the proposed method can significantly improve the predictions of fractional transport rates for nonuniform sediment mixtures.

  2. Transport model of underground sediment in soils.

    Science.gov (United States)

    Jichao, Sun; Guangqian, Wang

    2013-01-01

    Studies about sediment erosion were mainly concentrated on the river channel sediment, the terrestrial sediment, and the underground sediment. The transport process of underground sediment is studied in the paper. The concept of the flush potential sediment is founded. The transport equation with stable saturated seepage is set up, and the relations between the flush potential sediment and water sediment are discussed. Flushing of underground sediment begins with small particles, and large particles will be taken away later. The pore ratio of the soil increases gradually. The flow ultimately becomes direct water seepage, and the sediment concentration at the same position in the water decreases over time. The concentration of maximal flushing potential sediment decreases along the path. The underground sediment flushing model reflects the flushing mechanism of underground sediment.

  3. Sediment Transport in Rivers and Coastal Waters

    Institute of Scientific and Technical Information of China (English)

    杨树清; 余建星; 王元战

    2003-01-01

    Following Bagnold′s approach, a relationship between sediment transport and energy dissipation is developed. The major assumption made in the study is that the near bed velocity plays a dominant role in the process of sediment transport. A general relationship between energy dissipation and sediment transport is first proposed. Then the equations for total sediment transport are derived by introducing the appropriate expression of energy dissipation rate under different conditions, such as open channel flows, combination of wave and current, as well as longshore sediment transport. Within the flows investigated, the derived relationships are fairly consistent with the available data over a wide range of conditions.

  4. Spatial distribution of soil erosion and suspended sediment transport rate for Chou-Shui river basin

    Indian Academy of Sciences (India)

    Chin-Ping Lin; Ching-Nuo Chen; Yu-Min Wang; Chih-Heng Tsai; Chang-Tai Tsai

    2014-10-01

    In this study, a Physiographic Soil Erosion–Deposition Model (PSED) is applied for better management of a watershed. The PSED model can effectively evaluate the key parameters of watershed management: surface runoff discharge, suspended sediment transport rate, quantity of soil erosion, and spatial distribution of soil erosion and deposition. A basin usually contains multiple watersheds. These watersheds may have complex topography and heterogeneous physiographic properties. The PSED model, containing a physiographic rainfall-runoff model and a basin scale erosion–deposition model, can simulate the physical mechanism of the entire erosion process based on a detailed calculation of bed-load transportation, surface soil entrainment, and the deposition mechanism. With the assistance of Geographic Information Systems (GIS), the PSED model can handle and analyze extremely large hydrologic and physiographic datasets and simulate the physical erosion process without the need for simplification. We verified the PSED model using three typhoon events and 40 rainfall events. The application of PSED to Chou-Shui River basin shows that the PSED model can accurately estimate discharge hydrographs, suspended sediment transport rates, and sediment yield. Additionally, we obtained reasonable quantities of soil erosion as well as the spatial distribution of soil erosion and deposition. The results show that the PSED model is capable of calculating spatially distributed soil erosion and suspended sediment transport rates for a basin with multiple watersheds even if these watersheds have complex topography and heterogeneous physiographic properties.

  5. Lateral erosion in an experimental bedrock channel: The influence of bed roughness on erosion by bed load impacts

    Science.gov (United States)

    Fuller, Theodore K.; Gran, Karen B.; Sklar, Leonard S.; Paola, Chris

    2016-05-01

    Physical experiments were conducted to evaluate the efficacy of bed load particle impacts as a mechanism of lateral bedrock erosion. In addition, we explored how changes in channel bed roughness, as would occur during development of an alluvial cover, influence rates of lateral erosion. Experimental channels were constructed to have erodible walls and a nonerodible bed using different mixtures of sand and cement. Bed roughness was varied along the length of the channel by embedding sediment particles of different size in the channel bed mixture. Lateral wall erosion from clear-water flow was negligible. Lateral erosion during periods in which bed load was supplied to the channel removed as much as 3% of the initial wetted cross-sectional area. The vertical distribution of erosion was limited to the base of the channel wall, producing channels with undercut banks. The addition of roughness elements to an otherwise smooth bed caused rates of lateral erosion to increase by as much as a factor of 7 during periods of bed load supply. However, a minimum roughness element diameter of approximately half the median bed load particle diameter was required before a substantial increase in erosion was observed. Beyond this minimum threshold size, further increases in the relative size of roughness elements did not substantially change the rate of wall erosion despite changes in total boundary shear stress. The deflection of saltating bed load particles into the channel wall by fixed roughness elements is hypothesized to be the driver of the observed increase in lateral erosion rates.

  6. Filtering mountain landscapes and hydrology through sediment transport

    Science.gov (United States)

    Phillips, C. B.; Jerolmack, D. J.

    2013-12-01

    Long-term denudation of landscapes is balanced, and sometimes limited by, the sediment mass flux leaving the system through rivers. Suspended sediment represents the largest fraction of mass exiting the landscape, however coarse bed load transport may be the rate-limiting process of landscape denudation through its control on bedrock channel erosion and incision. We present research linking particle mechanics for a coarse alluvial gravel stream at the flood scale to particle dynamics at the annual timescale, and examine the implications of these results on channel geometry and the hydrology of mountain rivers. We examine the transport dynamics of individual cobbles tagged with passive radio transponder tags from the Mameyes River in the Luquillo Mountains of Puerto Rico, in both bedrock and alluvial stretches. These data are composed of measured 'flight' lengths for each transported particle, the fraction of tagged particles mobilized, and high-resolution river stage measurements. At the single flood scale, measured tracer particle flight lengths are exponentially distributed, and modal flight lengths scale linearly with excess shear velocity (U*-U*c). This is in quantitative agreement with recent theory and laboratory experiments, suggesting that moving particles' velocity is determined by momentum balance with the fluid. Examining tracer displacement at long timescales we use a dimensionless impulse (I*) - obtained by integrating the cumulative excess shear velocity over the duration of a flood (normalized by grain size) - and find that the mean travel distance collapses onto a linear relationship. Data show that partial bed load transport with intermittent motion is the dominant mode for the duration of record. Examining flood statistics, we find that the frequency-magnitude distribution of shear velocity is a power law; however, this scaling is truncated at the threshold of motion, beyond which it displays exponential scaling. The thin-tailed scaling of (U

  7. Resuspension created by bedload transport of macroalgae

    DEFF Research Database (Denmark)

    Canal Vergés, Paula; Kristensen, Erik; Flindt, Mogens

    2009-01-01

    surface sediment while drifting as bed load. To improve the understanding of this ballistic effect of moving plants on the sediment surface, controlled annular flume experiments were performed. Plant transport was measured together with turbidity and suspended particulate matter during increasing water...

  8. Multi-Fraction Bayesian Sediment Transport Model

    Directory of Open Access Journals (Sweden)

    Mark L. Schmelter

    2015-09-01

    Full Text Available A Bayesian approach to sediment transport modeling can provide a strong basis for evaluating and propagating model uncertainty, which can be useful in transport applications. Previous work in developing and applying Bayesian sediment transport models used a single grain size fraction or characterized the transport of mixed-size sediment with a single characteristic grain size. Although this approach is common in sediment transport modeling, it precludes the possibility of capturing processes that cause mixed-size sediments to sort and, thereby, alter the grain size available for transport and the transport rates themselves. This paper extends development of a Bayesian transport model from one to k fractional dimensions. The model uses an existing transport function as its deterministic core and is applied to the dataset used to originally develop the function. The Bayesian multi-fraction model is able to infer the posterior distributions for essential model parameters and replicates predictive distributions of both bulk and fractional transport. Further, the inferred posterior distributions are used to evaluate parametric and other sources of variability in relations representing mixed-size interactions in the original model. Successful OPEN ACCESS J. Mar. Sci. Eng. 2015, 3 1067 development of the model demonstrates that Bayesian methods can be used to provide a robust and rigorous basis for quantifying uncertainty in mixed-size sediment transport. Such a method has heretofore been unavailable and allows for the propagation of uncertainty in sediment transport applications.

  9. Towards a better understanding on how large wood is controlling longitudinal sediment (dis)connectivity in mountain streams - concepts and first results

    Science.gov (United States)

    Schuchardt, Anne; Pöppl, Ronald; Morche, David

    2016-04-01

    Large wood (LW) provides various ecological and morphological functions. Recent research has focused on habitat diversity and abundance, effects on channel planforms, pool formation, flow regimes and increased storage of organic matter as well as storage of fine sediment. While LW studies and sediment transport rates are the focus of numerous research questions, the influence of large channel blocking barriers (e.g. LW) and their impact on sediment trapping and decoupling transportation pathways is less studied. This project tries to diminish the obvious gap and deals with the modifications of the sediment connectivity by LW. To investigate the influence of large wood on sediment transporting processes and sediment connectivity, the spatial distribution and characterization of LW (>1 m in length and >10 cm in diameter) in channels is examined by field mapping and dGPS measurements. Channel hydraulic parameters are determined by field measurements of channel long profiles and cross sections. To quantify the direct effects of LW on discharge and bed load transport the flow velocity and bed load up- and downstream of LW is measured using an Ott-Nautilus and a portable Helley-Smith bed load sampler during different water stages. Sediment storages behind LWD accumulations will be monitored with dGPS. While accumulation of sediment indicates in-channel sediment storage and thus disconnection from downstream bed load transport, erosion of sediment evidences downstream sediment connectivity. First results will be presented from two study areas in mountain ranges in Germany (Wetterstein Mountain Range) and Austria (Bohemian Massif).

  10. Inter- and intra-annual variability of fluvial sediment transport in the proglacial river Riffler Bach (Weißseeferner, Ötztal Alps, Tyrol)

    Science.gov (United States)

    Baewert, Henning; Weber, Martin; Morche, David

    2015-04-01

    The hydrology of a proglacial river is strongly affected by glacier melting. Due to glacier retreat the effects of snow melt and rain storms will become more important in future decades. Additionally, the development of periglacial landscapes will play a more important role in the hydrology of proglacial rivers. The importance of paraglacial sediment sources in sediment budgets of glacier forefields is increasing, while the role of glacial erosion is declining. In two consecutive ablation seasons the fluvial sediment transport of the river Riffler Bach in the Kaunertal (Tyrol/Austria) was quantified. The catchment area of this station is 20 km² with an altitudinal range from 1929 m to 3518 m above msl. The "Weißseeferner" glacier (2.34 km² in 2012) is the greatest of the remaining glaciers. An automatic water sampler (AWS 2002) and a probe for water level were installed were installed at the outlet of the catchment. In order to calculate annual stage-discharge-relations, discharge (Q) was repeatedly measured with current meters. Concurrent to the discharge measurements bed load was collected using a portable Helley-Smith sampler. Bed load (BL) samples were weighted and sieved in the laboratory to gain annual bed load rating curves and grain size distributions. In 2012, 154 water samples were sampled during 7 periods and subsequently filtered to quantify suspended sediment concentrations (SSC). A Q-SSC-relation was calculated for every period due to the high variability in suspended sediment transport. In addition, the grain size distribution of the filtered material was determined by laser diffraction analysis. In 2013, the same procedure was performed for 232 water samples which were collected during 9 periods. Meteorological data were logged at the climate station "Weißsee", which is located in the centre of the study area. First results show a high variability of discharge and solid sediment transport both at the inter-annual as well as at the intra

  11. Sediment transport capacity of hyperconcentrated flow

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    As one of the most important components of river mechanics,sediment transport capacity of sediment-laden flows has attracted much attention from many researchers working on river mechanics and hydraulic engineering. Based on the time-averaged equation for a turbulent energy equilibrium in solid and liquid two-phase flow,an expression for the efficiency coefficient of suspended load movement was derived for the two-dimensional,steady,uniform,fully-developed turbulent flow. A new structural expression of sediment transport capacity was achieved. Using 115 runs of flume experimental data,which were obtained through two kinds of sediment transport experiments in the state of equilibrium,in combination with the basic rheological and sediment transporting characteristics of hyperconcentrated flow,the main parameters in the structural expression of sediment transport capacity were calibrated,and a new formula of sediment transport capacity for hyperconcentrated flow was developed. A large amount of field data from the Yellow River,Wuding River,and Yangtze River,etc. were adopted to verify the new formula and good agreement was obtained. These results above contribute to an improved theoretical system of river mechanics and a reliable tool for management of rivers carrying high concentration of sediments.

  12. Sediment transport capacity of hyperconcentrated flow

    Institute of Scientific and Technical Information of China (English)

    SHU AnPing; FEI XiangJun

    2008-01-01

    As one of the most important components of river mechanics, sediment transport capacity of sediment-laden flows has attracted much attention from many re-searchers working on river mechanics and hydraulic engineering. Based on the time-averaged equation for a turbulent energy equilibrium in solid and liquid two-phase flow, an expression for the efficiency coefficient of suspended load movement was derived for the two-dimensional, steady, uniform, fully-developed turbulent flow. A new structural expression of sediment transport capacity was achieved. Using 115 runs of flume experimental data, which were obtained through two kinds of sediment transport experiments in the state of equilibrium, in combi-nation with the basic rheological and sediment transporting characteristics of hy-perconcentrated flow, the main parameters in the structural expression of sediment transport capacity were calibrated, and a new formula of sediment transport ca-pacity for hyperconcentrated flow was developed. A large amount of field data from the Yellow River, Wuding River, and Yangtze River, etc. were adopted to verify the new formula and good agreement was obtained. These results above contribute to an improved theoretical system of river mechanics and a reliable tool for man-agement of rivers carrying high concentration of sediments.

  13. Uncertainty in tsunami sediment transport modeling

    Science.gov (United States)

    Jaffe, Bruce E.; Goto, Kazuhisa; Sugawara, Daisuke; Gelfenbaum, Guy R.; La Selle, SeanPaul M.

    2016-01-01

    Erosion and deposition from tsunamis record information about tsunami hydrodynamics and size that can be interpreted to improve tsunami hazard assessment. We explore sources and methods for quantifying uncertainty in tsunami sediment transport modeling. Uncertainty varies with tsunami, study site, available input data, sediment grain size, and model. Although uncertainty has the potential to be large, published case studies indicate that both forward and inverse tsunami sediment transport models perform well enough to be useful for deciphering tsunami characteristics, including size, from deposits. New techniques for quantifying uncertainty, such as Ensemble Kalman Filtering inversion, and more rigorous reporting of uncertainties will advance the science of tsunami sediment transport modeling. Uncertainty may be decreased with additional laboratory studies that increase our understanding of the semi-empirical parameters and physics of tsunami sediment transport, standardized benchmark tests to assess model performance, and development of hybrid modeling approaches to exploit the strengths of forward and inverse models.

  14. Pollutant transport and sediment dispersal in the Washington-Oregon Coastal Zone. Report of progress, October 1978 through September 1979

    Energy Technology Data Exchange (ETDEWEB)

    Hickey, B.M. (comp.)

    1979-01-01

    Progress is reported in work performed in the program that seeks to provide tested predictive models for the transport of dissolved and particulate matter in coastal regions. Modeling efforts in coastal circulation, boundary layer mechanics, sediment transport, and animal-sediment interactions are underway. The program is restricted to measurements of flow outside the logarithmic boundary layer. These measurements provide the information necessary to allow modeling of the flow and the transport of sediment in the benthic boundary layer. Transmissometer and current meter measurements were made at several near-bottom locations in the vicinity of Quinault Canyon. Results of a study on the effects of a narrow submarine canyon (Astoria) on low-frequency shelf circulation are reported. Two components of the sediment-animal-flow interaction triad were studied. They are: the effects of organisms on sediment characteristics and the effects of the activities of the benthic organisms on the near wall flow characteristics. Progress is also reported in the development of a bed load transport equation. (JGB)

  15. Vertical sorting in bed forms: flume experiments with a natural and a trimodal sediment mixture

    NARCIS (Netherlands)

    Blom, Astrid; Ribberink, Jan S.; Vriend, de Huib J.

    2003-01-01

    Two sets of flume experiments were conducted to examine grain size selective transport and vertical sorting in conditions with migrating bed forms and bed load transport. In the two sets of experiments we used a sediment mixture from the river Rhine and a trimodal mixture, respectively. The vertical

  16. SEDIMENT TRANSPORT IN THE YANGTZE RIVER ESTUARY

    Institute of Scientific and Technical Information of China (English)

    SHEN Zhigang

    2001-01-01

    The hydrodynamic and the sediment transport patterns within the estuary of the Yangtze River are complex because of interaction of fluvial and the tidal forces, depending on freshwater discharge and tidal range. Based on the data measured in recent years, this paper discusses the characteristics of flow and sediment movement in the Yangtze River Estuary and their influences on the evolution of the estuary.

  17. Modeling Transport of Flushed Reservoir Sediment

    Science.gov (United States)

    Dubinski, I. M.

    2014-12-01

    Drawdown flushing of a reservoir is often part of a reservoir sediment management program. Flushing can deliver higher than normal sediment loads to the river channel located downstream of a reservoir. The flushed sediment may contain a higher proportion of finer sediment than what was delivered to a channel prior to the presence of the reservoir. The extent of long-term impacts caused by the flushed sediment on the channel morphology and habitat will in part depend on the residence time of the sediment within the channel. In this study we used MIKE 21C to model the fate of flushed sediment through a river channel where the bed material consists of an armoring layer of gravels overlying finer sediment. MIKE 21C is a two-dimensional curvilinear morphological model for rivers developed by DHI. Curvilinear means that the model grid may curve to better follow the channel and flow direction, for example in a meandering channel. Multiple bed material layers are included in the model to represent the armoring and underlying layers existing in the bed separately from the overlying flushed sediment. These layers may also mix. The nature of the interactions between these two layers helps regulate transport and deposition of the flushed sediment, thus are critical to assessing the fate of the flushed sediment and associated potential impacts.

  18. Erosion, sediment transportation and accumulation in rivers

    Institute of Scientific and Technical Information of China (English)

    N.I.ALEKSEEVSKIY; K.M.BERKOVICH; R.S.CHALOV

    2008-01-01

    The present paper analyses the interrelation between erosion,sediment transportation and accumulation proposed by N.I.Makkaveyev (1908-1983) and its further development in modem studies of river channel processes in Russia.Spatio-temporal linkages between erosion and accumulation are defined considering channel processes at different scales - river longitudinal profile,channel morphological patterns,alluvial bedforms (bars,dunes) and individual sediment particles.Relations between river geomorphic activity,flow transportation capacity and sediment budgets are established (sediment input and output;channel bed erosion and sediment entrainment into flow -termination of sediment transport and its deposition).Channel planforms,floodplain segments separated by the latter and alluvial channel bedforms are shown to be geomorphic expressions of sediment transport process at different spatial and temporal scales.This paper is dedicated to the 100th anniversary of N.I.Makkaveyev,Professor of the Moscow State University,author of the book "River channel and erosion in its basin" (1955).That book is regarded in Russia as the pioneering work which initiated the complex hydrological and geographical studies of channel processes and laid a basis for the theory of unified fluvial erosion-accumulation process.

  19. Flux saturation length of sediment transport.

    Science.gov (United States)

    Pähtz, Thomas; Kok, Jasper F; Parteli, Eric J R; Herrmann, Hans J

    2013-11-22

    Sediment transport along the surface drives geophysical phenomena as diverse as wind erosion and dune formation. The main length scale controlling the dynamics of sediment erosion and deposition is the saturation length Ls, which characterizes the flux response to a change in transport conditions. Here we derive, for the first time, an expression predicting Ls as a function of the average sediment velocity under different physical environments. Our expression accounts for both the characteristics of sediment entrainment and the saturation of particle and fluid velocities, and has only two physical parameters which can be estimated directly from independent experiments. We show that our expression is consistent with measurements of Ls in both aeolian and subaqueous transport regimes over at least 5 orders of magnitude in the ratio of fluid and particle density, including on Mars.

  20. On the hydrology and fluvial sediment transport of the proglacial river Riffler Bach (Weißseeferner, Ötztal Alps, Tyrol)

    Science.gov (United States)

    Morche, David; Baewert, Henning; Weber, Martin; Schmidt, Karl-Heinz

    2013-04-01

    The hydrology of proglacial rivers is strongly affected by glacier melting. With ongoing glacier retreat the proportion of glacier meltwater in proglacial rivers is declining over longer time periods. Snow melt or rain fall events will play a more important role as water source. Due to glacial erosion the glacier system is also an important player in the orchestra of sediment sources/processes contributing to proglacial sediment budgets. The consequence of increasing deglaciation is a growing importance of other sediment sources/processes, mainly known as paraglacial, for sediment budgets in glacier forefields. The sediment export out of proglacial areas is mainly done by solid river load. Knowledge on the quantity of the exported sediments is important for reservoir management and torrent control. In order to measure fluvial sediment transport in the catchment area of the Gepatsch reservoir in the Ötztal Alps (Tyrol/Austria) we have installed a gauging station at the proglacial river Riffler Bach in June 2012. The catchment area of this station is about 20 km² with an altitudinal range from 1929 m to 3518 m. The higher altitudes in the southern part of the area are covered by the glacier Weißseeferner. Our station is equipped with an automatic water sampler (AWS 2002) and probes for water level, turbidity and electrical conductivity. All parameters are recorded in 5-15 minute intervals during the ablation period. Discharge is measured with current meters during wadable stages and salt dilution during higher floods. Bed load is measured concurrent to discharge measurements using a Helley-Smith sampler. In 2012, 189 water samples were taken and will be analyzed for suspended sediment concentration and ion content. Additionally, the grain size distribution will be determined using a Malvern laser diffractometer. Rating-curves will be used to calculate discharge from stage recordings. Solid load of the Riffler Bach will be quantified using the discharge data and

  1. CRITICAL UNIT STREAM POWER FOR SEDIMENT TRANSPORT

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Yang's (1996) sediment transport theory based on unit stream power is one of the most accurate theories, but in his equations the use of product of slope and critical velocity instead for critical unit stream power is not suitable. Dimensionless critical unit stream power required at incipient motion can be derived from the principle of conservation of power as a function of dimensionless particle diameter and relative roughness. Based on a lot of data sets, this new criterion was developed. By use of this new criteria, Yang's (1973) sand transport formula and his 1984 gravel transport formula could be improved when sediment concentration is less than about 100 ppm by weight.

  2. Quantification of the bed load effects on turbulent open-channel flows

    Science.gov (United States)

    Liu, Detian; Liu, Xiaofeng; Fu, Xudong; Wang, Guangqian

    2016-04-01

    With a computational model combining large eddy simulation and a discrete element model, detailed quantification of the bed load effects on turbulent open-channel flows is presented. The objective is the revelation of bed load particle impact on the mean flow properties and coherent structures. Two comparative numerical experiments with mobile and immobile beds are conducted. Mean properties (e.g., velocity and Reynolds stress profiles) show good agreement with experimental data. Comparing the mobile and immobile cases, the effective bed position is nearly the same, whereas the equivalent sand roughness is changed. The flow experiences higher bottom shear stress over immobile bed. To quantify impact on turbulent structures, a revised quadrant analysis is performed to calculate four key parameters of ejection and sweep events (duration, maximum shear stress, transported momentum, and period). Results show that the ejection and sweep events have comparable importance in the outer region. However, sweep becomes dominant in the near-wall region. The motion of particles enhances the sweep dominance by breaking up the ejection structures and decreasing their occurrence ratio. The results also suggest that the ejection events are easier to be influenced by the particle motions because they originate from the near-wall region. The duration, maximum shear stress, and transported momentum decrease close to the bed. The period remains relatively constant in the outer region but decreases near the bed. Visualization of the coherent structure reveals that the instantaneous particle motion has strong correlation with the bursting cycle events.

  3. SEDIMENT TRANSPORT IN YALU RIVER ESTUARY

    Institute of Scientific and Technical Information of China (English)

    GAO Jian-hua; GAO Shu; CHENG Yan; DONG Li-xian; ZHANG Jing

    2003-01-01

    Tidal cycle measurements of tidal currents, salinity and water temperature, and suspended sediment conc entra-tions were measured at four stations, together with surveys along two profiles short core collection within the Yalu River estuary.Grain size analysis of the three core sediment showed that: 1) the sediment from B1 to B3 became finer, worse sorting andpositively skewed; 2) the diversification of matter origin became more and more evident from east to west; 3) the sediments overthe region were of the same origin, as indicated by their similar colors and grain sizes. The data indicated that stratiticationoccurred in the flood season, from upstream to downstream, and a salt wedge was formed. The water column was well mixed, butthe longitudinal gradient of the salinity was larger on spring tide. The results also showed that the dominating mechanisnt ofsuspended sediment transport in the Yalu River estuary was T1, T2, T3 and T5. The non-tidal steady advection transport wasrestricted by the net transport of suspended sediment induced by mass Stoked drift directed to landwards, then the net sedimenttransport rate were decreased and the turbidity maxima was also favored to forming and extending.

  4. Sediment transport in the nearshore area of Phoenix Island

    Science.gov (United States)

    Hu, Rijun; Ma, Fang; Wu, Jianzheng; Zhang, Wei; Jiang, Shenghui; Xu, Yongchen; Zhu, Longhai; Wang, Nan; Liu, Aijiang

    2016-10-01

    Based on the measured data, suspended sediment concentration, surface sediment grain size, current and waves, the sediment transport mechanisms and pathways in the Phoenix Island area were analyzed using methods of flux decomposition and Grain Size Trend Analysis (GSTA). The results show that net suspended sediment is mainly transported by average current, Stokes drift, and gravitational circulation. The transport direction of suspended sediment is varying and basically following the direction of residual tidal currents. Surface sediment transport pathways are primarily parallel to the coastline along with two convergent centers. Waves and longshore currents have a significant influence on sediment transport, but the influence is limited due to a steep and deep underwater bank. Tidal current is the main controlling factor for sediment transport, especially in the deep water area. Neither suspended nor surface sediment is transported towards the southwest. The South Shandong Coastal Current (SSCC) has little effect on sediment transport processes in the nearshore area of Phoenix Island.

  5. Density gradation in cross-shore sediment transport

    NARCIS (Netherlands)

    Koomans, RL; de Meijer, RJ

    2004-01-01

    One of the fundamental properties of a coastline is its sediment composition. Coastal sediments are rarely composed of one type of sediment. Due to these differences, the sediments are sorted on the beach and foreshore. The effect of density variations of the sediment on coastal sediment transport h

  6. Modelling sheet-flow sediment transport in wave-bottom boundary layers using discrete-element modelling.

    Science.gov (United States)

    Calantoni, Joseph; Holland, K Todd; Drake, Thomas G

    2004-09-15

    Sediment transport in oscillatory boundary layers is a process that drives coastal geomorphological change. Most formulae for bed-load transport in nearshore regions subsume the smallest-scale physics of the phenomena by parametrizing interactions amongst particles. In contrast, we directly simulate granular physics in the wave-bottom boundary layer using a discrete-element model comprised of a three-dimensional particle phase coupled to a one-dimensional fluid phase via Newton's third law through forces of buoyancy, drag and added mass. The particulate sediment phase is modelled using discrete particles formed to approximate natural grains by overlapping two spheres. Both the size of each sphere and the degree of overlap can be varied for these composite particles to generate a range of non-spherical grains. Simulations of particles having a range of shapes showed that the critical angle--the angle at which a grain pile will fail when tilted slowly from rest--increases from approximately 26 degrees for spherical particles to nearly 39 degrees for highly non-spherical composite particles having a dumbbell shape. Simulations of oscillatory sheet flow were conducted using composite particles with an angle of repose of approximately 33 degrees and a Corey shape factor greater than about 0.8, similar to the properties of beach sand. The results from the sheet-flow simulations with composite particles agreed more closely with laboratory measurements than similar simulations conducted using spherical particles. The findings suggest that particle shape may be an important factor for determining bed-load flux, particularly for larger bed slopes.

  7. Cross-shore suspended sediment transport in the surf zone: A fieldbased parameterization

    DEFF Research Database (Denmark)

    Aagaard, Troels; Black, Kerry; Greenwood, Brian

    2002-01-01

    sediment transport, sediment concentrations, incident waves, undertow, morphodynamics, beach processes......sediment transport, sediment concentrations, incident waves, undertow, morphodynamics, beach processes...

  8. An update of the sediment fluxes investigation in the Rio Cordon (Italy after 25 years of monitoring

    Directory of Open Access Journals (Sweden)

    Lorenzo Picco

    2012-12-01

    Full Text Available Quantification of bed-load transport in high-gradient mountain streams is important, but the field data needed to test transport models are scarce and difficult to obtain. In the present study, we describe the experimental station for monitoring water and sediment fluxes built in 1985 on the Rio Cordon, a small step-pool channel in the eastern Italian Alps. The measuring station consists of an inclined frame that separates fine from coarse sediments (D>20 mm, which are continuously measured by a series of ultrasonic sensors fitted above a storage area. The acquired 25-year dataset, which comprises a high-magnitude/ low-recurrence flood event, has allowed a magnitude-frequency analysis of bed-load volumes to be performed. Results from a combined frequency analysis of peak water discharge and total bed-load volumes are presented. In addition, the integration between the sediment transport dataset and the repeated surveys of sediment sources and of channel changes allowed us to assess the geomorphological effectiveness of different flood events. Despite the importance of the experimental station for making these bed-load observations possible, its maintenance costs are not low and these may have an impact on its future existence. At the same time, improving current instrumentation and future installations with novel technology would make the station an ideal location for calibrating surrogate techniques for sediment transport monitoring.

  9. Modeling sediment transport in river networks

    Science.gov (United States)

    Wang, Xu-Ming; Hao, Rui; Huo, Jie; Zhang, Jin-Feng

    2008-11-01

    A dynamical model is proposed to study sediment transport in river networks. A river can be divided into segments by the injection of branch streams of higher rank. The model is based on the fact that in a real river, the sediment-carrying capability of the stream in the ith segment may be modulated by the undergone state, which may be erosion or sedimentation, of the i-1th and ith segments, and also influenced by that of the ith injecting branch of higher rank. We select a database about the upper-middle reach of the Yellow River in the lower-water season to test the model. The result shows that the data, produced by averaging the erosion or sedimentation over the preceding transient process, are in good agreement with the observed average in a month. With this model, the steady state after transience can be predicted, and it indicates a scaling law that the quantity of erosion or sedimentation exponentially depends on the number of the segments along the reach of the channel. Our investigation suggests that fluctuation of the stream flow due to random rainfall will prevent this steady state from occurring. This is owing to the phenomenon that the varying trend of the quantity of erosion or sedimentation is opposite to that of sediment-carrying capability of the stream.

  10. DESIGN OF SEDIMENT TRANSPORTING CANAL SECTIONS

    Institute of Scientific and Technical Information of China (English)

    Prabhata K.SWAMEE; Nimisha SWAMEE

    2004-01-01

    Design equations for minimum area or maximum velocity canal-sections for transport of bulk sediment carried by water have been obtained. Such canals are economically feasible in the terrain where large slopes are available. The design procedure is illustrated by a practical example.

  11. A Sediment Transport Model for Sewers

    DEFF Research Database (Denmark)

    Mark, Ole; Larsson, Johan; Larsen, Torben

    1993-01-01

    This paper describes a mathematical model for transport processes in sewers. The model consists of three sub models, a surface model for the description of the buildup and the washoff of sediment particles from the surface area, a morphological model and an advection-dispersion model. The model...

  12. A Field Exercise in Fluvial Sediment Transport.

    Science.gov (United States)

    Tharp, Thomas M.

    1983-01-01

    Describes an investigation which introduces the mathematical principles of stream hydraulics and fluvial sediment in a practical context. The investigation has four stages: defining hydrology of the stream; defining channel hydraulics in a study reach; measuring grain size; and calculating transportable grain size and comparing measure stream-bed…

  13. Modeling of sediment transport along Mangalore coast using mike 21

    Digital Repository Service at National Institute of Oceanography (India)

    Babu, K.S.; Dwarakish, G.S.; Jayakumar, S.

    The objective of the present study is to understand the sediment transport along Mangalore Coast and to quantify the sediment transport rates. The data used in the present study includes Wave, Wind, Tide, Naval Hydrographic Chart (Bathymetry Chart...

  14. Longshore sediment transport model for the Indian west coast

    Digital Repository Service at National Institute of Oceanography (India)

    Chandramohan, P.; Nayak, B.U.

    Longshore sediment transport rates for the Indian west coast from Cochin to Porbandar are estimated from ship observed wave data (1968 to 1986). The sediment transport rate is relatively high during the southwest monsoon period from June...

  15. Sediment transport monitoring for sustainable hydropower development

    Science.gov (United States)

    Rüther, Nils; Guerrero, Massimo; Stokseth, Siri

    2015-04-01

    Due to the increasing demand of CO2 neutral energy not only in Europe but also in World, a relatively large amount of new hydro power plants (HPP) are built. In addition, will existing ones refurbished and renewed in order to run them more cost effective. A huge thread to HPPs is incoming sediments in suspension from the rivers upstream. The sediments settle in the reservoir and reduce the effective head and volume and reduce consequently the life time of the reservoir. In addition are the fine sediments causing severe damages to turbines and infrastructure of a HPP. For estimating the amount of incoming sediments in suspension and therefore planning efficient counter measures, it is essential to monitor the rivers within the catchment of the HPP for suspended sediments. This work is considerably time consuming and requires highly educated personnel and is therefore expensive. Consequently will this study present a method to measure suspended sediment concentrations and their grain size distribution with a dual frequency acoustic Doppler current profiler (ADCP). This method is more cost effective and reliable in comparison to traditional measurement methods. Having more detailed information about the sediments being transported in a river, the hydro power plant can be planned, built, and operated much more efficiently and sustainable. The two horizontal ADCPs are installed at a measurement cross section in the Devoll river in Albania. To verify the new method, the suspended load concentrations will be monitored also in the traditional ways at the same cross sections. It is planned to install turbidity measurement devices included with an automatic sampling devices. It is also planned to use an optical in situ measurement device (LISST SL by Sequoia Inc.) to have detailed information of sediment concentration and grain sizes over the depth.

  16. Sediment transport in two mediterranean regulated rivers.

    Science.gov (United States)

    Lobera, G; Batalla, R J; Vericat, D; López-Tarazón, J A; Tena, A

    2016-01-01

    Mediterranean climate is characterized by highly irregular rainfall patterns with marked differences between wet and dry seasons which lead to highly variable hydrological fluvial regimes. As a result, and in order to ensure water availability and reduce its temporal variability, a high number of large dams were built during the 20th century (more than 3500 located in Mediterranean rivers). Dams modify the flow regime but also interrupt the continuity of sediment transfer along the river network, thereby changing its functioning as an ecosystem. Within this context, the present paper aims to assess the suspended sediment loads and dynamics of two climatically contrasting Mediterranean regulated rivers (i.e. the Ésera and Siurana) during a 2-yr period. Key findings indicate that floods were responsible for 92% of the total suspended sediment load in the River Siurana, while this percentage falls to 70% for the Ésera, indicating the importance of baseflows on sediment transport in this river. This fact is related to the high sediment availability, with the Ésera acting as a non-supply-limited catchment due to the high productivity of the sources (i.e. badlands). In contrast, the Siurana can be considered a supply-limited system due to its low geomorphic activity and reduced sediment availability, with suspended sediment concentration remaining low even for high magnitude flood events. Reservoirs in both rivers reduce sediment load up to 90%, although total runoff is only reduced in the case of the River Ésera. A remarkable fact is the change of the hydrological character of the River Ésera downstream for the dam, shifting from a humid mountainous river regime to a quasi-invariable pattern, whereas the Siurana experiences the opposite effect, changing from a flashy Mediterranean river to a more constant flow regime below the dam.

  17. Drainage, sediment transport, and denudation rates on the Nanga Parbat Himalaya, Pakistan

    Science.gov (United States)

    Cornwell, Kevin; Norsby, Doug; Marston, Richard

    2003-09-01

    does the higher slope (0.12) of the upper Raikot drainage basin (1925 Pa). Dissolved and suspended sediment loads were measured from water/sediment samples collected throughout the day and night over a period of 10 days at the height of the summer melt season but proved to be a minor variable in transport flux. Channel bed loads were measured using a pebble count method of bank material and then used to generate ratings curves of bed loads relative to discharge volumes. When coupled with discharge data and basin area, mean annual sediment yield and denudation rates for Nanga Parbat are produced. Denudation rates calculated in this fashion range from 0.2 mm year -1 in the slower, more sluggish Rupal drainage basin to almost 6 mm year -1 in the steeper, faster flowing Raikot and Buldar drainage basins.

  18. Longshore sediment transport at Golden Sands (Bulgaria

    Directory of Open Access Journals (Sweden)

    Hristo Nikolov

    2006-09-01

    Full Text Available The paper presents the results of studies on the qualitative and quantitative features of the littoral drift at Golden Sands (Bulgaria, carried out jointly by Polish and Bulgarian researchers. The mathematical modelling of physical coastal processes took wave transformation (wave diffraction and refraction; the effects of shoaling and wave breaking and longshore sediment transport into account. The computations were carried out for the mean statistical annual wave climate, determined on the basis of IO BAS wave data, simulated using the WAM method from long-term Black Sea wind data. The results of sediment transport computations clearly show that its direction off the Golden Sands shore is from north to south.

  19. INFLUENCE OF SEDIMENT TRANSPORT ON ARMORED SURFACES

    Institute of Scientific and Technical Information of China (English)

    Katinka KOLL; Andreas DITTRICH

    2001-01-01

    Laboratory experiments have been carried out to study the characteristics of sediment transport in steep streams. The question is discussed wether an armoured surfaces is destroyed due to the transport of material, because additional impulses are acting on it, or the layer is sheltered by the transported material, because a part of the stream power is used to move the material. According to the results of the presented experiments, in which the influence of the feeding rate and the feeding duration have been investigated, transported material reaching an armoured river section from upstream always remobilzes bed material, which is immobile under clear water flow conditions. To decide if a static armour layer is either destroyed or not, two simple criteria were chosen: oneconsidering the grain-size distribution of the eroded bed material, and another, which referes to the amount of eroded bed material.

  20. Continental margin sedimentation: from sediment transport to sequence stratigraphy

    Science.gov (United States)

    Nittrouer, Charles A.; Austin, James A.; Field, Michael E.; Kravitz, Joseph H.; Syvitski, James P.M.; Wiberg, Patricia L.; Nittrouer, Charles A.; Austin, James A.; Field, Michael E.; Kravitz, Joseph H.; Syvitski, James P. M.; Wiberg, Patricia L.

    2007-01-01

    This volume on continental margin sedimentation brings together an expert editorial and contributor team to create a state-of-the-art resource. Taking a global perspective, the book spans a range of timescales and content, ranging from how oceans transport particles, to how thick rock sequences are formed on continental margins. - Summarizes and integrates our understanding of sedimentary processes and strata associated with fluvial dispersal systems on continental shelves and slopes - Explores timescales ranging from particle transport at one extreme, to deep burial at the other - Insights are presented for margins in general, and with focus on a tectonically active margin (northern California) and a passive margin (New Jersey), enabling detailed examination of the intricate relationships between a wide suite of sedimentary processes and their preserved stratigraphy - Includes observational studies which document the processes and strata found on particular margins, in addition to numerical models and laboratory experimentation, which provide a quantitative basis for extrapolation in time and space of insights about continental-margin sedimentation - Provides a research resource for scientists studying modern and ancient margins, and an educational text for advanced students in sedimentology and stratigraphy

  1. Mathematical modeling of sediment transport jn estuaries and coastal regions

    Institute of Scientific and Technical Information of China (English)

    窦国仁; 董凤舞; 窦希萍; 李禔来

    1995-01-01

    Based on the suspended sediment transport equation and transport capacity formula under the action of tidal currents and wind waves, a horizontal 2-D mathematical model of suspended sediment transport for estuaries and coastal regions is established. The verification of calculations shows that the sediment concentration distribution and sea bed deformation in the estuaries and coastal regions can be successfully simulated. Therefore, a new method for studying and solving the sediment problems in the estuarine and coastal engineering is presented.

  2. Bed load size distribution and flow conditions in a high mountain catchment of Central Pyrenees

    Directory of Open Access Journals (Sweden)

    Martínez-Castroviejo, Ricardo

    1990-06-01

    Full Text Available The bed load size distribution caused by different types of flow are compared in a high mountain catchment located in the upper Gallego river basin (Central Spanish’ Pyrenees. Three kinds of hydrologic events could be defined: those triggered by heavy autumn rainfalls, those originated by isolated summer rainstorms and those promoted by snowmelting. Each one is characterized by a peculiar bed load size distribution. Thus, it could be demonstrated that the coarser fractions, above 30 mm in diameter, are up to six times more abundant, in percentage of total weight, in transports caused by heavy rainfalls than in the material collected after snowmelt flows. In its turn, bed load mobilized by snowmelt flows is mainly composed by medium and fine gravel, from 2 to 8 mm. These may amount up to 60 % of total weight of bed load. The reasons for these so different size distributions are discussed.

    [es] En una cuenca de alta montaña localizada en el alto valle del río Gallego (Pirineo central se comparan las distribuciones por tamaños de los acarreos movilizados por diferentes tipos de caudal. Tres tipos de eventos hidrológicos han podido ser caracterizados: los ocasionados por intensas lluvias de otoño, los originados por tormentas estivales aisladas y los producidos por la fusión de la nieve acumulada durante el invierno. Se concluye que cada uno de ellos lleva asociada una distribución por tamaños típica de la carga de fondo. Así, se ha comprobado que las fracciones más gruesas consideradas -superiores a los 30 mm de diámetro- son hasta seis veces más abundantes -en porcentaje sobre el peso total- en las exportaciones causadas por lluvias de gran intensidad que en las generadas por caudales de fusión. A su vez, las descargas ocasionadas por la fusión arrastran principalmente gravas de calibre medio y fino -entre 2y8 mm- que llegan a suponer el 60 % en peso del volumen movilizado. Este artículo discute las razones que provocan

  3. Mathematical simulation of sediment and radionuclide transport in estuaries

    Energy Technology Data Exchange (ETDEWEB)

    Onishi, Y.; Trent, D.S.

    1982-11-01

    The finite element model LFESCOT (Flow, Energy, Salinity, Sediment and Contaminant Transport Model) was synthesized under this study to simulate radionuclide transport in estuaries to obtain accurate radionuclide distributions which are affected by these factors: time variance, three-dimensional flow, temperature, salinity, and sediments. Because sediment transport and radionuclide adsorption/desorption depend strongly on sizes or types of sediments, FLESCOT simulates sediment and a sediment-sorbed radionuclide for the total of three sediment-size fractions (or sediment types) of both cohesive and noncohesive sediments. It also calculates changes of estuarine bed conditions, including bed elevation changes due to sediment erosion/deposition, and three-dimensional distributions of three bed sediment sizes and sediment-sorbed radionuclides within the bed. Although the model was synthesized for radionuclide transport, it is general enough to also handle other contaminants such as heavy metals, pesticides, or toxic chemicals. The model was checked for its capability for flow, water surface elevation change, salinity, sediment and radionuclide transport under various simple conditions first, confirming the general validity of the model's computational schemes. These tests also revealed that FLESCOT can use large aspect ratios of computational cells, which are necessary in handling long estuarine study areas. After these simple tests, FLESCOT was applied to the Hudson River estuary between Chelsea and the mouth of the river to examine how well the model can predict radionuclide transport through simulating tidally influenced three-dimensional flow, salinity, sediment and radionuclide movements with their interactions.

  4. Sediment Transport in Rivers with Overbank Flow

    Institute of Scientific and Technical Information of China (English)

    Donald; W; KNIGHT

    2005-01-01

    Some concepts related to sediment transport in rivers with overbank flow are described.Following a description of the physical processes that are involved when a river inundates its floodplains,some simple com- putational methods are presented which permit the depth-averaged velocity and boundary shear stress to be pre- dicted within a cross section of variable,but prismatic shape.The methoda account for the strong transverse shear in velocity that occurs when the stage is just above bankfull,as well as ...

  5. Sediment transport along the Goa-north Karnataka Coast, western India

    Digital Repository Service at National Institute of Oceanography (India)

    Kunte, P.D.

    of sediment transport. Although sediment-transport direction is bi-directional, net major sediment transport is southward. The geomorphic study identified possible sediment sources and sinks. Contributions of sources and losses due to sinks are assessed...

  6. Detailed simulation of morphodynamics: 2. Sediment pickup, transport, and deposition

    NARCIS (Netherlands)

    Nabi, M.; De Vriend, H.J.; Mosselman, E.; Sloff, C.J.; Shimizu, Y.

    2013-01-01

    The paper describes a numerical model for simulating sediment transport with eddy-resolving 3-D models. This sediment model consists of four submodels: pickup, transport over the bed, transport in the water column and deposition, all based on a turbulent flow model using large-eddy simulation. The

  7. Detailed simulation of morphodynamics: 2. Sediment pickup, transport, and deposition

    NARCIS (Netherlands)

    Nabi, M.; De Vriend, H.J.; Mosselman, E.; Sloff, C.J.; Shimizu, Y.

    2013-01-01

    The paper describes a numerical model for simulating sediment transport with eddy-resolving 3-D models. This sediment model consists of four submodels: pickup, transport over the bed, transport in the water column and deposition, all based on a turbulent flow model using large-eddy simulation. The s

  8. River sediment supply, sedimentation and transport of the highly turbid sediment plume in Malindi Bay, Kenya

    Institute of Scientific and Technical Information of China (English)

    JOHNSON U.Kitheka

    2013-01-01

    The paper presents results of a study on the sediment supply and movement of highly turbid sediment plume within Malindi Bay in the Northern region of the Kenya coast.The current velocities,tidal elevation,salinity and suspended sediment concentrations (TSSC)were measured in stations located within the bay using Aanderaa Recording Current Meter (RCM-9),Turbidity Sensor mounted on RCM-9,Divers Gauges and Aanderaa Temperature-Salinity Meter.The study established that Malindi Bay receives a high terrigenous sediment load amounting to 5.7 × 106 ton·yr-1.The river freshwater supply into the bay is highly variable ranging from 7 to 680 m3·s-1.The high flows that are > 150 m3·s-1 occurred in May during the South East Monsoon (SEM).Relatively low peak flows occurred in November during the North East Monsoon (NEM) but these were usually <70 m3·s-1.The discharge of highly turbidity river water into the bay in April and May occurs in a period of high intensity SEM winds that generate strong north flowing current that transports the river sediment plume northward.However,during the NEM,the river supply of turbid water is relatively low occurring in a period of relatively low intensity NEM winds that result in relatively weaker south flowing current that transports the sediment plume southward.The mechanism of advection of the sediment plume north or south of the estuary is mainly thought to be due to the Ekman transport generated by the onshore monsoon winds.Limited movement of the river sediment plume southward towards Ras Vasco Da Gama during NEM has ensured that the coral reef ecosystem in the northern parts of Malindi Marine National Park has not been completely destroyed by the influx of terrigenous sediments.However,to the north there is no coral reef ecosystem.The high sediment discharge into Malindi Bay can be attributed to land use change in the Athi-Sabaki River Basin in addition to rapid population increase which has led to clearance of forests to open land

  9. Transport of sediments in Himalaya-Karakorum and its influence on hydropower plants; Sedimenttransportprozesse im Himalaya-Karakorum und ihre Bedeutung fuer Wasserkraftanlagen

    Energy Technology Data Exchange (ETDEWEB)

    Palt, S.M.

    2001-07-01

    In the present study the sediment transport processes in alpine mountain areas and their impact on hydropower development projects are investigated. The aim of the present work is to contribute to the understanding of the transport process system, which is characterized by high magnitude-low frequency - events, to ensure an appropriate layout of high head hydropower projects in mountain regions. The sediment transport in large areas in the macro scale is triggered by natural hazards, such as earthquakes, rock slides, earth movements, debris flows, glacial lake outbursts and floods. The basic principle of complex transport processes in this scale is described and explained on the example of the Himalaya-Karakorum-region. The sediment transport process in the smaller scale, so called meso scale, is investigated by means of extensive field measurements at river reaches of 16 different mountain rivers of a 80000 km{sup 2} large project area. The measurements include topographic survey works and measurements of discharge, bed load and suspended load. Since the conditions of mountain rivers in terms of size of bed material as well as available flow velocities can be considered as extreme, an appropriate bed load sampler named B-69 was developed, constructed and used in the field. Moreover the hydraulic as well as the sedimentological efficiency of the sampler was tested in the laboratory tests. Due to the nice performance of the bed load sampler B-69 at high flow velocities it might be useful for flood conditions in gravel-bed rivers in other parts of the world as well. Based on the results of the study the parameter of the river slope can be considered as the most important one for the characteristics of the morphology, the flow conditions, the bed stability as well as the bed load transport in steep mountain rivers. With increasing slope morphological structures in the longitudinal direction will develop from flat bed conditions. The so called step-pool-systems consist

  10. Resuspension created by bedload transport of macroalgae

    DEFF Research Database (Denmark)

    Canal Vergés, Paula; Kristensen, Erik; Flindt, Mogens

    2009-01-01

    Earlier studies have quantified that plant bound transport in shallow lagoons and estuaries may periodically be the dominating nutrient transport form. In some of these field studies turbidity increased when plant transport increased. The hypothesis in this study is therefore that macroalgae erode...... surface sediment while drifting as bed load. To improve the understanding of this ballistic effect of moving plants on the sediment surface, controlled annular flume experiments were performed. Plant transport was measured together with turbidity and suspended particulate matter during increasing water...

  11. Intense sediment transport: Collisional to turbulent suspension

    Science.gov (United States)

    Berzi, Diego; Fraccarollo, Luigi

    2016-02-01

    A recent simple analytical approach to the problem of steady, uniform transport of sediment by a turbulent shearing fluid dominated by interparticle collisions is extended to the case in which the mean turbulent lift may partially or totally support the weight of the sediment. We treat the granular-fluid mixture as a continuum and make use of constitutive relations of kinetic theory of granular gases to model the particle phase and a simple mixing-length approach for the fluid. We focus on pressure-driven flows over horizontal, erodible beds and divide the flow itself into layers, each dominated by different physical mechanisms. This permits a crude analytical integration of the governing equations and to obtain analytical expressions for the distribution of particle concentration and velocity. The predictions of the theory are compared with existing laboratory measurements on the flow of glass spheres and sand particles in water. We also show how to build a regime map to distinguish between collisional, turbulent-collisional, and fully turbulent suspensions.

  12. A process-based model for aeolian sediment transport and spatiotemporal varying sediment availability

    Science.gov (United States)

    Hoonhout, Bas M.; Vries, Sierd de

    2016-08-01

    Aeolian sediment transport is influenced by a variety of bed surface properties, like moisture, shells, vegetation, and nonerodible elements. The bed surface properties influence aeolian sediment transport by changing the sediment transport capacity and/or the sediment availability. The effect of bed surface properties on the transport capacity and sediment availability is typically incorporated through the velocity threshold. This approach appears to be a critical limitation in existing aeolian sediment transport models for simulation of real-world cases with spatiotemporal variations in bed surface properties. This paper presents a new model approach for multifraction aeolian sediment transport in which sediment availability is simulated rather than parameterized through the velocity threshold. The model can cope with arbitrary spatiotemporal configurations of bed surface properties that either limit or enhance the sediment availability or sediment transport capacity. The performance of the model is illustrated using four prototype cases, the simulation of two wind tunnel experiments from literature and a sensitivity analysis of newly introduced parameters.

  13. A longshore sediment transport estimation for the Indian coast

    Digital Repository Service at National Institute of Oceanography (India)

    Nayak, B.U.; Chandramohan, P

    An empirical sediment transport model has been developed based on longshore energy flux equation. Study indicates that annual gross sediment transport rate is high (1.5 x 10 super(6) m super(3) to 2.0 x 10 super(6) m super(3)) along the coasts...

  14. Numerical Modelling of Sediment Transport in Combined Sewer Systems

    DEFF Research Database (Denmark)

    Schlütter, Flemming

    A conceptual sediment transport model has been developed. Through a case study a comparison with other numerical models is performed.......A conceptual sediment transport model has been developed. Through a case study a comparison with other numerical models is performed....

  15. A Simplified Analytic Investigation of the Riverside Effects of Sediment Diversions

    Science.gov (United States)

    2013-09-01

    wash load is composed of cohesive (silt and clay ) sediments. By contrast, in estuaries, cohesive sediments may become a significant component of the...load consists of very fine silts and clays . Non-cohesive sediment transport is generally characterized by two separate modes of transport: bed...suspended load and bed load transport are given as follows: . . æ ö÷ç= = ÷ç ÷çè ø Sn S S S S POT S S ρQSQ β Q β α b b (2) ( ) ( ). . æ ö÷ç

  16. The suspended sediment transport equation and its near-bed sediment flux

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    The suspended sediment transport equation and its near-bed sediment flux are one of the key problems of sediment transport research under nonequilibrium condition. Based on the three-dimensional primitive suspended transport equation, the two-dimensional suspended sediment transport equation is deduced. The derived process indicates that the physical essence of the near-bed sediment flux is right the bottom boundary condition for the suspended sediment transport equation. This paper analyzes the internal relations between the two methods of sediment carrying capacity and shear stress in common use, points out the consistency of these two methods in terms of form and physical meaning, and unifies these two methods theoretically. Furthermore, based on the analysis and comparison of the expressions of the near-bed sediment flux, this paper summarizes some problems to which attention should be paid, thus offering a novel approach to the study and the solution of the problems of suspended sediment transport and exchange flux of near-bed water sediment.

  17. The suspended sediment transport equation and its near-bed sediment flux

    Institute of Scientific and Technical Information of China (English)

    LI RuiJie; LUO Feng; ZHU WenJin

    2009-01-01

    The suspended sediment transport equation and its near-bed sediment flux are one of the key prob-lems of sediment transport research under nonequilibrium condition. Based on the three-dimensional primitive suspended transport equation, the two-dimensional suspended sediment transport equation is deduced. The derived process indicates that the physical essence of the near-bed sediment flux is right the bottom boundary condition for the suspended sediment transport equation. This paper ana-lyzes the internal relations between the two methods of sediment carrying capacity and shear stress in common use, points out the consistency of these two methods in terms of form and physical meaning, and unifies these two methods theoretically. Furthermore, based on the analysis and comparison of the expressions of the near-bed sediment flux, this paper summarizes some problems to which attention should be paid, thus offering a novel approach to the study and the solution of the problems of sus-pended sediment transport and exchange flux of near-bed water sediment.

  18. Numerical Modelling Approaches for Sediment Transport in Sewer Systems

    DEFF Research Database (Denmark)

    Mark, Ole

    A study of the sediment transport processes in sewers has been carried out. Based on this study a mathematical modelling system has been developed to describe the transport processes of sediments and dissolved matter in sewer systems. The modelling system consists of three sub-models which...... constitute the basic modelling system necessary to give a discription of the most dominant physical transport processes concerning particles and dissolved matter in sewer systems: A surface model. An advection-dispersion model. A sediment transport model....

  19. Transport simulation of sorptive contaminants considering sediment-associated processes

    Institute of Scientific and Technical Information of China (English)

    LI Ruijie; LU Shasha; ZHENG Jun

    2012-01-01

    Sediment-associated processes,such as sediment erosion,deposition,and pore water diffusion/advection affect sorptive contaminant transport.By considering these processes,we developed an equation to simulate contaminant transport.Erosion and deposition processes are considered as erosion and deposition fluxes of sediment,and adsorption-desorption processes of contaminants by sediment are simulated using the Langmuir Equation.Pore water diffusion is calculated based on the contaminant concentration gradient across the sediment-water interface.Pore water advection is estimated using pore water contained in the sediments of erosion flux.The equation is validated to simulate total phosphorus concentrations in Guanhe estuary in the northern Jiangsu,China.The simulated total phosphorus concentrations show better agreement with field observations compared to estimations that do consider sediment-associated processes.

  20. SUSPENDED SEDIMENT TRANSPORT IN THE OFFSHORE NEAR YANGTZE ESTUARY

    Institute of Scientific and Technical Information of China (English)

    CHEN Bin; WANG Kai

    2008-01-01

    Based on the Estuarine, Coastal and Ocean Modeling System with Sediments (ECOMSED) model, a 3-D hydrodynamic-transport numerical model was established for the offshore area near the Yangtze Estuary in the East China Sea .The hydrodynamic module was driven by tide and wind. Sediment module included sediment resuspension, transport and deposition of cohesive and non-cohesive sediment. The settling of cohesive sediment in the water column was modeled as a function of aggregation (flocculation) and deposition. The numerical results were compared with observation data for August, 2006. It shows that the sediment concentration reduces gradually from the seashore to the offshore area. Numerical results of concentration time series in the observation stations show two peaks and two valleys, according with the observation data. It is mainly affected by tidal current. The suspended sediment concentration is related to the tidal current during a tidal cycle, and the maximum concentration appears 1 h-4 h after the current maximum velocity has reached.

  1. Transport and distribution of bottom sediments at Pirita Beach

    Directory of Open Access Journals (Sweden)

    Soomere, Tarmo

    2007-12-01

    Full Text Available The basic factors affecting sediment supply for and transport processes at Pirita Beach, a sandy section of the south­eastern coast of Tallinn Bay, are analysed. Observations of bathymetry, sediment properties and sources, sediment transport processes and their changes arising from coastal engineering activities are reported. The mean grain size is about 0.12 mm, with the fine sand fraction (0.063–0.125 mm accounting for about 77% of the sediments. Coarse sand dominates only along the waterline. The content of coarser sediments is greater in the northern part of the beach. A number of coastal engineering structures have blocked natural sediment supplies. The beach suffers from sediment deficit now and has lost about 400 m3 of sand annually from the dry beach between 1997 and 2005.

  2. Probability distributions of bed load particle velocities, accelerations, hop distances, and travel times informed by Jaynes's principle of maximum entropy

    Science.gov (United States)

    Furbish, David J.; Schmeeckle, Mark; Schumer, Rina; Fathel, Siobhan L.

    2016-01-01

    We describe the most likely forms of the probability distributions of bed load particle velocities, accelerations, hop distances, and travel times, in a manner that formally appeals to inferential statistics while honoring mechanical and kinematic constraints imposed by equilibrium transport conditions. The analysis is based on E. Jaynes's elaboration of the implications of the similarity between the Gibbs entropy in statistical mechanics and the Shannon entropy in information theory. By maximizing the information entropy of a distribution subject to known constraints on its moments, our choice of the form of the distribution is unbiased. The analysis suggests that particle velocities and travel times are exponentially distributed and that particle accelerations follow a Laplace distribution with zero mean. Particle hop distances, viewed alone, ought to be distributed exponentially. However, the covariance between hop distances and travel times precludes this result. Instead, the covariance structure suggests that hop distances follow a Weibull distribution. These distributions are consistent with high-resolution measurements obtained from high-speed imaging of bed load particle motions. The analysis brings us closer to choosing distributions based on our mechanical insight.

  3. On extracting sediment transport information from measurements of luminescence in river sediment

    CERN Document Server

    Gray, Harrison J; Mahan, Shannon A; McGuire, Chris; Rhodes, Edward J

    2016-01-01

    Accurately quantifying sediment transport rates in rivers remains an important goal for geomorphologists, hydraulic engineers, and environmental scientists. However, current techniques for measuring transport rates are laborious, and formulae to predict transport are notoriously inaccurate. Here, we attempt to estimate sediment transport rates using luminescence, a property of common sedimentary minerals that is used by the geoscience community for geochronology. This method is advantageous because of the ease of measurement on ubiquitous quartz and feldspar sand. We develop a model based on conservation of energy and sediment mass to explain the patterns of luminescence in river channel sediment from a first-principles perspective. We show that the model can accurately reproduce the luminescence observed in previously published field measurements from two rivers with very different sediment transport styles. The parameters from the model can then be used to estimate the time-averaged virtual velocity, charac...

  4. Rainfall, runoff and sediment transport in a Mediterranean mountainous catchment.

    Science.gov (United States)

    Tuset, J; Vericat, D; Batalla, R J

    2016-01-01

    The relation between rainfall, runoff, erosion and sediment transport is highly variable in Mediterranean catchments. Their relation can be modified by land use changes and climate oscillations that, ultimately, will control water and sediment yields. This paper analyses rainfall, runoff and sediment transport relations in a meso-scale Mediterranean mountain catchment, the Ribera Salada (NE Iberian Peninsula). A total of 73 floods recorded between November 2005 and November 2008 at the Inglabaga Sediment Transport Station (114.5 km(2)) have been analysed. Suspended sediment transport and flow discharge were measured continuously. Rainfall data was obtained by means of direct rain gauges and daily rainfall reconstructions from radar information. Results indicate that the annual sediment yield (2.3 t km(-1) y(-1) on average) and the flood-based runoff coefficients (4.1% on average) are low. The Ribera Salada presents a low geomorphological and hydrological activity compared with other Mediterranean mountain catchments. Pearson correlations between rainfall, runoff and sediment transport variables were obtained. The hydrological response of the catchment is controlled by the base flows. The magnitude of suspended sediment concentrations is largely correlated with flood magnitude, while sediment load is correlated with the amount of direct runoff. Multivariate analysis shows that total suspended load can be predicted by integrating rainfall and runoff variables. The total direct runoff is the variable with more weight in the equation. Finally, three main hydro-sedimentary phases within the hydrological year are defined in this catchment: (a) Winter, where the catchment produces only water and very little sediment; (b) Spring, where the majority of water and sediment is produced; and (c) Summer-Autumn, when little runoff is produced but significant amount of sediments is exported out of the catchment. Results show as land use and climate change may have an important

  5. Sediment transport-based metrics of wetland stability

    Science.gov (United States)

    Ganju, Neil K.; Kirwan, Matthew L.; Dickhudt, Patrick J.; Guntenspergen, Glenn R.; Cahoon, Donald R.; Kroeger, Kevin D.

    2015-01-01

    Despite the importance of sediment availability on wetland stability, vulnerability assessments seldom consider spatiotemporal variability of sediment transport. Models predict that the maximum rate of sea level rise a marsh can survive is proportional to suspended sediment concentration (SSC) and accretion. In contrast, we find that SSC and accretion are higher in an unstable marsh than in an adjacent stable marsh, suggesting that these metrics cannot describe wetland vulnerability. Therefore, we propose the flood/ebb SSC differential and organic-inorganic suspended sediment ratio as better vulnerability metrics. The unstable marsh favors sediment export (18 mg L−1 higher on ebb tides), while the stable marsh imports sediment (12 mg L−1 higher on flood tides). The organic-inorganic SSC ratio is 84% higher in the unstable marsh, and stable isotopes indicate a source consistent with marsh-derived material. These simple metrics scale with sediment fluxes, integrate spatiotemporal variability, and indicate sediment sources.

  6. Sediment transport and carbon sequestration characteristics along mangrove fringed coasts

    Institute of Scientific and Technical Information of China (English)

    TU Qiang; YANG Shengyun; ZHOU Qiulin; YANG Juan

    2015-01-01

    Mangroves play an important role in sequestering carbon and trapping sediments. However, the effectiveness of such functions is unclear due to the restriction of knowledge on the sedimentation process across the vegetation boun-daries. To detect the effects of mangrove forests on sediment transportation and organic carbon sequestration, the granulometric and organic carbon characteristics of mangrove sediments were investigated from three vegetation zones of four typical mangrove habitats on the Leizhou Peninsula coast. Based on our results, sediment transport was often“environmentally sensitive”to the vegetation friction. A transition of the sediment transport mode from the mudflat zone to the interior/fringe zone was often detected from the cumulative frequency curve. The vegetation cover also assists the trapping of material, resulting in a significantly higher concentration of organic carbon in the interior surface sediments. However, the graphic parameters of core sediments reflected a highly temporal variability due to the sedimentation process at different locations. The sediment texture ranges widely from sand to mud, altho-ugh the sedimentary environments are restricted within the same energy level along the fluvial-marine transition zone. Based on the PCA results, the large variation was mainly attributed to either the mean grain size features or the organic carbon features. A high correlation between the depth andδ13C value also indicated an increasing storage of mangrove-derived organic carbon with time.

  7. Analytical model for flux saturation in sediment transport.

    Science.gov (United States)

    Pähtz, Thomas; Parteli, Eric J R; Kok, Jasper F; Herrmann, Hans J

    2014-05-01

    The transport of sediment by a fluid along the surface is responsible for dune formation, dust entrainment, and a rich diversity of patterns on the bottom of oceans, rivers, and planetary surfaces. Most previous models of sediment transport have focused on the equilibrium (or saturated) particle flux. However, the morphodynamics of sediment landscapes emerging due to surface transport of sediment is controlled by situations out of equilibrium. In particular, it is controlled by the saturation length characterizing the distance it takes for the particle flux to reach a new equilibrium after a change in flow conditions. The saturation of mass density of particles entrained into transport and the relaxation of particle and fluid velocities constitute the main relevant relaxation mechanisms leading to saturation of the sediment flux. Here we present a theoretical model for sediment transport which, for the first time, accounts for both these relaxation mechanisms and for the different types of sediment entrainment prevailing under different environmental conditions. Our analytical treatment allows us to derive a closed expression for the saturation length of sediment flux, which is general and thus can be applied under different physical conditions.

  8. Preliminary Study on Formulae of Bed Load Sediment Transport Rate in Downstream of Jinshajiang River%金沙江下游支流河段推移质输沙率公式初探

    Institute of Scientific and Technical Information of China (English)

    惠晓晓; 刘同宦; 徐海涛

    2009-01-01

    选取金沙江下游龙川江、小江、牛栏江3条典型支流,对其进行水槽平衡输沙试验,并分析总结现有的推移质输沙率公式,以计算该3条支流的推移质输沙率.将试验成果与计算结果进行对比分析,结果表明:①从公式立论基础上看,以能量平衡为主要理论依据的公式计算值偏大;②从公式形式上看,以河段比降为主要参数的公式计算值偏大;③综合考虑各水力要素,Ackers-White公式,Einstein-Brown公式和长江科学院输沙曲线,较适用于金沙江下游支流河段的推移质输沙率的计算.

  9. Shallow sediment transport flow computation using time-varying sediment adaptation length

    Institute of Scientific and Technical Information of China (English)

    Jaan Hui PU; Khalid HUSSAIN; Song-dong SHAO; Yue-fei HUANG

    2014-01-01

    Based on the common approach, the adaptation length in sediment transport is normally estimated astemporally independent. However, this approach might not be theoretically justified as the process of reaching the sediment transport equilibrium stage is affected by the flow conditions in time, especially for fast moving flows, such as scour-hole developing flows. In this study, the two-dimensional (2D) shallow water formulation together with a sediment continuity-concentration (SCC) model were applied to flow with mobile sediment boundary. A time-varying approach was proposed to determine the sediment transport adaptation length to simulate the sediment erosion-deposition rate. The proposed computational model was based on the Finite Volume (FV) method. The Monotone Upwind Scheme of Conservative Laws (MUSCL)-Hancock scheme was used with the Harten Lax van Leer-contact (HLLC) approximate Riemann solver to discretize the FV model. In the flow applications of this paper, a highly discontinuous dam-break, fast sediment transport flow was used to calibrate the proposed time-varying sediment adaptation length model. Then the calibrated model was further applied to two separate experimental sediment transport flow applications documented in the literature, i.e. a highly concentrated sediment transport flow in a wide alluvial channel and a sediment aggradation flow. Good agreement with the experimental data were obtained with the proposed model simulations. The tests prove that the proposed model, which was calibrated by the discontinuous dam-break bed scouring flow, also performed well to represent rapid bed change and steady sediment mobility conditions.

  10. Contemporary sediment-transport processes in submarine canyons.

    Science.gov (United States)

    Puig, Pere; Palanques, Albert; Martín, Jacobo

    2014-01-01

    Submarine canyons are morphological incisions into continental margins that act as major conduits of sediment from shallow- to deep-sea regions. However, the exact mechanisms involved in sediment transfer within submarine canyons are still a subject of investigation. Several studies have provided direct information about contemporary sedimentary processes in submarine canyons that suggests different modes of transport and various triggering mechanisms. Storm-induced turbidity currents and enhanced off-shelf advection, hyperpycnal flows and failures of recently deposited fluvial sediments, dense shelf-water cascading, canyon-flank failures, and trawling-induced resuspension largely dominate present-day sediment transfer through canyons. Additionally, internal waves periodically resuspend ephemeral deposits within canyons and contribute to dispersing particles or retaining and accumulating them in specific regions. These transport processes commonly deposit sediments in the upper- and middle-canyon reaches for decades or centuries before being completely or partially flushed farther down-canyon by large sediment failures.

  11. A VERTICAL 2-D NUMERICAL SIMULATION OF SUSPENDED SEDIMENT TRANSPORT

    Institute of Scientific and Technical Information of China (English)

    ZHANG Jing-xin; LIU Hua

    2007-01-01

    Numerical simulation of sediment transport and bed evolution has become an important technique in the sediment research. In this article, a numerical model of suspended sediment transport was proposed, which was established in the vertical coordinate for fitting the free surface and bottom. In the research of the sediment transport, the predominant factors were found to be the eddy diffusion, the settling velocity, the bed condition and so on. By the aid of the model in the article, the contribution of the Rouse parameter to the vertical profile of sediment concentration was clarified, which was identical to the theoretical results. In the comparison of the numerical results with laboratory data, the agreement between experimental data and numerical results was reached except for some data. And the possible reasons for the disagreement were discussed.

  12. Sediment transport mechanisms through the sustainable vegetated flow networks

    Science.gov (United States)

    Allen, Deonie; Haynes, Heather; Arthur, Scott

    2016-04-01

    Understanding the pollution treatment efficiency of a sustainable urban drainage (SuDS) asset or network requires the influx, transport, detention and discharge of the pollutant within the system. To date event specific monitoring of sediment (primarily total suspended solids) concentrations in the inflow and discharge from SuDS have been monitored. Long term analysis of where the sediment is transported to and the residency time of this pollutant within the SuDS asset or network have not been unraveled due to the difficulty in monitoring specific sediment particulate movement. Using REO tracing methodology, sediment particulate movement has become possible. In tracing sediment movement from an urban surface the internal residency and transportation of this sediment has illustrated SuDS asset differences in multi-event detention. Of key importance is the finding that sediment remains within the SuDS asset for extended periods of time, but that the location sediment detention changes. Thus, over multiple rainfall-runoff events sediment is seen to move through the SuDS assets and network proving the assumption that detained sediment is permanent and stationary to be inaccurate. Furthermore, mass balance analysis of SuDS sediment indicates that there is notable re-suspension and ongoing release of sediment from the SuDS over time and cumulative rainfall-runoff events. Continued monitoring of sediment deposition and concentration in suspension illustrates that sediment detention within SuDS decreases over time/multiple events, without stabilizing within a 12 month period. Repeated experiments show a consistent pattern of detention and release for the three SuDS networks monitored in Scotland. Through consideration of both rainfall and flow factors the drivers of sediment transport within the monitored SuDS have been identified. Within the limitation of this field study the key drivers to SuDS sediment detention efficiency (or transport of sediment through the system

  13. Sediment Transport at Density Fronts in Shallow Water

    Science.gov (United States)

    2012-09-30

    in the Hudson occurred at multiple locations along the salinity gradient rather than a single interface between salty and fresh water . The fronts in...1 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Sediment Transport at Density Fronts in Shallow Water ...suspended sediment concentration at density fronts in shallow water (< 1 m), - characterize flow and suspended sediment at a density front through the

  14. Impact of Bacterial NO3- Transport on Sediment Biogeochemistry

    DEFF Research Database (Denmark)

    Nielsen, Lars Peter

    2005-01-01

    Experiments demonstrated that Beggiatoa could induce a H2S-depleted suboxic zone of more than 10 mm in marine sediments and cause a divergence in sediment NO3- reduction from denitrification to dissimilatory NO3- reduction to ammonium. pH, O2, and H2S profiles indicated that the bacteria oxidized......2S with NO3- and transported S0 to the sediment surface for aerobic oxidation....

  15. Impact of bacterial NO3- transport on sediment biogeochemistry

    DEFF Research Database (Denmark)

    Sayama, Mikio; Risgaard-Petersen, Nils; Nielsen, Lars Peter

    2005-01-01

    Experiments demonstrated that Beggiatoa could induce a H2S-depleted suboxic zone of more than 10 mm in marine sediments and cause a divergence in sediment NO3– reduction from denitrification to dissimilatory NO3– reduction to ammonium. pH, O2, and H2S profiles indicated that the bacteria oxidized H......2S with NO3– and transported S0 to the sediment surface for aerobic oxidation....

  16. On extracting sediment transport information from measurements of luminescence in river sediment

    Science.gov (United States)

    Gray, Harrison J.; Tucker, Gregory E.; Mahan, Shannon A.; McGuire, Chris; Rhodes, Edward J.

    2017-03-01

    Accurately quantifying sediment transport rates in rivers remains an important goal for geomorphologists, hydraulic engineers, and environmental scientists. However, current techniques for measuring long-time scale (102-106 years) transport rates are laborious, and formulae to predict transport are notoriously inaccurate. Here we attempt to estimate sediment transport rates by using luminescence, a property of common sedimentary minerals that is used by the geoscience community for geochronology. This method is advantageous because of the ease of measurement on ubiquitous quartz and feldspar sand. We develop a model from first principles by using conservation of energy and sediment mass to explain the downstream pattern of luminescence in river channel sediment. We show that the model can accurately reproduce the luminescence observed in previously published field measurements from two rivers with very different sediment transport styles. The model demonstrates that the downstream pattern of river sand luminescence should show exponential-like decay in the headwaters which asymptotes to a constant value with further downstream distance. The parameters from the model can then be used to estimate the time-averaged virtual velocity, characteristic transport lengthscale, storage time scale, and floodplain exchange rate of fine sand-sized sediment in a fluvial system. The sediment transport values predicted from the luminescence method show a broader range than those reported in the literature, but the results are nonetheless encouraging and suggest that luminescence demonstrates potential as a sediment transport indicator. However, caution is warranted when applying the model as the complex nature of sediment transport can sometimes invalidate underlying simplifications.

  17. On extracting sediment transport information from measurements of luminescence in river sediment

    Science.gov (United States)

    Gray, Harrison J.; Tucker, Gregory E.; Mahan, Shannon; McGuire, Chris; Rhodes, Edward J.

    2017-01-01

    Accurately quantifying sediment transport rates in rivers remains an important goal for geomorphologists, hydraulic engineers, and environmental scientists. However, current techniques for measuring long-time scale (102–106 years) transport rates are laborious, and formulae to predict transport are notoriously inaccurate. Here we attempt to estimate sediment transport rates by using luminescence, a property of common sedimentary minerals that is used by the geoscience community for geochronology. This method is advantageous because of the ease of measurement on ubiquitous quartz and feldspar sand. We develop a model from first principles by using conservation of energy and sediment mass to explain the downstream pattern of luminescence in river channel sediment. We show that the model can accurately reproduce the luminescence observed in previously published field measurements from two rivers with very different sediment transport styles. The model demonstrates that the downstream pattern of river sand luminescence should show exponential-like decay in the headwaters which asymptotes to a constant value with further downstream distance. The parameters from the model can then be used to estimate the time-averaged virtual velocity, characteristic transport lengthscale, storage time scale, and floodplain exchange rate of fine sand-sized sediment in a fluvial system. The sediment transport values predicted from the luminescence method show a broader range than those reported in the literature, but the results are nonetheless encouraging and suggest that luminescence demonstrates potential as a sediment transport indicator. However, caution is warranted when applying the model as the complex nature of sediment transport can sometimes invalidate underlying simplifications.

  18. A three-dimensional k-ε-kp model in curvilinear coordinates for sediment movement and bed evolution

    Institute of Scientific and Technical Information of China (English)

    SHEN YongMing; LIU Cheng

    2009-01-01

    To aim at the substitution of the magnitude and direction of water flow movement near bed for those of bed load transport in solid-liquid two-phase one-fluid model, and to simulate the effect of secondary flow on transverse bed load transport in channel bends and the effect of bed slope on bed load transport in a better way, a three-dimensional k-ε-kp solid-liquid two-phase two-fluid model in curvilinear coordinates is solved numerically with a finite-volume method on an adaptive grid for studying water-sediment movements and bed evolution in a 120° channel bend. Numerical results show that the trajectories of solid-phase deviate from those of liquid-phase in the channel bend, and the deviation increases with the increase of the particle diameters. The calculated bed deformation by the k-ε-kpmodel is in better agreement with measured bed deformation than those by one-fluid model. It is proved that the k-ε-kp model can simulate the effect of secondary flow on lateral bed load transport with the higher accuracy than the one-fluid model.

  19. Sediment transport near the Peninsular tip of India

    Digital Repository Service at National Institute of Oceanography (India)

    Jena, B.K.; Chandramohan, P.

    sediment transport rates were estimated based on the observed data. Study shows that the wave activity was high throughout the year at Kolachel. The annual gross longshore sediment trasnport rate was higher 0.9 x 10 sup(6) m sup(3)/year and the annual net...

  20. Equilibrium sediment transport in lower Yellow River during later sediment-retaining period of Xiaolangdi Reservoir

    Institute of Scientific and Technical Information of China (English)

    Shao-lei Guo; Dong-po Sun; En-hui Jiang; Peng Li

    2015-01-01

    The Xiaolangdi Reservoir has entered the later sediment-retaining period, and new sediment transport phenomena and channel re-estab-lishing behaviors are appearing. A physical model test was used to forecast the scouring and silting trends of the lower Yellow River. Based on water and sediment data from the lower Yellow River during the period from 1960 to 2012, and using a statistical method, this paper analyzed the sediment transport in sediment-laden flows with different discharges and sediment concentrations in the lower Yellow River. The results show that rational water-sediment regulation is necessary to avoid silting in the later sediment-retaining period. The combination of 3 000 m3/ssediment concentration) at the Huayuankou section is considered an optimal combination for equilibrium sediment transport in the lower Yellow River over a long period of time.

  1. Hydrodynamics, sediment transport and light extinction off Cape Bolinao, Philippines

    NARCIS (Netherlands)

    Rivera, P.C.

    1997-01-01

    Observational and numerical modelling studies of the hydrodynamics, sediment transport, and light extinction were undertaken in the marine environment around Cape Bolinao in the Lingayen Gulf (Northwest Philippines). Abundant with ecologically important seagrasses and benthic organisms,

  2. Neural network-genetic programming for sediment transport

    Digital Repository Service at National Institute of Oceanography (India)

    Singh, A.K.; Deo, M.C.; SanilKumar, V.

    The planning, operation, design and maintenance of almost all harbour and coastal engineering facilities call for an estimation of the longshore sediment transport rate. This is currently and popularly done with the help of empirical equations...

  3. Numerical Modelling of Arctic Coastal Hydrodynamics and Sediment Transport

    OpenAIRE

    Borgersen, Benedicte T

    2016-01-01

    Coastal areas are experiencing an increase in human population and activities, both in temperate and in Arctic areas. This change in the coastal areas requires that the areas are safe and reliable in order to not put human lives and economical values in danger. To be about to protect the coastal areas it is important to know the hydrodynamics and sediment transport and their effect on coastal areas. Numerical modeling of coastal hydrodynamics and sediment transport is a normal approach to...

  4. Entrainment, motion, and deposition of coarse particles transported by water over a sloping mobile bed

    Science.gov (United States)

    Heyman, J.; Bohorquez, P.; Ancey, C.

    2016-10-01

    In gravel bed rivers, bed load transport exhibits considerable variability in time and space. Recently, stochastic bed load transport theories have been developed to address the mechanisms and effects of bed load transport fluctuations. Stochastic models involve parameters such as particle diffusivity, entrainment, and deposition rates. The lack of hard information on how these parameters vary with flow conditions is a clear impediment to their application to real-world scenarios. In this paper, we determined the closure equations for the above parameters from laboratory experiments. We focused on shallow supercritical flow on a sloping mobile bed in straight channels, a setting that was representative of flow conditions in mountain rivers. Experiments were run at low sediment transport rates under steady nonuniform flow conditions (i.e., the water discharge was kept constant, but bed forms developed and migrated upstream, making flow nonuniform). Using image processing, we reconstructed particle paths to deduce the particle velocity and its probability distribution, particle diffusivity, and rates of deposition and entrainment. We found that on average, particle acceleration, velocity, and deposition rate were responsive to local flow conditions, whereas entrainment rate depended strongly on local bed activity. Particle diffusivity varied linearly with the depth-averaged flow velocity. The empirical probability distribution of particle velocity was well approximated by a Gaussian distribution when all particle positions were considered together. In contrast, the particles located in close vicinity to the bed had exponentially distributed velocities. Our experimental results provide closure equations for stochastic or deterministic bed load transport models.

  5. Sediment characteristics and transportation dynamics of the Ganga River

    Science.gov (United States)

    Singh, Munendra; Singh, Indra Bir; Müller, German

    2007-04-01

    Understanding of river systems that have experienced various forcing mechanisms such as climate, tectonics, sea level fluctuations and their linkages is a major concern for fluvial scientists. The 2525-km-long Ganga River derives its fluvial flux from northern part of the Indian subcontinent and drops in the Ganga-Brahmaputra delta and the Bengal fan regions. This paper presents a study of the Ganga River sediments for their textural properties, grainsize characteristics, and transportation dynamics. A suite of recently deposited sediments (189 bedload samples and 27 suspended load samples) of the river and its tributaries was collected from 63 locations. Dry and wet sieve methods of grainsize analysis were performed and Folk and Ward's parameters were calculated. Transportation dynamics of the sediment load was assessed by means of channel hydrology, flow/sediment rating curves, bedform mechanics, grainsize images, and cumulative curves. Textural properties of the bedload sediments of the Ganga River tributaries originating from the Himalaya orogenic belt, the northern Indian craton and the Ganga alluvial plain regions are characterised by the predominance of fine to very fine sand, medium to fine sand, and very fine sand to clay, respectively. Downstream textural variations in the bedload and suspended load sediments of the Ganga River are, therefore, complex and are strongly influenced by lateral sediment inputs by the tributaries and channel slope. At the base of the Himalaya, a very sharp gravel-sand transition is present in which median grainsize of bedload sediments decreases from over - 0.16 Φ to 2.46 Φ within a distance of 35 km. Downstream decline in mean grainsize of bedload sediments in the upper Ganga River within the alluvial plain can be expressed by an exponential formula as: mean grainsize (in Φ) = 0.0024 × Distance (in kilometres from the Himalayan front) + 1.29. It is a result of selective transport phenomena rather than of abrasion, the

  6. Contemporary proglacial aeolian sediment transport in West Greenland

    Science.gov (United States)

    Bullard, J. E.; Austin, M. J.

    2007-12-01

    Glacial erosion processes produce significance quantities of fine sediments that are washed out from beneath glaciers by meltwater. When deposited on the glacier floodplain they dessicate and strong ice-driven winds can entrain and transport them across the landscape resulting in the formation of sand dunes and loess, and adding very fine particles (dust) to the atmosphere. Recent studies suggest that locally-generated dust can play an important role in regulating albedo and the melting rate of glaciers. Very few field process studies have examined the relationship between sediment-delivery to the proglacial floodplain by meltwater and the subsequent aeolian erosion and deposition of these fine sediments. This research reports the use of semi-isokinetic directional sediment samplers to make an initial assessment of the rates of transport of dust and sand in Sandflugtdalen, a valley adjacent to the West Greenland ice sheet. Vertical arrays (z(m) = 0.18, 0.43, 0.85, 1.4) of samplers were deployed in a down valley transect over a distance of 4 km. Trapped sediments were retrieved after intervals of 1 week and 9 weeks. The mass of sediment collected in the traps varied from 0.002-3.62 g cm2 wk-1. As expected, near surface traps collected more, and coarser, sediment than those deployed at 1.4 m height but the decrease in mass of sediment with height was highly variable. The array closest to the glacier trapped the greatest quantity of suspended sediment and the density of suspended sediment decreased with distance down valley. The flux of aeolian sediment comprises clays, silts and sand-sized particles. Areas of aeolian entrainment, transport and deposition are closely linked to the development and distribution of sediments on the proglacial floodplain which varies considerably in terms of surface roughness. At the east end of the valley, close to the ice sheet, aeolian sediment flux is controlled by sediment supply and topography rather than wind speed. Further down

  7. Progress towards Acoustic Suspended Sediment Transport Monitoring: Fraser River, BC

    Science.gov (United States)

    Attard, M. E.; Venditti, J. G.; Church, M. A.; Kostaschuk, R. A.

    2011-12-01

    Our ability to predict the timing and quantity of suspended sediment transport is limited because fine sand, silt and clay delivery are supply limited, requiring empirical modeling approaches of limited temporal stability. A solution is the development of continuous monitoring techniques capable of tracking sediment concentrations and grain-size. Here we examine sediment delivery from upstream sources to the lower Fraser River. The sediment budget of the lower Fraser River provides a long-term perspective of the net changes in the channels and in sediment delivery to Fraser Delta. The budget is based on historical sediment rating curves developed from data collected from 1965-1986 by the Water Survey of Canada. We explore the possibility of re-establishing the sediment-monitoring program using hydro-acoustics by evaluating the use of a 300 kHz side-looking acoustic Doppler current profiler (aDcp), mounted just downstream of the sand-gravel transition at Mission, for continuous measurement of suspended sediment transport. Complementary field observations include conventional bottle sampling with a P-63 sampler, vertical profiles with a downward-looking 600 kHz aDcp, and 1200 kHz aDcp discharge measurements. We have successfully completed calibration of the downward-looking aDcp with the P-63 samples; the side-looking aDcp signals remain under investigation. A comparison of several methods for obtaining total sediment flux indicates that suspended sediment concentration (SSC) closely follows discharge through the freshet and peaks in total SSC and sand SSC coincide with peak measurements of discharge. Low flows are dominated by fine sediment and grain size increases with higher flows. This research assesses several techniques for obtaining sediment flux and contributes to the understanding of sediment delivery to sand-bedded portions of the river.

  8. Modelling of Sediment Transport in Beris Fishery Port

    Directory of Open Access Journals (Sweden)

    Samira Ardani

    2015-06-01

    Full Text Available In this paper, the large amount of sedimentation and the resultant shoreline advancements at the breakwaters of Beris Fishery Port are studied. A series of numerical modeling of waves, sediment transport, and shoreline changes were conducted to predict the complicated equilibrium shoreline. The outputs show that the nearshore directions of wave components are not perpendicular to the coast which reveals the existence of longshore currents and consequently sediment transport along the bay. Considering the dynamic equilibrium condition of the bay, the effect of the existing sediment resources in the studied area is also investigated. The study also shows that in spite of the change of the diffraction point of Beris Bay after the construction of the fishery port, the bay is approaching its dynamic equilibrium condition, and the shoreline advancement behind secondary breakwater will stop before blocking the entrance of the port. The probable solutions to overcome the sedimentation problem at the main breakwater are also discussed.

  9. NUMERICAL SIMULATION OF SEDIMENT TRANSPORT IN ALLUVIAL RIVER WITH FLOODPLAINS

    Institute of Scientific and Technical Information of China (English)

    Jianchun HUANG; Blair GREIMANN; Chih Ted YANG

    2003-01-01

    This paper presents a one-dimensional numerical model for predicting sediment transport and bed evolution in natural rivers that have floodplains. The sediment transport in floodplains is generally different from that in the main channel. Even when erosion occurs in the main channel,the floodplain usually experiences deposition. To predict the erosion and deposition in the same cross section,the river is divided into three subchannels in the transversal direction: the main channel and the left and right floodplains. The non-equilibrium sediment transport equation is modified to account for the sediment exchanges between the subchannels. The numerical model has been applied to the stretch of the Rio Grande from San Acacia Diversion Dam to Elephant Butte Reservoir. Based on a comparison with field data,the bed profile and cumulative deposition are estimated satisfactorily by the numerical model.

  10. Transport of fine sediment over a coarse, immobile riverbed

    Science.gov (United States)

    Grams, Paul E.; Wilcock, Peter R.

    2014-01-01

    Sediment transport in cobble-boulder rivers consists mostly of fine sediment moving over a coarse, immobile bed. Transport rate depends on several interrelated factors: boundary shear stress, the grain size and volume of fine sediment, and the configuration of fine sediment into interstitial deposits and bed forms. Existing models do not incorporate all of these factors. Approaches that partition stress face a daunting challenge because most of the boundary shear is exerted on immobile grains. We present an alternative approach that divides the bed into sand patches and interstitial deposits and is well constrained by two clear end-member cases: full sand cover and absence of sand. Entrainment from sand patches is a function of their aerial coverage. Entrainment from interstices among immobile grains is a function of sand elevation relative to the size of the immobile grains. The bed-sand coverage function is used to predict the ratio of the rate of entrainment from a partially covered bed to the rate of entrainment from a completely sand-covered bed, which is determined using a standard sand transport model. We implement the bed-sand coverage function in a morphodynamic routing model and test it against observations of sand bed elevation and suspended sand concentration for conditions of nonuniform fine sediment transport in a large flume with steady uniform flow over immobile hemispheres. The results suggest that this approach may provide a simple and robust method for predicting the transport and migration of fine sediment through rivers with coarse, immobile beds.

  11. A three-dimensional k-ε-k_p model in curvilinear coordinates for sediment movement and bed evolution

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    To aim at the substitution of the magnitude and direction of water flow movement near bed for those of bed load transport in solid-liquid two-phase one-fluid model, and to simulate the effect of secondary flow on transverse bed load transport in channel bends and the effect of bed slope on bed load trans- port in a better way, a three-dimensional k-ε-kp solid-liquid two-phase two-fluid model in curvilinear coordinates is solved numerically with a finite-volume method on an adaptive grid for studying wa- ter-sediment movements and bed evolution in a 120° channel bend. Numerical results show that the trajectories of solid-phase deviate from those of liquid-phase in the channel bend, and the deviation increases with the increase of the particle diameters. The calculated bed deformation by the k-ε-kp model is in better agreement with measured bed deformation than those by one-fluid model. It is proved that the k-ε-kp model can simulate the effect of secondary flow on lateral bed load transport with the higher accuracy than the one-fluid model.

  12. Incorporation of Fine-Grained Sediment Erodibility Measurements into Sediment Transport Modeling, Capitol Lake, Washington

    Science.gov (United States)

    Stevens, Andrew W.; Gelfenbaum, Guy; Elias, Edwin; Jones, Craig

    2008-01-01

    Capitol Lake was created in 1951 with the construction of a concrete dam and control gate that prevented salt-water intrusion into the newly formed lake and regulated flow of the Deschutes River into southern Puget Sound. Physical processes associated with the former tidally dominated estuary were altered, and the dam structure itself likely caused an increase in retention of sediment flowing into the lake from the Deschutes River. Several efforts to manage sediment accumulation in the lake, including dredging and the construction of sediment traps upriver, failed to stop the lake from filling with sediment. The Deschutes Estuary Feasibility Study (DEFS) was carried out to evaluate the possibility of removing the dam and restoring estuarine processes as an alternative ongoing lake management. An important component of DEFS was the creation of a hydrodynamic and sediment transport model of the restored Deschutes Estuary. Results from model simulations indicated that estuarine processes would be restored under each of four restoration alternatives, and that over time, the restored estuary would have morphological features similar to the predam estuary. The model also predicted that after dam-removal, a large portion of the sediment eroded from the lake bottom would be deposited near the Port of Olympia and a marina located in lower Budd Inlet seaward of the present dam. The volume of sediment transported downstream was a critical piece of information that managers needed to estimate the total cost of the proposed restoration project. However, the ability of the model to predict the magnitude of sediment transport in general and, in particular, the volume of sediment deposition in the port and marina was limited by a lack of information on the erodibility of fine-grained sediments in Capitol Lake. Cores at several sites throughout Capitol Lake were collected between October 31 and November 1, 2007. The erodibility of sediments in the cores was later determined in the

  13. Sediment transport in nonlinear skewed oscillatory flows: Transkew experiments

    NARCIS (Netherlands)

    Silva, P.A.; Abreu, T.; A, D. van der; Sancho, F.; Ruessink, B.G.; Werf, J. van der; Ribberink, J.S.

    2011-01-01

    New experiments under sheet flow conditions were conducted in an oscillating water tunnel to study the effects of flow acceleration on sand transport. The simulated hydrodynamic conditions considered flow patterns that drive cross-shore sediment transport in the nearshore zone: the wave nonlineariti

  14. A phenomenological study of sediment transport in shallow overland flow

    Science.gov (United States)

    Soil erosion is a highly complicated phenomenon consisting of many component processes. On upland areas, these processes are usually thought of as detachment and transport of soil particles by rainfall and surface flow. One of the most difficult processes to quantify is sediment transport. This proc...

  15. Spatial Modelling of Sediment Transport over the Upper Citarum Catchment

    Directory of Open Access Journals (Sweden)

    Poerbandono

    2006-05-01

    Full Text Available This paper discusses set up of a spatial model applied in Geographic Information System (GIS environment for predicting annual erosion rate and sediment yield of a watershed. The study area is situated in the Upper Citarum Catchment of West Java. Annual sediment yield is considered as product of erosion rate and sediment delivery ratio to be modelled under similar modeling tool. Sediment delivery ratio is estimated on the basis of sediment resident time. The modeling concept is based on the calculation of water flow velocity through sub-catchment surface, which is controlled by topography, rainfall, soil characteristics and various types of land use. Relating velocity to known distance across digital elevation model, sediment resident time can be estimated. Data from relevance authorities are used. Bearing in mind limited knowledge of some governing factors due to lack of observation, the result has shown the potential of GIS for spatially modeling regional sediment transport. Validation of model result is carried out by evaluating measured and computed total sediment yield at the main outlet. Computed total sediment yields for 1994 and 2001 are found to be 1.96×106 and 2.10×106tons/year. They deviate roughly 54 and 8% with respect to those measured in the field. Model response due to land use change observed in 2001 and 1994 is also recognised. Under presumably constant rainfall depth, an increase of overall average annual erosion rate of 11% resulted in an increase of overall average sediment yield of 7%.

  16. Sediment transport on the Palos Verdes shelf, California

    Science.gov (United States)

    Ferre, B.; Sherwood, C.R.; Wiberg, P.L.

    2010-01-01

    Sediment transport and the potential for erosion or deposition have been investigated on the Palos Verdes (PV) and San Pedro shelves in southern California to help assess the fate of an effluent-affected deposit contaminated with DDT and PCBs. Bottom boundary layer measurements at two 60-m sites in spring 2004 were used to set model parameters and evaluate a one-dimensional (vertical) model of local, steady-state resuspension, and suspended-sediment transport. The model demonstrated skill (Brier scores up to 0.75) reproducing the magnitudes of bottom shear stress, current speeds, and suspended-sediment concentrations measured during an April transport event, but the model tended to underpredict observed rotation in the bottom-boundary layer, possibly because the model did not account for the effects of temperature-salinity stratification. The model was run with wave input estimated from a nearby buoy and current input from four to six years of measurements at thirteen sites on the 35- and 65-m isobaths on the PV and San Pedro shelves. Sediment characteristics and erodibility were based on gentle wet-sieve analysis and erosion-chamber measurements. Modeled flow and sediment transport were mostly alongshelf toward the northwest on the PV shelf with a significant offshore component. The 95th percentile of bottom shear stresses ranged from 0.09 to 0.16 Pa at the 65-m sites, and the lowest values were in the middle of the PV shelf, near the Whites Point sewage outfalls where the effluent-affected layer is thickest. Long-term mean transport rates varied from 0.9 to 4.8 metric tons m-1 yr-1 along the 65-m isobaths on the PV shelf, and were much higher at the 35-m sites. Gradients in modeled alongshore transport rates suggest that, in the absence of a supply of sediment from the outfalls or PV coast, erosion at rates of ???0.2 mm yr-1 might occur in the region southeast of the outfalls. These rates are small compared to some estimates of background natural sedimentation

  17. Sediment transport on the Palos Verdes shelf, California

    Science.gov (United States)

    Ferré, Bénédicte; Sherwood, Christopher R.; Wiberg, Patricia L.

    2010-04-01

    Sediment transport and the potential for erosion or deposition have been investigated on the Palos Verdes (PV) and San Pedro shelves in southern California to help assess the fate of an effluent-affected deposit contaminated with DDT and PCBs. Bottom boundary layer measurements at two 60-m sites in spring 2004 were used to set model parameters and evaluate a one-dimensional (vertical) model of local, steady-state resuspension, and suspended-sediment transport. The model demonstrated skill (Brier scores up to 0.75) reproducing the magnitudes of bottom shear stress, current speeds, and suspended-sediment concentrations measured during an April transport event, but the model tended to underpredict observed rotation in the bottom-boundary layer, possibly because the model did not account for the effects of temperature-salinity stratification. The model was run with wave input estimated from a nearby buoy and current input from four to six years of measurements at thirteen sites on the 35- and 65-m isobaths on the PV and San Pedro shelves. Sediment characteristics and erodibility were based on gentle wet-sieve analysis and erosion-chamber measurements. Modeled flow and sediment transport were mostly alongshelf toward the northwest on the PV shelf with a significant offshore component. The 95th percentile of bottom shear stresses ranged from 0.09 to 0.16 Pa at the 65-m sites, and the lowest values were in the middle of the PV shelf, near the Whites Point sewage outfalls where the effluent-affected layer is thickest. Long-term mean transport rates varied from 0.9 to 4.8 metric tons m -1 yr -1 along the 65-m isobaths on the PV shelf, and were much higher at the 35-m sites. Gradients in modeled alongshore transport rates suggest that, in the absence of a supply of sediment from the outfalls or PV coast, erosion at rates of ˜0.2 mm yr -1 might occur in the region southeast of the outfalls. These rates are small compared to some estimates of background natural sedimentation

  18. Time-Dependent Sediment Transport Subjected to Downward Seepage

    Institute of Scientific and Technical Information of China (English)

    刘小谢; 赵以明; 白玉川

    2014-01-01

    Experiments were conducted using cohesionless sand particles with median diameter of 0.48 mm to inves-tigate the time variation of sediment transport rate under the influence of local downward seepage. The experimental results show that the bedload transport rate in terms of volumetric sediment transport rate per unit width increased rapidly with time in the presence of suction, eventually reaching a peak beyond which it started to decrease. The trend of reduction was significantly reduced beyond 8 400 s after the test started. The analytical expression was derived in terms of dimensionless sediment transport rate and dimensionless time. The hypothesized relationships were compared with the experimental data, indicating a good agreement with each other.

  19. Simulation of suspended sediment transport initialized with satellite derived suspended sediment concentrations

    Indian Academy of Sciences (India)

    Ratheesh Ramakrishnan; A S Rajawat

    2012-10-01

    Suspended sediment transport in the Gulf of Kachchh is simulated utilizing the suspended sediment concentration (SSC) derived from Oceansat OCM imagery, as the initial condition in MIKE-21 Mud Transport model. Optimization of the model mud parameters, like settling velocity and critical shear stress for erosion are realized with respect to the sediment size distribution and the bottom bed materials observed in the Gulf. Simulated SSCs are compared with alternate OCM derived SSC. The results are observed to be impetus where the model is able to generate the spatial dynamics of the sediment concentrations. Sediment dynamics like deposition, erosion and dispersion are explained with the simulated tidal currents and OCM derived sediment concentrations. Tidal range is observed as the important physical factor controlling the deposition and resuspension of sediments within the Gulf. From the simulation studies; maximum residual current velocities, tidal fronts and high turbulent zones are found to characterise the islands and shoals within the Gulf, which results in high sediment concentrations in those regions. Remarkable variability in the bathymetry of the Gulf, different bed materials and varying tidal conditions induces several circulation patterns and turbulence creating the unique suspended sediment concentration pattern in the Gulf.

  20. Sediment supply versus local hydraulic controls on sediment transport and storage in a river with large sediment loads

    Science.gov (United States)

    Dean, David; Topping, David; Schmidt, John C.; Griffiths, Ronald; Sabol, Thomas

    2016-01-01

    The Rio Grande in the Big Bend region of Texas, USA, and Chihuahua and Coahuila, Mexico, undergoes rapid geomorphic changes as a result of its large sediment supply and variable hydrology; thus, it is a useful natural laboratory to investigate the relative importance of flow strength and sediment supply in controlling alluvial channel change. We analyzed a suite of sediment transport and geomorphic data to determine the cumulative influence of different flood types on changing channel form. In this study, physically based analyses suggest that channel change in the Rio Grande is controlled by both changes in flow strength and sediment supply over different spatial and temporal scales. Channel narrowing is primarily caused by substantial deposition of sediment supplied to the Rio Grande during tributary-sourced flash floods. Tributary floods have large suspended-sediment concentrations, occur for short durations, and attenuate rapidly downstream in the Rio Grande, depositing much of their sediment in downstream reaches. Long-duration floods on the mainstem have the capacity to enlarge the Rio Grande, and these floods, released from upstream dams, can either erode or deposit sediment in the Rio Grande depending upon the antecedent in-channel sediment supply and the magnitude and duration of the flood. Geomorphic and sediment transport analyses show that the locations and rates of sand erosion and deposition during long-duration floods are most strongly controlled by spatial changes in flow strength, largely through changes in channel slope. However, spatial differences in the in-channel sediment supply regulate sediment evacuation or accumulation over time in long reaches (greater than a kilometer).

  1. Suspended Sediment Transport and Fluid Mud Dynamics in Tidal Estuaries

    OpenAIRE

    Becker, Marius

    2011-01-01

    Cohesive sediments transport has been systematically studied for more than a century from field studies, laboratory experiments, and mathematical models. During the past decades, the accumulation of flocculated cohesive sediments and the formation of weakly consolidated mud deposits, including fluid mud, gained increased attention. Despite extensive research efforts, the governing processes of fluid mud formation are far from being fully understood. The primary objective of this study is to i...

  2. Harmonize input selection for sediment transport prediction

    Science.gov (United States)

    Afan, Haitham Abdulmohsin; Keshtegar, Behrooz; Mohtar, Wan Hanna Melini Wan; El-Shafie, Ahmed

    2017-09-01

    In this paper, three modeling approaches using a Neural Network (NN), Response Surface Method (RSM) and response surface method basis Global Harmony Search (GHS) are applied to predict the daily time series suspended sediment load. Generally, the input variables for forecasting the suspended sediment load are manually selected based on the maximum correlations of input variables in the modeling approaches based on NN and RSM. The RSM is improved to select the input variables by using the errors terms of training data based on the GHS, namely as response surface method and global harmony search (RSM-GHS) modeling method. The second-order polynomial function with cross terms is applied to calibrate the time series suspended sediment load with three, four and five input variables in the proposed RSM-GHS. The linear, square and cross corrections of twenty input variables of antecedent values of suspended sediment load and water discharge are investigated to achieve the best predictions of the RSM based on the GHS method. The performances of the NN, RSM and proposed RSM-GHS including both accuracy and simplicity are compared through several comparative predicted and error statistics. The results illustrated that the proposed RSM-GHS is as uncomplicated as the RSM but performed better, where fewer errors and better correlation was observed (R = 0.95, MAE = 18.09 (ton/day), RMSE = 25.16 (ton/day)) compared to the ANN (R = 0.91, MAE = 20.17 (ton/day), RMSE = 33.09 (ton/day)) and RSM (R = 0.91, MAE = 20.06 (ton/day), RMSE = 31.92 (ton/day)) for all types of input variables.

  3. Streambed Structure, Stream Power, and Bedload Transport: A Unified Outlook for Gravel-bed and Bedrock Streams

    Science.gov (United States)

    Chatanantavet, P.; Diplas, P.; Almedeij, J.

    2015-12-01

    Interactions among streambed structure, stream power, and sediment transport in rivers have been widely observed and documented. Perennial gravel-bed streams typically possess a surface bed layer that is coarser than the subsurface material. This coarser surface layer is, however, absent from some ephemeral gravel-bed streams and in some cases the reverse phenomenon occurs. Ephemeral streams also exhibit considerably higher efficiency in transporting sediment. In steep bedrock rivers, the hydraulic-rock interactive mechanism often self-creates step-pool or cascade bed configurations as forms of energy dissipation to control the transport efficiency of sediment. Here we aim to characterize bed structures and sediment transport in gravel-bed rivers and bedrock streams by using the concept of dimensionless stream power. We analyzed existing bed load data collected from field and experimental settings in an attempt to reach a unified outlook for both stream types and various channel bed features. We found that the mechanisms responsible for the features perceived to distinguish surface fining and surface coarsening are interrelated and triggered by different values of dimensionless stream power. The surface fining case has been attributed to fluidization of the entire bed material as demonstrated here in detail. The results also suggest that in bedrock rivers with large bedforms, such as stabled step-pool and immobile rock cascade, relatively medium-large values of stream power (i.e., floods of less than 30-year return period) do not equate with large bed load transport rates due to a portion of flow energy dissipating through local hydraulic jumps, leaving less energy to transport the bed load. Plot of transport efficiency values for each bed type and flood magnitude in bedrock rivers also helps us estimate how much fraction of flow energy is delivered to do bedrock erosive work by saltating bed load; hence, the implication for studies of landscape evolution.

  4. Complexities in coastal sediment transport studies by numerical modelling

    Digital Repository Service at National Institute of Oceanography (India)

    Ilangovan, D.; ManiMurali, R.

    stream_size 10748 stream_content_type text/plain stream_name Proc_Int_Conf_APAC_2013_364.pdf.txt stream_source_info Proc_Int_Conf_APAC_2013_364.pdf.txt Content-Encoding UTF-8 Content-Type text/plain; charset=UTF-8 Procee... could under estimate or over estimate the quantity of sediment transport and the result may not help to predict either erosion or accrction over a coastal region. CONCLUSIONS The authors conclude that sediment transport modelers need a thorough and long...

  5. Numerical Simulation of Sediment Transport due to Plunging Breaking Waves

    DEFF Research Database (Denmark)

    Pedersen, Claus

    A numerical model simulating the sediment transport due to plunging breaking waves has been developed. The model is two-dimensional, assuming conditions in the long-shore direction invariable. A plunging breaker is simulated by superimposing a non-breaking wave with a jet. Based on the description...... of the sediment transport rates, a simple model describing the morphological changes has been applied to simulate the evolution of a plunge point generated vorticity included, the bottom topography from the experiments by Dette & Uliczka was not in equilibrium according to the model....

  6. Effects of wave shape on sheet flow sediment transport

    Science.gov (United States)

    Hsu, T.-J.; Hanes, D.M.

    2004-01-01

    A two-phase model is implemented to study the effects of wave shape on the transport of coarse-grained sediment in the sheet flow regime. The model is based on balance equations for the average mass, momentum, and fluctuation energy for both the fluid and sediment phases. Model simulations indicate that the responses of the sheet flow, such as the velocity profiles, the instantaneous bed shear stress, the sediment flux, and the total amount of the mobilized sediment, cannot be fully parameterized by quasi-steady free-stream velocity and may be correlated with the magnitude of local horizontal pressure gradient (or free-stream acceleration). A net sediment flux in the direction of wave advance is obtained for both skewed and saw-tooth wave shapes typical of shoaled and breaking waves. The model further suggests that at critical values of the horizontal pressure gradient, there is a failure event within the bed that mobilizes more sediment into the mobile sheet and enhances the sediment flux. Preliminary attempts to parameterize the total bed shear stress and the total sediment flux appear promising. Copyright 2004 by the American Geophysical Union.

  7. Surficial sediment distribution and the associated net sediment transport pattern in the Pearl River Estuary, South China

    NARCIS (Netherlands)

    Zhang, W.; Zheng, J.H.; Ji, X.M.; Hoitink, A.J.F.; van der Vegt, M.

    2013-01-01

    Spatial variations in grain-size parameters contain information on sediment transport patterns. Therefore, in this study, 106 surficial sediment samples taken from the Pearl River Estuary (PRE), South China, were analyzed, to better understand the net sediment transport pattern in this region. The P

  8. Preliminary Results on Sediment Sorting Under Intense Bedload Transport

    Science.gov (United States)

    Hernandez Moreira, R. R.; Vautin, D.; Mathews, S. L.; Kuprenas, R.; Viparelli, E.

    2014-12-01

    Previous experiments show that parallel-laminated deposits are emplaced under upper plane bed regime by the migration of small-amplitude, long-wavelength bedforms. The present research focuses on how sediment is sorted under upper plane bed and sheet flow transport regimes, and whether parallel-lamination is inhibited during sheet flow transport. The problem of studying the sorting of sediment under so intense transport conditions is plagued by the uncertainties related to flow resistances and bedload transport rates. We simplify the problem by first running the experiments with uniform sediment, to establish a baseline that will aid in the design of the experiments with poorly sorted material. We are running experiments at the Hydraulics Laboratory of the Department of Civil and Environmental Engineering at the University of South Carolina in Columbia, in a unidirectional sediment-feed flume, 9 meters long by 0.2 meters wide, of which 7 meters are used as test section. During the experiments, water surface and bed elevations are periodically measured to characterize the global parameters of the flow, e.g. mean flow velocity and bed shear stress. When the flow and the sediment transport reach conditions of mobile bed equilibrium, bed elevation fluctuations are measured with ultrasonic transducer systems at six fixed locations. Channel bed aggradation is then induced by slowly raising the tail gate of the flume such that there is no change in transport regime, as confirmed by additional measurements of water surface and bed elevation and bed elevation fluctuations. Preliminary observations under upper plane bed regime show the formation of the small-amplitude and long-wavelength bedforms, as well as hints of parallel lamination in the deposits. In the near future we aim to achieve sheet flow transport conditions with both uniform and non-uniform grain size distributions to look at the internal structure of the emplaced deposit.

  9. Parameterization of wind turbine impacts on hydrodynamics and sediment transport

    Science.gov (United States)

    Rivier, Aurélie; Bennis, Anne-Claire; Pinon, Grégory; Magar, Vanesa; Gross, Markus

    2016-10-01

    Monopile foundations of offshore wind turbines modify the hydrodynamics and sediment transport at local and regional scales. The aim of this work is to assess these modifications and to parameterize them in a regional model. In the present study, this is achieved through a regional circulation model, coupled with a sediment transport module, using two approaches. One approach is to explicitly model the monopiles in the mesh as dry cells, and the other is to parameterize them by adding a drag force term to the momentum and turbulence equations. Idealised cases are run using hydrodynamical conditions and sediment grain sizes typical from the area located off Courseulles-sur-Mer (Normandy, France), where an offshore windfarm is under planning, to assess the capacity of the model to reproduce the effect of the monopile on the environment. Then, the model is applied to a real configuration on an area including the future offshore windfarm of Courseulles-sur-Mer. Four monopiles are represented in the model using both approaches, and modifications of the hydrodynamics and sediment transport are assessed over a tidal cycle. In relation to local hydrodynamic effects, it is observed that currents increase at the side of the monopile and decrease in front of and downstream of the monopile. In relation to sediment transport effect, the results show that resuspension and erosion occur around the monopile in locations where the current speed increases due to the monopile presence, and sediments deposit downstream where the bed shear stress is lower. During the tidal cycle, wakes downstream of the monopile reach the following monopile and modify the velocity magnitude and suspended sediment concentration patterns around the second monopile.

  10. Parameterization of wind turbine impacts on hydrodynamics and sediment transport

    Science.gov (United States)

    Rivier, Aurélie; Bennis, Anne-Claire; Pinon, Grégory; Magar, Vanesa; Gross, Markus

    2016-09-01

    Monopile foundations of offshore wind turbines modify the hydrodynamics and sediment transport at local and regional scales. The aim of this work is to assess these modifications and to parameterize them in a regional model. In the present study, this is achieved through a regional circulation model, coupled with a sediment transport module, using two approaches. One approach is to explicitly model the monopiles in the mesh as dry cells, and the other is to parameterize them by adding a drag force term to the momentum and turbulence equations. Idealised cases are run using hydrodynamical conditions and sediment grain sizes typical from the area located off Courseulles-sur-Mer (Normandy, France), where an offshore windfarm is under planning, to assess the capacity of the model to reproduce the effect of the monopile on the environment. Then, the model is applied to a real configuration on an area including the future offshore windfarm of Courseulles-sur-Mer. Four monopiles are represented in the model using both approaches, and modifications of the hydrodynamics and sediment transport are assessed over a tidal cycle. In relation to local hydrodynamic effects, it is observed that currents increase at the side of the monopile and decrease in front of and downstream of the monopile. In relation to sediment transport effect, the results show that resuspension and erosion occur around the monopile in locations where the current speed increases due to the monopile presence, and sediments deposit downstream where the bed shear stress is lower. During the tidal cycle, wakes downstream of the monopile reach the following monopile and modify the velocity magnitude and suspended sediment concentration patterns around the second monopile.

  11. Sediment transport in the presence of large reef bottom roughness

    Science.gov (United States)

    Pomeroy, Andrew W. M.; Lowe, Ryan J.; Ghisalberti, Marco; Storlazzi, Curt; Symonds, Graham; Roelvink, Dano

    2017-02-01

    The presence of large bottom roughness, such as that formed by benthic organisms on coral reef flats, has important implications for the size, concentration, and transport of suspended sediment in coastal environments. A 3 week field study was conducted in approximately 1.5 m water depth on the reef flat at Ningaloo Reef, Western Australia, to quantify the cross-reef hydrodynamics and suspended sediment dynamics over the large bottom roughness (˜20-40 cm) at the site. A logarithmic mean current profile consistently developed above the height of the roughness; however, the flow was substantially reduced below the height of the roughness (canopy region). Shear velocities inferred from the logarithmic profile and Reynolds stresses measured at the top of the roughness, which are traditionally used in predictive sediment transport formulations, were similar but much larger than that required to suspend the relatively coarse sediment present at the bed. Importantly, these stresses did not represent the stresses imparted on the sediment measured in suspension and are therefore not relevant to the description of suspended sediment transport in systems with large bottom roughness. Estimates of the bed shear stresses that accounted for the reduced near-bed flow in the presence of large roughness vastly improved the relationship between the predicted and observed grain sizes that were in suspension. Thus, the impact of roughness, not only on the overlying flow but also on bed stresses, must be accounted for to accurately estimate suspended sediment transport in regions with large bottom roughness, a common feature of many shallow coastal ecosystems.

  12. Sediment transport in the presence of large reef bottom roughness

    Science.gov (United States)

    Pomeroy, Andrew; Lowe, Ryan J.; Ghisalberti, Marco; Storlazzi, Curt; Symonds, Graham; Roelvink, Dano

    2017-01-01

    The presence of large bottom roughness, such as that formed by benthic organisms on coral reef flats, has important implications for the size, concentration, and transport of suspended sediment in coastal environments. A 3 week field study was conducted in approximately 1.5 m water depth on the reef flat at Ningaloo Reef, Western Australia, to quantify the cross-reef hydrodynamics and suspended sediment dynamics over the large bottom roughness (∼20–40 cm) at the site. A logarithmic mean current profile consistently developed above the height of the roughness; however, the flow was substantially reduced below the height of the roughness (canopy region). Shear velocities inferred from the logarithmic profile and Reynolds stresses measured at the top of the roughness, which are traditionally used in predictive sediment transport formulations, were similar but much larger than that required to suspend the relatively coarse sediment present at the bed. Importantly, these stresses did not represent the stresses imparted on the sediment measured in suspension and are therefore not relevant to the description of suspended sediment transport in systems with large bottom roughness. Estimates of the bed shear stresses that accounted for the reduced near-bed flow in the presence of large roughness vastly improved the relationship between the predicted and observed grain sizes that were in suspension. Thus, the impact of roughness, not only on the overlying flow but also on bed stresses, must be accounted for to accurately estimate suspended sediment transport in regions with large bottom roughness, a common feature of many shallow coastal ecosystems.

  13. Sediment Transport on Continental Shelves: Storm Bed Formation and Preservation in Heterogeneous Sediments

    Science.gov (United States)

    2012-01-01

    2007) Sediment-transport modeling on Southern Californian shelves: A ROMS case study. Cont. Shelf Res., 27, 832-853. Butman, B., Noble, M. and...Seas. /. Phys. Oceanogr., 19, 1039-1059. Hampson, G. J. (2010) Sediment dispersal and quantitative stratigraphic architecture across an ancient...shelf. Sedimentology, 57, 96-141. Hampson, G.J. (2000) Discontinuity surfaces, clinoforms, and facies architecture in a wave-dominated, shoreface

  14. Linking continental erosion to marine transport and sedimentation

    Science.gov (United States)

    Yuan, Xiaoping; Braun, Jean; Guerit, Laure

    2017-04-01

    Limited attention has been given to linking continental erosion to marine transport and sedimentation in large-scale landscape evolution models. Although either of the two environments has been thoroughly investigated, the details of how erosional events are recorded in the sedimentary and stratigraphic records have not been studied in a consistent quantitative manner. Here we present results obtained from a new numerical model for marine sediment transport and deposition that is directly coupled to FastScape, a landscape evolution model that solves the continental stream power law and hillslope diffusion equation using fully implicit and O(n) algorithms. The model of marine transport and sedimentation is simulated by a nonlinear 2D diffusion model where a source term represents mass flux arising from continental river erosion. It is based on the simplest representation of marine transport that assumes that flux is proportional to slope, which leads to a diffusion-type equation that we solve using an alternating direction implicit scheme. Multiple lithologies are implemented that vary by their transport coefficients. This method is also highly efficient (O(n) and implicit), which allows us to perform a large number of simulations to undertake a Bayesian inversion of stratigraphic data. Using our model we not only show the manner in which the stratigraphic record responds to tectonic and climate events but also how it is controlled by the coefficients for river erosion, hillslope diffusion, the transport coefficients in the ocean environment, and variations in sea level. The model is used to better constrain the nature and timing of erosional events on adjacent continents through an inversion of the stratigraphic record. In the longer term, we are looking at ways to improve the equations governing marine sediment transport especially, to better represent the deep part of that transport, i.e. in the abyssal plains or past the shelf and slope.

  15. FLOW STRUCTURE AND SEDIMENT TRANSPORT WITH IMPACTS OF AQUATIC VEGETATION

    Institute of Scientific and Technical Information of China (English)

    LIU Cheng; SHEN Yong-ming

    2008-01-01

    Aquatic vegetation plays an important role in the flow structure of open channels and thus changes the fate and the transport of sediment. This article proposes a three-dimensional turbulence model by introducing vegetation density and drag force into the control equations of water flow in the presence of vegetation. The model was used to calculate the impacts of submerged vegetation on the vertical profiles of longitudinal flow velocities, the changes of the depth-averaged flow velocities in a compound channel with emergent vegetation in the floodplain, the removal of suspended sediment from the channels by emergent vegetation, and the bed changes around and in a vegetated island. Numerical investigations show that aquatic vegetation retards flow in the vegetation zone, reduces the sediment transport capacity, and contributes to erosion on both sides of the vegetated island. Calculated results agree well with experimental results.

  16. Transport zonation limits coupled nitrification-denitrification in permeable sediments

    DEFF Research Database (Denmark)

    Kessler, Adam John; Glud, R.N.; Cardenas, M.B.

    2013-01-01

    Measurement of biogeochemical processes in permeable sediments (including the hyporheic zone) is difficult because of complex multidimensional advective transport. This is especially the case for nitrogen cycling, which involves several coupled redox-sensitive reactions. To provide detailed insig......- and N-15-N-2 gas. The measured two-dimensional profiles correlate with computational model simulations, showing a deep pool of N-2 gas forming, and being advected to the surface below ripple peaks. Further isotope pairing calculations on these data indicate that coupled nitrification......-denitrification is severely limited in permeable sediments because the flow and transport field limits interaction between oxic and anoxic pore water. The approach allowed for new detailed insight into subsurface denitrification zones in complex permeable sediments....

  17. A numerical investigation of fine sediment transport at intertidal flat

    Science.gov (United States)

    Hsu, T.; Chen, S.; Ogston, A. S.

    2010-12-01

    A detailed numerical model is developed to study the hydrodynamic and fine sediment transport processes at tidal flats. The critical science issues to be investigated here are to quantify the main mechanisms causing landward and seaward transports. Prior modeling studies have identified the settling-lag effects as the main mechanism causing landward fine sediment transport. Field studies have also observed pronounced landward transport due to the movement of shallow-water’s turbid edge which is associated with bed erodibility and wetting-drying process. Recent 3D coastal numerical modeling of Skagit tidal flat (Chen et al. 2010, J. Geophys. Res., in press) is able to model settling-lag-induced landward transport. However, the observed short residence time for river-delivered sediment cannot be reproduced by the model, suggesting that a key offshore transport mechanism is not captured by the exiting coastal models. Field studies carried out in the ongoing Tidal Flat DRI have observed the so-called ebb tide sediment pulse, which seems to support the export of sediment through channels (Nowacki et al. 2010, this meeting) that balances landward fluxes. Both the bed erosion at water’s edge and ebb tide sediment pulse occur at a very shallow water depths. Conventional coastal models have difficulties in resolving the shallow flow at the wetting and drying seabed and some numerical approximations, such as specifying a minimum artificial flow depth, are often adopted. Therefore, a small-scale study is necessary before an appropriate parameterization for these transport mechanisms can be adopted by an estuarine/coastal model. In this study, a two-dimensional-vertical numerical model solving Reynolds-averaged Navier-Stokes equations with a Volume of Fluid (VOF) scheme to track the free surface evolution is adopted. The VOF scheme allows a more realistic simulation of the wetting and drying processes. For the simulation of tidal flow over a flat of constant slope (slope

  18. Quantifying habitat interactions: sediment transport and freshwater mussels

    Science.gov (United States)

    Kozarek, J. L.; MacGregor, K. R.; Hornbach, D.; Hove, M.

    2016-12-01

    Freshwater mussel abundance and distribution are integrally linked with their habitat through sediment transport processes in moving waters, including suspended sediment loads and bed mobility. This research seeks to quantify these complex interactions using a combination of field data collection in the intensively agricultural Minnesota River Basin, and laboratory experiments in the Outdoor StreamLab (OSL) and flumes at St. Anthony Falls Laboratory (SAFL) at the University of Minnesota. The OSL is a field-scale sand-bed meandering stream channel with independent control over sediment feed (recirculated) and water flow (diverted from the Mississippi River). Experiments in the OSL focused on the interactions between moving bedload and freshwater mussel behavior. Flooding experiments were used to quantify the movement during and post flood for three mussel species with different shell sculptures: threeridge (Amblema plicata), plain pockebook (Lampsilus cardium), and white heelsplitter (Lasmigona complanata). Flow fields, bed shear stress, bedform migration, and bar topography were measured during each flooding event with and without mussels present (density = 4/m2) to examine the influence of flooding on mussel movement, and to quantify the influence of mussels on channel morphology under steady state bedload transport. Additional experiments were conducted with threeridge at low flow (no bedload), under aggrading and degrading bed conditions, and doubled mussel density (8/m2). Mussel response to suspended sediment loads was examined in a complementary series of experiments in an indoor flume with Mississippi River water. Mussels outfitted with gape sensors were utilized in paired control/treatment experiments to examine the influence of moderate term (48 hours) exposure to elevated suspended sediment loads on mussel filtering activity. Together, these experiments provide multiple measures of mussel stress under high sediment loads and reveal how freshwater mussels

  19. Drought conditions and sediment transport in the Sabie River

    Directory of Open Access Journals (Sweden)

    G.L. Heritage

    1995-09-01

    Full Text Available Drought conditions in the Sabie catchment in the eastern Transvaal (now called Mpumalanga, South Africa, has had an observable effect on the sediment dynamics of the river. Sediment production within the catchment is largely unaffected by a reduction in the frequency and magnitude of rainfall events, although the rate of translocation of the weathered material from the catchment into the river channel is noticeably altered. The infrequent storm events during drought conditions generate a greater sed- iment input to the river from the catchment than a similar-magnitude event under average conditions. This sediment is also less likely to be transported through the system due to the reduced frequency of intermediate flows which act to rework in-channel sed- iment accumulations. Thus, significant accumulations of alluvial material are likely to form at specific locations, particularly where the local sediment transport capacity of the channel is low. Studies of the transport dynamics of the Sabie River, under both nor- mal and drought conditions, reveal that there are major depositional zones between Kruger Weir and Skukuza, and in the area around Lower Sabie. The 1992 drought resulted in a significant build-up of sediment in these areas, with a consequent reduc- tion in geomorphic diversity. This sediment is becoming stabilised due to the lower and less variable flows of the recent drought and associated vegetative colonisation. An increase in the magnitude and frequency of high and intermediate flows is needed to mobilise this accumulated sediment and to prevent its stabilisation by riparian vegetation.

  20. Suspended sediment transport in an ephemeral stream following wildfire

    Science.gov (United States)

    Malmon, D.V.; Reneau, S.L.; Katzman, D.; Lavine, A.; Lyman, J.

    2007-01-01

    We examine the impacts of a stand-clearing wildfire on the characteristics and magnitude of suspended sediment transport in ephemeral streams draining the burn area. We report the results of a monitoring program that includes 2 years of data prior to the Cerro Grande fire in New Mexico, and 3 years of postfire data. Suspended sediment concentration (SSC) increased by about 2 orders of magnitude following the fire, and the proportion of silt and clay increased from 50% to 80%. For a given flow event, SSC is highest at the flood bore and decreases monotonically with time, a pattern evident in every flood sampled both before and after the fire. We propose that the accumulation of flow and wash load at the flow front is an inherent characteristic of ephemeral stream flows, due to amplified momentum losses at the flood bore. We present a new model for computing suspended sediment transport in ephemeral streams (in the presence or absence of wildfire) by relating SSC to the time following the arrival of the flood bore, rather than to instantaneous discharge. Using this model and a rainfall history, we estimate that in the 3 years following the fire, floods transported in suspension a mass equivalent to about 3 mm of landscape lowering across the burn area, 20% of this following a single rainstorm. We test the model by computing fine sediment delivery to a small reservoir in an adjacent watershed, where we have a detailed record of postfire sedimentation based on repeat surveys. Systematic discrepancies between modeled and measured sedimentation rates in the reservoir suggest rapid reductions in suspended sediment delivery in the first several years after the fire.

  1. Modelling of Cohesive Sediment Transport in the Maasmond Area

    NARCIS (Netherlands)

    Wang, L.

    2006-01-01

    In the Dutch coastal zone, where the marine environment is highly dynamic owing to tidal currents, wind-driven, wave-driven, and density-driven currents and waves, the cohesive sediment dynamics is always a great concern to transportation authority and coastal managers. So far, a lot research has

  2. Jokulhlaups and sediment transport in Watson River, Kangerlussuaq, West Greenland

    DEFF Research Database (Denmark)

    Mikkelsen, A. B.; Hasholt, Bent; Knudsen, N. T.

    2013-01-01

    For 3 years, during a 4-year observation period (2007-2010), jokulhlaups were observed from a lake at the northern margin of Russells Gletscher. At a gauging station located on a bedrock sill near the outlet of Watson River into Sdr Stromfjord, discharge and sediment transport was monitored during...

  3. Evaluation of 10 cross-shore sediment transport morphological models

    CSIR Research Space (South Africa)

    Schoonees, JS

    1995-05-01

    Full Text Available Cross-shore sediment transport models are used to model beach profile changes in order to determine, for example, coastal set-back lines, behaviour of beach fill and beach profile variations adjacent to coastal structures. A study was undertaken...

  4. Sediment transport, light and algal growth in the Markermeer.

    NARCIS (Netherlands)

    Duin, van E.H.S.

    1992-01-01

    This thesis reports on a study of the water quality in the Markermeer, focusing on the relationships between sediment transport, the light field and the growth of Oscillatoria agardhii . The study comprises two aspects: an extensive data collection program with the data analysis, and the development

  5. Annual variation in the net longshore sediment transport rate

    CSIR Research Space (South Africa)

    Schoonees, JS

    2000-05-01

    Full Text Available The annual variation in the net long shore sediment transport rates at three South African and at one North African site is investigated. The net rates at these sites, given in the first table, showed large variations. It was found that measurements...

  6. Sediment transport capacity under different subsurface hydrologic conditions

    Science.gov (United States)

    Sediment transport capacity (Tc) is a conceptual term used in soil erosion modeling to identify whether erosion or deposition process is dominating. Despite the wide use of this modeling concept, there are little experimental results to quantify Tc, particularly over an erodible surface under differ...

  7. Modelling of sediment transport: link in a chain

    NARCIS (Netherlands)

    De Vries, M.

    1977-01-01

    Rather than reporting on a specific topic of current research in the broad field of sediment transport and river morphology, the writer will give a general contemplation on the state of the art. This will not be a review in the usual sense. The alloted space would then be filled easily with referenc

  8. Measured Gradients in Alongshore Sediment Transport Along the Dutch Coast

    NARCIS (Netherlands)

    De Vries, S.; De Schipper, M.A.; Stive, M.J.F.

    2014-01-01

    In this paper it is aimed to quantify bulk (surf-zone integrated) alongshore sediment transport using morphological data collected along the Dutch coast. The collected morphological data covers a domain of 18 km alongshore including the beach, the foreshore and the intertidal zone in the cross shore

  9. Sediment transport modelling in wadi Chemora during flood flow events

    Directory of Open Access Journals (Sweden)

    Berghout Ali

    2016-12-01

    Full Text Available The sediment transport is a complex phenomenon by its intermittent nature, randomness and by its spatiotemporal discontinuity. By reason of its scale, it constitutes a major constraint for development; it decreases storage capacity of dams and degrades state of ancillary structures.

  10. Sediment Transport Dynamics in River Networks: A Model for Higher-Water Seasons

    Science.gov (United States)

    Huo, Jie; Wang, Xu-Ming; Hao, Rui; Zhang, Jin-Feng

    A dynamical model is proposed to study sediment transport in river networks in higher-water seasons. The model emphasizes the difference between the sediment-carrying capability of the stream in higher-water seasons and that in lower-water seasons. The dynamics of sediment transport shows some complexities such as the complex dependence of the sediment-carrying capability on sediment concentration, the response of the channel(via erosion or sedimentation) to the changes of discharge.

  11. Numerical modelling of sediment transport in the Adriatic Sea

    Directory of Open Access Journals (Sweden)

    A. Guarnieri

    2014-06-01

    Full Text Available A new sediment transport model, considering currents, tides and waves is presented for the Adriatic Sea basin. The simulations concentrate on the winter of 2002–2003 because of field data availability and interesting intermittent processes occurrence. A process oriented analysis is performed to investigate the impact that Sirocco and Bora wind regimes have on sediment transport. The comparisons of the simulations with the observed data show that the model is capable to capture the main dynamics of sediment transport along the Italian coasts and the sediment concentration within the water column. This latter can reach values up to several g L−1, especially within the first centimetres above the bottom. The sediments are transported mainly southwards along the Italian coasts, consistently with the known literature results, except during Sirocco wind events, which can be responsible for reversing the coastal circulation in the northern area of the basin, and consequently the sediment transport. The resuspension of sediments is also related to the specific wave regimes induced by Bora and Sirocco, the former inducing resuspension events near the coasts while the latter causing a more diffused resuspension regime in the Northern Adriatic basin. Beside the realistic representation of short timescales resuspension/deposition events due to storms, the model was also used to investigate persistent erosion or deposition areas in the Adriatic Sea. Two main depocenters were identified: one, very pronounced, in the surroundings of the Po river delta, and another one a few kilometres off the coast in front of the Ancona promontory. A third region of accumulation, even if less intense, was found to be offshore the southernmost limit of the Gargano region. On the contrary the whole western coast within a distance of a few kilometres from the shore was found to be subject to prevailing erosion. The comparison with observed accumulation and erosion data shows

  12. Sediment Transport by Spring Avalanches in the Southern Swiss Alps

    Science.gov (United States)

    Egloff, J. M.; Hunziker, M.; Moore, J. R.; Christen, M.

    2010-12-01

    Dense wet-snow avalanches breaking through to the base of the snow pack or overriding snow-free surfaces can entrain basal material and act as important agents of sediment transport in steep Alpine catchments. As part of an ongoing study, we investigated two debris fans in the Matter Valley of southern Switzerland during spring 2009 and 2010, with emphasis on quantifying avalanche sediment transport. Deposited debris ranged from soil parcels and plant material to cobbles and boulders greater than 1 m3. Large boulders were generally angular and fresh with clear signs of recent impacts. The seasonal sediment load transported by avalanches was estimated at one fan by sampling the debris content within a number of representative areas, and then extrapolating the cumulative volume. Results reveal a total transported sediment volume of ~150 m3 in 2009 and ~15 m3 in 2010, which likely reflects varying snowfall and avalanche frequency between years. When distributed over the deposition area on the fan, these results imply an average accumulated sediment thickness of 12 mm in 2009 and 3 mm in 2010. Calculated catchment-wide erosion rates are ~0.1 mm/yr for 2009 and ~0.01 mm/yr for 2010. Cross-sections through avalanche debris revealed that transported sediment generally resides on top of the snow surface. As the avalanches melt, entrained sediment is set down gently, often resulting in precariously balanced boulders and rows of blocks perched on the walls of the fan’s channels. In flat lying areas, snowmelt resulted in sparse sediment deposits with no clear structure or sorting. Observations show that the fan surface is usually protected from erosion by snow and older avalanche deposits, which provide a smooth gliding plane for new events. Within the bedrock gulley adjacent to the fan, and in the avalanche source region above, signs of abrasive wear were evident on exposed bedrock surfaces. These include rounded and scoured bedrock, fresh signs of boulder impacts, and

  13. The time compression in sediment transport: A review

    Science.gov (United States)

    Nadal Romero, Estela; González Hidalgo, Carlos

    2014-05-01

    A large amount of geomorphic work is caused by a small number of events that are mainly responsible for the time compression of geomorphic processes. This study reviews and discuses about time compression in sediment transport through bibliographic analyses. Data from studies conducted worldwide were collected from different sources, and many of the studies suggest that a large amount of total sediment transport is often associated with a very few limited number of days. Furthermore, the results demonstrate the importance of few events, not necessary extremes in the total sediment yield. The bibliographic analyses indicated that time compression occurs in plot and catchment databases. Moreover, time compression occurs in all climate conditions: (i) in arid and semiarid areas, time compression is due to the irregularities of precipitation and high rainfall intensities; (ii) in Mediterranean areas, it is due to the marked rainfall seasonality and strong interannual variation; (iii) in monsoon areas, time compression is conditioned by the rainfalls of the monsoon period; and (iv) in cold areas (mountain and cold areas) it is main due to the snowmelt processes period. Our review demonstrate that the interpretation of annual average erosion rates or sediment yield should be viewed with caution, because each year the largest events (not necessary extreme events) could represent a high percentage of the total annual sediment yield or soil loss value.

  14. Experimental investigation of the effect of sediment transport patterns on the adsorption of cadmium ions onto sediment particles

    Institute of Scientific and Technical Information of China (English)

    HUANG Sui-liang; NG Chiu-on; GUO Qi-zhong

    2007-01-01

    The mechanism of flow turbulence, sediment supply conditions, and sediment transport patterns that affect the adsorption of cadmium ions onto sediment particles in natural waters are experimentally simulated and studied in this study both in batch reactors and in a turbulence simulation tank. By changing the agitation conditions, the sediment transport in batch reactors can be categorized into bottom sediment-dominated sediment and suspended sediment-dominated sediment. It is found that the adsorption rate of bottom sediment is much less than that of suspended sediment, but the sediment transport pattern does not affect the final (equilibrium) concentration of dissolved cadmium. This result indicates that the parameters of an adsorption isotherm are the same regardless of the sediment transport pattern. In the turbulence simulation tank, the turbulence is generated by harmonic grid-stirred motions, and the turbulence intensity is quantified in terms of eddy diffusivity, which is equal to 9.84F(F is the harmonic vibration frequency) and is comparable to natural surface water conditions.When the turbulence intensity of flow is low and sediment particles stay as bottom sediment, the adsorption rate is significantly low, and the adsorption quantity compared with that of suspended sediment is negligible in the 6 h duration of the experiment. This result greatly favors the simplification of the numerical modeling of heavy metal pollutant transformation in natural rivers. When the turbulence intensity is high but bottom sediment persists, the rate and extent of descent of the dissolved cadmium concentration in the tank noticeably increase, and the time that is required to reach adsorption equilibrium also increases considerably due to the continuous exchange that occurs between the suspended sediment and the bottom sediment.A comparison of the results of the experiments in the batch reactor and those in the turbulence simulation tank reveals that the adsorption ability of

  15. Shelf sediment transport during hurricanes Katrina and Rita

    Science.gov (United States)

    Xu, Kehui; Mickey, Rangley C.; Chen, Qin; Harris, Courtney K.; Hetland, Robert D.; Hu, Kelin; Wang, Jiaze

    2016-05-01

    Hurricanes can greatly modify the sedimentary record, but our coastal scientific community has rather limited capability to predict hurricane-induced sediment deposition. A three-dimensional sediment transport model was developed in the Regional Ocean Modeling System (ROMS) to study seabed erosion and deposition on the Louisiana shelf in response to Hurricanes Katrina and Rita in the year 2005. Sensitivity tests were performed on both erosional and depositional processes for a wide range of erosional rates and settling velocities, and uncertainty analysis was done on critical shear stresses using the polynomial chaos approximation method. A total of 22 model runs were performed in sensitivity and uncertainty tests. Estimated maximum erosional depths were sensitive to the inputs, but horizontal erosional patterns seemed to be controlled mainly by hurricane tracks, wave-current combined shear stresses, seabed grain sizes, and shelf bathymetry. During the passage of two hurricanes, local resuspension and deposition dominated the sediment transport mechanisms. Hurricane Katrina followed a shelf-perpendicular track before making landfall and its energy dissipated rapidly within about 48 h along the eastern Louisiana coast. In contrast, Hurricane Rita followed a more shelf-oblique track and disturbed the seabed extensively during its 84-h passage from the Alabama-Mississippi border to the Louisiana-Texas border. Conditions to either side of Hurricane Rita's storm track differed substantially, with the region to the east having stronger winds, taller waves and thus deeper erosions. This study indicated that major hurricanes can disturb the shelf at centimeter to meter levels. Each of these two hurricanes suspended seabed sediment mass that far exceeded the annual sediment inputs from the Mississippi and Atchafalaya Rivers, but the net transport from shelves to estuaries is yet to be determined. Future studies should focus on the modeling of sediment exchange between

  16. Precise Sediment Yield and Riverbed Change Detected by using LiDAR DTMs before and after a Typhoon Season

    Science.gov (United States)

    Hsieh, Y.; Chan, Y.; Hu, J.; Lin, C.

    2009-12-01

    Sediment yield and riverbed change from watersheds greatly influence the conservation of water and soil, the planning of hydraulic engineering, and the river habitat, etc. At present, sediment yield calculation often used empirical or theoretical formula as well as data collected at hydrological stations, and rarely had the actual measured value through high-resolution topography. The Lanyang river is one of main rivers in Taiwan and often suffers the influence of typhoon during summer. In 2008, there are four significant typhoon events influencing this area, including the Kalmaegi, Fung-wong, Sinlaku, and Jangmi typhoons. This study of topographic variations surveyed the terrain of the Lanyang River before and after the 2008 typhoon season using airborne LiDAR technique. The variations of the terrain on the riverbed may be regarded as the sediment yield of the bed load transported during the typhoon season. This research used high-resolution terrain models to compute sediment yield of the bed load, and further discussed sediment yield volume in the watershed during the typhoon season. In the Lanyang river we discovered that the upstream and midstream channels had significant characteristics of erosion and transportation during the typhoon season. The sediment on the riverbed reduced approximately 2.3 million cubic meters; and the erosion rate of the bed load sediments were estimated about 3.4 mm during the 2008 typhoon season. The results indicate that considerable sediment yield and transportation in the Lanyang river during only a single typhoon season in which cumulated rain falls are high. Further analysis of the collected data in the Lanyang river are needed to better understand the typhoon influence and apply the results to the prevention of the common flash flooding hazards.

  17. Origin of the scaling laws of sediment transport

    Science.gov (United States)

    Ali, Sk Zeeshan; Dey, Subhasish

    2017-01-01

    In this paper, we discover the origin of the scaling laws of sediment transport under turbulent flow over a sediment bed, for the first time, from the perspective of the phenomenological theory of turbulence. The results reveal that for the incipient motion of sediment particles, the densimetric Froude number obeys the `(1 + σ)/4' scaling law with the relative roughness (ratio of particle diameter to approach flow depth), where σ is the spectral exponent of turbulent energy spectrum. However, for the bedforms, the densimetric Froude number obeys a `(1 + σ)/6' scaling law with the relative roughness in the enstrophy inertial range and the energy inertial range. For the bedload flux, the bedload transport intensity obeys the `3/2' and `(1 + σ)/4' scaling laws with the transport stage parameter and the relative roughness, respectively. For the suspended load flux, the non-dimensional suspended sediment concentration obeys the `-Z ' scaling law with the non-dimensional vertical distance within the wall shear layer, where Z is the Rouse number. For the scour in contracted streams, the non-dimensional scour depth obeys the `4/(3 - σ)', `-4/(3 - σ)' and `-(1 + σ)/(3 - σ)' scaling laws with the densimetric Froude number, the channel contraction ratio (ratio of contracted channel width to approach channel width) and the relative roughness, respectively.

  18. An integrated suspended sediment transport monitoring and analysis concept

    Institute of Scientific and Technical Information of China (English)

    Marlene HAIMANN; Marcel LIEDERMANN; Petra LALK; Helmut HABERSACK

    2014-01-01

    A new integrated suspended sediment monitoring strategy applying direct and indirect technologies is presented. Optical sensors continuously record the turbidity at one point in the channel cross section close to the river bank and are calibrated by water samples taken close to the sensor. Additionally measurements are performed to establish the distribution of suspended sediment in a cross section (bottle samples combined with acoustic devices). Using correction factors (probe and cross-sectional factor) these monitoring methods are combined and it is, thus, possible to fully document the temporal and spatial variability of the suspended sediment transport and to estimate the suspended sediment load for certain time periods. This monitoring strategy was implemented at various measurement sites in Austria as well as at the Hainburg Road Bridge site on the Danube River. It has already been successfully applied for three years at this measurement site and suspended sediment loads during high discharges up to a 15 year flood event have been monitored. To evaluate the new monitoring methods the results were compared with load estimation methods found in the literature including averaging and ratio estimators as well as rating curves. The results prove that with the new methodology, the temporal variability of the suspended sediment transport can be detected more accurately compared with the other methods. They also demonstrate that the additional consideration of the spatial distribution of the suspended sediment concentration in the cross section is crucial as the mean concentration in the cross section can significantly exceed the concentration near the banks, especially at large rivers like the Danube River.

  19. Monitoring Large-Scale Sediment Transport Dynamics with Multibeam Sonar

    Science.gov (United States)

    Parsons, D. R.; Simmons, S. M.; Best, J. L.; Keevil, G. M.; Oberg, K.; Czuba, J. A.

    2009-05-01

    Multibeam Echo-Sounder systems have developed rapidly over recent decades and are routinely deployed to provide high-resolution bathymetric information in and range of environments. Modern data handling and storage technologies now facilitate the logging of the raw acoustic back-scatter information that was previously discarded by these systems. This paper describes methodologies that exploit this logging capability to quantify both the concentration and dynamics of suspended sediment within the water column. This development provides a multi-purpose tool for the holistic surveying of sediment transport dynamics by imaging suspended sediment concentration, the associated flows and providing concurrent high-resolution bathymetry. Results obtained a RESON 7125 MBES are presented from both well constrained dock-side testing and full field deployment over dune bedforms in the Mississippi. The capacity of the system to image suspended sediment structures is demonstrated and a novel methodology for estimating 2D flow velocities, based on frame cross-correlation methods, is introduced. The results demonstrate the capability of MBES systems to successfully map spatial and temporal variations in suspended sediment concentration throughout a 2D swath and application of the velocity estimation algorithms allow real-time holistic monitoring of turbulent flow processes and suspended sediment fluxes at a scale previously unrealisable. Turbulent flow over a natural dune bedform on the Mississippi is used to highlight the process information provided and the insights that can be gleaned for this technical development.

  20. Runoff and sediment transport in a degraded area

    Directory of Open Access Journals (Sweden)

    Edivaldo Lopes Thomaz

    2012-02-01

    Full Text Available Gully erosion occurs by the combined action of splash, sheetwash and rill-wash (interrill and rill erosion. These erosion processes have a great capacity for both sediment production and sediment transport. The objectives of this experiment were to evaluate hydrological and sediment transport in a degraded area, severely dissected by gullies; to assess the hydraulic flow characteristics and their aggregate transport capacity; and to measure the initial splash erosion rate. In the study area in Guarapuava, State of Paraná, Brazil (lat 25º 24' S; long 51º24' W; 1034 m asl, the soil was classified as Cambissolo Húmico alumínico, with the following particle-size composition: sand 0.116 kg kg-1; silt 0.180 kg kg-1; and clay 0.704 kg kg-1. The approach of this research was based on microcatchments formed in the ground, to study the hydrological response and sediment transport. A total of eight rill systems were simulated with dry and wet soil. An average rainfall of 33.7 ± 4.0 mm was produced for 35 to 54 min by a rainfall simulator. The equipment was installed, and a trough was placed at the end of the rill to collect sediments and water. During the simulation, the following variables were measured: time to runoff, time to ponding, time of recession, flow velocity, depth, ratio of the initial splash and grain size. The rainsplash of dry topsoil was more than twice as high as under moist conditions (5 g m-2 min-1 and 2 g m-2 min-1, respectively. The characteristics of the flow hydraulics indicate transition from laminar to turbulent flow [Re (Reynolds number 1000-2000]. In addition, it was observed that a flow velocity of 0.12 m s-1 was the threshold for turbulent flow (Re > 2000, especially at the end of the rainfall simulation. The rill flow tended to be subcritical [Fr (Froude Number < 1.0]. The variation in hydrological attributes (infiltration and runoff was lower, while the sediment yield was variable. The erosion in the rill systems was

  1. Evaluating the controls of shear stress, sediment supply, alluvial cover, and channel morphology on experimental bedrock incision rate

    Science.gov (United States)

    Johnson, Joel P. L.; Whipple, Kelin X.

    2010-06-01

    We explored the dependence of experimental bedrock erosion rate on shear stress, bed load sediment flux, alluvial bed cover, and evolving channel morphology. We isolated these variables experimentally by systematically varying gravel sediment flux Qs and water discharge Qw in a laboratory flume, gradually abrading weak concrete "bedrock." All else held constant, we found that (1) erosion rate was insensitive to flume-averaged shear stress, (2) erosion rate increased linearly with sediment flux, (3) erosion rate decreased linearly with the extent of alluvial bed cover, and (4) the spatial distribution of bed cover was sensitive to local bed topography, but the extent of cover increased with Qs/Qt (where Qt is flume-averaged transport capacity) once critical values of bed roughness and sediment flux were exceeded. Starting from a planar geometry, erosion increased bed roughness due to feedbacks between preferential sediment transport through interconnected topographic lows, focused erosion along these zones of preferential bed load transport, and local shear stresses that depended on the evolving bed morphology. Finally, continued growth of bed roughness was inhibited by imposed variability in discharge and sediment flux, due to changes in spatial patterns of alluvial deposition and impact wear. Erosion was preferentially focused at lower bed elevations when the bed was cover-free, but was focused at higher bed elevations when static alluvial cover filled topographic lows. Natural variations in discharge and sediment flux may thus stabilize and limit the growth of roughness in bedrock channels due to the effects of partial bed cover.

  2. Sediment and radionuclide transport in rivers: radionuclide transport modeling for Cattaraugus and Buttermilk Creeks, New York

    Energy Technology Data Exchange (ETDEWEB)

    Onishi, Y.; Yabusaki, S.B.; Kincaid, C.T.; Skaggs, R.L.; Walters, W.H.

    1982-12-01

    SERATRA, a transient, two-dimensional (laterally-averaged) computer model of sediment-contaminant transport in rivers, satisfactorily resolved the distribution of sediment and radionuclide concentrations in the Cattaraugus Creek stream system in New York. By modeling the physical processes of advection, diffusion, erosion, deposition, and bed armoring, SERATRA routed three sediment size fractions, including cohesive soils, to simulate three dynamic flow events. In conjunction with the sediment transport, SERATRA computed radionuclide levels in dissolved, suspended sediment, and bed sediment forms for four radionuclides (/sup 137/Cs, /sup 90/Sr, /sup 239/ /sup 240/Pu, and /sup 3/H). By accounting for time-dependent sediment-radionuclide interaction in the water column and bed, SERATA is a physically explicit model of radionuclide fate and migration. Sediment and radionuclide concentrations calculated by SERATA in the Cattaraugus Creek stream system are in reasonable agreement with measured values. SERATRA is in the field performance phase of an extensive testing program designed to establish the utility of the model as a site assessment tool. The model handles not only radionuclides but other contaminants such as pesticides, heavy metals and other toxic chemicals. Now that the model has been applied to four field sites, including the latest study of the Cattaraugus Creek stream system, it is recommended that a final model be validated through comparison of predicted results with field data from a carefully controlled tracer test at a field site. It is also recommended that a detailed laboratory flume be tested to study cohesive sediment transport, deposition, and erosion characteristics. The lack of current understanding of these characteristics is one of the weakest areas hindering the accurate assessment of the migration of radionuclides sorbed by fine sediments of silt and clay.

  3. Sediment Transport Study in Haeundae Beach using Radioisotope Labelled Compound

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jin Seop; Kim, Jong Bum; Jung, Sung Hee [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of); Lee, Jong Sup [Pukyong National Univ., Busan (Korea, Republic of)

    2005-07-01

    Haeundae beach is one of the most famous resorts in Korea and plays an important role as a special tourism district. However, the length and width of the beach are being reduced continuously, which would have bad influence on the regional economy and be the financial burden to the local authority considering that a large amount of budget is spent in the beach nourishment annually. Hence, it is necessary to understand the dynamic behavior of sediments in the coast for the systematic preservation plan of coastal environment. Lately a monitoring system using radioactive isotope as tracers is considered as a novel technique in understanding the dynamic transport of sediments. The objective of this study is to investigate the possible variations in sedimentary distribution and quantify the characteristics of sediments using radiotracer.

  4. Longshore Sediment Transport on a Macrotidal Mixed Sediment Beach, Birling Gap, United Kingdom.

    Science.gov (United States)

    Curoy, J.; Moses, C. A.; Robinson, D. A.

    2012-04-01

    Mixed beaches (MBs), with sediment sizes ranging over three orders of magnitude, are an increasingly important coastal defence on > 1/3 of the shoreline of England and Wales. In East Sussex, the combined effect of coastal defence management schemes (extensive groyning and sea wall construction) has reduced beach sediment supply. Local authorities counteract the increased flood risk by recycling or artificially recharging beaches on the most vulnerable and populated areas. Beaches lose sediment predominantly via longshore transport (LST) whose accurate quantification is critical to calculating recharge amounts needed for effective beach management. Industry does this by using sediment transport modelling which depends on reliable input data and modelling assumptions. To improve understanding of processes and quantification of LST on MBs, this study has accurately measured sediment transport on a natural, macrotidal, MB. The 1.2 km natural MB at Birling Gap, East Sussex here is located on the downdrift end of an 80 km long sub-sedimentary cell and is oriented WNW-ESE. The beach lies on a low gradient chalk shore platform backed by sub-vertical chalk cliffs. It is composed primarily of flint gravel with a peak grain size distribution of 30 to 50 mm, and a sand content of up to 30%. Sediment transport was measured using pebble tracers and GPS surface surveys during three survey periods of three to five consecutive days in March, May and December 2006. Tracer pebbles, matching the beach pebbles' D50, were made of an epoxy resin with a copper core allowing their detection and recovery to a depth of 40 cm using a metal detector. Tracers were deployed on the upper, middle and lower beach, from the surface into the beach to depths of up to 40 cm. They were collected on the low tide following deployment. The wave conditions were recorded on a Valeport DWR wave recorder located seaward of the beach on the chalk platform. Over the three study periods a large spectrum of wave

  5. Effect of Vegetation on Sediment Transport across Salt Marshes

    Science.gov (United States)

    Coleman, D. J.; Kirwan, M. L.; Guntenspergen, G. R.; Ganju, N. K.

    2016-12-01

    Salt marshes are a classic example of ecogeomorphology where interactions between plants and sediment transport govern the stability of a rapidly evolving ecosystem. In particular, plants slow water velocities which facilitates deposition of mineral sediment, and the resulting change in soil elevation influences the growth and species distribution of plants. The ability of a salt marsh to withstand sea level rise (SLR) is therefore dependent, among other factors, on the availability of mineral sediment. Here we measure suspended sediment concentrations (SSC) along a transect from tidal channel to marsh interior, exploring the role biomass plays in regulating the magnitude and spatial variability in vertical accretion. Our study was conducted in Spartina alterniflora dominated salt marshes along the Atlantic Coast from Massachusetts to Georgia. At each site, we deployed and calibrated optical back scatter turbidity probes to measure SSC in 15 minute intervals in a tidal channel, on the marsh edge, and in the marsh interior. We visited each site monthly to measure plant biomass via clip plots and vertical accretion via two types of sediment tiles. Preliminary results confirm classic observations that biomass is highest at the marsh edge, and that SSC and vertical accretion decrease across the marsh platform with distance from the channel. We expect that when biomass is higher, such as in southern sites like Georgia and months late in the growing season, SSC will decay more rapidly with distance into the marsh. Higher biomass will likely also correspond to increased vertical accretion, with the greatest effect at marsh edge locations. Our study will likely demonstrate how salt marsh plants interact with sediment transport dynamics to control marsh morphology and thus contribute to marsh resilience to SLR.

  6. Modeling Sediment Transport to the Ganga-Brahmaputra-Meghna Delta

    Science.gov (United States)

    Silvestre, J.; Higgins, S.; Jennings, K. S.

    2016-12-01

    India's National River Linking Project (NRLP) will transfer approximately 174 Bm3/y of water from the mountainous, water-rich north to the water-scarce south and west. Although there are many short-term benefits of the NRLP, such as decreased flooding during the monsoon season and increased water resources for irrigation, long-term consequences may include decreased sedimentation to the Ganga-Brahmaputra-Meghna Delta (GBM). Currently the GBM has a vertical aggradation rate of approximately 1-2 cm/y and is able to compensate for a global mean sea level rise of 3.3 ± 0.4 mm/y. However, Bangladesh and the GBM stand to be geomorphically impacted should the aggradation rate fall below sea level rise. This study better constrains influences of anthropogenic activities and sediment transport to the GBM. We employ HydroTrend, a climate-driven hydrological and sediment transport model, to simulate daily sediment and water fluxes for the period 1982 - 2012. Simulations are calibrated and validated against water discharge data from the Farakka Barrage, and different ways of delineating the Ganga Basin into sub-catchments are explored. Preliminary results show a 47% difference between simulated and observed mean annual water discharge when using basin-averaged input values and only a 1% difference for the base-case scenario, where proposed dams and canals are not included. Comparisons between the canals simulation (proposed NRLP included) and validation data suggest a 60% reduction in sediment load. However, comparison between the base-case simulation and the canals simulation suggests that India's water transfer project could decrease sediment delivery to the GBM by 9%. Further work should investigate improvements in the agreement between base-case simulation and validation data.

  7. A phase resolving cross-shore sediment transport model for beach profile evolution

    DEFF Research Database (Denmark)

    Rakha, Karim A.; Deigaard, Rolf; Brøker, Ida

    1997-01-01

    A phase-resolving wave transformation module is combined with an intra-wave sediment transport module to calculate the on-/offshore sediment transport rates. The wave module is based on the Boussinesq equations extended into the surf zone. The vertical variation of the mean undertow and the intra......-wave sediment concentrations are calculated. The net sediment transport rates are calculated, and the equation for conservation of sediment is solved to predict the beach profile evolution, The results of the present paper showed that the undertow contribution to the sediment transport rates is not dominating...

  8. How does gas pass? Bubble transport through sediments

    Science.gov (United States)

    Fauria, K. E.; Rempel, A. W.

    2009-12-01

    The transport of gas through marine sediments is critical for both the formation and the ultimate fate of gas that is housed temporarily within hydrates. We monitored the gas flux produced by repeated bubble injections into a particle layer that was initially saturated with liquid. The size of ejected bubbles and the period between ejection events were different from the input size and period. Our observations clearly demonstrate bubble break-up as well as coalescence and the formation of preferred bubble migration pathways. We develop an elementary, semi-empirical model to interpret aspects of these results and predict the gas flux expected from a given size distribution of bubble inputs as a function of basic host sediment characteristics. Models of gas transport that use simple modifications to Darcy's law are not adequate to cope with bubble dynamics in the parameter regime that we observe.

  9. Sediment-transport experiments in zero-gravity

    Science.gov (United States)

    Iversen, James D.; Greeley, Ronald

    1987-01-01

    One of the important parameters in the analysis of sediment entrainment and transport is gravitational attraction. The availability of a laboratory in earth orbit would afford an opportunity to conduct experiments in zero and variable gravity environments. Elimination of gravitational attraction as a factor in such experiments would enable other critical parameters (such as particle cohesion and aerodynamic forces) to be evaluated much more accurately. A Carousel Wind Tunnel (CWT) is proposed for use in conducting experiments concerning sediment particle entrainment and transport in a space station. In order to test the concept of this wind tunnel design a one third scale model CWT was constructed and calibrated. Experiments were conducted in the prototype to determine the feasibility of studying various aeolian processes and the results were compared with various numerical analysis. Several types of experiments appear to be feasible utilizing the proposed apparatus.

  10. Chapman Conference on Sediment Transport Processes in Estuaries

    Science.gov (United States)

    Perillo, Gerardo M. E.; Lavelle, J. William

    During the week of June 13-17, 1988, 72 sediment transport researchers “aggregated” at the Universidad Nacional del Sur in Bahfa Blanca, Argentina, to participate in an AGU Chapman Conference on Sediment Transport Processes in Estuaries. The main goals of the meeting were to discuss recent advances in estuarine science, to appraise promising future research directions, and to develop contacts and establish working relationships between Latin American and non-Latin- American estuarine researchers. The meeting drew participants from Argentina, Brazil, Chile, Uruguay, Venezuela, the U.S., Canada, Britain, France, the Federal Republic of Germany, The Netherlands, and South Africa. Meeting cosponsors were UNESCO, Secretaria de Ciencía y Técnica, Consejo Nacional de Investigaciones Cientificas y Técnicas, Comision de Investigaciones Cientificas de la Provincia de Buenos Aires, Universidad del Sur, Municipalidad de Bahia Blanca, Asociaciôn Argentina de Geofisicos y Geodestas (AGU sister organization), and the Instituto Argentino de Oceanografia (IADO).

  11. Freshwater discharge and sediment transport to Kangerlussuaq Fjord, West Greenland

    DEFF Research Database (Denmark)

    Mikkelsen, Andreas Peter Bech

    River. Hydrological processes studied are: proglacial discharge volumes and timing of this, creation of runoff (i.e. melt), storage and release features such as ice dammed lakes (jökulhlaups lakes), the role of supraglacial lakes, storage and release inside or beneath the ice and the role of the so...... called firn zone are studied. Geomorphological processes studied are: Mass transfer from the glacial system and into the nearby fjord and delta systems. As a part of this glacial erosion rates are deduced. Extensive discharge and sediment transport measurements provided the basis for gaining insight....... The role of jökulhlaups in this catchment was found to be less than 2% of the total annual discharge and sediment transport in Watson River (WR). Thus, despite their spectacular appearance, they do not play an important hydrological role. Measurement campaigns carried out in the two other large glacially...

  12. Sediment transportation and bed morphology reshaping in Yellow River Delta

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    The Yellow River Delta supports the ecological function as a typical estuarine foreshore wetland. The wetland area is changing greatly every year because of sediment deposition and erosion, which influences the wetland function tremendously. Application of environmental fluid dynamics code (EFDC) to the Yellow River Delta is on the basis of the mobile bed dynamic model and wetting-drying process. Careful calibration is carried out for the numerical model which is set up for the Yellow River Delta, the sediment transport process of the model is compatible to the Yellow River situation. The simulated bed elevation by considering the sediment deposition in the Mouth is particularly focused on, the numerical results are in agreement with the measured bed morphology within 1992 2000. Simulation in this paper indicates that most of the sediment deposited just out of the Mouth which makes the mouth move forward into the sea 2.5 km per year. This paper presents good results in simulation of varying sediment deposition and provides further methods to predict the future morphology and area of the Yellow River Delta.

  13. Aeolian Sediment Transport Pathways and Aerodynamics at Troughs on Mars

    Science.gov (United States)

    Bourke, Mary C.; Bullard, Joanna E.; Barnouin-Jha, Olivier S.

    2004-01-01

    Interaction between wind regimes and topography can give rise to complex suites of aeolian landforms. This paper considers aeolian sediment associated wit11 troughs on Mars and identifies a wider range of deposit types than has previously been documented. These include wind streaks, falling dunes, "lateral" dunes, barchan dunes, linear dunes, transverse ridges, sand ramps, climbing dunes, sand streamers, and sand patches. The sediment incorporated into these deposits is supplied by wind streaks and ambient Planitia sources as well as originating within the trough itself, notably from the trough walls and floor. There is also transmission of sediment between dneTsh. e flow dynamics which account for the distribution of aeolian sediment have been modeled using two-dimensional computational fluid dynamics. The model predicts flow separation on the upwind side of the trough followed by reattachment and acceleration at the downwind margin. The inferred patterns of sediment transport compare well with the distribution of aeolian forms. Model data indicate an increase of wind velocity by approx. 30 % at the downwind trough margin. This suggests that the threshold wind speed necessary for sand mobilization on Mars will be more freqentmlye t in these inclined locations.

  14. Glider observations and modeling of sediment transport in Hurricane Sandy

    Science.gov (United States)

    Miles, Travis; Seroka, Greg; Kohut, Josh; Schofield, Oscar; Glenn, Scott

    2015-03-01

    Regional sediment resuspension and transport are examined as Hurricane Sandy made landfall on the Mid-Atlantic Bight (MAB) in October 2012. A Teledyne-Webb Slocum glider, equipped with a Nortek Aquadopp current profiler, was deployed on the continental shelf ahead of the storm, and is used to validate sediment transport routines coupled to the Regional Ocean Modeling System (ROMS). The glider was deployed on 25 October, 5 days before Sandy made landfall in southern New Jersey (NJ) and flew along the 40 m isobath south of the Hudson Shelf Valley. We used optical and acoustic backscatter to compare with two modeled size classes along the glider track, 0.1 and 0.4 mm sand, respectively. Observations and modeling revealed full water column resuspension for both size classes for over 24 h during peak waves and currents, with transport oriented along-shelf toward the southwest. Regional model predictions showed over 3 cm of sediment eroded on the northern portion of the NJ shelf where waves and currents were the highest. As the storm passed and winds reversed from onshore to offshore on the southern portion of the domain waves and subsequently orbital velocities necessary for resuspension were reduced leading to over 3 cm of deposition across the entire shelf, just north of Delaware Bay. This study highlights the utility of gliders as a new asset in support of the development and verification of regional sediment resuspension and transport models, particularly during large tropical and extratropical cyclones when in situ data sets are not readily available.

  15. Non-Equilibrium Sediment Transport Modeling - Extensions and Applications

    Science.gov (United States)

    2013-01-01

    non-cohesive and cohesive sediment mixtures has been rarely studied, but have gained more and more attention recently ( Ziegler and Nisbet, 1995; Lin...the mud dry density, organic material, temperature, pH value, the Sodium Absorption Ratio (SAR), etc. Partheniades (1965) found n to be 1. In the...ASCE, 133(9), 1000–1009. Gailani, J., Ziegler , C.K., Lick , W., (1991). Transport of suspended solids in the Lower Fox River. Journal of Great

  16. Miocene mass-transport sediments, Troodos Massif, Cyprus

    Science.gov (United States)

    Lord, A.R.; Harrison, R.W.; BouDagher-Fadel, M.; Stone, B.D.; Varol, O.

    2009-01-01

    Sediment mass-transport layers of submarine origin on the northern and southern flanks of the Troodos ophiolitic massif are dated biostratigraphically as early Miocene and late Miocene, respectively and therefore represent different seismogenic events in the uplift and erosional history of the Troodos terrane. Analysis of such events has potential for documenting Miocene seismic and uplift events regionally in the context of changing stress field directions and plate vectors through time. ?? 2009 The Geologists' Association.

  17. Application of Sediment Trend Analysis in the Examination of Sediment Transport Dynamics of Missisquoi Bay

    Science.gov (United States)

    Kraft, M. P.; Manley, P.; Singer, J.; Manley, T.; McLaren, P.

    2013-12-01

    Missisquoi Bay is located between Vermont and Quebec in the northeast sector of the Restricted Arm of Lake Champlain. The average depth of the Bay is slightly less than 3 meters with a surface area covering 77.5 km2. The Bay receives water from eastern and western catchment basins, most notably via the Missisquoi, Rock, and Pike Rivers. Circulation within Missisquoi Bay has been altered by the construction of railroad causeways in the late 19th century and highway construction in the early 20th century. Over the past several decades there have also been changes in land-use practices, including the intensification of agriculture, increased animal husbandry, and urbanization. As a consequence of construction and changing land use, loadings of nitrogen and phosphorus to the Bay have increased seasonal oxygen depletion causing eutrophication. Since monitoring began in 1992, Missisquoi Bay has displayed the highest mean total phosphorus concentrations and chlorophyll a concentrations in Lake Champlain. Various efforts have taken place to reduce nutrient loading to Missisquoi Bay, but persistent release of phosphorus from bottom sediments will continue to delay for decades the recovery from nutrient diversion. To better understand the causes and timing of eutrophication in Missisquoi Bay, one component of a 5-year integrated VT EPSCoR - RACC program included an examination of N and P loadings and their distribution throughout the Bay. Internal circulation patterns are also being studied. To determine the pattern of net sediment transport and determine sediment behavior (erosion and accretion), a Sediment Trend Analysis (STA) was performed using 369 grab samples collected in the Bay. Grain size distributions for the surface sediment samples were determined using a Malvern Mastersizer 2000 particle size analyzer. Sediment maps showing the proportion of gravel, sand, and mud show that near major river distributaries sand-sized sediment was dominant with muds becoming more

  18. Observations of coastal sediment dynamics of the Tijuana Estuary Fine Sediment Fate and Transport Demonstration Project, Imperial Beach, California

    Science.gov (United States)

    Warrick, Jonathan A.; Rosenberger, Kurt J.; Lam, Angela; Ferreiera, Joanne; Miller, Ian M.; Rippy, Meg; Svejkovsky, Jan; Mustain, Neomi

    2012-01-01

    Coastal restoration and management must address the presence, use, and transportation of fine sediment, yet little information exists on the patterns and/or processes of fine-sediment transport and deposition for these systems. To fill this information gap, a number of State of California, Federal, and private industry partners developed the Tijuana Estuary Fine Sediment Fate and Transport Demonstration Project ("Demonstration Project") with the purpose of monitoring the transport, fate, and impacts of fine sediment from beach-sediment nourishments in 2008 and 2009 near the Tijuana River estuary, Imperial Beach, California. The primary purpose of the Demonstration Project was to collect and provide information about the directions, rates, and processes of fine-sediment transport along and across a California beach and nearshore setting. To achieve these goals, the U.S. Geological Survey monitored water, beach, and seafloor properties during the 2008–2009 Demonstration Project. The project utilized sediment with ~40 percent fine sediment by mass so that the dispersal and transport of fine sediment would be easily recognizable. The purpose of this report is to present and disseminate the data collected during the physical monitoring of the Demonstration Project. These data are available online at the links noted in the "Additional Digital Information" section. Synthesis of these data and results will be provided in subsequent publications.

  19. Aeolian Sediment Transport Integration in General Stratigraphic Forward Modeling

    Directory of Open Access Journals (Sweden)

    T. Salles

    2011-01-01

    Full Text Available A large number of numerical models have been developed to simulate the physical processes involved in saltation, and, recently to investigate the interaction between soil vegetation cover and aeolian transport. These models are generally constrained to saltation of monodisperse particles while natural saltation occurs over mixed soils. We present a three-dimensional numerical model of steady-state saltation that can simulate aeolian erosion, transport and deposition for unvegetated mixed soils. Our model simulates the motion of saltating particles using a cellular automata algorithm. A simple set of rules is used and takes into account an erosion formula, a transport model, a wind exposition function, and an avalanching process. The model is coupled to the stratigraphic forward model Sedsim that accounts for a larger number of geological processes. The numerical model predicts a wide range of typical dune shapes, which have qualitative correspondence to real systems. The model reproduces the internal structure and composition of the resulting aeolian deposits. It shows the complex formation of dune systems with cross-bedding strata development, bounding surfaces overlaid by fine sediment and inverse grading deposits. We aim to use it to simulate the complex interactions between different sediment transport processes and their resulting geological morphologies.

  20. Erosion, storage, and transport of sediment in two subbasins of the Rio Puerco, New Mexico

    Science.gov (United States)

    Gellis, A.C.; Pavich, M.J.; Ellwein, A.L.; Aby, S.; Clark, I.; Wieczorek, M.E.; Viger, R.

    2012-01-01

    Arroyos in the American Southwest proceed through cut-and-fill cycles that operate at centennial to millennial time scales. The geomorphic community has put much effort into understanding the causes of arroyo cutting in the late Quaternary and in the modern record (late 1800s), while little effort has gone into understanding how arroyos fill and the sources of this fill. Here, we successfully develop a geographic information system (GIS)-modeled sediment budget that is based on detailed field measurements of hillslope and channel erosion and deposition. Field measurements were made in two arroyo basins draining different lithologies and undergoing different land disturbance (Volcano Hill Wash, 9.30 km2; Arroyo Chavez, 2.11 km2) over a 3 yr period. Both basins have incised channels that formed in response to the late nineteenth-century incision of the Rio Puerco. Large volumes of sediment were generated during arroyo incision, equal to more than 100 yr of the current annual total sediment load (bed load + suspended load) in each basin. Downstream reaches in both arroyos are presently aggrading, and the main source of the sediment is from channel erosion in upstream reaches and first- and second-order tributaries. The sediment budget shows that channel erosion is the largest source of sediment in the current stage of the arroyo cycle: 98% and 80% of the sediment exported out of Volcano Hill Wash and Arroyo Chavez, respectively. The geomorphic surface most affected by arroyo incision and one of the most important sediment sources is the valley alluvium, where channel erosion, gullying, soil piping, and grazing all occur. Erosion rates calculated for the entire Volcano Hill Wash (-0.26 mm/yr) and Arroyo Chavez (-0.53 mm/yr) basins are higher than the modeled upland erosion rates in each basin, reflecting the large contributions from channel erosion. Erosion rates in each basin are affected by a combination of land disturbance (grazing) and lithology

  1. Impacts of biological diversity on sediment transport in streams

    Science.gov (United States)

    Albertson, L. K.; Cardinale, B. J.; Sklar, L. S.

    2012-12-01

    Over the past decade, an increasing number of studies have shown that biological structures (e.g. plant roots) have large impacts on sediment transport, and that physical models that do not incorporate these biological impacts can produce qualitatively incorrect predictions. But while it is now recognized that biological structures influence sediment transport, work to date has focused primarily on the impacts of individual, usually dominant, species. Here, we ask whether competitive interactions cause multi-species communities to have fundamentally different impacts on sediment mobility than single-species systems. We use a model system with caddisfly larvae, which are insects that live in the benthic habitat of streams where they construct silken catchnets across pore spaces between rocks to filter food particles. Because caddisflies can reach densities of 1,000s per m2 with each larva spinning hundreds of silken threads between rocks, studies have shown that caddisflies reduce the probability of bed movement during high discharge events. To test whether streams with multiple species of caddisfly are stabilized any differently than single-species streams, we manipulated the presence or absence of two common species (Ceratopsyche oslari, Arctopsyche californica) in substrate patches (0.15 m2) in experimental stream channels (50-m long x 1-m wide) with fully controlled hydrology at the Sierra Nevada Aquatic Research Laboratory. This experiment was designed to extend the scale of previous laboratory mesocosm studies, which showed that critical shear stress is 31% higher in a multi-species flume mesocosm compared to a single-species mesocosm. Under these more realistic field conditions, we found that critical shear stress was, on average, 30% higher in streams with caddisflies vs. controls with no caddisflies. However, no differences were detected between treatments with 2 vs. 1 species. We hypothesize that the minimal effect of diversity on critical shear stress

  2. Sediment transport dynamics in steep, tropical volcanic catchments

    Science.gov (United States)

    Birkel, Christian; Solano Rivera, Vanessa; Granados Bolaños, Sebastian; Brenes Cambronero, Liz; Sánchez Murillo, Ricardo; Geris, Josie

    2017-04-01

    How volcanic landforms in tropical mountainous regions are eroded, and how eroded materials move through these mostly steep landscapes from the headwaters to affect sediment fluxes are critical to water resources management in their downstream rivers. Volcanic landscapes are of particular importance because of the short timescales (Central Volcanic Cordillera of Costa Rica (Figure 1A). Typical for tropical volcanic and montane regions, deeply incised V-form headwaters (Figure 1B) deliver the majority of water (>70%) and sediments to downstream rivers. At the catchment outlet (Figure 1C) of the San Lorencito stream, we established high temporal resolution (5min) water quantity and sediment monitoring (turbidity). We also surveyed the river network on various occasions to characterize fluvial geomorphology including material properties. We could show that the rainfall-runoff-sediment relationships and their characteristic hysteresis patterns are directly linked to variations in the climatic input (storm intensity and duration) and the size, form and mineralogy of the transported material. Such a relationship allowed us to gain the following insights: (i) periodic landslides contribute significant volumes of material (> 100m3 per year) to the stream network, (ii) rainfall events that exceed a threshold of around 30mm/h rain intensity activate superficial flow pathways with associated mobilization of sediments (laminar erosion). However, the erosion processes are spatially very heterogeneous and mostly linked to finer material properties of the soils that mostly developed on more highly weathered bedrock. (iii) extreme events (return period > 50 years) mainly erode the streambed and banks cutting deeper into the bedrock and re-distribute massive amounts of material in the form of removed old alluvial deposits and new deposits created elsewhere, (iv) recovery after such extreme events in the form of fine material transport even during low intensity rainfall towards pre

  3. Suspended sediment transport in the Gulf of Lions (NW Mediterranean): Impact of extreme storms and floods

    NARCIS (Netherlands)

    Ulses, C.; Estournel, C.; Durrieu de Madron, X.; Palanques, A.

    2008-01-01

    In situ observations were combined with 3D modeling to gain understanding of and to quantify the suspended sediment transport in the Gulf of Lions (NW Mediterranean Sea). The outputs of a hydrodynamic–sediment transport coupled model were compared to near-bottom current and suspended sediment

  4. Storm and tsunami induced sediment transport and morphology changes in vicinity of tidal inlets

    Digital Repository Service at National Institute of Oceanography (India)

    Jayakumar, S.; ManiMurali, R.

    was used in estimation of the sediment transport using the three non-cohesive sediment transport (ST) equations used in MIKE21. Of the three different formulations used in MIKE21 sediment transport model, the 79 INDO-JAPAN Workshop on River mouths..., Tidal Flats and Lagoons 15-16 September 2014, IIT Madras, INDIA Engelund and Hansen (1972) (hereinafter referred as EH formulation) which is based on total-load transport theory is considered. The dimensionless total...

  5. Littoral Hydrodynamics and Sediment Transport Around a Semi-Permeable Breakwater

    Science.gov (United States)

    2015-09-18

    Transport 1 Li, H., L. Lin, C.-C. Lu, C. Reed, and A. Shak (2015). Littoral Hydrodynamics and Sediment Transport around a Semi-Permeable Breakwater...Coasts and Ports 2015, Auckland, New Zealand, 15-18 September, 2015, 7 pp. Littoral Hydrodynamics and Sediment Transport Around a Semi...Dana Point Harbor requires a better understanding of hydrodynamics and sediment transport around a permeable breakwater. In this study, an integrated

  6. A model of the sediment transport on a river network

    Science.gov (United States)

    Wang, Xu-Ming; Hao, Rui; Zhang, Jin-Feng; Huo, Jie

    2007-03-01

    A dynamical model is proposed to mimic the sediment transport on a river network. A river can be divided into some segments. For the ith segment the schlepping sediment ability of the flow may be scouring or depositing, which is influenced by that of the (i- 1)th segment. In order to compare our model simulation results with the empirical data obtained in Yellow River, the model is equipped with an experiential relation between the flow rate and the depositing rate of the Yellow River. After this, the simulation results show an excellent agreement with the empirical conclusions obtained with the upper and middle parts of Yellow River when it is in the low-water periods (for instance, in Dec., Jan. and Feb.). This indicates that our model may successfully describe the scouring-depositing of river networks.

  7. Clay mineral distribution in surface sediments of the South China Sea and its significance for in sediment sources and transport

    Institute of Scientific and Technical Information of China (English)

    刘建国; 陈木宏; 陈忠; 颜文

    2010-01-01

    Clay minerals of surface sediments in the South China Sea (SCS) are analyzed with X-ray diffraction, and their transport is explored with a grain size trend analysis (GSTA) model. Results show that clay mineral types in various sedimentary environments have different sediment sources and transport routes. Sediments in the northern SCS (north of 20°N) between the southwest of Taiwan Island and the outer mouth of the Pearl River have high contents of illite and chlorite, which are derived mainly from sediment...

  8. Interpreting sediment transport data with channel cross section analysis

    Science.gov (United States)

    Park, J.; Hunt, J. R.

    2013-12-01

    Suspended sediment load estimation is important for the management of stream environments. However suspended load data are uncommon and scalable models are needed to take maximum advantage of the measurements available. One of the most commonly used models for correlating suspended sediment load is an empirical power law relationship (Qs=aQ^b, Qs: suspended load, Q: flow rate). However, the relationship of log-scaled suspended load to flow rate has multiple exponents for different flow regimes at a given site, so a single power law relationship is not a good fit. Thus we are exploring an alternative approach that employs channel cross section data historically collected by the US Geological Survey during stream gauge calibration. For our research, daily flow and sediment discharge were selected from about 180 possible USGS gauging sites in California. Among those, about 20 sites were relatively unaffected by human activities, and had more than three years of data including near monthly measurements of channel cross section data. From our analysis, a slope break was consistently observed in the relationship of log-scaled suspended load to flow rate as illustrated in Figure 1 for Redwood Creek at Orick, CA. Most of the selected natural sites clearly show this slope break. The slope break corresponds to a transition of flow from a flat, wide stream to flow constrained by steep banks as verified in Figure 2 for the same site. This suggests that physical factors in the streams such as shear stress are affected by this channel morphological change and result in the greater exponent of sediment load during higher flow regime. Figure1. Daily values of measured sediment transport and flow rate reported by USGS between 1970 and 2001. Figure2. Near monthly values of measured mean water depth and width reported by USGS between 1969 and 1987.

  9. Check dams effects on sediment transport in steep slope flume

    Science.gov (United States)

    Piton, Guillaume; Recking, Alain

    2014-05-01

    Depending on many influences (geology, relief, hydrology, land use, etc.) some mountainous watershed are prone to cause casualties and facilities damages. Large amounts of sediments episodically released by torrents are often the biggest problem in torrent related hazard mitigation. Series of transversal structures as check dams and ground sills are often used in the panel of risk mitigation technics. A large literature exits on check dams and it mainly concerns engineering design, e.g. toe scouring, stability stress diagram, changes in upper and lower reaches equilibrium slopes. Check dams in steep slope rivers constitute fixed points in the bed profile and prevent general bed incision. However their influence on sediment transport once they are filled is not yet clear. Two flume test campaigns, synthetize in Table 1, were performed to investigate this question: Table 1 : experiment plan Run (duration) Ref1 (50h)CD1a (30h)CD1b (30h)Ref2 (92h)CD2 (18h) Solid feeding discharge (g.s^-1) 44 44 44 60 60 Number of check dams none 1 3 none 2 A nearly 5-m-long, 10-cm-wide and 12%-steep flume was used. The water discharge was set to 0,55 l/s in all runs. A mixture of poorly sorted natural sediments with diameters between 0.8 and 40 mm was used. An open solid-discharge-feeding circuit kept the inlet sediment flux constant during all experiments. As both feeding rates did not present variation, changes in outlet solid discharge were assumed to be due to bed variations in the bed storage. We observed strong fluctuations of solid flux and slope in each reaches of all runs between: (i) steep aggradating armoured bed and (ii) less steep and finer bed releasing bedload sheets during erosion events and inducing bedload pulses. All experiments showed consistent results: transported volume associated with erosion event decreased with the length between two subsequent check dams. Solid transversal structures shorten the upstream erosion-propagation and avoid downstream change in the

  10. Tailings dam-break flow - Analysis of sediment transport

    Science.gov (United States)

    Aleixo, Rui; Altinakar, Mustafa

    2015-04-01

    A common solution to store mining debris is to build tailings dams near the mining site. These dams are usually built with local materials such as mining debris and are more vulnerable than concrete dams (Rico et al. 2008). of The tailings and the pond water generally contain heavy metals and various toxic chemicals used in ore extraction. Thus, the release of tailings due to a dam-break can have severe ecological consequences in the environment. A tailings dam-break has many similarities with a common dam-break flow. It is highly transient and can be severely descructive. However, a significant difference is that the released sediment-water mixture will behave as a non-Newtonian flow. Existing numerical models used to simulate dam-break flows do not represent correctly the non-Newtonian behavior of tailings under a dam-break flow and may lead to unrealistic and incorrect results. The need for experiments to extract both qualitative and quantitative information regarding these flows is therefore real and actual. The present paper explores an existing experimental data base presented in Aleixo et al. (2014a,b) to further characterize the sediment transport under conditions of a severe transient flow and to extract quantitative information regarding sediment flow rate, sediment velocity, sediment-sediment interactions a among others. Different features of the flow are also described and analyzed in detail. The analysis is made by means of imaging techniques such as Particle Image Velocimetry and Particle Tracking Velocimetry that allow extracting not only the velocity field but the Lagrangian description of the sediments as well. An analysis of the results is presented and the limitations of the presented experimental approach are discussed. References Rico, M., Benito, G., Salgueiro, AR, Diez-Herrero, A. and Pereira, H.G. (2008) Reported tailings dam failures: A review of the European incidents in the worldwide context , Journal of Hazardous Materials, 152, 846

  11. Bottom Sediment Transport in the Flood and Ebb Channels of the Changjiang Estuary

    Institute of Scientific and Technical Information of China (English)

    刘高峰; 沈焕庭; 王永红; 吴加学

    2004-01-01

    Nanxiaohong and Nangang main south channel are chosen as the typical flood and ebb channels. Hydrodynamics analysis based on field hydrological and sediment data is conducted with Gao-Collins model to analyse sediment transport trends. Also, the grain size distribution analysis of the bottom sediment sampled in Sep. 2001 is used as the base of the analysis. The result shows that the sediment in Nanxiaohong is from the rive mouth area. The sediment transports upwards with the flood flow which is stronger than the ebb flow, i.e., in the direction of SE-WN. The sediment in main south channel comes from upward. They transport downwards with the ebb flow, which is stronger than the flood flow, i.e., in the direction of WN-SE. The directions, sources and mechanism of sediment transport are identified according to comprehensive analyses of the observed data on hydrodynamics and sediment.

  12. The effects of Thailand's Great Flood of 2011 on river sediment discharge in the upper Chao Phraya River basin, Thailand

    Institute of Scientific and Technical Information of China (English)

    Butsawan Bidorn; Seree Chanyotha; Stephen A. Kish; Joseph F. Donoghue; Komkrit Bidorn; Ruetaitip Mama

    2015-01-01

    Severe flooding that occurred during the 2011 monsoon season in Thailand was the heaviest flooding in the past 50 yr. The rainfall over the northern part of Thailand, especially during July–August 2011, was 150% higher than average. During the flooding period, river flows of the four major Chao Phraya River tributaries (Ping, Wang, Yom, and Nan rivers) increased in the range of 1.4–5 times the average discharge. This study examined the river sediment discharge of the four major rivers in the upper Chao Phraya River basin in Thailand. The four rivers are considered the main sources of sediment supply to the Chao Phraya Estuary. River surveys of the Ping, Wang, Yom, and Nan rivers were carried out in October 2011 (during the Great Flood) and October 2012 (one year after the flood). Survey data included river cross sections, flow velocities, suspended sediment concentrations, and bed load transport in each river. Analyses of these data indicated that total sediment transport rates for the four main rivers during the flooding of 2011 were 2.3–5.6 times higher than the average sediment discharge over 60 yr. The flood of 2011 sig-nificantly affected the sediment characteristics including the proportions of suspended and bed sediment loads in each river though in different ways. The rates of sediment transport per unit discharge for the Ping and Wang rivers dramatically increased during the 2011 flood, but the flooding had minimal effects on the sediment characteristics in the Yom and Nan rivers. The amount of total sediment discharge in each river caused by the 2011 flooding varied between 0.3 and 1.6 Mt. Additionally, the bed load transport in these rivers varied between ? 0%and 26%of the suspended sediment discharge.

  13. Sediment transport through self-adjusting, bedrock-walled waterfall plunge pools

    Science.gov (United States)

    Scheingross, Joel S.; Lamb, Michael P.

    2016-05-01

    Many waterfalls have deep plunge pools that are often partially or fully filled with sediment. Sediment fill may control plunge-pool bedrock erosion rates, partially determine habitat availability for aquatic organisms, and affect sediment routing and debris flow initiation. Currently, there exists no mechanistic model to describe sediment transport through waterfall plunge pools. Here we develop an analytical model to predict steady-state plunge-pool depth and sediment-transport capacity by combining existing jet theory with sediment transport mechanics. Our model predicts plunge-pool sediment-transport capacity increases with increasing river discharge, flow velocity, and waterfall drop height and decreases with increasing plunge-pool depth, radius, and grain size. We tested the model using flume experiments under varying waterfall and plunge-pool geometries, flow hydraulics, and sediment size. The model and experiments show that through morphodynamic feedbacks, plunge pools aggrade to reach shallower equilibrium pool depths in response to increases in imposed sediment supply. Our theory for steady-state pool depth matches the experiments with an R2 value of 0.8, with discrepancies likely due to model simplifications of the hydraulics and sediment transport. Analysis of 75 waterfalls suggests that the water depths in natural plunge pools are strongly influenced by upstream sediment supply, and our model provides a mass-conserving framework to predict sediment and water storage in waterfall plunge pools for sediment routing, habitat assessment, and bedrock erosion modeling.

  14. Effect of vortex formation on sediment transport at dual pipe intakes

    Indian Academy of Sciences (India)

    M R KHANARMUEI; H RAHIMZADEH; A R KAKUEI; H SARKARDEH

    2016-09-01

    Vortex formation and subsequent sediment transport into the intake due to sea water withdrawal is one of the problems in coastal engineering. The effect of vortex formation on rate of sediment transport at coastal dual pipe intakes was investigated using a scaled physical model. Experiments were performed on dual pipe intakes at three common intake withdrawal directions (vertical, horizontal and with angle of 45°). In eachexperiment, the class of vortex with respect to its strength was determined. Particle tracking velocimetry (PTV) was employed to measure tangential velocity of vortices. Results indicated that the rate of sediment transport was considerably affected by the strength of formed vortices. The rate of transported sediment was increased by increasing the strength of formed vortex. Moreover, amount of sediment transport was affected by angle of pipe intakes. It could be concluded that the minimum and maximum rates of sediment transport occur for inclined and horizontal intakes, respectively.

  15. Port Areas and Approach Channels Sinoimeri by Rivers Sediment Transport

    Directory of Open Access Journals (Sweden)

    Konstantin N. Makarov

    2015-12-01

    Full Text Available When designing ports, one important task is to predict sinoimeri port areas and approach channels sandy or pebbly silt. On the basis of this forecast are determined by the methods of protection from sinoimeri, as well as the frequency and volume of maintenance dredging works. Out at sea the river flow becomes turbulent inertial jet. Friction on the bottom and the interaction with sea water leads to an overall reduction of jet velocity and its spreading. An important regularity is also spreading muddy river flow on the surface of the denser seawater. This creates conditions for rapid deposition of large fractions of the sediment on the bottom. The bulk of the sediment particles larger than 5 mm is deposited on the surface of the river bar and further transported along the shore wave energy currents. Outside of the bar shall be made only fine-grained material. The particle size of sediment deposited on the bottom outside of the bar decreases sharply with depth. Thus, sinoimeri of harbors and access channels is mainly suspended river sediments. To calculate the distribution of the river flow, in the coastal zone in the presence of long chore currents developed a special method that implements the theory of turbulent planar jet in a drifting thread. The solid portion of the jet flow that enters the waters of the port or channel as a result of increasing depth and, consequently, reduce turbidity settles, causing shoaling waters. The example of calculation of sinoimeri berth 1a in the port of Tuapse by solid flow of Tuapse river.

  16. Bead-Based Microfluidic Sediment Analogues: Fabrication and Colloid Transport.

    Science.gov (United States)

    Guo, Yang; Huang, Jingwei; Xiao, Feng; Yin, Xiaolong; Chun, Jaehun; Um, Wooyong; Neeves, Keith B; Wu, Ning

    2016-09-13

    Mobile colloids can act as carriers for low-solubility contaminants in the environment. However, the dominant mechanism for this colloid-facilitated transport of chemicals is unclear. Therefore, we developed a bead-based microfluidic platform of sediment analogues and measured both single and population transport of model colloids. The porous medium is assembled through a bead-by-bead injection method. This approach has the versatility to build both electrostatically homogeneous and heterogeneous media at the pore scale. A T-junction at the exit also allowed for encapsulation and enumeration of colloids effluent at single particle resolution to give population dynamics. Tortuosity calculated from pore-scale trajectory analysis and its comparison with lattice Boltzmann simulations revealed that transport of colloids was influenced by the size exclusion effect. The porous media packed by positively and negatively charged beads into two layers showed distinctive colloidal particle retention and significant remobilization and re-adsorption of particles during water flushing. We demonstrated the potential of our method to fabricate porous media with surface heterogeneities at the pore scale. With both single and population dynamics measurement, our platform has the potential to connect pore-scale and macroscale colloid transport on a lab scale and to quantify the impact of grain surface heterogeneities that are natural in the subsurface environment.

  17. Bedload transport controls bedrock erosion under sediment-starved conditions

    Science.gov (United States)

    Beer, A. R.; Turowski, J. M.

    2015-07-01

    Fluvial bedrock incision constrains the pace of mountainous landscape evolution. Bedrock erosion processes have been described with incision models that are widely applied in river-reach and catchment-scale studies. However, so far no linked field data set at the process scale had been published that permits the assessment of model plausibility and accuracy. Here, we evaluate the predictive power of various incision models using independent data on hydraulics, bedload transport and erosion recorded on an artificial bedrock slab installed in a steep bedrock stream section for a single bedload transport event. The influence of transported bedload on the erosion rate (the "tools effect") is shown to be dominant, while other sediment effects are of minor importance. Hence, a simple temporally distributed incision model, in which erosion rate is proportional to bedload transport rate, is proposed for transient local studies under detachment-limited conditions. This model can be site-calibrated with temporally lumped bedload and erosion data and its applicability can be assessed by visual inspection of the study site. For the event at hand, basic discharge-based models, such as derivatives of the stream power model family, are adequate to reproduce the overall trend of the observed erosion rate. This may be relevant for long-term studies of landscape evolution without specific interest in transient local behavior. However, it remains to be seen whether the same model calibration can reliably predict erosion in future events.

  18. Tidal and meteorological forcing of sediment transport in tributary mudflat channels.

    Science.gov (United States)

    Ralston, David K; Stacey, Mark T

    2007-06-01

    Field observations of flow and sediment transport in a tributary channel through intertidal mudflats indicate that suspended sediment was closely linked to advection and dispersion of a tidal salinity front. During calm weather when tidal forcing was dominant, high concentrations of suspended sediment advected up the mudflat channel in the narrow region between salty water from San Francisco Bay and much fresher runoff from the small local watershed. Salinity and suspended sediment dispersed at similar rates through each tidal inundation, such that during receding ebbs the sediment pulse had spread spatially and maximum concentrations had decreased. Net sediment transport was moderately onshore during the calm weather, as asymmetries in stratification due to tidal straining of the salinity front enhanced deposition, particularly during weaker neap tidal forcing. Sediment transport by tidal forcing was periodically altered by winter storms. During storms, strong winds from the south generated wind waves and temporarily increased suspended sediment concentrations. Increased discharge down the tributary channels due to precipitation had more lasting impact on sediment transport, supplying both buoyancy and fine sediment to the system. Net sediment transport depended on the balance between calm weather tidal forcing and perturbations by episodic storms. Net transport in the tributary channel was generally off-shore during storms and during calm weather spring tides, and on-shore during calm weather neap tides.

  19. Experimental and numerical investigation of the coupling of turbulence and sediment transport over dunes

    Science.gov (United States)

    Schmeeckle, M. W.; Leary, K. P.

    2016-12-01

    We investigate the spatiotemporal coupling of sediment transport over dunes using a turbulence- and particle-resolving numerical model and high-speed video in a laboratory flume. The model utilizes the Large Eddy Simulation (LES) for the fluid turbulence and a Discrete Element Method (DEM) simulation for the sediment. Previous experiments assessing the effects of flow separation on downstream fluid turbulent structures and bedload transport suggest that localized, intermittent, high-magnitude transport events, called permeable splat events, play an important role in both downstream and cross-stream transport near flow reattachment. The flume was lined with 17 concrete ripples that had a 2 cm high crest and were 30 cm long. A high-speed camera observed sediment transport along the entirety of the bedform at 250 Hz. Downstream and vertical fluid velocity was observed at 1mm and 3 mm above the bed using Laser Doppler Velocitmetry (LDV) at 15 distances along bedform profile. As observed in our previous backward-facing step experiments and simulations, mean downstream fluid velocity increases nonlinearly with increasing distance along the ripple. Observed sediment transport, however, increases linearly with increasing distance along the ripple with an exception at the crest of the bedform, where both mean downstream fluid velocity and sediment transport decrease significantly. Previous experiments assessing only the effect of flow separation showed that calculating sediment transport as a function of boundary shear stress using a Meyer-Peter Müller type equation, produced a zone of underestimated transport near flow reattachment. Results reported here show that calculating sediment transport in this way underestimates observed sediment transport along the entire profile of the bedform, not just near flow reattachment. Preliminary sediment transport time-series data show a zone of high-magnitude cross-stream transport near flow reattachment, suggesting that permeable

  20. Disobedient sediments can feedback on their transportation, deposition and geomorphology

    Science.gov (United States)

    Ginsburg, Robert N.

    2005-04-01

    Most sediments are obedient to the winds, waves and currents, which direct their transportation and deposition. It has long been recognized however, that the grain size, and/or grain kind, of sediments can feedback on the processes of their own transportation, deposition and geomorphology as well as that of succeeding deposits. This note is to review three examples of marine sediments in which a single grain size or grain kind produces multiple feedbacks. Tidal bars of Holocene ooid sands on Great Bahama Bank are an example of multiple feedbacks of one grain kind on tidal currents, wave action and accumulations. These feedbacks are responsible for the distinctive pattern of elongated bars and channels, which in turn amplify tidal currents. The near constant movement of grains on the shallow bars and in the channels is where pellet nuclei are coated to form ooids; thus the development and growth of bars feeds back to produce more ooids. Regional encrinites, which consist predominantly of the disarticulated highly porous skeletons of crinoids, are common from Ordovician to Jurassic during blooms of these filter feeders. The resulting grains, which are equivalent to quartz grains a tenth of their size, can be entrained by currents as low as a knot (ca 0.5 m/s). The resulting mobile substrate deters other invertebrates (taphonomic feedback) and results in the prevalence of layering produced by traction transport of low velocity. The belt of mud extending for some 1600 km between the Amazon and Orinocco rivers is a special example of the feedback of mud on depositional processes, sedimentary structures and geomorphology of the accumulations. The clay-rich mud from the Amazon produces fluid mud which dampens and transforms wave action from the open sea to promote its own accumulation in giant bars in the inner shelf and shoreline with a variety of familiar laminations. The result is a wedge of mud-rich deposits some 24 m thick and 30 km wide capped with cheniers of sand

  1. Towards a complete contemporary sediment budget of a major Himalayan river: Kali Gandaki, Nepal

    Science.gov (United States)

    Struck, Martin; Andermann, Christoff; Bista, Raj; Korup, Oliver

    2013-04-01

    The tectonic evolution of mountain ranges is always accompanied by enhanced denudation. In the Himalayas these denudation rates are among the highest in the world, where high topography and prominent relief ensure supply of sediment to the drainage network mainly by mass wasting processes. These processes take place almost exclusively during the summer monsoon season, but remain poorly quantified in terms of resulting sediment flux. Here we study short-term variations in contemporary sediment flux of the Kali Gandaki River, one of the large rivers traversing the Himalayas from the Tibetan Plateau in the north to the Ganges foreland in the south. We analysed seven years of continuous daily suspended sediment and river discharge measurements at a hydropower facility in the lesser part of the Mahambra range. This new dataset is unique for the whole Himalayan range in terms of temporal resolution. We used these data to derive a preliminary sediment budget for the Kali Gandaki River for the years 2006-2012, based on continuous river discharge, suspended sediment load, bed material and dissolved load measurements. First results show that the Kali Gandaki River has transported 1.5-2.7 x 107 m3 of sediment per year. This equals around 4.0-7.0 x 107t/yr, out of which 25-45% is transported as bed-load. Inferred rates of upstream erosion range between 2-3.5 mm/yr, in good agreement with complementary estimates integrating much longer timespans for example derived by low temperature thermochronometry. Our results include one of the first calculations of bed-load transport for a large Himalayan river. Such temporally highly resolved constraints on contemporary sediment transport and erosion in the Himalayan Range not only provide field-based benchmark data for erosion studies across multiple timescales, but also yield valuable data for optimizing hydropower schemes, and the planning of flood control measures in major Himalayan rivers.

  2. Electrically induced displacement transport of immiscible oil in saline sediments.

    Science.gov (United States)

    Pamukcu, Sibel; Shrestha, Reena A; Ribeiro, Alexandra B; Mateus, Eduardo P

    2016-08-01

    Electrically assisted mitigation of coastal sediment oil pollution was simulated in floor-scale laboratory experiments using light crude oil and saline water at approximately 1/10 oil/water (O/W) mass ratio in pore fluid. The mass transport of the immiscible liquid phases was induced under constant direct current density of 2A/m(2), without water flooding. The transient pore water pressures (PWP) and the voltage differences (V) at and in between consecutive ports lined along the test specimen cell were measured over 90days. The oil phase transport occurred towards the anode half of the test specimen where the O/W volume ratio increased by 50% over its initial value within that half-length of the specimen. In contrast, the O/W ratio decreased within the cathode side half of the specimen. During this time, the PWP decreased systematically at the anode side with oil bank accumulation. PWP increased at the cathode side of the specimen, signaling increased concentration of water there as it replaced oil in the pore space. Electrically induced transport of the non-polar, non-conductive oil was accomplished in the opposing direction of flow by displacement in absence of viscous coupling of oil-water phases.

  3. Sediment management plan for river Gudbrandsdalslagen, Southern Norway

    Science.gov (United States)

    Bogen, Jim; Moquet Stenback, Agnes; Bonsnes, Truls; Xu, Mengzhen

    2016-04-01

    During recent years, several large magnitude flood events have led to an increase in the input of sediment to the Gudbrandsdalslagen river system. The increased sediment delivery have caused bank erosion, aggradation and channel changes and resulted in severe damage to infrastructure and arable land and it was decided to make a sediment management plan for this river basin. It is important to have an understanding of the processes that is contributing to the sediment delivery and knowledge about the volumes of sediments involved, to choose which measures are most efficient. The data collection techniques involved the use of repeated airborne laser scans to build digital terrain models (DTM) used to compute eroded volumes. In addition, airborne photos were also used to observe changes due to erosion and deposition of sediments. At some stations, automatic water samplers were used to collect samples 1-2 times a day for suspended sediment transport calculations. Bed load rates was determined from repeated volumetric measurements of sediment deposition in dams. At the Harpefoss water reservoir, the bed load was measured to 13000 tonnes/yr over a period of 50 yrs amounting to about 19% of the total load. The catchment area of the Gudbrandsdalslagen is 11200km2 consisting of a river system with lake Losna lying downstream. A number of steep tributaries drain the surrounding mountain areas to the main river stem supplying large amounts of sediments. The study of sediment sources from12 tributaries revealed that undercutting and erosion of slopes adjacent to the river bed is the most dominant process, but gullying and debris flows also supply much sediments. In the river Veikleai near Kvam, laser scan measurements gave a removed volume of 200 000 - 270 000 tonnes delivered from the undercutting of slopes adjacent to the river channel during the flood of 2013, whereas 80 000tonnes was delivered by debris flows. A total of 40 000 tonnes were accumulated in the river channel

  4. Flood-Induced Riverbed Changes and Sediment Yields Revealed by Twice LiDAR Surveys

    Science.gov (United States)

    Hsieh, Yu-Chung; Chan, Yu-Chang; Hu, Jyr-Ching; Lin, Chao-Chung

    2010-05-01

    Riverbed changes and sediment yields from watersheds greatly influence the conservation of water and soil, the planning of hydraulic engineering, and the river habitat, etc. At present, sediment yield calculation often used empirical or theoretical formula as well as data collected at hydrological stations, and rarely had the actual measured value through high-resolution topography. The Lanyang River is one of main rivers in Taiwan and often suffers the influence of typhoon during summer. Most of sediments generated from slump and soil erosion into river were transported from the upstream watershed and resulted in the riverbed changes during the typhoon season. In 2008, there are four significant typhoon events influencing this area, including the Kalmaegi, Fung-wong, Sinlaku, and Jangmi typhoons. This topographic research funded by the Taiwan Central Geological Survey, surveyed the terrain of the Lanyang River before and after the typhoon season using Airborne LiDAR technique, and computed the terrain variations. The variations of the terrain on the riverbed may be regarded as the sediment yield of the bed load transported during the typhoon season. This research used high-resolution terrain models to compute sediment yield of the bed load, and further discussed volumes of sediment yield in watershed during the typhoon season. In the Lanyang River we discovered that the upstream and midstream channel still had the characteristics of erosion and transportation during the typhoon season. The sediment on the river bed reduced approximately 2.3 million cubic meters; and the erosion rate of the bed load sediments were estimated about 3.4 mm during the 2008 typhoon season. The results imply significant sediment yield and transportation from the upstream watershed of the Lanyang River during only single typhoon season in which cumulated rain falls are high. The leading factors of the riverbed erosion include the riverbed slope, channel curvature, channel width, lithology

  5. Efficiency of sediment transport by flood and its control in the Lower Yellow River

    Institute of Scientific and Technical Information of China (English)

    NI; Jinren; LIU; Xiaoyong; LI; Tianhong; ZHAO; Yean; JIN; L

    2004-01-01

    This paper presents the characteristics of sediment transport by flood in the Lower Yellow River with the reach from Huayuankou to Gaocun, which is regarded as a typical braided pattern. The Artificial Neural Network Model on Water Use for Sediment Transport (WUST) by flood was established based on the measured data from 1980 to 1998. Consequently, simulations of controlling process of sediment transport by flood were made in terms of the control theory under different scenarios. According to the situation of sediment transport by flood in the Lower Yellow River, Open-Loop control system and feedback control system were adopted in system design. In the Open-Loop control system, numerical simulations were made to reveal the relationship between average discharge of flood and the WUST with varying sediment concentrations. The results demonstrate that sediment concentration has significant influence on the controlling process of flood flow to WUST. It is practical and efficient to control WUST if sediment concentration is less than 20 kg/m3. In the feedback control system, controlling processes of sediment concentration and flood discharge for sediment transport were simulated respectively under given conditions, and it was found that sediment transport process could be controlled completely by sediment concentration and discharge at the inlet of the reach from Huayuankou to Gaocun. Using the same method, controlling processes of sediment transport by flood in other reaches in the Lower Yellow River were also simulated. For the case of sediment concentration being 20 kg/m3, the optimized controlling discharge ranges from 2390 to 2900 m3/s in the lower reach of Huayuankou.This study is also of significance to flood control and flushing sediment in the Lower Yellow River with proper operation modes of Xiaolangdi Reservoir.

  6. ONE-DIMENSIONAL HYDRODYNAMIC/SEDIMENT TRANSPORT MODEL FOR STREAM NETWORKS: TECHNICAL REPORT

    Science.gov (United States)

    This technical report describes a new sediment transport model and the supporting post-processor, and sampling procedures for sediments in streams. Specifically, the following items are described herein: EFDC1D - This is a new one-dimensional hydrodynamic and sediment tr...

  7. Effect of sediment transport boundary conditions on the numerical modeling of bed morphodynamics

    Science.gov (United States)

    Experimental sediment transport studies in laboratory flumes can use two sediment-supply methods: an imposed feed at the upstream end or recirculation of sediment from the downstream end to the upstream end. These methods generally produce similar equilibrium bed morphology, but temporal evolution c...

  8. Aeolian sediment transport over gobi: Field studies atop the Mogao Grottoes, China

    Science.gov (United States)

    Tan, Lihai; Zhang, Weimin; Qu, Jianjun; Wang, Junzhan; An, Zhishan; Li, Fang

    2016-06-01

    This paper reports on field studies of aeolian sediment transport over a rough surface-gobi atop the Mogao Grottoes, China, in relation to sediment entrainment, saltation mass flux and transport rate prediction. Wind speeds were measured with five cup anemometers at different heights and sediment entrainment and transport measured with horizontal and vertical sediment traps coupled to weighing sensors, where sediment entrainment and transport were measured synchronously with wind speeds. Four sediment transport events, with a measurement duration ranging between 2.5 and 11 h, were studied. The entrainment threshold determined by the horizontal sediment trap varied between 0.28 and 0.33 m s-1, and the effect of non-erodible roughness elements-gravels increased the entrainment threshold approximately by 1.8 times compared to a uniform sand surface. Unlike the non-monotone curve shape of sediment flux density profile over gobi measured in wind tunnels, the flux density profile measured in the field showed an exponential form. Aeolian sediment transport over gobi could be predicted by an Owen-type saltation model: q = Aρ /gu∗ (u∗2- u∗t2), where q is sediment transport rate, A is a soil-related dimensionless factor, u∗ is the friction velocity, u∗t is the threshold friction velocity, g is the gravitational acceleration, ρ is the air density. This study indicates that the sediment flux sampling using horizontal and vertical sediment traps coupled to weighing sensors provides a practical method to determine values for A in this model that can provide good estimates of sediment transport rates in gobi areas.

  9. Sediment transport on Cape Sable, Everglades National Park, Florida

    Science.gov (United States)

    Zucker, Mark; Boudreau, Carrie

    2010-01-01

    The Cape Sable peninsula is located on the southwestern tip of the Florida peninsula within Everglades National Park (ENP). Lake Ingraham, the largest lake within Cape Sable, is now connected to the Gulf of Mexico and western Florida Bay by canals built in the early 1920's. Some of these canals breached a natural marl ridge located to the north of Lake Ingraham. These connections altered the landscape of this area allowing for the transport of sediments to and from Lake Ingraham. Saline intrusion into the formerly fresh interior marsh has impacted the local ecology. Earthen dams installed in the 1950's and 1960's in canals that breached the marl ridge have repeatedly failed. Sheet pile dams installed in the early 1990's subsequently failed resulting in the continued alteration of Lake Ingraham and the interior marsh. The Cape Sable Canals Dam Restoration Project, funded by ENP, proposes to restore the two failed dams in Lake Ingraham. The objective of this study was to collect discharge and water quality data over a series of tidal cycles and flow conditions to establish discharge and sediment surrogate relations prior to initiating the Cape Sable Canals Dam Restoration Project. A dry season synoptic sampling event was performed on April 27-30, 2009.

  10. Analogue White Hole Horizon and its Impact on Sediment Transport

    CERN Document Server

    Chatterjee, Debasmita; Ghosh, Subir; Mazumder, B S

    2015-01-01

    Motivated by the ideas of analogue gravity, we have performed experiments in a flume where an analogue White Hole horizon is generated, in the form of a wave blocking region, by suitably tuned uniform fluid (water) flow and counter-propagating shallow water waves. We corroborate earlier experimental observations by finding a critical wave frequency for a particular discharge above which the waves are effectively blocked beyond the horizon. An obstacle, in the form of a bottom wave, is introduced to generate a sharp blocking zone. All previous researchers used this obstacle. A novel part of our experiment is where we do not introduce the obstacle and find that wave blocking still takes place, albeit in a more diffused zone. Lastly we replace the fixed bottom wave obstacle by a movable sand bed to study the sediment transport and the impact of the horizon or wave blocking phenomenon on the sediment profile. We find signatures of the wave blocking zone in the ripple pattern.

  11. Numerical Simulation of Flow and Suspended Sediment Transport in the Distributary Channel Networks

    Directory of Open Access Journals (Sweden)

    Wei Zhang

    2014-01-01

    Full Text Available Flow and suspended sediment transport in distributary channel networks play an important role in the evolution of deltas and estuaries, as well as the coastal environment. In this study, a 1D flow and suspended sediment transport model is presented to simulate the hydrodynamics and suspended sediment transport in the distributary channel networks. The governing equations for river flow are the Saint-Venant equations and for suspended sediment transport are the nonequilibrium transport equations. The procedure of solving the governing equations is firstly to get the matrix form of the water level and suspended sediment concentration at all connected junctions by utilizing the transformation of the governing equations of the single channel. Secondly, the water level and suspended sediment concentration at all junctions can be obtained by solving these irregular spare matrix equations. Finally, the water level, discharge, and suspended sediment concentration at each river section can be calculated. The presented 1D flow and suspended sediment transport model has been applied to the Pearl River networks and can reproduce water levels, discharges, and suspended sediment concentration with good accuracy, indicating this that model can be used to simulate the hydrodynamics and suspended sediment concentration in the distributary channel networks.

  12. Rheology of sediment transported by a laminar flow

    Science.gov (United States)

    Houssais, M.; Ortiz, C. P.; Durian, D. J.; Jerolmack, D. J.

    2016-12-01

    Understanding the dynamics of fluid-driven sediment transport remains challenging, as it occurs at the interface between a granular material and a fluid flow. Boyer, Guazzelli, and Pouliquen [Phys. Rev. Lett. 107, 188301 (2011)], 10.1103/PhysRevLett.107.188301 proposed a local rheology unifying dense dry-granular and viscous-suspension flows, but it has been validated only for neutrally buoyant particles in a confined and homogeneous system. Here we generalize the Boyer, Guazzelli, and Pouliquen model to account for the weight of a particle by addition of a pressure P0 and test the ability of this model to describe sediment transport in an idealized laboratory river. We subject a bed of settling plastic particles to a laminar-shear flow from above, and use refractive-index-matching to track particles' motion and determine local rheology—from the fluid-granular interface to deep in the granular bed. Data from all experiments collapse onto a single curve of friction μ as a function of the viscous number Iv over the range 3 ×10-5 ≤Iv≤2 , validating the local rheology model. For Iv<3 ×10-5 , however, data do not collapse. Instead of undergoing a jamming transition with μ →μs as expected, particles transition to a creeping regime where we observe a continuous decay of the friction coefficient μ ≤μs as Iv decreases. The rheology of this creep regime cannot be described by the local model, and more work is needed to determine whether a nonlocal rheology model can be modified to account for our findings.

  13. Monte Carlo path sampling approach to modeling aeolian sediment transport

    Science.gov (United States)

    Hardin, E. J.; Mitasova, H.; Mitas, L.

    2011-12-01

    Coastal communities and vital infrastructure are subject to coastal hazards including storm surge and hurricanes. Coastal dunes offer protection by acting as natural barriers from waves and storm surge. During storms, these landforms and their protective function can erode; however, they can also erode even in the absence of storms due to daily wind and waves. Costly and often controversial beach nourishment and coastal construction projects are common erosion mitigation practices. With a more complete understanding of coastal morphology, the efficacy and consequences of anthropogenic activities could be better predicted. Currently, the research on coastal landscape evolution is focused on waves and storm surge, while only limited effort is devoted to understanding aeolian forces. Aeolian transport occurs when the wind supplies a shear stress that exceeds a critical value, consequently ejecting sand grains into the air. If the grains are too heavy to be suspended, they fall back to the grain bed where the collision ejects more grains. This is called saltation and is the salient process by which sand mass is transported. The shear stress required to dislodge grains is related to turbulent air speed. Subsequently, as sand mass is injected into the air, the wind loses speed along with its ability to eject more grains. In this way, the flux of saltating grains is itself influenced by the flux of saltating grains and aeolian transport becomes nonlinear. Aeolian sediment transport is difficult to study experimentally for reasons arising from the orders of magnitude difference between grain size and dune size. It is difficult to study theoretically because aeolian transport is highly nonlinear especially over complex landscapes. Current computational approaches have limitations as well; single grain models are mathematically simple but are computationally intractable even with modern computing power whereas cellular automota-based approaches are computationally efficient

  14. Numerical Model of Turbulence, Sediment Transport, and Sediment Cover in a Large Canyon-Bound River

    Science.gov (United States)

    Alvarez, L. V.; Schmeeckle, M. W.

    2013-12-01

    The Colorado River in Grand Canyon is confined by bedrock and coarse-grained sediments. Finer grain sizes are supply limited, and sandbars primarily occur in lateral separation eddies downstream of coarse-grained tributary debris fans. These sandbars are important resources for native fish, recreational boaters, and as a source of aeolian transport preventing the erosion of archaeological resources by gully extension. Relatively accurate prediction of deposition and, especially, erosion of these sandbar beaches has proven difficult using two- and three-dimensional, time-averaged morphodynamic models. We present a parallelized, three-dimensional, turbulence-resolving model using the Detached-Eddy Simulation (DES) technique. DES is a hybrid large eddy simulation (LES) and Reynolds-averaged Navier Stokes (RANS). RANS is applied to the near-bed grid cells, where grid resolution is not sufficient to fully resolve wall turbulence. LES is applied further from the bed and banks. We utilize the Spalart-Allmaras one equation turbulence closure with a rough wall extension. The model resolves large-scale turbulence using DES and simultaneously integrates the suspended sediment advection-diffusion equation. The Smith and McLean suspended sediment boundary condition is used to calculate the upward and downward settling of sediment fluxes in the grid cells attached to the bed. The model calculates the entrainment of five grain sizes at every time step using a mixing layer model. Where the mixing layer depth becomes zero, the net entrainment is zero or negative. As such, the model is able to predict the exposure and burial of bedrock and coarse-grained surfaces by fine-grained sediments. A separate program was written to automatically construct the computational domain between the water surface and a triangulated surface of a digital elevation model of the given river reach. Model results compare favorably with ADCP measurements of flow taken on the Colorado River in Grand Canyon

  15. Principles and approaches for numerical modelling of sediment transport in sewers

    DEFF Research Database (Denmark)

    Mark, Ole; Larsen, Torben; Appelgren, Cecilia

    1994-01-01

    A study has been carried out at the University of Aalborg, Denmark and VBB VIAK, Sweden with the objectives to describe the effect of sediment deposits on the hydraulic capacity of sewer systems and to investigate the sediment transport in sewer systems. A results of the study is a mathematical...... model MOUSE ST which describes the sediment transport in sewers. This paper discusses the applicability and the limitations of various modelling approaches and sediment transport formulations in MOUSE ST. The study was founded by the Swedish Water and Waste Works Association and the Nordic Industrial...

  16. A COMPARATIVE STUDY OF SOME OF THE SEDIMENT TRANSPORT EQUATIONS FOR AN ALLUVIAL CHANNEL WITH DUNES

    Directory of Open Access Journals (Sweden)

    Vajapeyam Srirangachar Srinivasan

    2008-06-01

    Full Text Available The present work is a comparative evaluation of some of the well known sediment transport equations for the condition of dunes on the bed. It is fairly clear that no single equation provides reliable estimates of the total load of sediment transported for all types of bed forms. The most frequently occurring bed form being dunes, only this case is considered in this paper. The measurements of sediment transport were realized in the laboratory for various sediment sizes, utilizing a computerized tilting recirculation flume. The Yang equation (1973 was found to provide the best results for dunes.

  17. Sediment Transport Model For Storm Sewer Networks Towards The Operational Risks

    Directory of Open Access Journals (Sweden)

    I. RÁTKY

    2016-11-01

    Full Text Available Sediment transport in sewer networks can be critical in economical and safety point of view. To improve the operation of the sewer networks we are presenting a model, which is capable of numerical simulations of the sediment transport in storm water network. The developed model is calculating the change of the particle distribution of the sediment fractions including the effects of settling and mixing up processes. The results of the model calculations in a simplified network are also presented. We are also planning to apply the developed sediment transport module by coupling to a hydrodynamic simulation for practical tasks supporting the design and operation of sewers networks.

  18. Principles and Approaches for Numerical Modelling of Sediment Transport in Sewers

    DEFF Research Database (Denmark)

    Mark, Ole; Appelgren, Cecilia; Larsen, Torben

    1995-01-01

    A study has been carried out with the objectives of describing the effect of sediment deposits on the hydraulic capacity of sewer systems and to investigate the sediment transport in sewer systems. A result of the study is a mathematical model MOUSE ST which describes sediment transport in sewers....... This paper discusses the applicability and the limitations of various modelling approaches and sediment transport formulations in in MOUSE ST. Further, the paper presents a simple application of MOUSE ST to the Rya catchment in Gothenburg, Sweden....

  19. A hybrid model of swash-zone longshore sediment transport on refelctive beaches

    NARCIS (Netherlands)

    Jiang, A.W.; Hughes, M.; Cowell, P.; Gordon, A.; Savioli, J.C.; Ranasinghe, R.W.M.R.J.B.

    2010-01-01

    The hydrodynamics and sediment transport in the swash zone is currently outside the domain of coastal-area models, which is a significant limitation in obtaining littoral sediment-transport estimates, especially on steep reflective beaches where the waves practically break on the beachface. In this

  20. Cross-shore sediment transport; analysis of Delta Flume data and mathematical modelling

    NARCIS (Netherlands)

    Zhang, C.

    1994-01-01

    In the last decade, several mathematical models for cross-shore sediment transport have been developed under the assumption that the instantaneous sediment transport is directly related to the instantaneous horizontal velocity just above the boundary layer. Although some models took beach slopes

  1. Distribution of longshore sediment transport along the Indian coast based on empirical model

    Digital Repository Service at National Institute of Oceanography (India)

    Chandramohan, P.; Nayak, B.U.

    An empirical sediment transport model has been developed based on longshore energy flux equation. Study indicates that annual gross sediment transport rate is high (1.5 x 10 super(6) cubic meters to 2.0 x 10 super(6) cubic meters) along the coasts...

  2. A hybrid model of swash-zone longshore sediment transport on refelctive beaches

    NARCIS (Netherlands)

    Jiang, A.W.; Hughes, M.; Cowell, P.; Gordon, A.; Savioli, J.C.; Ranasinghe, R.W.M.R.J.B.

    2010-01-01

    The hydrodynamics and sediment transport in the swash zone is currently outside the domain of coastal-area models, which is a significant limitation in obtaining littoral sediment-transport estimates, especially on steep reflective beaches where the waves practically break on the beachface. In this

  3. Cross-shore sediment transport; analysis of Delta Flume data and mathematical modelling

    NARCIS (Netherlands)

    Zhang, C.

    1994-01-01

    In the last decade, several mathematical models for cross-shore sediment transport have been developed under the assumption that the instantaneous sediment transport is directly related to the instantaneous horizontal velocity just above the boundary layer. Although some models took beach slopes int

  4. EVALUATION OF THE STATE-OF-THE-ART CONTAMINATED SEDIMENT TRANSPORT AND FATE MODELING SYSTEM

    Science.gov (United States)

    Modeling approaches for evaluating the transport and fate of sediment and associated contaminants are briefly reviewed. The main emphasis is on: 1) the application of EFDC (Environmental Fluid Dynamics Code), the state-of-the-art contaminated sediment transport and fate public do...

  5. The effect of sediment transport on eelgrass development – and vice versa

    NARCIS (Netherlands)

    Dijkstra, J.T.

    2007-01-01

    By changing flow patterns and sediment transport, aquatic vegetation can affect the development of estuarine bed topography. Besides, since the sediment transport also determines the amount of light available for photosynthetic growth, the presence of vegetation can also affect its own development.

  6. Large River Sediment Transport and Deposition: An Annotated Bibliography.

    Science.gov (United States)

    1998-04-01

    Keywords: Measurement, navigation, river, sediment, suspended sediment AHEARN, S. C, R. D. MARTIN , AND J. H. WLOSINSKI. 1989. Recommendations for...patterns. Keywords: Climate, discharge, Mississippi River, precipitation, river 130. KEOWN , M. P. 1977. Inventory of sediment sample collection...suspended sediment 131. KEOWN , M. P. 1986. Historic trends in the sediment flow regime of the Mississippi River. U.S. Army Corps of Engineers Waterways

  7. Exploring the effects of hydrograph shape on unimodal and bimodal sediment mixtures.

    Science.gov (United States)

    Phillips, C. B.; Singer, M. B.; Hill, K. M.; Paola, C.

    2016-12-01

    Under steady flow within a river the rate of bed load transport has been shown to vary both spatially and temporally due to various hydrologic and granular phenomena. Variability within particle size distributions and their spatial arrangement on the river bed (e.g. armoring, segregation) has been observed to affect the flux for a particular value of the applied flow stress, while hydrology is primarily assumed to control the magnitude of applied bed stress. Prediction of bed load transport in natural rivers is further complicated due to the inherent transience within a flood hydrograph, however relatively little is known about how flood transience, intermittence and/or unsteadiness in flow, differs from steady flow. Here we investigate the role of flood transience for unimodal and bimodal bed load sediment transport through controlled laboratory flume experiments under the conditions of constant sediment feed with steady and unsteady flow. Experimental runs consist of sequences of steady or unsteady flood hydrographs with a variety of competent flow durations and peak stress magnitudes for both a unimodal and bimodal particle size distribution. We demonstrate for the unimodal sediment mixture that the total bed load flux for a flood scales linearly with the integrated excess transport capacity for both steady and unsteady flow, in agreement with prior field scale results. This indicates that to a first order the effects of flow unsteadiness and granular interactions are minimal for determining the bulk transport. Interestingly and in contrast to the unimodal mixture, the bimodal mixture behaves differently under steady and unsteady flow hydrographs, where unsteady flow conditions promote both greater degrees of armoring, bed patchiness, and size selective transport. We find that even under steady flow conditions the total flux output for the bimodal mixture can vary by a factor of five and depends strongly on the local bed state. These results suggest a surprising

  8. Improving Sediment Transport Prediction by Assimilating Satellite Images in a Tidal Bay Model of Hong Kong

    Directory of Open Access Journals (Sweden)

    Peng Zhang

    2014-03-01

    Full Text Available Numerical models being one of the major tools for sediment dynamic studies in complex coastal waters are now benefitting from remote sensing images that are easily available for model inputs. The present study explored various methods of integrating remote sensing ocean color data into a numerical model to improve sediment transport prediction in a tide-dominated bay in Hong Kong, Deep Bay. Two sea surface sediment datasets delineated from satellite images from the Moderate Resolution Imaging Spectra-radiometer (MODIS were assimilated into a coastal ocean model of the bay for one tidal cycle. It was found that remote sensing sediment information enhanced the sediment transport model ability by validating the model results with in situ measurements. Model results showed that root mean square errors of forecast sediment both at the surface layer and the vertical layers from the model with satellite sediment assimilation are reduced by at least 36% over the model without assimilation.

  9. Mathematical model for interactions and transport of phosphorus and sediment in the Three Gorges Reservoir.

    Science.gov (United States)

    Huang, Lei; Fang, Hongwei; Reible, Danny

    2015-11-15

    Phosphorus fate and transport in natural waters plays a crucial role in the ecology of rivers and reservoirs. In this paper, a coupled model of hydrodynamics, sediment transport, and phosphorus transport is established, in which the effects of sediment on phosphorus transport are considered in detail. Phosphorus adsorption is estimated using a mechanistic surface complexation model which is capable of simulating the adsorption characteristics under various aquatic chemistry conditions. The sediment dynamics are analyzed to evaluate the deposition and release of phosphorus at the bed surface. In addition, the aerobic layer and anaerobic layer of the sediments are distinguished to study the distribution of phosphorus between dissolved and particulate phases in the active sediment layer. The proposed model is applied to evaluate the effects of various operating rules on sediment and phosphorus retention in the Three Gorges Reservoir (TGR). Results show that the proposed model can reasonably reflect the phosphorus transport with sediment, and management scenarios that influence sediment retention will also influence the phosphorus balance in the TGR. However, modest operational changes which have only minor effects on sediment retention also have limited influence on the phosphorous balance. Copyright © 2015 Elsevier Ltd. All rights reserved.

  10. Longterm Measurements of Bedload-Transport in alpine Catchments

    Science.gov (United States)

    Achleitner, Stefan; Kammerlander, Johannes; Eichner, Bernhard; Schöber, Johannes; Chiari, Michael

    2016-04-01

    In recent years the necessity of predicting the long-term behavior of sediment transport has increased. On the one hand, the effects of technical measures (e.g. retaining measures, hydropower, etc.) in the natural system are to be evaluated. On the other hand long term ecological studies that are strongly linked to the sediment budgets and its variation are more and more evolving. The ACRP Project DevoBeta-CC addresses the dynamics of long term sediment transport dynamics and its temporal altering. The focus is put on smaller tributary catchments enabling the model development. In total the data from ten catchments connected to the hydropower station Kaunertal (Tyrol/Austria) and eleven catchments linked to the power plant group Sellrain-Silz (Tyrol/Austria) are available. The considered catchments vary regarding their characteristics such as size (3 km³ to 27 km²), glaciation (0 % to 53 %), mean catchment slope (53 % to 92 %) and mean channel gradient (4 % to 49 %). The main data basis are records from the water intake structures operated (partly since 1965) by the TIWAG (Tiroler Wasserkraft AG). The sedimentation dynamics and operational flushings of the connected settling basins are used to measure the transported sediments. Since 1985 even high resolution data (15min intervals) are available. At selected catchments, the operationally recorded data (flushings, load membrane measurements,...) are verified within measuring campaigns using bed load traps upstream. Further, the sedimentation dynamics and grain size distributions in the settling basins are evaluated. Therefor two water intakes were put temporally out of operation, allowing an improved measurement of settled volumes by means of terrestrial surveying. Uncertainty assessments reveal an overall accuracy of estimated annual bed load volumes lower than a factor of two. Additionally, the data set enables to address sediment transport at a sub-annual basis, hence, the presented data set is unique regarding

  11. Modelling the erosive effects of sewer flushing using different sediment transport formulae.

    Science.gov (United States)

    Shirazi, R H S M; Campisano, A; Modica, C; Willems, P

    2014-01-01

    A numerical investigation to simulate the cleaning effects of successive flushes over sediment beds in prismatic channels is presented in this paper. The 1D De Saint Venant-Exner equations were used to describe the temporal evolution of the sediment bed after each flush. The predictive capacity of two sediment transport formulae was explored against experimental results from laboratory tests. Results show that the adopted model can successfully describe the evolution of the sediment bed due to the flushes exerted during the experiments, with differences between the used transport formulae depending on the channel invert slope and on the flush energy.

  12. Quantifying fluvial sediment transport in a mountain catchment (Schöttlbach, Styria) using sediment impact sensors

    Science.gov (United States)

    Stangl, Johannes; Sass, Oliver; Schneider, Josef; Harb, Gabriele

    2013-04-01

    Sediment transport in river systems, being the output of geomorphic processes in the catchment, is a recurrent problem for geomorphological sediment budget studies, natural hazard assessment and river engineering. Sediment budgets of alpine catchments are likely to be modified by changing total precipitation and the probability of heavy precipitation events in the context of climate change, even if projections of precipitation change for Austria and the entire Alpine region are still very uncertain. Effective sediment management requires profound knowledge on the sediment cascade in the head-waters. However, bedload measurements at alpine rivers or torrents are rare; in Styria, they are altogether missing. Due to a three hour heavy rainfall event on 07-Jul 2011, which caused cata-strophic flooding with massive damage in the city of Oberwölz and its surrounding, we chose the catchment area of the Schöttlbach in the upper Mur river valley in Styria (Austria) as our study area. In the framework of the ClimCatch project, we intend to develop a conceptual model of coupled and decoupled sediment routing to quantify the most prominent sediment fluxes and sediment sinks, combining up-to-date geomorphological and river engineering techniques. Repeated Airborne Laser Scans will provide an overview of ongoing processes, diachronous TLS surveys (cut-and-fill analysis), ground-penetrating radar and 2D-geoelectric surveys should quantity the most important mass fluxes on the slopes and in the channels and derive a quantitative sediment budget, including the volume of temporary sediment stores. Besides quantifying slope processes, sediment sinks and total sediment output, the sediment trans-port in the torrents is of particular interest. We use sediment impact sensors (SIS) which were in-stalled in several river sections in the main stretch of the Schöttlbach and in its tributaries. The SIS mainly consists of two parts connected by a coated cable, the steel shell with the

  13. Applicative limitations of sediment transport on predictive modeling in geomorphology

    Institute of Scientific and Technical Information of China (English)

    WEIXiang; LIZhanbin

    2004-01-01

    Sources of uncertainty or error that arise in attempting to scale up the results of laboratory-scale sediment transport studies for predictive modeling of geomorphic systems include: (i) model imperfection, (ii) omission of important processes, (iii) lack of knowledge of initial conditions, (iv) sensitivity to initial conditions, (v) unresolved heterogeneity, (vi) occurrence of external forcing, and (vii) inapplicability of the factor of safety concept. Sources of uncertainty that are unimportant or that can be controlled at small scales and over short time scales become important in large-scale applications and over long time scales. Control and repeatability, hallmarks of laboratory-scale experiments, are usually lacking at the large scales characteristic of geomorphology. Heterogeneity is an important concomitant of size, and tends to make large systems unique. Uniqueness implies that prediction cannot be based upon first-principles quantitative modeling alone, but must be a function of system history as well. Periodic data collection, feedback, and model updating are essential where site-specific prediction is required.

  14. Implications of sediment transport by subglacial water flow for interpreting contemporary glacial erosion rates

    Science.gov (United States)

    Beaud, Flavien; Flowers, Gwenn E.; Venditti, Jeremy G.

    2017-04-01

    The role of glaciers in landscape evolution is central to the interactions between climate and tectonic forces at high latitudes and in mountainous regions. Sediment yields from glacierized basins are used to quantify contemporary erosion rates on seasonal to decadal timescales, often under the assumption that subglacial water flow is the main contributor to these yields. Two recent studies have furthermore used such sediment fluxes to calibrate a glacial erosion rule, where erosion rate scales with ice sliding speed raised to a power greater than one. Subglacial sediment transport by water flow has however seldom been studied, thus the controls on sediment yield from glacierized basins remain enigmatic. To bridge this gap, we develop a 1-D model of morphodynamics in semi-circular bedrock-floored subglacial channels. We adapt a sediment conservation law from the fluvial literature, developed for both mixed bedrock / alluvial and alluvial conditions, to subglacial channels. Channel evolution is a function of the traditional melt-opening due to viscous heat dissipation from the water flow, and creep closure of the overlying ice, to which we add the closure or enlargement due to sediment deposition or removal, respectively. Using a simple ice geometry representing a land-terminating glacier, we find that the shear stresses produced by the water flow on the bed decrease significantly near the terminus. As the ice thins, creep closure decreases and large hydraulic potential gradients cannot be sustained. The resulting gradients in sediment transport lead to a bottleneck, and sediment accumulates if the sediment supply is adequate. A similar bottleneck occurs if a channel is well established and water discharge drops. Whether such constriction happens in space of time, in the presence of a sufficiently large sediment supply sediment accumulates temporarily near the terminus, followed shortly thereafter by enhanced sediment transport. Reduction in the cross-sectional area

  15. Engineering Modeling of Wave-Related Suspended Sediment Transport Over Ripples

    CERN Document Server

    Absi, Rafik

    2011-01-01

    The aim of our study is to improve the description of suspended sediment transport over wave ripples. We will first show the importance of sediment diffusivity with convective transfer (hereafter called) which is different from the sediment diffusivity associated to turbulent flux . It is possible to interpret concentration profiles, in semi-log plots, thanks to a relation between second derivative of the logarithm of concentration and derivative of (Absi, 2010). An analytical profile for will be presented and validated by experimental data obtained by Thorne et al. (2009) for medium sand. The proposed profile allows a good description of suspended sediment concentrations for fine and coarse sediments.

  16. Quantifying the relative importance of flow regulation and grain size regulation of suspended sediment transport α and tracking changes in grain size of bed sediment β

    Science.gov (United States)

    Rubin, David M.; Topping, David J.

    2001-01-01

    To predict changes in sediment transport, it is essential to know whether transport is regulated mainly by changes in flow or by changes in grain size of sediment on the bed. In flows where changes in suspended sediment transport are regulated purely by changes in flow (grain size of bed sediment is constant), increases in flow strength cause increases in both concentration and grain size of sediment in suspension (because stronger flows are able to suspend more sediment and coarser grains). Under this constraint of constant grain size of bed sediment concentration and median diameter of suspended sediment are positively correlated. In contrast, where transport is regulated purely by changes in grain size of sediment on the bed, concentration and median diameter of suspended sediment are negatively correlated (because increasing the median diameter of the bed sediment causes the concentration to decrease while causing the median grain size in suspension to increase). Where both flow strength and grain size on the bed are free to vary, the relation between concentration and grain size in suspension can be used to quantify the importance of grain size regulation relative to flow regulation of sediment transport, a measure defined as α. To predict sediment transport in systems that are regulated dominantly by changes in grain size on the bed, it is more useful to measure sediment input events or changes in grain size on the bed than to measure changes in flow. More commonly, grain size of bed sediment may be secondary to flow in regulating transport but may, nevertheless, be important. The relative coarseness of bed sediment (β) can be measured directly or, like α, can be calculated from measurements of concentration and grain size of suspended sediment.

  17. Quantifying the relative importance of flow regulation and grain size regulation of suspended sediment transport a and tracking changes in grain size of bed sediment B

    Science.gov (United States)

    Rubin, David M.; Topping, David J.

    2001-01-01

    To predict changes in sediment transport, it is essential to know whether transport is regulated mainly by changes in flow or by changes in grain size of sediment on the bed. In flows where changes in suspended sediment transport are regulated purely by changes in flow (grain size of bed sediment is constant), increases in flow strength cause increases in both concentration and grain size of sediment in suspension (because stronger flows are able to suspend more sediment and coarser grains). Under this constraint of constant grain size of bed sediment concentration and median diameter of suspended sediment are positively correlated. In contrast, where transport is regulated purely by changes in grain size of sediment on the bed, concentration and median diameter of suspended sediment are negatively correlated (because increasing the median diameter of the bed sediment causes the concentration to decrease while causing the median grain size in suspension to increase). Where both flow strength and grain size on the bed are free to vary, the relation between concentration and grain size in suspension can be used to quantify the importance of grain size regulation relative to flow regulation of sediment transport, a measure defined as α. To predict sediment transport in systems that are regulated dominantly by changes in grain size on the bed, it is more useful to measure sediment input events or changes in grain size on the bed than to measure changes in flow. More commonly, grain size of bed sediment may be secondary to flow in regulating transport but may, nevertheless, be important. The relative coarseness of bed sediment (β) can be measured directly or, like α, can be calculated from measurements of concentration and grain size of suspended sediment.

  18. Predictability of sediment transport in the Yellow River using selected transport formulas

    Institute of Scientific and Technical Information of China (English)

    Baosheng WU; D.S.van MAREN; Lirigyun LI

    2008-01-01

    This paper evaluates the applicability of the sediment transport methods developed by Engelund and Hansen,Ackers and White,Yang et al.,and van Rijn,together with the Wuhan methods developed in China,to the Yellow River,which has highly concentrated and fine-grained sediment.The sediment data includes over 1000 observations from the Yellow River,32 sets of data from a canal,and 266 sets of data from laboratory flumes.The best predictions were obtained by the Yang 1996 method,the Wuhan method,and the modified Wuhan method by Wu and Long,while reasonably good predictions were also provided by the van Rijn 2004 method.The Engelund and Hansen,the Aekers and White,and the van Rijn 1984 methods in their original forms are not applicable to the Yellow River.The predicted results for total load concentrations were as good as for bed-material concentrations,even though the total load includes a large portion of wash load.

  19. Acoustical and optical backscatter measurements of sediment transport in the 1988 1989 STRESS experiment

    Science.gov (United States)

    Lynch, J. F.; Gross, T. F.; Sherwood, C. R.; Irish, J. D.; Brumley, B. H.

    1997-04-01

    During the 1988-1989 Sediment Transport Events on Shelves and Slopes (STRESS) experiment, a 1-MHz acoustic backscatter system (ABSS), deployed in 90 m of water off the California coast measured vertical profiles of suspended sediment concentration from 1.5 to (nominally) 26 meters above bottom (m.a.b.). An 8-week-long time series was obtained, showing major sediment transport events (storms) in late December and early January. Comparison of the acoustics measurements from 1.5 m.a.b. are made with optical backscatter system (OBS) concentration estimates lower in the boundary layer (0.25 m.a.b.). Correlations between ABSS and OBS concentration measurements and the boundary layer forcing functions (waves, currents, and their non-linear interaction) provided a variety of insights into the nature of the sediment transport of the STRESS site. Transport rates and integrated transport are seen to be dominated by the largest storm events.

  20. Transport of Algal Cells in Hyporheic Sediments of the River Elbe (Germany)

    Science.gov (United States)

    Kloep, Frank; Röske, Isolde

    2004-01-01

    The advective transport of algal cells into the interstices of the hyporheic zone of the River Elbe was spatially and temporally heterogenous. Even deep sediment layers were reached by large phytoplankton species. Therefore, it is suggested that (i) the advective interstitial transport patterns vary between different algal sizes and morphotypes and (ii) sediment characteristics, expressed by the permeability coefficient kf of porous media, affect retention and retardation of surface water algae during subsurface transport. The transport behaviour of different green algae (Chlorella sp., Scenedesmus acuminatus, Desmodesmus communis, and Pediastrum duplex) and algal sized microspheres was tested in flow-through column experiments with hyporheic sediments. The algal cell transport was directly related to the permeability of the column sediments. (

  1. Large-scale quantification of suspended sediment transport and deposition in the Mekong Delta

    Directory of Open Access Journals (Sweden)

    N. V. Manh

    2014-04-01

    Full Text Available Sediment dynamics play a major role for the agricultural and fishery productivity of the Mekong Delta. However, the understanding of sediment dynamics in the Mekong Delta, one of the most complex river deltas in the world, is very limited. This is a consequence of its large extent, the intricate system of rivers, channels and floodplains and the scarcity of observations. This study quantifies, for the first time, the suspended sediment transport and sediment-nutrient deposition in the whole Mekong Delta. To this end, a quasi-2-D hydrodynamic model is combined with a cohesive sediment transport model. The combined model is calibrated automatically using six objective functions to represent the different aspects of the hydraulic and sediment transport components. The model is calibrated for the extreme flood season in 2011 and shows good performance for the two validation years with very different flood characteristics. It is shown how sediment transport and sediment deposition vary from Kratie at the entrance of the Delta to the coast. The main factors influencing the spatial sediment dynamics are the setup of rivers, channels and dike-rings, the sluice gate operations, the magnitude of the floods and tidal influences. The superposition of these factors leads to high spatial variability of sediment transport, in particular in the Vietnamese floodplains. Depending on the flood magnitude, the annual sedimentation rate averaged over the Vietnamese floodplains varies from 0.3 to 2.1 kg m−2 yr−1, and the ring dike floodplains trap between 1 and 6% of the total sediment load at Kratie. This is equivalent to 29 × 103–440 × 103 t of nutrients (N, P, K, TOC deposited in the Vietnamese floodplains. This large-scale quantification provides a basis for estimating the benefits of the annual Mekong floods for agriculture and fishery, and is important information for assessing the effects of deltaic subsidence and climate change related sea level rise.

  2. The transport and fate of riverine fine sediment exported to a semi-open system

    Science.gov (United States)

    Delandmeter, Philippe; Lewis, Stephen E.; Lambrechts, Jonathan; Deleersnijder, Eric; Legat, Vincent; Wolanski, Eric

    2015-12-01

    Understanding the transport and fate of suspended sediment exported by rivers is crucial for the management of sensitive marine ecosystems. Sediment transport and fate can vary considerably depending on the geophysical characteristics of the coastal environment. Fine sediment transport was studied in a setting in between "open" (uninterrupted coasts) and "semi-enclosed" (bays) coastal systems, namely a "semi-open" system of shallow coastal water with long (˜20 km) stretches of open coasts separated by capes and headlands. The case study was the large, seasonal, Burdekin River that discharges to a wide continental shelf containing headlands and shallow embayments adjacent to the Great Barrier Reef, Australia. A new three-dimensional fine sediment module for the unstructured-mesh SLIM 3D hydrodynamic model was developed. The model was successfully validated against available field data. The results were compared to previous studies on the Burdekin River sediment transport and differences were analysed. Wind direction and speed during river floods largely control the dynamics and the fate of the fine sediment. Most (67% for 2007) of the riverine fine sediment load is deposited near the river mouth; the remaining sediment is transported further afield in a riverine freshwater plume; that sediment can reach sensitive marine ecosystems and should be a priority for management. During the rest of the year, when the river flow has ceased, wind-driven resuspension events redistribute the deposited sediment within embayments but generate negligible longshore transport. This study suggests that semi-open systems trap most of the riverine fine sediment, somewhat like semi-enclosed systems.

  3. Changes in sediment transport in the Kuye River in the Loess Plateau in China

    Institute of Scientific and Technical Information of China (English)

    Jueyi SUI; Yun HE; Cheng LIU

    2009-01-01

    In this paper, the changes in sediment transport over 51 years from 1955 to 2006 in the Kuye River in the Loess Plateau in China are assessed. Key factors affecting sediment yield and sediment transport, such as precipitation depth, discharge, and human activities are studied. To investigate the changes in sediment yield in this watershed, a trend analysis on sediment concentration, precipitation depth, and discharge is conducted. Precipitation depths at 2 Climate Stations (CSs), as well as discharge and sediment transport at 3 Gauging Stations (GSs) are used to assess the features of sediment transport in the Kuye River. The runoff modulus (defined as the annual average discharge per unit area, L/(s'km2)) and the sediment transport modulus (defined as the annual suspended sediment transport per unit area, t/(yr km2)) are introduced in this study to assess the changes in runoff and sediment yield for this watershed. The results show that the highest average monthly discharge during the study period in the Kuye River is 66.23 m3/s in August with an average monthly sediment concentration of 88.9 kg/m3. However, the highest average monthly sediment concentration during the study period in the Kuye River is 125.34 kg/m3 and occurs in July, which has an average discharge of 42.6 m3/s that is much less than the average monthly discharge in August. It is found that both the runoff modulus and sediment transport modulus at Wenjiachuan GS on the Kuye River has a clear downward trend. During the summer season from July to August, the sediment transport modulus at Wenjiachuan GS is much higher than those at Toudaoguai and Longmen GSs on the Yellow River. The easily erodible loess in the Kuye River watershed and the sparse vegetation are responsible for the extremely high sediment yield from the Kuye River watershed. The analyses of the grain size distribution of suspended load in the Kuye River are presented. The average monthly median grain size of suspended load in the Kuye

  4. The reason why sediment transport in a Newtonian fluid behaves analogous to sliding friction

    CERN Document Server

    Pähtz, Thomas

    2016-01-01

    The old idea of Bagnold to describe sediment transport in Newtonian fluids by a constant friction coefficient $\\mu_b$ at the bed surface has been an essential ingredient of many historical and modern theoretical attempts to derive predictions for the sediment transport rate. Here, using approximations validated through direct numerical simulations of sediment transport in Newtonian fluids, we analytically derive $\\mu_b\\approx\\mathrm{const}$ from microscopic Newtonian dynamics, linking the origin of friction to energy conversion processes during low-angle particle-bed impacts.

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

    Institute of Scientific and Technical Information of China (English)

    Jianjun ZHOU; Bingnan LIN

    2004-01-01

    Field data from the Lower Yellow River (LYR) covering a period of ten 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.

  6. A biogeochemical model of contaminant fate and transport in river waters and sediments.

    Science.gov (United States)

    Massoudieh, Arash; Bombardelli, Fabián A; Ginn, Timothy R

    2010-03-01

    A quasi-two-dimensional model is presented for simulating transport and transformation of contaminant species in river waters and sediments, taking into account the effect of both biotic and abiotic geochemical reactions on the contaminant fate and mobility. The model considers the downstream transport of dissolved and sediment-associated species, and the mass transfer with bed sediments due to erosion and resuspension, using linked advection-dispersion-reaction equations. The model also couples both equations to the reactive transport within bed sediment phases. This is done by the use of a set of vertical one-dimensional columns representing sediment layers that take into account the reactive transport of chemicals, burial, sorption/desorption to/from the solid phase, and the diffusive transport of aqueous species. Kinetically-controlled reversible solid-water mass exchange models are adopted to simulate interactions between suspended sediments and bulk water, as well as the mass exchange between bed sediments and pore water. An innovative multi-time step approach is used to model the fully kinetic nonlinear reaction terms using a non-iterative explicit method. This approach enables the model to handle fast and near-equilibrium reactions without a significant increase in computational burden. At the end, two demonstration cases are simulated using the model, including transport of a sorbing, non-reactive trace metal and nitrogen cycling, both in the Colusa Basin Drain in the Central Valley of California.

  7. Physical context for theoretical approaches to sediment transport magnitude-frequency analysis in alluvial channels

    Science.gov (United States)

    Sholtes, Joel; Werbylo, Kevin; Bledsoe, Brian

    2014-10-01

    Theoretical approaches to magnitude-frequency analysis (MFA) of sediment transport in channels couple continuous flow probability density functions (PDFs) with power law flow-sediment transport relations (rating curves) to produce closed-form equations relating MFA metrics such as the effective discharge, Qeff, and fraction of sediment transported by discharges greater than Qeff, f+, to statistical moments of the flow PDF and rating curve parameters. These approaches have proven useful in understanding the theoretical drivers behind the magnitude and frequency of sediment transport. However, some of their basic assumptions and findings may not apply to natural rivers and streams with more complex flow-sediment transport relationships or management and design scenarios, which have finite time horizons. We use simple numerical experiments to test the validity of theoretical MFA approaches in predicting the magnitude and frequency of sediment transport. Median values of Qeff and f+ generated from repeated, synthetic, finite flow series diverge from those produced with theoretical approaches using the same underlying flow PDF. The closed-form relation for f+ is a monotonically increasing function of flow variance. However, using finite flow series, we find that f+ increases with flow variance to a threshold that increases with flow record length. By introducing a sediment entrainment threshold, we present a physical mechanism for the observed diverging relationship between Qeff and flow variance in fine and coarse-bed channels. Our work shows that through complex and threshold-driven relationships sediment transport mode, channel morphology, flow variance, and flow record length all interact to influence estimates of what flow frequencies are most responsible for transporting sediment in alluvial channels.

  8. Past, present and prospect of an Artificial Intelligence (AI) based model for sediment transport prediction

    Science.gov (United States)

    Afan, Haitham Abdulmohsin; El-shafie, Ahmed; Mohtar, Wan Hanna Melini Wan; Yaseen, Zaher Mundher

    2016-10-01

    An accurate model for sediment prediction is a priority for all hydrological researchers. Many conventional methods have shown an inability to achieve an accurate prediction of suspended sediment. These methods are unable to understand the behaviour of sediment transport in rivers due to the complexity, noise, non-stationarity, and dynamism of the sediment pattern. In the past two decades, Artificial Intelligence (AI) and computational approaches have become a remarkable tool for developing an accurate model. These approaches are considered a powerful tool for solving any non-linear model, as they can deal easily with a large number of data and sophisticated models. This paper is a review of all AI approaches that have been applied in sediment modelling. The current research focuses on the development of AI application in sediment transport. In addition, the review identifies major challenges and opportunities for prospective research. Throughout the literature, complementary models superior to classical modelling.

  9. Transport of Gas and Solutes in Permeable Estuarine Sediments

    Science.gov (United States)

    2012-09-30

    document contains color images. 14. ABSTRACT 15. SUBJECT TERMS 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT SAR 18. NUMBER OF...Florida. The left pane represents sediment shortly after sunrise , the right pane sediment after 3 h sunshine. Red areas are areas of high acoustic...bubbles in stagnant water (blue circles) and sediment (red circles) from the study site. Dark colors indicate 10 ml gas volume, light colors 5 ml gas

  10. The importance of biotic entrainment for base flow fluvial sediment transport

    Science.gov (United States)

    Rice, Stephen P.; Johnson, Matthew F.; Mathers, Kate; Reeds, Jake; Extence, Chris

    2016-05-01

    Sediment transport is regarded as an abiotic process driven by geophysical energy, but zoogeomorphological activity indicates that biological energy can also fuel sediment movements. It is therefore prudent to measure the contribution that biota make to sediment transport, but comparisons of abiotic and biotic sediment fluxes are rare. For a stream in the UK, the contribution of crayfish bioturbation to suspended sediment flux was compared with the amount of sediment moved by hydraulic forcing. During base flow periods, biotic fluxes can be isolated because nocturnal crayfish activity drives diel turbidity cycles, such that nighttime increases above daytime lows are attributable to sediment suspension by crayfish. On average, crayfish bioturbation contributed at least 32% (474 kg) to monthly base flow suspended sediment loads; this biotic surcharge added between 5.1 and 16.1 t (0.21 to 0.66 t km-2 yr-1) to the annual sediment yield. As anticipated, most sediment was moved by hydraulic forcing during floods and the biotic contribution from baseflow periods represented between 0.46 and 1.46% of the annual load. Crayfish activity is nonetheless an important impact during baseflow periods and the measured annual contribution may be a conservative estimate because of unusually prolonged flooding during the measurement period. In addition to direct sediment entrainment by bioturbation, crayfish burrowing supplies sediment to the channel for mobilization during floods so that the total biotic effect of crayfish is potentially greater than documented in this study. These results suggest that in rivers, during base flow periods, bioturbation can entrain significant quantities of fine sediment into suspension with implications for the aquatic ecosystem and base flow sediment fluxes. Energy from life rather than from elevation can make significant contributions to sediment fluxes.

  11. Moiré method applied to sediment transport in a small-scale braided river

    Science.gov (United States)

    Leduc, P.; Bellot, H.; Recking, A.

    2012-04-01

    Braided river patterns and sediment supply interactions are significant. Small-scale braided rivers were studied in a rectangular flume with an adjustable slope to investigate these relationships and to gain insight into the effect of grain sorting on bedform formation and migration. We used a 1.20-m-wide and 4.5-m-long flume and a mixture of fine and coarse sand ranging from 0.5 mm to 1.5 mm and from 1.5 to 3 mm (with median sizes 1 and 2 mm, respectively). The sediment feed rate and water discharge were maintained constant. The initial bed was flat with a 3% slope. The mean bed load discharge was calculated by weighing output sediments. The experiment produced bedforms and braided patterns. Equilibrium was reached with a constant number of moving bars. The Moiré method was used to study the bed topography and bedform migration precisely. This optical method considers deformations of grey fringes projected by a video projector on the bed topography. These deformations were recorded with a digital camera and analysed using the phase shifting method (with a special algorithm adapted to the experimental setup). Data produced by this algorithm were mapped with GIS software such as ArcGis. We chose the Moiré method among other methods (laser, photogrammetric, point gauge, etc.) because of its high spatial resolution and its simplicity. However, several technical aspects had to be resolved. Bed topography accuracy depends on the distance between the camera's focal plane and a reference plane parallel to the flume. As the flume and the rail supporting the camera were not parallel, this distance changed along the flume. Instead of moving constantly along a physical reference plane, two wedges were placed on the flume sides to create a virtual reference plane: a 2-cm-wide surface on the top of each wedge was extracted from photographs using image processing software, and these surfaces were used to extrapolate a single virtual reference plane for the whole flume. Two

  12. Coastal processes and longshore sediment transport along Kundapura coast, central west coast of India.

    Digital Repository Service at National Institute of Oceanography (India)

    Shanas, P.R.; SanilKumar, V.

    for evaluation of LSTR, but it does not take into account the sediment size and the longshore current. 3.4.2. Kamphuis (2002) Kamphuis (1991) developed an empirical formula which includes the beach slope, wave period and sediment grain size based... interval should be 3 h or less. Key words: Longshore currents, sediment transport, nearshore waves, nearshore processes, littoral drift 1. Introduction The coastal environment constitutes a fragile and complex ecosystem that is an important resource...

  13. Impact of Bacterial NO3- Transport on Sediment Biogeochemistry

    DEFF Research Database (Denmark)

    Nielsen, Lars Peter

    2005-01-01

    Experiments demonstrated that Beggiatoa could induce a H2S-depleted suboxic zone of more than 10 mm in marine sediments and cause a divergence in sediment NO3- reduction from denitrification to dissimilatory NO3- reduction to ammonium. pH, O2, and H2S profiles indicated that the bacteria oxidized H......2S with NO3- and transported S0 to the sediment surface for aerobic oxidation....

  14. Importance of measuring discharge and sediment transport in lesser tributaries when closing sediment budgets

    Science.gov (United States)

    Griffiths, Ronald; Topping, David

    2017-01-01

    Sediment budgets are an important tool for understanding how riverine ecosystems respond to perturbations. Changes in the quantity and grain size distribution of sediment within river systems affect the channel morphology and related habitat resources. It is therefore important for resource managers to know if a river reach is in a state of sediment accumulation, deficit or stasis. Many sediment-budget studies have estimated the sediment loads of ungaged tributaries using regional sediment-yield equations or other similar techniques. While these approaches may be valid in regions where rainfall and geology are uniform over large areas, use of sediment-yield equations may lead to poor estimations of loads in regions where rainfall events, contributing geology, and vegetation have large spatial and/or temporal variability.Previous estimates of the combined mean-annual sediment load of all ungaged tributaries to the Colorado River downstream from Glen Canyon Dam vary by over a factor of three; this range in estimated sediment loads has resulted in different researchers reaching opposite conclusions on the sign (accumulation or deficit) of the sediment budget for particular reaches of the Colorado River. To better evaluate the supply of fine sediment (sand, silt, and clay) from these tributaries to the Colorado River, eight gages were established on previously ungaged tributaries in Glen, Marble, and Grand canyons. Results from this sediment-monitoring network show that previous estimates of the annual sediment loads of these tributaries were too high and that the sediment budget for the Colorado River below Glen Canyon Dam is more negative than previously calculated by most researchers. As a result of locally intense rainfall events with footprints smaller than the receiving basin, floods from a single tributary in semi-arid regions can have large (≥ 10 ×) differences in sediment concentrations between equal magnitude flows. Because sediment loads do not

  15. Sediment transport capacity of concentrated flows on steep loessial slope with erodible beds.

    Science.gov (United States)

    Xiao, Hai; Liu, Gang; Liu, Puling; Zheng, Fenli; Zhang, Jiaqiong; Hu, Feinan

    2017-05-24

    Previous research on sediment transport capacity has been inadequate and incomplete in describing the detachment and transport process of concentrated flows on slope farmlands during rill development. An indoor concentrated flow scouring experiment was carried out on steep loessial soil slope with erodible bed to investigate the sediment transport capacity under different flow rates and slope gradients. The results indicated that the sediment transport capacity increases with increasing flow rate and slope gradient, and these relationships can be described by power functions and exponential functions, respectively. Multivariate, nonlinear regression analysis showed that sediment transport capacity was more sensitive to slope gradient than to flow rate, and it was more sensitive to unit discharge per unit width than to slope gradient for sediment transport capacity in this study. When similar soil was used, the results were similar to those of previous research conducted under both erodible and non-erodible bed conditions. However, the equation derived from previous research under non-erodible bed conditions with for river bed sand tends to overestimate sediment transport capacity in our experiment.

  16. Multiple effects of sediment transport and geomorphic processes within flood events:Modelling and understanding

    Institute of Scientific and Technical Information of China (English)

    Mingfu Guan n; NigeLG. Wright; P. AndreWSleigh

    2015-01-01

    Flood events can induce considerable sediment transport which in turn influences flow dynamics. This study investigates the multiple effects of sediment transport in floods through modelling a series of hydraulic scenarios, including small-scale experimental cases and a full-scale glacial outburst flood. A non-uniform, layer-based morphodynamic model is presented which is composed of a combination of three modules: a hydrodynamic model governed by the two-dimensional shallow water equations involving sediment effects;a sediment transport model controlling the mass conservation of sediment;and a bed deformation model for updating the bed elevation. The model is solved by a second-order Godunov-type numerical scheme. Through the modelling of the selected sediment-laden flow events, the interactions of flow and sediment transport and geomorphic processes within flood events are elucidated. It is found that the inclusion of sediment transport increases peak flow discharge, water level and water depth in dam-break flows over a flat bed. For a partial dam breach, sediment material has a blockage effect on the flood dynamics. In comparison with the‘sudden collapse’ of a dam, a gradual dam breach significantly delays the arrival time of peak flow, and the flow hydrograph is changed similarly. Considerable bed erosion and deposition occur within the rapid outburst flood, which scours the river channel severely. It is noted that the flood propagation is accelerated after the incorporation of sediment transport, and the water level in most areas of the channel is reduced.

  17. Modeling suspended sediment transport and assessing the impacts of climate change in a karstic Mediterranean watershed.

    Science.gov (United States)

    Nerantzaki, S D; Giannakis, G V; Efstathiou, D; Nikolaidis, N P; Sibetheros, I Α; Karatzas, G P; Zacharias, I

    2015-12-15

    Mediterranean semi-arid watersheds are characterized by a climate type with long periods of drought and infrequent but high-intensity rainfalls. These factors lead to the formation of temporary flow tributaries which present flashy hydrographs with response times ranging from minutes to hours and high erosion rates with significant sediment transport. Modeling of suspended sediment concentration in such watersheds is of utmost importance due to flash flood phenomena, during which, large quantities of sediments and pollutants are carried downstream. The aim of this study is to develop a modeling framework for suspended sediment transport in a karstic watershed and assess the impact of climate change on flow, soil erosion and sediment transport in a hydrologically complex and intensively managed Mediterranean watershed. The Soil and Water Assessment Tool (SWAT) model was coupled with a karstic flow and suspended sediment model in order to simulate the hydrology and sediment yield of the karstic springs and the whole watershed. Both daily flow data (2005-2014) and monthly sediment concentration data (2011-2014) were used for model calibration. The results showed good agreement between observed and modeled values for both flow and sediment concentration. Flash flood events account for 63-70% of the annual sediment export depending on a wet or dry year. Simulation results for a set of IPCC "A1B" climate change scenarios suggested that major decreases in surface flow (69.6%) and in the flow of the springs (76.5%) take place between the 2010-2049 and 2050-2090 time periods. An assessment of the future ecological flows revealed that the frequency of minimum flow events increases over the years. The trend of surface sediment export during these periods is also decreasing (54.5%) but the difference is not statistically significant due to the variability of the sediment. On the other hand, sediment originating from the springs is not affected significantly by climate change.

  18. Cadmium transport in sediments by tubificid bioturbation: an assessment of model complexity

    NARCIS (Netherlands)

    Delmotte, S.; Meysman, F.J.R.; Ciutat, A.; Boudou, A.; Sauvage, S.; Gerino, M.

    2007-01-01

    Biogeochemistry of metals in aquatic sediments is strongly influenced by bioturbation. To determine the effects of biological transport on cadmium distribution in freshwater sediments, a bioturbation model is explored that describes the conveyor-belt feeding of tubificid oligochaetes. A stepwise

  19. A sediment transport model for incision of gullies on steep topography

    Science.gov (United States)

    Erkan Istanbulluoglu; David G. Tarboton; Robert T. Pack; Charles H. Luce

    2003-01-01

    We have conducted surveys of gullies that developed in a small, steep watershed in the Idaho Batholith after a severe wildfire followed by intense precipitation. We measured gully length and cross sections to estimate the volumes of sediment loss due to gully formation. These volume estimates are assumed to provide an estimate of sediment transport capacity at each...

  20. Sediment Transport from Urban, Urbanizing, and Rural Areas in Johnson County, Kansas, 2006-08

    Science.gov (United States)

    Lee, Casey J.

    2013-01-01

    1. Studies have commonly illustrated that erosion and sediment transport from construction sites is extensive, typically 10-100X that of background levels. 2. However, to our knowledge, the affects of construction and urbanization have rarely been assessed (1) since erosion and sediment controls have been required at construction sites, and (2) at watershed (5-65 mi2) scales. This is primarily because of difficulty characterizing sediment loads in small basins. Studies (such as that illustrated from Timble, 1999) illustrated how large changes in surface erosion may not result in substantive changes in downstream sediment loads (b/c of sediment deposition on land-surfaces, floodplains, and in stream channels). 3. Improved technology (in-situ turbidity) sensors provide a good application b/c they provide an independent surrogate of sediment concentration that is more accurate at estimating sediment concentrations and loads that instantaneous streamflow.

  1. Studies on sediment transport along Kerala Coast, south west coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Sajeev, R.; Chandramohan, P.; Josanto, V.; Sanakaranarayanan, V.N.

    Longshore sediment transport characteristics of the Kerala Coast have been examined to delineate various physical processes affecting the different coastal environments. Monthly averages of the daily LEO (Littoral Environmental Observation) data...

  2. Sediment transport and erosion in the Fourchon area of Lafourche parish. [south Louisiana

    Science.gov (United States)

    Whitehurst, C. A.; Self, R. P.

    1974-01-01

    NASA aerial photography in the form of color infrared and color positive transparencies is used as an aid in evaluating the rate and effect of erosion and sediment transport in Bay Champagne Louisiana.

  3. Long-distance electron transport by cable bacteria in mangrove sediments

    NARCIS (Netherlands)

    Burdorf, L.D.; Hidalgo-Martinez, S.; Cook, P.L.M.C.; Meysman, F.

    2016-01-01

    Cable bacteria are long, filamentoussulphur-oxidizing bacteria that induce long-distanceelectron transport in aquatic sediments. They turnthe seafloor into an electro-active environment, characterizedby currents and electrical fields, and whenpresent, they exert a strong impact on the

  4. Waves, Hydrodynamics and Sediment Transport Modeling at Grays Harbor, WA

    Science.gov (United States)

    2010-12-01

    flocculation of cohesive sediment. IAHR J. Hydraul . Res. 36 (3), 309-326. Winterwerp, J. C., and W. G. M. van Kesteren. 2004. Introduction to the...Coastal and Hydraulics Laboratory U.S. Army Engineer Research and Development Center 3909 Halls Ferry Road Vicksburg, MS 39180-6199 David R. Michalsen...93  Sediment processes during dredged material placement operations

  5. Conceptual Site Model for Newark Bay—Hydrodynamics and Sediment Transport

    Directory of Open Access Journals (Sweden)

    Parmeshwar L. Shrestha

    2014-02-01

    Full Text Available A conceptual site model (CSM has been developed for the Newark Bay Study Area (NBSA as part of the Remedial Investigation/Feasibility Study (RI/FS for this New Jersey site. The CSM is an evolving document that describes the influence of physical, chemical and biological processes on contaminant fate and transport. The CSM is initiated at the start of a project, updated during site activities, and used to inform sampling and remediation planning. This paper describes the hydrodynamic and sediment transport components of the CSM for the NBSA. Hydrodynamic processes are influenced by freshwater inflows, astronomical forcing through two tidal straits, meteorological conditions, and anthropogenic activities such as navigational dredging. Sediment dynamics are driven by hydrodynamics, waves, sediment loading from freshwater sources and the tidal straits, sediment size gradation, sediment bed properties, and particle-to-particle interactions. Cohesive sediment transport is governed by advection, dispersion, aggregation, settling, consolidation, and erosion. Noncohesive sediment transport is governed by advection, dispersion, settling, armoring, and transport in suspension and along the bed. The CSM will inform the development and application of a numerical model that accounts for all key variables to adequately describe the NBSA’s historical, current, and future physical conditions.

  6. Modeling chemical accumulation in sediment of small waterbodies accounting for sediment transport and water-sediment exchange processes over long periods.

    Science.gov (United States)

    Patterson, David Albert; Strehmel, Alexander; Erzgräber, Beate; Hammel, Klaus

    2017-07-20

    In a recent scientific opinion of the European Food Safety Authority it is argued that the accumulation of plant protection products in sediments over long time periods may be an environmentally significant process. Therefore, the European Food Safety Authority proposed a calculation to account for plant protection product accumulation. This calculation, however, considers plant protection product degradation within sediment as the only dissipation route, and does not account for sediment dynamics or back-diffusion into the water column. The hydraulic model Hydrologic Engineering Center-River Analysis System (HEC-RAS; US Army Corps of Engineers) was parameterized to assess sediment transport and deposition dynamics within the FOrum for Co-ordination of pesticide fate models and their USe (FOCUS) scenarios in simulations spanning 20 yr. The results show that only 10 to 50% of incoming sediment would be deposited. The remaining portion of sediment particles is transported across the downstream boundary. For a generic plant protection product substance this resulted in deposition of only 20 to 50% of incoming plant protection product substance. In a separate analysis, the FOCUS TOXSWA model was utilized to examine the relative importance of degradation versus back-diffusion as loss processes from the sediment compartment for a diverse range of generic plant protection products. In simulations spanning 20 yr, it was shown that back-diffusion was generally the dominant dissipation process. The results of the present study show that sediment dynamics and back-diffusion should be considered when calculating long-term plant protection product accumulation in sediment. Neglecting these may lead to a systematic overestimation of accumulation. Environ Toxicol Chem 2017;9999:1-9. © 2017 SETAC. © 2017 SETAC.

  7. Pesticide transport to tile-drained fields in SWAT model – macropore flow and sediment

    DEFF Research Database (Denmark)

    Lu, Shenglan; Trolle, Dennis; Blicher-Mathiesen, Gitte;

    2015-01-01

    as a fraction of effective rainfall and transported to the tile drains directly. Macropore sediment transport is calculated similarly to the MACRO model (Jarvis et al., 1999). Mobile pesticide transport is calculated with a decay function with the flow, whereas sorbed pesticides transport is associated...... Tool (SWAT) to simulate transport of both mobile (e.g. Bentazon) and strongly sorbed (e.g. Diuron) pesticides in tile drains. Macropore flow is initiated when soil water content exceeds a threshold and rainfall intensity exceeds infiltration capacity. The amount of macropore flow is calculated......Preferential flow and colloidal facilitated transport via macopores connected to tile drains are the main pathways for pesticide transport from agricultural areas to surface waters in some area. We developed a macropore flow module and a sediment transport module for the Soil and Water Assessment...

  8. Characterization of sediment transport upstream and downstream grom Lake Emory on the Little Tennessee River near Franklin, North Carolina, 2014–15

    Science.gov (United States)

    Huffman, Brad A.; Hazell, William F.; Oblinger, Carolyn J.

    2017-09-06

    Federal, State, and local agencies and organizations have expressed concerns regarding the detrimental effects of excessive sediment transport on aquatic resources and endangered species populations in the upper Little Tennessee River and some of its tributaries. In addition, the storage volume of Lake Emory, which is necessary for flood control and power generation, has been depleted by sediment deposition. To help address these concerns, a 2-year study was conducted in the upper Little Tennessee River Basin to characterize the ambient suspended-sediment concentrations and suspended-sediment loads upstream and downstream from Lake Emory in Franklin, North Carolina. The study was conducted by the U.S. Geological Survey in cooperation with Duke Energy. Suspended-sediment samples were collected periodically, and time series of stage and turbidity data were measured from December 2013 to January 2016 upstream and downstream from Lake Emory. The stage data were used to compute time-series streamflow. Suspended-sediment samples, along with time-series streamflow and turbidity data, were used to develop regression models that were used to estimate time-series suspended-sediment concentrations for the 2014 and 2015 calendar years. These concentrations, along with streamflow data, were used to compute suspended-sediment loads. Selected suspended-sediment samples were collected for analysis of particle-size distribution, with emphasis on high-flow events. Bed-load samples were also collected upstream from Lake Emory.The estimated annual suspended-sediment loads (yields) for the upstream site for the 2014 and 2015 calendar years were 27,000 short tons (92 short tons per square mile) and 63,300 short tons (215 short tons per square mile), respectively. The annual suspended-sediment loads (yields) for the downstream site for 2014 and 2015 were 24,200 short tons (75 short tons per square mile) and 94,300 short tons (292 short tons per square mile), respectively. Overall, the

  9. Microbial Transport, Survival, and Succession in a Sequence of Buried Sediments

    Energy Technology Data Exchange (ETDEWEB)

    Kieft, T.L.; Murphy, E.M.; Haldeman, D.L.; Amy, P.S.; Bjornstad, B.N.; McDonald, E.V.; Ringelberg, D.B.; White, D.C.; Stair, J.; Griffiths, R.P.; Gsell, T.C.; Holben, W.E.; Boone, D.R.

    1995-01-05

    Two chronosequence of unsaturated buried loess sediments ranging in age from <10,000 years to >1 million years were investigated to reconstruct patterns of microbial ecological succession that have occurred since sediment burial. The relative importance of microbial transport and survival to succession were inferred from sediment ages, porewater ages, patterns of abundance (measured by direct counts, counts of culturable cells, and total phospholipid fatty acids), activities (measured by radiotracer and enzyme assays), and community composition (measured by phospholipid fatty acid patterns and Biolog substrate usage). Samples were collected by coring at two sites 40 km apart in the Palouse region of eastern Washington State near the towns of Washtucna and Winona. The Washtucna site was flooded multiple times during the Pleistocene by glacial outburst floods; the elevation of the Winona site is above flood stage. Sediments at the Washtucna site were collected from near surface to 14.9 m depth, where the sediment age was {approx}250 ka and the porewater age was 3700 years; sample intervals at the Winona site ranged from near surface to 38 m (sediment age: {approx}1 Ma; porewater age: 1200 years). Microbial abundance and activities declined with depth at both sites; however, even the deepest, oldest sediments showed evidence of viable microorganisms. Sediments of equivalent age had equal quantities of microorganisms, but differing community types. Differences in community make-up between the two sites can be attributed to differences in groundwater recharge and paleoflooding. Estimates of the ages of the microbial communities can be constrained by porewater and sediment ages. In the shallower sediments (<9 m at Washtucna, <12 m at Winona), the microbial communities are likely similar in age to the groundwater; thus, microbial succession has been influenced by recent transport of microorganisms from the surface. In the deeper sediments, the populations may be

  10. Investigations of grain size dependent sediment transport phenomena on multiple scales

    Science.gov (United States)

    Thaxton, Christopher S.

    Sediment transport processes in coastal and fluvial environments resulting from disturbances such as urbanization, mining, agriculture, military operations, and climatic change have significant impact on local, regional, and global environments. Primarily, these impacts include the erosion and deposition of sediment, channel network modification, reduction in downstream water quality, and the delivery of chemical contaminants. The scale and spatial distribution of these effects are largely attributable to the size distribution of the sediment grains that become eligible for transport. An improved understanding of advective and diffusive grain-size dependent sediment transport phenomena will lead to the development of more accurate predictive models and more effective control measures. To this end, three studies were performed that investigated grain-size dependent sediment transport on three different scales. Discrete particle computer simulations of sheet flow bedload transport on the scale of 0.1--100 millimeters were performed on a heterogeneous population of grains of various grain sizes. The relative transport rates and diffusivities of grains under both oscillatory and uniform, steady flow conditions were quantified. These findings suggest that boundary layer formalisms should describe surface roughness through a representative grain size that is functionally dependent on the applied flow parameters. On the scale of 1--10m, experiments were performed to quantify the hydrodynamics and sediment capture efficiency of various baffles installed in a sediment retention pond, a commonly used sedimentation control measure in watershed applications. Analysis indicates that an optimum sediment capture effectiveness may be achieved based on baffle permeability, pond geometry and flow rate. Finally, on the scale of 10--1,000m, a distributed, bivariate watershed terain evolution module was developed within GRASS GIS. Simulation results for variable grain sizes and for

  11. Determing the beneficial lifetime of Emad Deh dam (Iran) based on hydraulic methods of sediment transfer & its comparison with the MPSIAC experimental method

    Science.gov (United States)

    Rahimi, A.; Karimi, A.; Mohaghegh Zadeh, N.; Samani, B.

    2009-04-01

    Emad Deh watershed has extended more than 64 km2 and is located in Emad Deh village in the southeastern Fars, Iran. In this research the total load of Emad Deh River's sediment is computed by using hydraulic and sedimentary features such as flow depth, river slope canal declivity, river width, flow velocity, discharge, constancy angle of sedimentary particles and definite particles' size (d90,d50,dm). Furthermore by measuring the river water temperature the kinematics viscose of water is specified for its effect on the sedimentary materials movement. The estimated amount of bed load of sediment is equal to 1093.3 ton over year according to the modified method of Meyer, Peter & Muller. The research reveals that the bed load, based on the method of Meyer - Peter & Muller, is nearly %12 of the total load which is estimated 10625.19 ton/year according to the Ackers and White method. Then the specific weight of transported sediments to the reservoir in different interval times can be estimated by the method of Miller (1953) which is modified by Joris de Vente (2004). According to reservoir volume and dam height the beneficial lifetime of the dam computed more than 75 years. Along with the estimation of sediment volume by hydraulic methods, the total load of sediment is also estimated by the experimental method in the Emad Deh basin can be confirmed in comparison to the method of Ackers and White.

  12. Vertical distribution of denitrification in an estuarine sediment: integrating sediment flowthrough reactor experiments and microprofiling via reactive transport modeling.

    Science.gov (United States)

    Laverman, Anniet M; Meile, Christof; Van Cappellen, Philippe; Wieringa, Elze B A

    2007-01-01

    Denitrifying activity in a sediment from the freshwater part of a polluted estuary in northwest Europe was quantified using two independent approaches. High-resolution N(2)O microprofiles were recorded in sediment cores to which acetylene was added to the overlying water and injected laterally into the sediment. The vertical distribution of the rate of denitrification supported by nitrate uptake from the overlying water was then derived from the time series N(2)O concentration profiles. The rates obtained for the core incubations were compared to the rates predicted by a forward reactive transport model, which included rate expression for denitrification calibrated with potential rate measurements obtained in flowthrough reactors containing undisturbed, 1-cm-thick sediment slices. The two approaches yielded comparable rate profiles, with a near-surface, 2- to 3-mm narrow zone of denitrification and maximum in situ rates on the order of 200 to 300 nmol cm(-3) h(-1). The maximum in situ rates were about twofold lower than the maximum potential rate for the 0- to 1-cm depth interval of the sediment, indicating that in situ denitrification was nitrate limited. The experimentally and model-derived rates of denitrification implied that there was nitrate uptake by the sediment at a rate that was on the order of 50 (+/- 10) nmol cm(-2) h(-1), which agreed well with direct nitrate flux measurements for core incubations. Reactive transport model calculations showed that benthic uptake of nitrate at the site is particularly sensitive to the nitrate concentration in the overlying water and the maximum potential rate of denitrification in the sediment.

  13. Biostabilization and Transport of Cohesive Sediment Deposits in the Three Gorges Reservoir.

    Science.gov (United States)

    Fang, Hongwei; Fazeli, Mehdi; Cheng, Wei; Huang, Lei; Hu, Hongying

    2015-01-01

    Cohesive sediment deposits in the Three Gorges Reservoir, China, were used to investigate physical and geochemical properties, biofilm mass, and erosion and deposition characteristics. Biofilm cultivation was performed in a recirculating flume for three different periods (5, 10 and 15 days) under ambient temperature and with sufficient nutrients supply. Three groups of size-fractionated sediment were sequentially used, including 0-0.02 mm, 0.02-0.05 mm and 0.05-0.10 mm. Desired conditions for erosion and deposition were designed by managing high bed shear stress at the narrow part of upstream flume and low shear stress at the wide part of downstream flume. Biostabilization and transport characteristics of the biofilm coated sediment (bio-sediment) were strongly influenced by the cultivation period, and the results were compared with clean sediment. The bio-sediment was more resistant to erosion, and the mean shear stress was increased by factors of 2.65, 2.73 and 5.01 for sediment with 5, 10 and 15 days of biofilm growth compared with clean sediment, resulting in less sediment being eroded from the bed. Simultaneously, the settling velocity was smaller for bio-sediment due to higher organic content and porosity (i.e., lower density). Additionally, there was a smaller probability of deposition for sediment with a longer cultivation period after erosion, resulting in more retention time in aquatic systems. These results will benefit water management in natural rivers.

  14. Human impact on erosion patterns and sediment transport in the Yangtze River

    Science.gov (United States)

    Sun, Xilin; Li, Chang'an; Kuiper, K. F.; Zhang, Zengjie; Gao, Jianhua; Wijbrans, J. R.

    2016-08-01

    Sediment load in rivers is an indicator of erosional processes in the upstream river catchments. Understanding the origin and composition of the sediment load can help to assess the influence of natural processes and human activities on erosion. Tectonic uplift, precipitation and run-off, hill slopes and vegetation can influence erosion in natural systems. Agriculture and deforestation are expected to increase the sediment yield, but dams and reservoirs can trap much of this sediment before it reaches the ocean. Here, we use major element composition and 40Ar/39Ar ages of detrital muscovites to constrain the sediment contribution of various tributaries to sedimentation in the Yangtze delta. The sediment contribution calculated from muscovite data was compared with that estimated from current sediment load data from gauging stations. Muscovite data show that the main contributor to the Yangtze delta sands is the Min River, while the current sediment load suggests that the Jinsha and Jialing rivers are the most important current contributors to delta sediments. We suggest that this difference reflects an "old" and "young" erosion pattern, respectively as medium grained muscovite could be transported much slower than suspended sediment load in the complex river-lake systems of the Yangtze River basin. These two different erosion patterns likely reflect enhanced human activity (deforestation, cultivation, and mining) that increasingly overwhelmed long-time natural factors controls on erosion since ~ 1900 cal years B.P.

  15. Bathymetric controls on sediment transport in the Hudson River estuary: Lateral asymmetry and frontal trapping

    Science.gov (United States)

    Ralston, David K.; Geyer, W. Rockwell; Warner, John C.

    2012-01-01

    Analyses of field observations and numerical model results have identified that sediment transport in the Hudson River estuary is laterally segregated between channel and shoals, features frontal trapping at multiple locations along the estuary, and varies significantly over the spring-neap tidal cycle. Lateral gradients in depth, and therefore baroclinic pressure gradient and stratification, control the lateral distribution of sediment transport. Within the saline estuary, sediment fluxes are strongly landward in the channel and seaward on the shoals. At multiple locations, bottom salinity fronts form at bathymetric transitions in width or depth. Sediment convergences near the fronts create local maxima in suspended-sediment concentration and deposition, providing a general mechanism for creation of secondary estuarine turbidity maxima at bathymetric transitions. The lateral bathymetry also affects the spring-neap cycle of sediment suspension and deposition. In regions with broad, shallow shoals, the shoals are erosional and the channel is depositional during neap tides, with the opposite pattern during spring tides. Narrower, deeper shoals are depositional during neaps and erosional during springs. In each case, the lateral transfer is from regions of higher to lower bed stress, and depends on the elevation of the pycnocline relative to the bed. Collectively, the results indicate that lateral and along-channel gradients in bathymetry and thus stratification, bed stress, and sediment flux lead to an unsteady, heterogeneous distribution of sediment transport and trapping along the estuary rather than trapping solely at a turbidity maximum at the limit of the salinity intrusion.

  16. Remobilization of polychlorinated biphenyls from sediment and its consequences for their transport in river waters.

    Science.gov (United States)

    Gdaniec-Pietryka, Monika; Mechlińska, Agata; Wolska, Lidia; Gałuszka, Agnieszka; Namieśnik, Jacek

    2013-05-01

    A laboratory experiment was performed to examine the remobilization of indicator polychlorinated biphenyls (iPCBs) from sediments and its results were applied to the real-world data for explaining the transport of PCBs in river. Seven PCB concentrations were determined in three series of model water-sediment systems (3 g of river sediment, three different volumes of distilled water (0.5, 0.25, and 0.15 ml), and 5 mg of biocide) after 11 days of incubation. Solid-phase extraction was used for separation of analytes from the aqueous phase and solvent extraction for isolation of analytes from the sediments, respectively. The extracts were analyzed for individual iPCB congeners using gas chromatography-mass spectrometry method. For each series of the experiment, the concentrations of PCBs in aqueous phase were similar. The average sediment/water partition coefficient value was 10(4) l/kg. The solubility of individual PCB congeners in water did not influence the desorption of PCBs from the sediment. Although the dominant form of PCBs in a water-sediment system occurs as suspended and colloidal fractions, these compounds are transported mostly in a dissolved form. Suspended and colloidal matter is a major sink for PCBs in low-energy aquatic environments. In contrast, the dissolved PCBs are readily transported in running waters. The mobilization of PCBs from sediments to aqueous phase, with respect to their solubility in water, seems to be limited, thus reducing the risk of secondary pollution.

  17. Hydrology, sediment transport dynamics and geomorphology of a ...

    African Journals Online (AJOL)

    2009-01-21

    Jan 21, 2009 ... hysteresis effect, such that sediment concentration peaked prior to discharge in the early .... To assess seasonal aspects of rainfall in the catchment, precipi- ...... HERITAGE GL, LARGE ARG, MOON BP and JEWITT G (2004).

  18. Large-eddy simulation of suspended sediment transport in turbulent channel flow

    Institute of Scientific and Technical Information of China (English)

    ZHU Hai; WANG Ling-ling; TANG Hong-wu

    2013-01-01

    The numerical simulation of the non-cohesive sediment transport in a turbulent channel flow with a high concentration is a challenging but practical task.A modified coherent dynamic eddy model of the Large Eddy Simulation (LES) with a pick-up function is used in the present study to simulate the sediment erosion and the deposition in a turbulent channel flow.The rough wall model is used instead of the LES with the near-wall resolution to obtain the reasonable turbulent flow characteristics while avoiding the high costs in the computation.Good results are obtained,and are used to analyze the sediment transport properties.The results show that the streamwise vortices play an important role in the riverbed erosion and the sediment pick-up,which may serve as guidelines for the sediment management and the water environment protection engineering.

  19. Distributed model of hydrological and sediment transport processes in large river basins in Southeast Asia

    Science.gov (United States)

    Zuliziana, S.; Tanuma, K.; Yoshimura, C.; Saavedra, O. C.

    2015-07-01

    Soil erosion and sediment transport have been modeled at several spatial and temporal scales, yet few models have been reported for large river basins (e.g., drainage areas > 100 000 km2). In this study, we propose a process-based distributed model for assessment of sediment transport at a large basin scale. A distributed hydrological model was coupled with a process-based distributed sediment transport model describing soil erosion and sedimentary processes at hillslope units and channels. The model was tested on two large river basins: the Chao Phraya River Basin (drainage area: 160 000 km2) and the Mekong River Basin (795 000 km2). The simulation over 10 years showed good agreement with the observed suspended sediment load in both basins. The average Nash-Sutcliffe efficiency (NSE) and average correlation coefficient (r) between the simulated and observed suspended sediment loads were 0.62 and 0.61, respectively, in the Chao Phraya River Basin except the lowland section. In the Mekong River Basin, the overall average NSE and r were 0.60 and 0.78, respectively. Sensitivity analysis indicated that suspended sediment load is sensitive to detachability by raindrop (k) in the Chao Phraya River Basin and to soil detachability over land (Kf) in the Mekong River Basin. Overall, the results suggest that the present model can be used to understand and simulate erosion and sediment transport in large river basins.

  20. Distributed model of hydrological and sediment transport processes in large river basins in Southeast Asia

    Directory of Open Access Journals (Sweden)

    S. Zuliziana

    2015-07-01

    Full Text Available Soil erosion and sediment transport have been modeled at several spatial and temporal scales, yet few models have been reported for large river basins (e.g., drainage areas > 100 000 km2. In this study, we propose a process-based distributed model for assessment of sediment transport at a large basin scale. A distributed hydrological model was coupled with a process-based distributed sediment transport model describing soil erosion and sedimentary processes at hillslope units and channels. The model was tested on two large river basins: the Chao Phraya River Basin (drainage area: 160 000 km2 and the Mekong River Basin (795 000 km2. The simulation over 10 years showed good agreement with the observed suspended sediment load in both basins. The average Nash–Sutcliffe efficiency (NSE and average correlation coefficient (r between the simulated and observed suspended sediment loads were 0.62 and 0.61, respectively, in the Chao Phraya River Basin except the lowland section. In the Mekong River Basin, the overall average NSE and r were 0.60 and 0.78, respectively. Sensitivity analysis indicated that suspended sediment load is sensitive to detachability by raindrop (k in the Chao Phraya River Basin and to soil detachability over land (Kf in the Mekong River Basin. Overall, the results suggest that the present model can be used to understand and simulate erosion and sediment transport in large river basins.

  1. Aeolian particle transport inferred using a ~150-year sediment record from Sayram Lake, arid northwest China

    Directory of Open Access Journals (Sweden)

    Long Ma

    2015-05-01

    Full Text Available We studied sediment cores from Sayram Lake in the Tianshan Mountains of northwest China to evaluate variations in aeolian transport processes over the past ~150 years. Using an end-member modeling algorithm of particle size data, we interpreted end members with a strong bimodal distribution as having been transported by aeolian processes, whereas other end members were interpreted to have been transported by fluvial processes. The aeolian fraction accounted for an average of 27% of the terrigenous components in the core. We used the ratio of aeolian to fluvial content in the Sayram Lake sediments as an index of past intensity of aeolian transport in the Tianshan Mountains. During the interval 1910-1930, the index was high, reflecting the fact that dry climate provided optimal conditions for aeolian dust transport. From 1930-1980, the intensity of aeolian transport was weak. From the 1980s to the 2000s, aeolian transport to Sayram Lake increased. Although climate in northwest China became more humid in the mid-1980s, human activity had by that time altered the impact of climate on the landscape, leading to enhanced surface erosion, which provided more transportable material for dust storms. Comparison of the Lake Sayram sediment record with sediment records from other lakes in the region indicates synchronous intervals of enhanced aeolian transport from 1910 to 1930 and 1980 to 2000.

  2. Transport of Gas and Solutes in Permeable Estuarine Sediments

    Science.gov (United States)

    2011-09-30

    shallow sand sediments colonized by photosynthetizing diatoms and cyanobacteria . Photosynthetically active radiation at the water surface raged from... space and time. 6 Fig. 3. Acoustic scans conducted at St. Joseph Bay, Florida. The three left panes represent Site 1 upper pane: shortly after...expanding and gas moves into the pore space . This results in rough bubble surfaces that eventually form extrusions that penetrate further into the sediment

  3. Modeling flow, sediment transport and morphodynamics in rivers

    Science.gov (United States)

    Nelson, Jonathan M.; McDonald, Richard R.; Shimizu, Yasuyuki; Kimura, Ichiro; Nabi, Mohamed; Asahi, Kazutake

    2016-01-01

    Predicting the response of natural or man-made channels to imposed supplies of water and sediment is one of the difficult practical problems commonly addressed by fluvial geomorphologists. This problem typically arises in three situations. In the first situation, geomorphologists are attempting to understand why a channel or class of channels has a certain general form; in a sense, this is the central goal of fluvial geomorphology. In the second situation, geomorphologists are trying to understand and explain how and why a specific channel will evolve or has evolved in response to altered or unusual sediment and water supplies to that channel. For example, this would include explaining the short-term response of a channel to an unusually large flood or predicting the response of a channel to long-term changes in flow or sediment supply due to various human activities such as damming or diversions. Finally, geomorphologists may be called upon to design or assess the design of proposed man-made channels that must carry a certain range of flows and sediment loads in a stable or at least quasi-stable manner. In each of these three situations, the problem is really the same: geomorphologists must understand and predict the interaction of the flow field in the channel, the sediment movement in the channel and the geometry of the channel bed and banks. In general, the flow field, the movement of sediment making up the bed and the morphology of the bed are intricately linked; the flow moves the sediment, the bed is altered by erosion and deposition of sediment and the shape of the bed is critically important for predicting the flow. This complex linkage is precisely what makes understanding channel form and process such a difficult and interesting challenge.

  4. Meso-scale aeolian sediment input to coastal dunes: The nature of aeolian transport events

    Science.gov (United States)

    Delgado-Fernandez, Irene; Davidson-Arnott, Robin

    2011-03-01

    Observations of aeolian transport in coastal areas have focused on short-term experiments because of limitations imposed by instrumentation. This paper uses a case study at Greenwich Dunes, Prince Edward Island National Park, Canada, to analyze how sediment transport takes place at the beach over periods of weeks to months. A monitoring station provided hourly time series of vegetation cover, shoreline position, fetch distances, surficial moisture content, presence of ice and snow, wind speed and direction and transport processes over nine months. Analysis shows that high wind speeds may not generate any net transport into the dunes because of the limitations imposed by snow/ice cover, moisture, and short fetch distances. Despite extreme winds during intense storms, such events often lead to wave scarping rather than aeolian sediment input to the foredunes. When sediment was transported on the beach, the magnitude was regulated by a combination of factors including: angle of wind approach, fetch distance, moisture content, and duration of the wind event. In particular, angle of wind approach (and therefore fetch distance) may demote a high magnitude wind event with strong transport potential to one with no transport at all, which poses challenges for predicting the effects of individual storms over the course of several months. A significant proportion of sediment delivery to the foredunes was associated with wind events of low to medium magnitude. It is suggested here that large magnitude wind events have low probabilities of resulting in transport towards the foredune because factors such as wave inundation play an increasing role in preventing sediment movement across the beach. This has implications for modelling and management, and highlights differences between the magnitude and frequency of aeolian transport events in the coastal environment compared to those in deserts and to fluvial sediment transport.

  5. Structural practices for controlling sediment transport from erosion

    Science.gov (United States)

    Gabriels, Donald; Verbist, Koen; Van de Linden, Bruno

    2013-04-01

    Erosion on agricultural fields in the hilly regions of Flanders, Belgium has been recognized as an important economical and ecological problem that requires effective control measures. This has led to the implementation of on-site and off-site measures such as reduced tillage and the installation of grass buffers trips, and dams made of vegetative materials. Dams made out of coir (coconut) and wood chips were evaluated on three different levels of complexity. Under laboratory conditions, one meter long dams were submitted to two different discharges and three sediment concentrations under two different slopes, to assess the sediment delivery ratios under variable conditions. At the field scale, discharge and sediment concentrations were monitored under natural rainfall conditions on six 3 m wide plots, of which three were equipped with coir dams, while the other three served as control plots. The same plots were also used for rainfall simulations, which allowed controlling sediment delivery boundary conditions more precisely. Results show a clear advantage of these dams to reduce discharge by minimum 49% under both field and laboratory conditions. Sediment delivery ratios (SDR) were very small under laboratory and field rainfall simulations (4-9% and 2% respectively), while larger SDRs were observed under natural conditions (43%), probably due to the small sediment concentrations (1-5 g l-1) observed and as such a larger influence of boundary effects. Also a clear enrichment of larger sand particles (+167%) could be observed behind the dams, showing a significant selective filtering effect.

  6. RANS-based simulation of turbulent wave boundary layer and sheet-flow sediment transport processes

    DEFF Research Database (Denmark)

    Fuhrman, David R.; Schløer, Signe; Sterner, Johanna

    2013-01-01

    suspended sediment concentrations, (2) turbulence suppression due to density gradients in the water–sand mixture, (3) boundary layer streaming due to convective terms, and (4) converging–diverging effects due to a sloping bed. The present model therefore provides a framework for simultaneous inclusion...... of a number of local factors important within cross-shore wave boundary layer and sediment transport dynamics. The hydrodynamic model is validated for both hydraulically smooth and rough conditions, based on wave friction factor diagrams and boundary layer streaming profiles, with the results in excellent...... to investigate the importance of boundary layer streaming effects on sediment transport in selected velocity-skewed conditions. For the medium sand grain conditions considered, the model results suggest that streaming effects can enhance onshore sediment transport rates by asmuch as a factor of two...

  7. Flood-ebb asymmetry in current velocity and suspended sediment transport in the Changjiang Estuary

    Institute of Scientific and Technical Information of China (English)

    LI Zhanhai; WANG Yaping; CHENG Peng; ZHANG Guoan; LI Jiufa

    2016-01-01

    Time series measurements were conducted on suspended sediment and current velocity from neap tide to spring tide in the South Branch of the upper Changjiang Estuary in the summer of 2011. Strong flood-ebb asymmetry in the current velocity was observed in the South Branch as a result of high river runoff and tide deformation, in which the magnitude and duration of ebb currents were significantly greater than those of flood currents. The suspended sediment concentration (SSC) and suspended median grain size also exhibited remarkable flood-ebb variation; these variables were considerably larger during the ebb than during the flood and increased from neap to spring tide. Affected by the strong asymmetry in the current velocity and SSC between the flood and ebb, suspended sediment flux during the ebb was notably larger than during the flood, and a seaward tidal net flux was observed in each tidal cycle. The balance of sediment flux illustrates that the seaward sediment transport was dominated by river flow and tidal trapping and the landward sediment transport was dominated by the Stokes drift and the shear effect. Notable resuspension occurred during the spring and moderate tides. The critical velocity for the resuspension of bed sediments was estimated based on the correlation between current velocity with SSC and suspended median grain size. The results show that the critical velocity was approximately 40 cm/s during the flood phases and approximately 80 cm/s during the ebb phases because the surficial flood bed sediments located in the lower reach are much finer than the surficial ebb bed sediments located in the upper reach. The flood-ebb variation in the critical erosion velocity has significant effect on the intratidal variation of SSC and sediment transport process, and it is a common phenomenon in many estuaries of the world due to the complicated spatial distribution of bed sediments.

  8. Sediment transport off Bangladesh: the power of tropical cyclones recorded in a submarine canyon

    Science.gov (United States)

    Meyer, I.; Kudrass, H.; Palamenghi, L.

    2011-12-01

    Marine sediments offshore Bangladesh are mainly supplied by the Ganges-Brahmaputra river system and are accumulated on the shelf of Bangladesh. The average sediment discharge of the world's biggest river system is estimated to be 0.8-1 billion tons per year. The shallow shelf is cut by a steep and up to 1000 m deep anaerobic canyon, called the "Swatch of No Ground", which acts as a sediment trap. An extremely high annual sedimentation flux of 20-45 cm was determined for the last 50 years by 137Cs and 210Pb measurements. In order to investigate the sediment transport in the Bay of Bengal a marine sediment core was taken from the mid-part of the Swatch of No Ground (21°18N/89°34E) and analyzed for element composition and grain-size distributions. Results show a sequence of graded fine-sand-silt-clay layers. These sequences can be directly related to the historical record of tropical storms, which move across the northern Bay of Bengal during pre- and post-monsoon flood peak and mobilize huge amounts of the shallow marine and coastal sediments into turbid hyperpycnal water masses. Due to the anti-clockwise rotation of the cyclones and their northward path the main transport direction is westward. The coarse grained sediment, remobilized by storm waves, is supported by cyclone-induced currents toward the canyon while the fine grained fraction follows afterward supported by the storm swell plus the semi-diurnal tidal component. Despite the high riverine input the amount of sediment mobilized during normal weather conditions is minimal compared to the sediment mobilized by the cyclonic high-energy input. Similar cyclone-induced sediment transport probably also governs erosion and deposition in most tropical shelf areas affected by the monsoon regime.

  9. Critical review: Radionuclide transport, sediment transport, and water quality mathematical modeling; and radionuclide adsorption/desorption mechanisms

    Energy Technology Data Exchange (ETDEWEB)

    Onishi, Y.; Serne, R.J.; Arnold, E.M.; Cowan, C.E.; Thompson, F.L. [Pacific Northwest Lab., Richland, WA (United States)

    1981-01-01

    This report describes the results of a detailed literature review of radionuclide transport models applicable to rivers, estuaries, coastal waters, the Great Lakes, and impoundments. Some representatives sediment transport and water quality models were also reviewed to evaluate if they can be readily adapted to radionuclide transport modeling. The review showed that most available transport models were developed for dissolved radionuclide in rivers. These models include the mechanisms of advection, dispersion, and radionuclide decay. Since the models do not include sediment and radionuclide interactions, they are best suited for simulating short-term radionuclide migration where: (1) radionuclides have small distribution coefficients; (2) sediment concentrations in receiving water bodies are very low. Only 5 of the reviewed models include full sediment and radionuclide interactions: CHMSED developed by Fields; FETRA SERATRA, and TODAM developed by Onishi et al, and a model developed by Shull and Gloyna. The 5 models are applicable to cases where: (1) the distribution coefficient is large; (2) sediment concentrations are high; or (3) long-term migration and accumulation are under consideration. The report also discusses radionuclide absorption/desorption distribution ratios and addresses adsorption/desorption mechanisms and their controlling processes for 25 elements under surface water conditions. These elements are: Am, Sb, C, Ce, Cm, Co, Cr, Cs, Eu, I, Fe, Mn, Np, P, Pu, Pm, Ra, Ru, Sr, Tc, Th, {sup 3}H, U, Zn and Zr.

  10. Fate and Transport of Cohesive Sediment and HCB in the Middle Elbe River Basin

    Science.gov (United States)

    Moshenberg, Kari; Heise, Susanne; Calmano, Wolfgang

    2014-05-01

    Chemical contamination of waterways and floodplains is a pervasive environmental problem that threatens aquatic ecosystems worldwide. Due to extensive historical contamination and redistribution of contaminated sediments throughout the basin, the Elbe River transports significant loads of contaminants downstream, particularly during flood events. This study focuses on Hexachlorobenzene (HCB), a persistent organic pollutant that has been identified as a contaminant of concern in the Elbe Basin. To better understand the fate and transport of cohesive sediments and sediment-sorbed HCB, a hydrodynamic, suspended sediment, and contaminated transport model for the 271-km reach of the Elbe River basin between Dresden and Magdeburg was developed. Additionally, trends in suspended sediment and contaminant transport were investigated in the context of the recent high frequency of floods in the Elbe Basin. This study presents strong evidence that extreme high water events, such as the August, 2002 floods, have a permanent effect on the sediment transport regime in the Elbe River. Additionally, results indicate that a significant component annual HCB loads are transported downstream during floods. Additionally, modeled results for suspended sediment and HCB accumulation on floodplains are presented and discussed. Uncertainty and issues related to model development are also addressed. A worst case analysis of HCB uptake by dairy cows and beef cattle indicate that significant, biologically relevant quantities of sediment-sorbed HCB accumulate on the Elbe floodplains following flood events. Given both the recent high frequency of floods in the Elbe Basin, and the potential increase in flood frequency due to climate change, an evaluation of source control measures and/or additional monitoring of floodplain soils and grasses is recommended.

  11. Aeolian processes across transverse dunes. II: Modelling the sediment transport and profile development

    NARCIS (Netherlands)

    van Dijk, P.M.; Arens, S.M.; van Boxel, J.H.

    1999-01-01

    This paper discusses a model which simulates dune development resulting from aeolian saltation transport. The model was developed for application to coastal foredunes, but is also applicable to sandy deserts with transverse dunes. Sediment transport is calculated using published deterministic and em

  12. Longshore sediment transport rate-measurement and estimation, central west coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    SanilKumar, V.; Anand, N.M.; Chandramohan, P.; Naik, G.N.

    transport rate were measured with traps deployed on a line spanning the surf zone. Sediment transport in the swash zone was not considered in the present study. The longshore current was measured at each trap location. The breaking wave parameters were...

  13. Computational modeling of 137Cs contaminant transfer associated with sediment transport in Abukuma River.

    Science.gov (United States)

    Iwasaki, T; Nabi, M; Shimizu, Y; Kimura, I

    2015-01-01

    A numerical model capable of simulating the transfer of (137)Cs in rivers associated with transport of fine sediment is presented. The accident at Fukushima Dai-ichi Nuclear Power Plant (FDNPP) released radionuclides into the atmosphere, and after fallout several radionuclides in them, such as radiocesium ((134)Cs, (137)Cs) and radioiodine ((131)I) were adsorbed on surface soil particles around FDNPP and transported by surface water. To understand the transport and deposition of the radioactive contaminant along with surface soil particles and its flux to the ocean, we modeled the transport of the (137)Cs contaminant by computing the water flow and the associated washload and suspended load transport. We have developed a two-dimensional model to simulate the plane flow structure, sediment transport and associated (137)Cs contaminant transport in rivers by combining a shallow water flow model and an advection-diffusion equation for the transport of sediment. The proposed model has been applied to the lower reach of Abukuma River, which is the main river in the highly contaminated area around FDNPP. The numerical results indicate that most (137)Cs supplied from the upstream river reach with washload would directly reach to Pacific Ocean. In contrast, washload-oriented (137)Cs supplied from the upstream river basin has a limited role in the radioactive contamination in the river. The results also suggest that the proposed framework of computational model can be a potential tool for understanding the sediment-oriented (137)Cs behavior in rivers.

  14. Aeolian processes across transverse dunes. II: Modelling the sediment transport and profile development

    NARCIS (Netherlands)

    van Dijk, P.M.; Arens, S.M.; van Boxel, J.H.

    1999-01-01

    This paper discusses a model which simulates dune development resulting from aeolian saltation transport. The model was developed for application to coastal foredunes, but is also applicable to sandy deserts with transverse dunes. Sediment transport is calculated using published deterministic and

  15. Aeolian processes across transverse dunes. II: Modelling the sediment transport and profile development

    NARCIS (Netherlands)

    van Dijk, P.M.; Arens, S.M.; van Boxel, J.H.

    1999-01-01

    This paper discusses a model which simulates dune development resulting from aeolian saltation transport. The model was developed for application to coastal foredunes, but is also applicable to sandy deserts with transverse dunes. Sediment transport is calculated using published deterministic and em

  16. Reduced sediment transport in the Yellow River due to anthropogenic changes

    Science.gov (United States)

    Wang, Shuai; Fu, Bojie; Piao, Shilong; Lü, Yihe; Ciais, Philippe; Feng, Xiaoming; Wang, Yafeng

    2016-01-01

    The erosion, transport and redeposition of sediments shape the Earth’s surface, and affect the structure and function of ecosystems and society. The Yellow River was once the world’s largest carrier of fluvial sediment, but its sediment load has decreased by approximately 90% over the past 60 years. The decline in sediment load is due to changes in water discharge and sediment concentration, which are both influenced by regional climate change and human activities. Here we use an attribution approach to analyse 60 years of runoff and sediment load observations from the traverse of the Yellow River over China’s Loess Plateau -- the source of nearly 90% of its sediment load. We find that landscape engineering, terracing and the construction of check dams and reservoirs were the primary factors driving reduction in sediment load from the 1970s to 1990s, but large-scale vegetation restoration projects have also reduced soil erosion from the 1990s onwards. We suggest that, as the ability of existing dams and reservoirs to trap sediments declines in the future, erosion rates on the Loess Plateau will increasingly control the Yellow River’s sediment load.

  17. Residual fluxes and suspended sediment transport in the lower reaches of Muvattupuzha River, southwest coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Revichandran, C.; Balachandran, K.K.; Xavier, J.K.; Rejendran, N.C.

    Spatial and seasonal variation of different physical processes governing the transport of salt and sediment of the Muvattupuzha River, in Kerala, India are discussed. Salt and suspended sediment due to tidal pumping was directed upstream, salt...

  18. Impact of river regulation on potential sediment mobilization and transport in an Alpine catchment

    Science.gov (United States)

    Costa, Anna; Molnar, Peter; Lane, Stuart N.; Bakker, Maarten

    2015-04-01

    The upper Rhône basin (upstream of Lake Geneva) has been heavily affected by human activities during the last century. The most evident impacts are related to river regulation, specifically flow impoundement, flow abstraction and channelization. In the last century and mainly since 1960, several large dams have been built along the main tributaries of the Rhône River, resulting in the water storage of a volume equal to 20% of the total annual river flow. The dams are part of hydropower systems which abstract water from streams and transfer it through complex networks (intakes, tunnels and pumping stations) to the reservoirs. Hydropower production leads to regulated flow in the Rhône: mostly an increase of winter flows, a reduction of summer flows, and a decrease of flood peaks. The sediment supply into Lake Geneva has decreased following dam construction (Loizeau & Dominik, 2000) due to the storage of sediment in upstream reservoirs, in rivers with reduced sediment transport capacity due to flow abstraction, and due to the development of sediment mining. Our hypothesis is that streamflow regulation itself has dramatically impacted the sediment transport dynamics of the system. We investigate the impacts of flow regulation on the sediment transport regime, by analysing the effects on potential sediment transport capacity (bedload). By the use of different bedload transport formulae (Meyer-Peter Müller, Wilcock and Crowe), the potential sediment transport capacity is computed at different cross sections within the basin. Potential sediment mobility occurs when the applied bed shear stress exceeds a critical value, τ>τc. The applied bed shear stress is computed as τ=ρghS, with water depth (h) measured from rating curves. We obtain an estimate of the energy slope (S) from the analysis of the river cross section, assuming uniform flow. The critical value of bed shear stress τc is computed using empirical formulae as a function of the grain diameter (ds). To

  19. Coupling climate conditions, sediment sources and sediment transport in an alpine basin

    Science.gov (United States)

    Rainato, Riccardo; Picco, Lorenzo; Cavalli, Marco; Mao, Luca; Neverman, Andrew J.; Tarolli, Paolo

    2017-04-01

    In a fluvial system, mountain basins control sediment export to the lowland rivers. Hence, the analysis of the erosion processes and sediment delivery patterns that act in mountain basins is important. Several studies have investigated the alterations triggered by recent climatic change on the hydrological regime, whilst only a few works have explored the consequences on the sediment dynamics. Here we combined and analyzed the quasi-unique dataset of climatic conditions, landscape response, and sediment export produced, since 1986 in the Rio Cordon basin (5 km2, Eastern Italian Alps) to examine the sediment delivery processes occurring in the last three decades. The temperature, precipitation, and fluvial sediment fluxes in the basin were analyzed using continuous measurement executed by a permanent monitoring station, while the landscape evolution was investigated by three sediment source inventories established in 1994, 2006, and 2016. Thus, the analysis focused on the trends exhibited during the periods 1986-1993, 1994-2006, and 2007-2015. In terms of climatic conditions, three distinct climate forcing stages can be observed in the periods analyzed: a relatively stable phase (1986-1993), a period characterized by temperature and rainfall fluctuations (1994-2006), and a more recent warmer and wetter phase (2007-2015). In the 1986-1993 period, the fluvial sediment fluxes reflected the stable trend exhibited by the climatic conditions. In the subsequent 1994-2006 period, the average temperature and precipitation were in line with that previously observed, although with higher interannual variability. Notwithstanding the climate forcing and the occurrence of high magnitude/low frequency floods that strongly influenced the source areas, between 1994 and 2006 the Rio Cordon basin showed relatively limited erosion activity. Hence, the climatic conditions and the landscape response can only partially explain the strong increase of sediment export recorded in the 1994

  20. Sediment transport time measured with U-Series isotopes: Resultsfrom ODP North Atlantic Drill Site 984

    Energy Technology Data Exchange (ETDEWEB)

    DePaolo, Donald J.; Maher, Kate; Christensen, John N.; McManus,Jerry

    2006-06-05

    High precision uranium isotope measurements of marineclastic sediments are used to measure the transport and storage time ofsediment from source to site of deposition. The approach is demonstratedon fine-grained, late Pleistocene deep-sea sediments from Ocean DrillingProgram Site 984A on the Bjorn Drift in the North Atlantic. The sedimentsare siliciclastic with up to 30 percent carbonate, and dated by sigma 18Oof benthic foraminifera. Nd and Sr isotopes indicate that provenance hasoscillated between a proximal source during the last three interglacialperiods volcanic rocks from Iceland and a distal continental sourceduring glacial periods. An unexpected finding is that the 234U/238Uratios of the silicate portion of the sediment, isolated by leaching withhydrochloric acid, are significantly less than the secular equilibriumvalue and show large and systematic variations that are correlated withglacial cycles and sediment provenance. The 234U depletions are inferredto be due to alpha-recoil loss of234Th, and are used to calculate"comminution ages" of the sediment -- the time elapsed between thegeneration of the small (<_ 50 mu-m) sediment grains in the sourceareas by comminution of bedrock, and the time of deposition on theseafloor. Transport times, the difference between comminution ages anddepositional ages, vary from less than 10 ky to about 300 to 400 ky forthe Site 984A sediments. Long transport times may reflect prior storagein soils, on continental shelves, or elsewhere on the seafloor. Transporttime may also be a measure of bottom current strength. During the mostrecent interglacial periods the detritus from distal continental sourcesis diluted with sediment from Iceland that is rapidly transported to thesite of deposition. The comminution age approach could be used to dateQuaternary non-marine sediments, soils, and atmospheric dust, and may beenhanced by concomitant measurement of 226Ra/230Th, 230Th/234U, andcosmogenic nuclides.

  1. Modelling intertidal sediment transport for nutrient change and climate change scenarios.

    Science.gov (United States)

    Wood, Rose; Widdows, John

    2003-10-01

    A model of intertidal sediment transport, including effects of bioturbation and biostabilisation, was applied to two transects on the east coast of England: Leverton (within the Wash) and Skeffling (in the Humber Estuary). The physical and biological parameters were chosen to represent four 1-year scenarios: a baseline year (1995), the same year but with estuarine nitrate inputs reduced by 50% and by 16%, and a year with climate change effects estimated for 2050. The changes in nitrate supply can potentially change microphytobenthos numbers within the surface sediment, which will then affect erodibility. The model results show a range of behaviour determined by bathymetry, external forcing and biotic state. When intertidal sediment transport is dominated by external sediment supply, the model produces highest deposition at the most offshore point, and there is greatest deposition in the winter and spring, when offshore sediment concentrations are highest. When intertidal processes dominate intertidal sediment transport, there is a peak of deposition at the high-shore level and erosion at mid-tide levels. The greatest deposition now occurs in winter and summer, when low chlorophyll levels mean that the sediment is most erodible. The Skeffling transect was dominated by intertidal processes for the baseline scenario and with a 16% reduction in nitrate. Under the climate change (warm winter) scenario, the Skeffling transect was dominated by external sediment supply. The scenario with 50% reduction in nitrate gave intermediate behaviour at Skeffling (intertidally driven during the winter and summer, and governed by offshore sediment supply during spring and autumn). The Leverton transect was dominated by offshore sediment supply for all the scenarios.

  2. Geologic evidence for onshore sediment transport from the inner continental shelf: Fire Island, New York

    Science.gov (United States)

    Schwab, William C.; Baldwin, Wayne E.; Hapke, Cheryl J.; Lentz, Erika E.; Gayes, Paul T.; Denny, Jane F.; List, Jeffrey H.; Warner, John C.

    2013-01-01

    Sediment budget analyses along the south shore of Fire Island, New York, have been conducted and debated in the scientific and coastal engineering literature for decades. It is well documented that a primary component of sediment transport in this system is directed alongshore from E to W, but discrepancies in volumetric sediment budget calculations remain. An additional quantity of sand, averaging about 200,000 m3/y is required to explain the growth of the western segment of the barrier island, a prograding spit. Littoral sediment derived from updrift erosion of the coast, addition of beach nourishment fill, and onshore transport of inner continental shelf, shoreface sediments, or both have all been proposed as potential sources of the additional sediment needed to balance the sediment budget deficit. Analysis of high-resolution seafloor mapping data collected in 2011, including seismic reflection profiles and inteferometric sonar acoustic backscatter and swath bathymetry; comparison with seafloor mapping data collected in 1996–1997; and shoreline change analysis from 1933 to 2011 support previous suggestions that the inner-shelf Holocene sedimentary deposit is a likely source to resolve this sediment budget discrepancy.

  3. An effective Euler-Lagrange model for suspended sediment transport by open channel flows

    Institute of Scientific and Technical Information of China (English)

    Huabin Shi; Xiping Yu n

    2015-01-01

    An Euler–Lagrange two-phase flow model is developed to study suspended sediment transport by open-channel flows with an Eddy Interaction Model (EIM) applied to consider the effect of fluid turbulence on sediment diffusion. For the continuous phase, the mean fluid velocity, the turbulent kinetic energy and its dissipation rate are directly estimated by well-established empirical formulas. For the dispersed phase, sediment particles are tracked by solving the equation of motion. The EIM is applied to compute the particle fluctuation velocity. Neglecting the effect of particles on flow turbulence as usually suggested for dilute cases in the literature, the Euler–Lagrange model is applied to simulate suspended sediment transport in open channels. Although the numerical results agree well with those by the well-known random walk particle tracking model (RWM) and with the laboratory data for fine sediment cases, it is clearly shown that such an Euler–Lagrange model underestimates the sediment concentration for the medium-sized and coarse sediment cases. To improve the model, a formula is proposed to consider the local fluid turbulence enhancement around a particle due to vortex shedding in the wake. Numerical results of the modified model then agree very well with laboratory data for not only the fine but also the coarse sediment cases.

  4. Dynamic release process of pollutants during suspended sediment transport in aquatic system

    Institute of Scientific and Technical Information of China (English)

    朱红伟; 王道增; 程鹏达

    2014-01-01

    Pollutants release is highly consistent with suspended sediment concentration (SSC) in water column, especially during re-suspension and transport events. The present research focuses on pollutant dynamic release from re-suspended sediment, especially the vertical distribution relationship between them. The sediment erosion experiments on a series of uniform flow are conducted in a circulate flume. Reactive tracer (phosphorus) is used as the contaminant in fine-grained sediments to identify the release characteristic length and time. Experimental results show that the flow condition near-bed depends on the sediment surface roughness. The region with high turbulent intensities corresponds to a high concentration sediment layer. In addition, the SSC decreases with the distance, water depth, and particle grain size. The sediment in a smaller grain size takes much more time to reach equilibrium concentration. Total phosphorus (TP) concentration changes along the water depth as SSC in the initial re-suspension stage, appearing in two obvi-ous concentration regimes: the upper low-concentration layer and the high-concentration near-bottom layer. This layered phenomenon remains for about 3 hours until SSC distri-bution tends to be uniform. Longitudinal desorption plays an important role in long-way transport to reduce the amount of suspended sediment in water column.

  5. Modeling sediment transport after ditch network maintenance of a forested peatland

    Science.gov (United States)

    Haahti, K.; Marttila, H.; Warsta, L.; Kokkonen, T.; Finér, L.; Koivusalo, H.

    2016-11-01

    Elevated suspended sediment (SS) loads released from peatlands after drainage operations and the resulting negative effect on the ecological status of the receiving water bodies have been widely recognized. Understanding the processes controlling erosion and sediment transport within the ditch network forms a prerequisite for adequate sediment control. While numerous experimental studies have been reported in this field, model based assessments are rare. This study presents a modeling approach to investigate sediment transport in a peatland ditch network. The transport model describes bed erosion, rain-induced bank erosion, floc deposition, and consolidation of the bed. Coupled to a distributed hydrological model, sediment transport was simulated in a 5.2 ha forestry-drained peatland catchment for 2 years after ditch cleaning. Comparing simulation results to measured SS concentrations suggested that the loose peat material, produced during excavation, contributed markedly to elevated SS concentrations immediately after ditch cleaning. Both snowmelt and summer rainstorms contributed critically to annual loads. Springtime peat erosion during snowmelt was driven by ditch flow whereas during summer rainfalls, bank erosion by raindrop impact was identified as an important process. Relating modeling results to observed spatial topographic changes in the ditch network was challenging and the results were difficult to verify. Nevertheless, the model has potential to identify risk areas for erosion. The results demonstrate that modeling is effective in separating the importance of different processes and complements pure experimental approaches. Modeling results can aid planning and designing efficient sediment control measures and guide the focus of experimental studies.

  6. Sediment transport in an active erodible channel bend of Brahmaputra river

    Indian Academy of Sciences (India)

    Tapas Karmaker; Y Ramprasad; Subashisa Dutta

    2010-12-01

    Spatial variation of sediment transport in an alluvial sand-bed river bend needs to be understood with its influencing factors such as bank erosion, secondary current formation, land spur and bed-material characteristics. In this study, detailed hydrographic surveys with Acoustic Doppler Current Profiler (ADCP) were conducted at an active erodible river bend to measure suspended load, velocity, bathymetric profile and characteristics of the bed material. Study indicates the presence of multi-thread flow in the channel bend. Local variation of sediment transport is primarily controlled by active bank erosion, land spur and sand bar formation. Vertical distribution of suspended sediment concentration follows a power function with normalized depth. Average bed-material concentration at the reach level is computed from observed sediment profiles, and is compared against various sediment transport functions. Results show that the sediment transport function suggested by Yang gives better predictions for this reach. Transverse bed slopes at critical survey transects were computed from the bathymetric data and evaluated with analytical approaches. Out of three analytical approaches used, Odgaard’s approach estimates the bed slopes fairly close to the observed one. These two functions are suitable in the Brahmaputra river for further morphological studies.

  7. Fate and transport modeling of cohesive sediment and sediment-bound HCB in the middle Elbe river basin

    OpenAIRE

    2013-01-01

    Chemical contamination of waterways and floodplains is a pervasive environmental problem that threatens aquatic ecosystems worldwide. The Elbe River is the third largest river in Central Europe, starting in the Czech Republic and running through Dresden and Hamburg before empting into the North Sea. Due to extensive historical contamination and redistribution of contaminated sediments throughout the basin, the Elbe River transports significant loads of contaminants downstream, particularly du...

  8. Sediment and Hydraulic Measurements with Computed Bed Load on the Missouri River, Sioux City to Hermann, 2014

    Science.gov (United States)

    2017-05-01

    Development Center 3909 Halls Ferry Road Vicksburg, MS 39180-6199 John Shelley U.S. Army Corps of Engineers, Kansas City District 601 E 12th St. Kansas...Center. ERDC/CHL TR-17-8 5 channel from bank to bank if possible, depending on boat accessibility and safety . For the subsequent surveys, the covered...3909 Halls Ferry Road Vicksburg, MS 39180-6199 8. PERFORMING ORGANIZATION REPORT NUMBER ERDC/CHL TR-17-8 9. SPONSORING/MONITORING AGENCY

  9. Effect of hydraulic parameters on sediment transport capacity in overland flow over erodible beds

    Science.gov (United States)

    Ali, M.; Sterk, G.; Seeger, M.; Boersema, M.; Peters, P.

    2012-02-01

    Sediment transport is an important component of the soil erosion process, which depends on several hydraulic parameters like unit discharge, mean flow velocity, and slope gradient. In most of the previous studies, the impact of these hydraulic parameters on transport capacity was studied for non-erodible bed conditions. Hence, this study aimed to examine the influence of unit discharge, mean flow velocity and slope gradient on sediment transport capacity for erodible beds and also to investigate the relationship between transport capacity and composite force predictors, i.e. shear stress, stream power, unit stream power and effective stream power. In order to accomplish the objectives, experiments were carried out in a 3.0 m long and 0.5 m wide flume using four well sorted sands (0.230, 0.536, 0.719, 1.022 mm). Unit discharges ranging from 0.07 to 2.07 × 10-3 m2 s-1 were simulated inside the flume at four slopes (5.2, 8.7, 13.2 and 17.6%) to analyze their impact on sediment transport rate. The sediment transport rate measured at the bottom end of the flume by taking water and sediment samples was considered equal to sediment transport capacity, because the selected flume length of 3.0 m was found sufficient to reach the transport capacity. The experimental result reveals that the slope gradient has a stronger impact on transport capacity than unit discharge and mean flow velocity due to the fact that the tangential component of gravity force increases with slope gradient. Our results show that unit stream power is an optimal composite force predictor for estimating transport capacity. Stream power and effective stream power can also be successfully related to the transport capacity, however the relations are strongly dependent on grain size. Shear stress showed poor performance, because part of shear stress is dissipated by bed irregularities, bed form evolution and sediment detachment. An empirical transport capacity equation was derived, which illustrates that

  10. Transport of phosphorus, wash load and suspended sediment in the River Varde A in southwest Jutland, Denmark

    DEFF Research Database (Denmark)

    Thodsen, Hans; Hasholt, Bent; Pejrup, Morten

    2004-01-01

    . Transport rates of TP, suspended sediment and wash load at the three stations, calculated using rating curves, indicate the dependence of TP transport on the transport of suspended sediment and wash load. Two stations are located on tributaries flowing upstream of the third station located at a weir...

  11. Meso-scale aeolian transport of beach sediment via dune blowout pathways within a linear foredune

    Science.gov (United States)

    O'Keeffe, Nicholas; Delgado-Fernandez, Irene; Jackson, Derek; Aplin, Paul; Marston, Christopher

    2016-04-01

    The evolution of coastal foredunes is largely controlled by sediment exchanges between the geomorphic sub-units of the nearshore, beach, foredune and dune field. Although blowouts are widely recognised as efficient sediment transport pathways, both event-scale and meso-scale quantification of their utility in transferring beach sediments landwards is limited. Foredunes characterised by multiple blowouts may be more susceptible to coastline retreat through the enhanced landwards transport of beach or foredune sediments. To date, a key constraint for investigations of such scenarios has been the absence of accurate blowout sediment transport records. Here we use the Sefton coast in north-west England as a study area where an unprecedented temporal coverage of LIDAR data is available between 1999 and 2015. Additionally, an extensive set of aerial photography also exists, dating back to 1945 allowing comparison of blowout frequency and magnitude together with the alongshore limits of coastline retreat. Digital terrain models are derived for each year that LIDAR data is available. Informed by LIDAR based topography and areas of bare sand (aerial photos) terrain models have been created containing individual blowouts. Differentials in 'z' values between each terrain model of each available year has identified topographic change and total levels of transport. Preliminary results have confirmed the importance of blowouts in transporting beach or foredune sediment landwards and thus potentially promoting coastline retreat. Repetition of processes across a larger number of blowout topographies will allow better identification of individual blowouts for 'event' scale field investigations to examine spatial and temporal variability of beach sediment transport via blowouts routes.

  12. Sediment Transport at Density Fronts in Shallow Water

    Science.gov (United States)

    2014-07-16

    mobilization, redistribution, trapping, and deposition of suspended sediment. This current award was a continuation of the original YIP award in order to...including the surface expressions that can be assessed with remote sensing. RELATED PROJECTS This a continuation of the YIP awarded to Ralston

  13. Transport of Gas and Solutes in Permeable Estuarine Sediments

    Science.gov (United States)

    2013-09-30

    profiles in sediment affected by groundwater seepage. Free methane gas builds up below 10 cm depth. The average gas production rate recorded at St...of the nearshore zone (< 2 m water depth), which according to the National Geophysical data center (ETOPO data set, http://www.ngdc.noaa.gov

  14. Simulation and control of sediment transport due to dam removal

    Science.gov (United States)

    This paper presents two case studies of post dam removal sedimentation in the United States. Two different one-dimensional channel evolution simulation models were used: CCHE1D and CONCEPTS, respectively. The first case is the application of CCHE1D to assess a long-term morphological response to the...

  15. A three-dimensional, wave-current coupled, sediment transport model for POM

    Institute of Scientific and Technical Information of China (English)

    WANG Xiao-hua

    2010-01-01

    In the high-energy environment of coastal seas and estuaries,strong sediment resuspension/ deposition events are driven by surface waves,tides,winds and buoyancy driven currents.In recent years,A POM based three-dimensional ,wave-current coupled ,sediment transport model has been developed by the University of New South Wales.This paper presents several examples of the model applications to study sediment dynamics in the environments where forcings such as waves,tides, and winds are equally important to affect sediment fluxes and distributions.Firstly,the sediment transport model coupled to the Yellow Sea general circulation model and a third generation wave model SWAN was implemented in the Yellow Sea to study the dynamics of the sediment transport and resuspension in the northern Jiangsu shoal-water(NJSW).The sediment distributions and fluxes and their inter-annual variability were studied by realistic numerical simulations.The study found that the surface waves played a dominant role over the tides to form the turbidity maxima along the muddy coast of NJSW. Secondly,the sediment transport model was used to explore the effect of suspended sediment-induced stratificationin the bottom boundary layer(BBL).The model uses a re-parameterized bottom drag coefficient Cd that incorporates a linear stability function of flux Richardson number RsThe study has shown that the sediment induced stratification in the BBL reduces the vertical eddy viscosity and bottom shear stress in comparison with the model prediction in a neutrally stratified BBL.In response to these apparent reductions,the tidal current shear is increased and sediments are abnormally concentrated within a thin wall layer that is overlain by a thicker layer with much smaller concentration.The formation of this fluid-mud layer near the seabed has led to a significant reduction in the total sediment transport.This study contributes to the understanding of formations of tidal flats along the coasts of turbid seas

  16. One-dimensional numerical simulation of non-uniform sediment transport under unsteady flows

    Institute of Scientific and Technical Information of China (English)

    Hongwei FANG; Minghong CHEN; Qianhai CHEN

    2008-01-01

    One-dimensional numerical models are popularly used in sediment transport research because they can be easily programmed and cost less time compared with two-and three-dimensional numerical models.In particular,they possess greater capacity to be applied in large river basins with many tributaries.This paper presents a one-dimensional numerical model capable of calculating total-load sediment transport.The cross-section-averaged sediment transport capacity and recovery coefficient are addressed in the suspended load model.This one-dimensional model,therefore,can be applied to fine suspended loads and to hyperconcentrated flows in the Yellow River.Moreover,a new discretization scheme for the equation of unsteady non-uniform suspended sediment transport is proposed.The model is calibrated using data measured from the Yantan Reservoir on the Hongshui River and the Sanmenxia Reservoir on the Yellow River.A comparison of the calculated water level and river bed deformation with field measurements shows that the improved numerical model is capable of predicting flow,sediment transport,bed changes,and bed-material sorting in various situations,with reasonable accuracy and reliability.

  17. Monitoring suspended sediment transport in an ice-affected river using acoustic Doppler current profilers

    Science.gov (United States)

    Moore, S. A.; Ghareh Aghaji Zare, S.; Rennie, C. D.; Ahmari, H.; Seidou, O.

    2013-12-01

    Quantifying sediment budgets and understanding the processes which control fluvial sediment transport is paramount to monitoring river geomorphology and ecological habitat. In regions that are subject to freezing there is the added complexity of ice. River ice processes impact flow distribution, water stage and sediment transport. Ice processes typically have the largest impact on sediment transport and channel morphodynamics when ice jams occur during ice cover formation and breakup. Ice jams may restrict flow and cause local acceleration when released. Additionally, ice can mechanically scour river bed and banks. Under-ice sediment transport measurements are lacking due to obvious safety and logistical reasons, in addition to a lack of adequate measurement techniques. Since some rivers can be covered in ice during six months of the year, the lack of data in winter months leads to large uncertainty in annual sediment load calculations. To address this problem, acoustic profilers are being used to monitor flow velocity, suspended sediment and ice processes in the Lower Nelson River, Manitoba, Canada. Acoustic profilers are ideal for under-ice sediment flux measurements since they can be operated autonomously and continuously, they do not disturb the flow in the zone of measurement and acoustic backscatter can be related to sediment size and concentration. In March 2012 two upward-facing profilers (1200 kHz acoustic Doppler current profiler, 546 KHz acoustic backscatter profiler) were installed through a hole in the ice on the Nelson River, 50 km downstream of the Limestone Generating Station. Data were recorded for four months, including both stable cover and breakup periods. This paper presents suspended sediment fluxes calculated from the acoustic measurements. Velocity data were used to infer the vertical distribution of sediment sizes and concentrations; this information was then used in the interpretation of the backscattered intensity data. It was found that

  18. Modeling sediment transport in the lower Yellow River and dynamic equilibrium threshold value

    Institute of Scientific and Technical Information of China (English)

    HU; Chunhong; GUO; Qingchao

    2004-01-01

    A major problem in the lower Yellow River is the insufficient incoming water and excessive sediment supply, which results in serious deposition, continuous rise of the river bed, and austere flood control situation. To understand the sediment transport regularity of the lower Yellow River and determine the relationship between sedimentation,incoming water and sediment, and zone water diversion, a mathematical model of the sediment suitable for the characteristics of the lower Yellow River has been developed.This model is first rated and verified by large quantity of observed data, and it is then used to analyze silting reduction for the lower Yellow River by Xiaolangdi Reservoir's operation,the relationship between zone water diversion and channel sedimentation, and critical equilibrium of sedimentation in the lower Yellow River. The threshold values of equilibrium of sedimentation in the lower Yellow River are estimated and they suggest that deposition in the lower Yellow River can be effectively reduced by the operation of regulating flow and sediment from Xiaolangdi Reservoir, water-soil conservation, and controlling water diversion along the lower Yellow River.

  19. Shifting sources and transport paths for the late Quaternary Escanaba Trough sediment fill (northeast Pacific)

    Science.gov (United States)

    Zuffa, G.G.; De Rosa, R.; Normark, W.R.

    1997-01-01

    Escanaba Trough, which forms the southernmost part of the axial valley of the actively spreading Gorda Ridge, is filled with several hundred meters of sediment of presumed late Quaternary age. Surficial sediment samples from gravity cores, deeper samples (as much as 390 m) from Site 35 of the Deep Sea Drilling Program (Leg 5), and the acoustic character of the sediment fill observed on seismic-reflection profiles indicate that much of the sediment fill is of turbidite origin. Gross composition and heavy- mineral analyses of sand samples show that two distinct petrofacies comprise the sediment fill. The lower part of the fill was derived primarily from the Klamath River source of northern California while the younger fill, including the surficial sand beds, are from the Columbia River drainage much farther north. The Escanaba Trough sediment provides an opportunity to evaluate concepts for paleogeographic and paleotectonic reconstructions that are based on facies analysis and compositional and textural data for the volcanic components because both intrabasinal and extrabasinal sources are present as well as coeval (neovolcanic) and non coeval (paleovolcanic) sourcre This study of a modern basin shows, that although the sediment sources could be identified, it was useful to have some knowledge of the sediment pathway(s), the effects of diagenesis, and the possible effects of sediment sorting as a result of long transport distances from the source area for some components. Application of these same techniques to ancient deposits without benefit of the additional parameters will face limitations.

  20. Comparing Two Numerical Models in Simulating Hydrodynamics and Sediment Transport at a Dual Inlet System, West-Central Florida

    Science.gov (United States)

    2015-05-15

    1 COMPARING TWO NUMERICAL MODELS IN SIMULATING HYDRODYNAMICS AND SEDIMENT TRANSPORT AT A DUAL INLET SYSTEM, WEST-CENTRAL FLORIDA PING WANG1...numerical modeling systems, CMS and DELFT3D, in simulating the hydrodynamic and sediment transport processes. The model results are compared with...Introduction Simulating complex fields of wave, current, sediment transport , and morphology change in the vicinity of tidal inlets is a

  1. Limitations of empirical sediment transport formulas for shallow water and their consequences for swash zone modelling

    CERN Document Server

    Li, Wei; Pähtz, Thomas; He, Zhiguo; Cao, Zhixian

    2016-01-01

    Volumetric sediment concentrations computed by phase-resolving swash morphodynamic models are shown to exceed unity minus porosity (i.e. the maximal physically possible concentration value) by up to factor of $10^5$ when using standard expressions to compute the sediment transport rate. An ad hoc limit of sediment concentration is introduced as a means to evaluate consequences of exceeding physically realistic concentration by standard expressions. We find that implementation of this ad hoc limit strongly changes the quantitative and qualitative predictions of phase-resolving swash morphodynamic models, suggesting that existing swash predictions are unreliable. This is because standard expressions inappropriately consider or ignore the fact that the shallow swash water depth limits the storage capacity of transported sediment.

  2. Linking Arenicola marina irrigation behavior to oxygen transport and dynamics in sandy sediments

    DEFF Research Database (Denmark)

    Timmermann, Karen; Banta, Gary T.; Glud, Ronnie Nøhr

    2007-01-01

    In this study we examine how the irrigation behavior of the common lugworm Arenicola marina affects the distribution, transport and dynamics of oxygen in sediments using microelectrodes, planar optodes and diagenetic modeling. The irrigation pattern was characterized by a regular recurring periods...... mediated oxygen uptake of the burrow wall. Approximately 28% of the oxygen was consumed by the feeding pocket/funnel characterized by advective porewater transport. Model simulations indicated that oxygen injected into the sediment was usually consumed in a very narrow zone around the feeding pocket...... concentration in the burrow was high (80% air saturation) and oxygen was detected at distances up to 0.7 mm from the burrow wall. Volume specific oxygen consumption rates calculated from measured oxygen profiles were up to 4 times higher for sediments surrounding worm burrows as compared to surface sediments...

  3. The onset of sediment transport in vegetated channels predicted by turbulent kinetic energy

    Science.gov (United States)

    Yang, J. Q.; Chung, H.; Nepf, H. M.

    2016-11-01

    This laboratory study advances our understanding of sediment transport in vegetated regions, by describing the impact of stem density on the critical velocity, Ucrit, at which sediment motion is initiated. Sparse emergent vegetation was modeled with rigid cylinders arranged in staggered arrays of different stem densities. The sediment transport rate, Qs, was measured over a range of current speeds using digital imaging, and the critical velocity was selected as the condition at which the magnitude of Qs crossed the noise threshold. For both grain sizes considered here (0.6-0.85 mm and 1.7-2 mm), Ucrit decreased with increasing stem density. This dependence can be explained by a threshold condition based on turbulent kinetic energy, kt, suggesting that near-bed turbulence intensity may be a more important control than bed shear stress on the initiation of sediment motion. The turbulent kinetic energy model unified the bare bed and vegetated channel measurements.

  4. Sediment processes and mercury transport in a frozen freshwater fluvial lake (Lake St. Louis, QC, Canada).

    Science.gov (United States)

    Canário, João; Poissant, Laurier; O'Driscoll, Nelson; Vale, Carlos; Pilote, Martin; Lean, David

    2009-04-01

    An open-bottom and a closed-bottom mesocosm were developed to investigate the release of mercury from sediments to the water column in a frozen freshwater lake. The mesoscosms were deployed in a hole in the ice and particulate mercury (Hg(P)) and total dissolved mercury (TDHg) were measured in sediments and in water column vertical profiles. In addition, dissolved gaseous mercury (DGM) in water and mercury water/airflux were quantified. Concentrations of TDHg, DGM, and mercury flux were all higher in the open-bottom mesocosm than in the closed-bottom mesocosm. In this paper we focus on the molecular diffusion of mercury from the sediment in comparison with the TDHg accumulation in the water column. We conclude that the molecular diffusion and sediment resuspension play a minor role in mercury release from sediments suggesting that solute release during ebullition is an important transport process for mercury in the lake.

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

    Institute of Scientific and Technical Information of China (English)

    ZHANG Hongwu; HUANG Yuandong; ZHAO Lianjun

    2001-01-01

    A one-dimensional mathematical model for unsteady sediment transport in the Lower Yellow River is developed. A coefficient of sediment distribution is defined to represent the ratio of the bottom to the average concentration under the equilibrium conditions. The coefficient is not constant and is evaluated by using an empirical expression obtained by integrating the sediment concentration along water depth.The concentration distributions and the mean diameter distributions of suspended sediment in the transversal direction are also estimated in this model. A four-point (Preismann type) finite difference scheme and TDMA are employed in the numerical method. Three typical floods occurd in 1977,1982 and 1996, respectively, in the Lower Yellow River from Tiexie to Shunkou with a length of 393.67km are numerically simulated with the model. The computed results, such as the water stage, discharge,and sediment concentration agree well with the measured data.

  6. Cable bacteria associated with long-distance electron transport in New England salt marsh sediment.

    Science.gov (United States)

    Larsen, Steffen; Nielsen, Lars Peter; Schramm, Andreas

    2015-04-01

    Filamentous Desulfobulbaceae have been proposed as 'cable bacteria', which electrically couple sulfide oxidation and oxygen reduction in marine sediment and thereby create a centimetre-deep suboxic zone. We incubated New England salt marsh sediment and found long-distance electron transport across 6 mm and 16S rRNA genes identical to those of previously observed cable bacteria in Aarhus Bay sediment incubations. Cable bacteria density in sediment cores was quantified by fluorescence in situ hybridization. In contrast to the coastal, subtidal sediments with short-termed blooms of cable bacteria based on rapidly depleted iron sulfide pools, the salt marsh cable community was based on ongoing sulfate reduction and therefore probably more persistent. Previously observed seasonal correlation between Desulfobulbaceae dominance and extensive reduced sulfur oxidation in salt marshes suggest that cable bacteria at times may have an important role in situ.

  7. Including Flocculation in a Numerical Sediment Transport Model for a Partially-Mixed Estuary

    Science.gov (United States)

    Tarpley, D.; Harris, C. K.; Friedrichs, C. T.

    2016-12-01

    Particle settling velocity impacts the transport of suspended sediment to the first order but fine-grained material like muds tend to form loosely bound aggregates (flocs) whose settling velocity can vary widely. Properties of flocculated sediment such as settling velocity and particle density are difficult to predict because they change in response to several factors including salinity, suspended sediment concentration, turbulent mixing, and organic content. Knowledge of the mechanisms governing flocculation of cohesive sediment is rapidly expanding; especially in response to recent technical advances. As the understanding of particle dynamics progresses, numerical models describing flocculation and break-up are being developed with varying degrees of complexity. While complex models capture the dynamics of the system, their computational costs may prohibit their incorporation into larger model domains. It is important to determine if the computational costs of intricate floc models are justifiable compared to simpler formulations. For this study, we implement an idealized two-dimensional model designed to represent a longitudinal section of a partially mixed estuary that neglects across-channel variation but exhibits salinity driven estuarine circulation. The idealized domain is designed to mimic the primary features of the York River, VA. Suspended load, erosion and deposition are calculated within the sediment transport routines of the COAWST modeling system. We compare different methods for prescribing settling velocity of fine-grained material. The simplest, standard model neglects flocculation dynamics while the complex treatment is a size-class-based flocculation model (FLOCMOD). Differences in tidal and daily averages of suspended load, bulk settling velocity and bed deposition are compared between the standard and FLOCMOD runs, to examine the relative impact of flocculation on sediment transport patterns. We expect FLOCMOD to have greater variability and

  8. Flocculation, Optics and Turbulence in the Community Sediment Transport Model System: Application of Oasis Results

    Science.gov (United States)

    2012-09-30

    1 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Flocculation , Optics and Turbulence in the Community...www.phys.ocean.dal.ca/~phill LONG-TERM GOALS The goal of this research is to develop greater understanding of how the flocculation of fine-grained sediment...COVERED - 4. TITLE AND SUBTITLE Flocculation , Optics and Turbulence in the Community Sediment Transport Model System: Application of Oasis

  9. A Multiphase First Order Model for Non-Equilibrium Sand Erosion, Transport and Sedimentation

    CERN Document Server

    Preziosi, Luigi; Bruno, Luca

    2015-01-01

    Three phenomena are involved in sand movement: erosion, wind transport, and sedimentation. This paper presents a comprehensive easy-to-use multiphase model that include all three aspects with a particular attention to situations in which erosion due to wind shear and sedimentation due to gravity are not in equilibrium. The interest is related to the fact that these are the situations leading to a change of profile of the sand bed.

  10. Observations of pockmark flow structure in Belfast Bay, Maine, Part 3: implications for sediment transport

    Science.gov (United States)

    Fandel, Christina L.; Lippmann, Thomas C.; Foster, Diane L.; Brothers, Laura L.

    2017-01-01

    Current observations and sediment characteristics acquired within and along the rim of two pockmarks in Belfast Bay, Maine, were used to characterize periods of sediment transport and to investigate conditions favorable to the settling of suspended sediment. Hourly averaged Shields parameters determined from horizontal current velocity profiles within the center of each pockmark never exceed the critical value (approximated with the theoretical model of Dade et al. 1992). However, Shields parameters estimated at the pockmark rims periodically exceed the critical value, consistent with conditions that support the onset of sediment transport and suspension. Below the rim in the near-center of each pockmark, depth-averaged vertical velocities were less than zero (downward) 60% and 55% of the time in the northern and southern pockmarks, and were often comparable to depth-averaged horizontal velocities. Along the rim, depth-averaged vertical velocities over the lower 8 m of the water column were primarily downward but much less than depth-averaged horizontal velocities indicating that suspended sediment may be moved to distant locations. Maximum grain sizes capable of remaining in suspension under terminal settling flow conditions (ranging 10–170 μm) were typically much greater than the observed median grain diameter (about 7 μm) at the bed. During upwelling flow within the pockmarks, and in the absence of flocculation, suspended sediment would not settle. The greater frequency of predicted periods of sediment transport along the rim of the southern pockmark is consistent with pockmark morphology in Belfast Bay, which transitions from more spherical to more elongated toward the south, suggesting near-bed sediment transport may contribute to post-formation pockmark evolution during typical conditions in Belfast Bay.

  11. Observations of pockmark flow structure in Belfast Bay, Maine, Part 3: implications for sediment transport

    Science.gov (United States)

    Fandel, Christina L.; Lippmann, Thomas C.; Foster, Diane L.; Brothers, Laura L.

    2017-02-01

    Current observations and sediment characteristics acquired within and along the rim of two pockmarks in Belfast Bay, Maine, were used to characterize periods of sediment transport and to investigate conditions favorable to the settling of suspended sediment. Hourly averaged Shields parameters determined from horizontal current velocity profiles within the center of each pockmark never exceed the critical value (approximated with the theoretical model of Dade et al. 1992). However, Shields parameters estimated at the pockmark rims periodically exceed the critical value, consistent with conditions that support the onset of sediment transport and suspension. Below the rim in the near-center of each pockmark, depth-averaged vertical velocities were less than zero (downward) 60% and 55% of the time in the northern and southern pockmarks, and were often comparable to depth-averaged horizontal velocities. Along the rim, depth-averaged vertical velocities over the lower 8 m of the water column were primarily downward but much less than depth-averaged horizontal velocities indicating that suspended sediment may be moved to distant locations. Maximum grain sizes capable of remaining in suspension under terminal settling flow conditions (ranging 10-170 μm) were typically much greater than the observed median grain diameter (about 7 μm) at the bed. During upwelling flow within the pockmarks, and in the absence of flocculation, suspended sediment would not settle. The greater frequency of predicted periods of sediment transport along the rim of the southern pockmark is consistent with pockmark morphology in Belfast Bay, which transitions from more spherical to more elongated toward the south, suggesting near-bed sediment transport may contribute to post-formation pockmark evolution during typical conditions in Belfast Bay.

  12. Turbulent Flow and Sand Dune Dynamics: Identifying Controls on Aeolian Sediment Transport

    Science.gov (United States)

    Weaver, C. M.; Wiggs, G.

    2007-12-01

    Sediment transport models are founded on cubic power relationships between the transport rate and time averaged flow parameters. These models have achieved limited success and recent aeolian and fluvial research has focused on the modelling and measurement of sediment transport by temporally varying flow conditions. Studies have recognised turbulence as a driving force in sediment transport and have highlighted the importance of coherent flow structures in sediment transport systems. However, the exact mechanisms are still unclear. Furthermore, research in the fluvial environment has identified the significance of turbulent structures for bedform morphology and spacing. However, equivalent research in the aeolian domain is absent. This paper reports the findings of research carried out to characterise the importance of turbulent flow parameters in aeolian sediment transport and determine how turbulent energy and turbulent structures change in response to dune morphology. The relative importance of mean and turbulent wind parameters on aeolian sediment flux was examined in the Skeleton Coast, Namibia. Measurements of wind velocity (using sonic anemometers) and sand transport (using grain impact sensors) at a sampling frequency of 10 Hz were made across a flat surface and along transects on a 9 m high barchan dune. Mean wind parameters and mass sand flux were measured using cup anemometers and wedge-shaped sand traps respectively. Vertical profile data from the sonic anemometers were used to compute turbulence and turbulent stress (Reynolds stress; instantaneous horizontal and vertical fluctuations; coherent flow structures) and their relationship with respect to sand transport and evolving dune morphology. On the flat surface time-averaged parameters generally fail to characterise sand transport dynamics, particularly as the averaging interval is reduced. However, horizontal wind speed correlates well with sand transport even with short averaging times. Quadrant

  13. Basic problems and new potentials in monitoring sediment transport using Japanese pipe type geophone

    Science.gov (United States)

    Sakajo, Saiichi

    2016-04-01

    The authors have conducted a lot of series of monitoring of sediment transport by pipe type geophone in a model hydrological channel with various gradients and water discharge, using the various size of particles from 2 to 21 mm in the diameter. In the case of casting soils particle by particle into the water channel, 1,000 test cases were conducted. In the case of casting all soils at a breath into the water channel, 100 test cases were conducted. The all test results were totally analyzed by the conventional method, with visible judgement by video pictures. Then several important basic problems were found in estimating the volume and particle distributions by the conventional method, which was not found in the past similar studies. It was because the past studies did not consider the types of collisions between sediment particle and pipe. Based on these experiments, the authors have firstly implemented this idea into the old formula to estimate the amount of sediment transport. In the formula, two factors of 1) the rate of sensing in a single collision and 2) the rate of collided particles to a cast all soil particles were concretely considered. The parameters of these factors could be determined from the experimental results and it was found that the obtained formula could estimate grain size distribution. In this paper, they explain the prototype formula to estimate a set of volume and distribution of sediment transport. Another finding in this study is to propose a single collision as a river index to recognize its characteristics of sediment transport. This result could characterize the risk ranking of sediment transport in the rivers and mudflow in the mountainous rivers. Furthermore, in this paper the authors explain how the preciseness of the pipe geophone to sense the smaller sediment particles shall be improved, which has never been able to be sensed.

  14. Processes and controls of ditch erosion and suspended sediment transport in drained peatland forests

    Science.gov (United States)

    Tuukkanen, Tapio; Stenberg, Leena; Marttila, Hannu; Finér, Leena; Piirainen, Sirpa; Koivusalo, Harri; Kløve, Bjørn

    2016-04-01

    Drainage and periodic ditch cleaning are needed in peatland forests to allow adequate tree growth. The downside is that these practices usually increase erosion and transport of organic and inorganic matter to downstream waterbodies. In this study, our aim was to assess the role of hydrological factors and ditch-level bed and bank erosion processes in controlling suspended sediment (SS) transport in peatland forests after ditch cleaning. To do this, a 113 ha catchment and a nested sub-catchment (5.2 ha) in eastern Finland were instrumented for continuous hydrological and SS concentration (turbidity) measurements and for the detection of ditch bed and bank erosion with erosion pins. The impacts of ditch cleaning on instantaneous unit hydrographs were also assessed against two reference catchments. The results suggested that, in small intensively drained catchments, SS transport is likely to be limited by the availability of easily erodible sediment in the ditch network, and that ditch cleaning operations as well as preparatory bank erosion processes such as peat desiccation and frost action can be important in producing erodible sediment for transport. Detachment of soil particle from ditch banks by raindrop impact can also be an important factor explaining variations in SS concentrations in small catchments. In larger drainage areas, peak runoff characteristics may play a more dominant role in SS transport. The results give new insights into the dynamics of sediment transport in drained peatland catchments, which can be useful, for example, for planning and implementation of water conservation measures.

  15. Sediment transport following water transfer from Yangtze River to Taihu Basin

    Directory of Open Access Journals (Sweden)

    Zheng GONG

    2011-12-01

    Full Text Available To meet the increasing need of fresh water and to improve the water quality of Taihu Lake, water transfer from the Yangtze River was initiated in 2002. This study was performed to investigate the sediment distribution along the river course following water transfer. A rainfall-runoff model was first built to calculate the runoff of the Taihu Basin in 2003. Then, the flow patterns of river networks were simulated using a one-dimensional river network hydrodynamic model. Based on the boundary conditions of the flow in tributaries of the Wangyu River and the water level in Taihu Lake, a one-dimensional hydrodynamic and sediment transport numerical model of the Wangyu River was built to analyze the influences of the inflow rate of the water transfer and the suspended sediment concentration (SSC of inflow on the sediment transport. The results show that the water transfer inflow rate and SSC of inflow have significant effects on the sediment distribution. The higher the inflow rate or SSC of inflow is, the higher the SSC value is at certain cross-sections along the river course of water transfer. Higher inflow rate and SSC of inflow contribute to higher sediment deposition per kilometer and sediment thickness. It is also concluded that a sharp decrease of the inflow velocity at the entrance of the Wangyu River on the river course of water transfer induces intense sedimentation at the cross-section near the Changshu hydro-junction. With an increasing distance from the Changshu hydro-junction, the sediment deposition and sedimentation thickness decrease gradually along the river course.

  16. Modeling the sediment transport induced by deep sea mining in the Pacific Ocean

    Science.gov (United States)

    Purkiani, Kaveh; Paul, André; Schulz, Michael; Vink, Annemiek; Walter, Maren

    2017-04-01

    A numerical modeling study is conducted in the German license area in northeastern Pacific Ocean to investigate the sediment dispersal of mining exploitation. A sediment transport module is implemented in a hydrodynamic model. All differently sized particles can aggregate and break up until equilibrium floc sizes are obtained. A nested model approach using the MITgcm (Massachusetts Institute of Technology general circulation model) is applied and validated against hydrographic and hydrodynamic measurements obtained in this region. Two different sediment discharge scenarios have been examined to investigate the effect of flocculation on sediment transport distribution in the deep ocean. The suspended sediment is mainly influenced by a dominant SW current far away from the sediment discharge location. Independent of initial particle size all initial particles larger than 30 μm attain similar floc size equilibrium. In contrast to coastal seas and estuaries where floc size equilibrium can be obtained in a few hours, due to low shear rate (G) the flocculation process at deep ocean is completed within 1˜2 days. Considering temporal evolution of the floc size in the model, an increase in floc sinking velocity consequently enhances the sediment deposition at seafloor. The analysis of different sediment concentration scenarios suggests that floc sinking velocity increases at higher suspended sediment concentration (SSC). The presence of a dominant current in this region induces a fine sediment plume in SW direction. The dispersed SSC plume at 20 km downstream the discharge location is able to form the flocculation process and induces a spatial variation of floc size and floc sinking velocity.

  17. Sediment Characteristics and Transport in the Kootenai River White Sturgeon Critical Habitat near Bonners Ferry, Idaho

    Science.gov (United States)

    Fosness, Ryan L.; Williams, Marshall L.

    2009-01-01

    Recovery efforts for the endangered Kootenai River population of white sturgeon require an understanding of the characteristics and transport of suspended and bedload sediment in the critical habitat reach of the river. In 2007 and 2008, the U.S. Geological Survey in cooperation with the Kootenai Tribe of Idaho, conducted suspended- and bedload-sediment sampling in the federally designated critical habitat of the endangered Kootenai River white sturgeon population. Three sediment-sampling sites were selected that represent the hydraulic differences in the critical habitat. Suspended- and bedload-sediment samples along with acoustic Doppler current profiles were collected at these sites during specific river discharges. Samples were analyzed to determine suspended- and bedload-sediment characteristics and transport rates. Sediment transport data were analyzed to provide total loading estimates for suspended and bedload sediment in the critical habitat reach. Total suspended-sediment discharge primarily occurred as fine material that moved through the system in suspension. Total suspended-sediment discharge ranged from about 300 metric tons per day to more than 23,000 metric tons per day. Total suspended sediment remained nearly equal throughout the critical habitat, with the exception of a few cases where mass wasting of the banks may have caused sporadic spikes in total suspended sediment. Bedload-sediment discharge averaged 0-3 percent of the total loading. These bedload discharges ranged from 0 to 271 tons per day. The bedload discharge in the upper part of the critical habitat primarily consisted of fine to coarse gravel. A decrease in river competence in addition to an armored channel may be the cause of this limited bedload discharge. The bedload discharge in the middle part of the white sturgeon critical habitat varied greatly, depending on the extent of the backwater from Kootenay Lake. A large quantity of fine-to-coarse gravel is present in the braided

  18. Comparison between Measured and Calculated Sediment Transport Rates in North Fork Caspar Creek, California

    Science.gov (United States)

    Kim, T. W.; Yarnell, S. M.; Yager, E.; Leidman, S. Z.

    2015-12-01

    Caspar Creek is a gravel-bedded stream located in the Jackson Demonstration State Forest in the coast range of California. The Caspar Creek Experimental Watershed has been actively monitored and studied by the Pacific Southwest Research Station and California Department of Forestry and Fire Protection for over five decades. Although total annual sediment yield has been monitored through time, sediment transport during individual storm events is less certain. At a study site on North Fork Caspar Creek, cross-section averaged sediment flux was collected throughout two storm events in December 2014 and February 2015 to determine if two commonly used sediment transport equations—Meyer-Peter-Müller and Wilcock—approximated observed bedload transport. Cross-section averaged bedload samples were collected approximately every hour during each storm event using a Helley-Smith bedload sampler. Five-minute composite samples were collected at five equally spaced locations along a cross-section and then sieved to half-phi sizes to determine the grain size distribution. The measured sediment flux values varied widely throughout the storm hydrographs and were consistently less than two orders of magnitude in value in comparison to the calculated values. Armored bed conditions, changing hydraulic conditions during each storm and variable sediment supply may have contributed to the observed differences.

  19. Well-balanced and flexible morphological modeling of swash hydrodynamics and sediment transport

    CERN Document Server

    Hu, Peng; He, Zhiguo; Pähtz, Thomas; Yue, Zhiyuan

    2014-01-01

    Existing numerical models of the swash zone are relatively inflexible in dealing with sediment transport due to a high dependence of the deployed numerical schemes on empirical sediment transport relations. Moreover, these models are usually not well-balanced, meaning they are unable to correctly simulate quiescent flow. Here a well-balanced and flexible morphological model for the swash zone is presented. The nonlinear shallow water equations and the Exner equation are discretized by the shock-capturing finite volume method, in which the numerical flux and the bed slope source term are estimated by a well-balanced version of the SLIC (Slope LImited Centered) scheme that does not depend on empirical sediment transport relations. The satisfaction of the well-balanced property is demonstrated through simulating quiescent coastal flow. The quantitative accuracy of the model in reproducing key parameters (i.e., the notional shoreline position, the swash depth, the flow velocity, the overtopping flow volume, the b...

  20. Impacts of ship movement on the sediment transport in shipping channel

    Institute of Scientific and Technical Information of China (English)

    JI Sheng-cheng; OUAHSINE Abdellatif; SMAOUI Hassan; SERGENT Philippe; JING Guo-qing

    2014-01-01

    The duration of ship-generated waves (wake waves) and accelerated currents can generate significant influences on the sediment transport. A 3-D numerical model is presented to estimate these effects. The hydrodynamic model is the 3-D Reynolds averaged Navier-Stokes (RANS) equations including the standardk-e model while the 3-D convection-diffusion model is for the resuspended sediment transport. This hydro-sedimentary model is firstly validated with the trench experimental results, and then applied to the open channel with a moving ship. The computed results demonstrate that the resuspension generation mainly depends on ship speeds, barge number, and the relative distance away from ship. The acceleration effects of ship on the sediment transport are analyzed as well.

  1. 3D modelling of the transport and fate of riverine fine sediment exported to a semi-enclosed system

    Science.gov (United States)

    Delandmeter, Philippe; Lambrechts, Jonathan; Lewis, Stephen; Legat, Vincent; Deleersnijder, Eric; Wolanski, Eric

    2015-04-01

    Understanding the transport and fate of suspended sediment exported by rivers is crucial for the management of sensitive marine ecosystems. Sediment transport and fate can vary considerably depending on the geophysical characteristics of the offshore environment (i.e. open, semi-enclosed and enclosed systems and the nature of the continental shelf). In this presentation, we focus on a semi-enclosed setting in the Great Barrier Reef, NE Australia. In this system, the large tropical Burdekin River discharges to a long and narrow continental shelf containing numerous headlands and embayments. Using a new 3D sediment model we developed and SLIM 3D, a Finite Element 3D model for coastal flows, we highlight the key processes of sediment transport for such a system. We validate the model with available measured data from the region. Wind direction and speed during the high river flows are showed to largely control the dynamics and final fate of the sediments. Most (71%) of the sediment load delivered by the river is deposited and retained near the river mouth. The remaining sediment is transported further afield in riverine freshwater plumes. The suspended sediment transported longer distances in the freshwater plumes can reach sensitive marine ecosystems. These results are compared to previous studies on the Burdekin River sediment fate and differences are analysed. The model suggests that wind-driven resuspension events will redistribute sediments within an embayment but have little influence on transporting sediments from bay to bay.

  2. Hydrodynamics and Associated Sediment Transport over Coastal Wetlands in Quanzhou Bay,China

    Institute of Scientific and Technical Information of China (English)

    WANG Ai-jun

    2011-01-01

    Coastal salt marshes represent an important coastal wetland system.In order to understand the differences between boundary layer parameters of vegetated and unvegetated areas,as well as the mechanisms of sediment transport,several electromagnetic current meters(AEM HR,products of Alec Electronics Co.Ltd.)were deployed in coastal wetlands in Quanzhou Bay,China,to measure current velocity.During the low tide phase,the surficial sediment was collected at 10 m intervals.In situ measurements show that the current velocities on the bare flat were much higher than those in the Spartina alterniora marsh.Current velocity also varied with distance from marsh edge and plant canopy height and diameter.Around 63% of the velocity profiles in the tidal creek can be described by a logarithmic equation.Over the bare flat and Spartina alterniglora marsh,a logarithmic profile almost occurs during the flood tide phase.Sediment analysis shows that mean grain size was 6.7(D along the marsh edge,and surface sediments were transported from bare flat to marsh;the tidal creeks may change this sediment transport pattern.The hydrodynamics at early flood tide and late ebb tide phases determined the net transport direction within the study area.

  3. Experimental investigation of internal structure of open-channel flow with intense transport of sediment

    Directory of Open Access Journals (Sweden)

    Matoušek Václav

    2015-12-01

    Full Text Available Gravity-driven open-channel flows carrying coarse sediment over an erodible granular deposit are studied. Results of laboratory experiments with artificial sediments in a rectangular tilting flume are described and analyzed. Besides integral quantities such as flow rate of mixture, transport concentration of sediment and hydraulic gradient, the experiments include measurements of the one-dimensional velocity distribution across the flow. A vertical profile of the longitudinal component of local velocity is measured across the vertical axis of symmetry of a flume cross section using three independent measuring methods. Due to strong flow stratification, the velocity profile covers regions of very different local concentrations of sediment from virtually zero concentration to the maximum concentration of bed packing. The layered character of the flow results in a velocity distribution which tends to be different in the transport layer above the bed and in the sediment-free region between the top of the transport layer and the water surface. Velocity profiles and integral flow quantities are analyzed with the aim of evaluating the layered structure of the flow and identifying interfaces in the flow with a developed transport layer above the upper plane bed.

  4. A depth-averaged 2-D model of flow and sediment transport in coastal waters

    Science.gov (United States)

    Sanchez, Alejandro; Wu, Weiming; Beck, Tanya M.

    2016-11-01

    A depth-averaged 2-D model has been developed to simulate unsteady flow and nonuniform sediment transport in coastal waters. The current motion is computed by solving the phase-averaged 2-D shallow water flow equations reformulated in terms of total-flux velocity, accounting for the effects of wave radiation stresses and general diffusion or mixing induced by current, waves, and wave breaking. The cross-shore boundary conditions are specified by assuming fully developed longshore current and wave setup that are determined using the reduced 1-D momentum equations. A 2-D wave spectral transformation model is used to calculate the wave height, period, direction, and radiation stresses, and a surface wave roller model is adopted to consider the effects of surface roller on the nearshore currents. The nonequilibrium transport of nonuniform total-load sediment is simulated, considering sediment entrainment by current and waves, the lag of sediment transport relative to the flow, and the hiding and exposure effect of nonuniform bed material. The flow and sediment transport equations are solved using an implicit finite volume method on a variety of meshes including nonuniform rectangular, telescoping (quadtree) rectangular, and hybrid triangular/quadrilateral meshes. The flow and wave models are integrated through a carefully designed steering process. The model has been tested in three field cases, showing generally good performance.

  5. Three-dimensional airflow and sediment transport patterns over barchan dunes

    Science.gov (United States)

    Smith, Alexander B.; Jackson, Derek W. T.; Cooper, J. Andrew G.

    2017-02-01

    Airflow dynamics and potential sediment transport were measured and modelled across various barchan dune topographies and incident wind conditions. Modification of near surface flow was recorded simultaneously in three dimensions (3D) using dense arrays of high-resolution 3D ultrasonic anemometers. In situ measurements provided rigorous validation and calibration for computational fluid dynamics (CFD) modelling. Measured and modelled results show good agreement between flow velocity, directionality, and turbulence intensity. Modelling of characteristic airflow conditions and surface shear stress beyond the instrument locations, elucidated airflow dynamics across the entire landform surface at an unprecedented level of detail. Emergent turbulent airflow patterns were identified in the form of two counter-rotating vortices that converge at the dune centreline downwind of the dune crest. Integrating a sediment transport function with CFD surface airflow allows for the spatial mapping of flux patterns across the entirety of the dune and interdune surface. On the stoss slope and laterally along the outer barchan arms, there is strong potential sediment flux in response to increased streamwise stress. In lee-side locations, sediment transport remains at 'above threshold' conditions and is redirected in response to complex turbulent vortices identified in the overlying wake zone. The precision of the models allows for the identification of complex flow perturbations and associated surface stresses that prove difficult to measure in the field. CFD in combination with a sediment transport function is demonstrated to be a useful tool in investigating morphodynamics of mobile dune systems.

  6. Regional Sediment Management (RSM) Modeling Tools: Integration of Advanced Sediment Transport Tools into HEC-RAS

    Science.gov (United States)

    2014-06-01

    Regional Sediment Management (RSM) Point of Contact, Dr. Paul M. Boyd (Paul.M.Boyd@ usace.army.mil), or to Dr. Standford A. Gibson (Stanford.Gibson...Parker. 2004. Experiments on upstream-migrating erosional narrowing and widening of an incisional channel caused by dam removal. Water Resources

  7. Turbulent Processes and Sediment Transport in a Salt Marsh Tidal Channel

    Science.gov (United States)

    Meyers, S. T.; Voulgaris, G.

    2001-05-01

    The North Inlet marsh system of South Carolina is an extensive system (32.2 km2) of meandering tidal channels of which some are terminal while others are connected to neighboring Winyah Bay to the south. Long-term (yearly/decadal) studies have shown that the marsh continues to accrete sediment at a rate equal to relative sea level rise and even grows laterally despite short-term (daily/weekly) suspended sediment flux data that imply net export of sediment from the marsh. Turbulence levels were examined in order to gain more insight into the poorly known hydrodynamic conditions of this marsh and how sediment transport is affected by these conditions. Turbulence values were estimated using 3D point velocities measured by a Sontek Acoustic Doppler Velocimeter (ADV). Suspended sediment concentrations and size distributions were obtained using a Laser In-Situ Scattering and Transmissometry (LISST-100) particle size analyzer at a single point in addition to measurements from an OBS-3 optical backscatter instrument. Water samples were collected and filtered to 0.5 μ m to obtain mass concentrations for instrument calibration. These concentrations were coupled with velocity distributions to examine the dynamics of suspended sediment flux in the upper reaches of the terminal channel. Greater velocities were consistently observed during ebb tidal flow producing a signature asymmetry to the time vs. velocity characteristics of this system. Ebb velocities were in the range of 20cm greater than flood, representing the potential for suspended sediment concentrations to be higher via entrainment during this portion of the tidal cycle. Shear friction velocity (u*) values were obtained using the covariance method with Reynolds stress estimates (). Suspended sediment concentrations were found to be the highest approaching low tide. The temporal comparison of velocity, sediment size, and sediment concentration implies that, in addition to re-entrainment, flocculation may play an

  8. Sediment transport and deposition in Lakes Marion and Moultrie, South Carolina, 1942-85

    Science.gov (United States)

    Patterson, G.G.; Cooney, T.W.; Harvey, R.M.

    1996-01-01

    Lakes Marion and Moultrie, two large reservoirs in the South Carolina Coastal Plain, receive large inflows of sediment from the Santee River. The average rate of sediment deposition for both lakes during the period 1942-85 was about 0.06 inch per year, or about 800 acre-feet per year. The rate during 1983-85 was about 0.037 inch per year, or about 490 acre-feet per year, reflecting the decreasing trend in sediment inflow. This is a reversal of a trend toward increasing suspended- sediment concentrations in streams that were caused by farming practices in the southern Piedmont from about 1800 to about 1920. Only a small part of the eroded sediment has been carried out of the Piedmont, but the remaining sediment is becoming less available for transport. Sediment deposition is concentrated in several areas of upper Lake Marion where the velocity of the incoming water decreases significantly. Beds of aquatic macrophytes appear to encourage deposition which, in turn, creates favorable habitat for the plants. The rate of sediment accumulation in Lakes Marion and Moultrie averaged 650,000 tons per year during 1983-85, reflecting a trap efficiency of 79 percent of the total sediment inflow of 825,000 tons per year. Thickness of post-impoundment sediment varies from about 11 feet near the mouth of the Santee River in Lake Marion to 0 feet in Lake Moultrie near Bonneau. Sediments in Lake Marion tend to have finer texture and higher contents of organic matter, nutrients, and trace metals than those in Lake Moultrie.

  9. Ebullition-facilitated transport of manufactured gas plant tar from contaminated sediment.

    Science.gov (United States)

    McLinn, Eugene L; Stolzenburg, Thomas R

    2009-11-01

    Manufactured gas plant (MGP) tar and wastewater solids historically were discharged into the Penobscot River, Maine,USA, via a sewer at the Bangor Landing site. The tar and wastewater solids accumulated in riverbed sediment over a 5-hectare area downstream from the sewer outfall. Much of the tarry sediment is a hardened mass at the bottom of the river, but in part of the tar deposit (the active zone), the tar remains unhardened. In the active zone, anaerobic biodegradation of organic matter generates methane and carbon dioxide; as gas accumulates and migrates upward, it entrains tar, eventually dragging the tar from the sediment to surface water. Understanding the migration mechanisms in different portions of the tar deposit is critical for modeling the risk posed by the tar at the Bangor Landing site, because during gas-facilitated tar migration, the tar is brought to the water surface, instead of remaining in the sediment. Tar migration from sediment poses a potential human health risk because of the high concentrations of polycyclic aromatic hydrocarbons in the tar. Migration from sediment to the water surface greatly increases the potential exposure of human and ecological receptors to tar that reaches the water surface. In order for tar to migrate from sediment to surface water, three conditions are necessary: the sediment must contain liquid tar, the sediment must produce gas bubbles, and the gas must come into contact with the tarry sediment. Failure to consider facilitated transport of MGP tar from sediment can cause underestimation of site risk and can lead to failure of remedial measures.

  10. Rip channel development on nonbarred beaches: The importance of a lag in suspended-sediment transport

    Science.gov (United States)

    Murray, A. Brad

    2004-04-01

    On approximately planar beaches, rip channel development is often preceded by a period in which jet-like rip currents develop in apparently random locations, and dissipate after minutes to tens of minutes. The subsequent development of sharp-edged, trough-like channels extending across the surf zone suggests that rip currents on planar beaches cause local erosion. Conversely, channels are known to cause localized offshore-directed flow, and once channels have formed on approximately planar beaches, rip currents no longer occur in apparently random locations, but are restricted to the locations of the channels. Apparently, the excavation of channels by rip currents on planar beaches triggers a positive feedback between the morphological development and the flow. However, theoretical analysis indicates that, when depth increases with distance from shore, and sediment transport is treated as a function only of local flow conditions, channel development in the vicinity of a rip current may not occur. In numerical simulations (using a "cellular" model of nonbathymetrically driven rip currents) in which sediment flux on a planar beach is driven by approximately realistic rip current velocity patterns, deposition occurs under parts of the rip currents (especially in the seaward half of the surf zone), and these "rip ridges" cause a negative feedback. In these simulations, as in most models treating surf zone sediment transport, sediment flux is assumed to be strictly a function of local hydrodynamic conditions. However, Observations of sediment-laden rip-current plumes extending well beyond the surf zone suggest that suspended sediment transport is not always in equilibrium with local conditions. Other simulations employ a treatment of suspended-sediment transport that allows for a lag in the adjustment of fluxes to the changes in local hydrodynamic conditions that the sediment is advected through. With this nonlocal sediment-transport, the flux of sediment out of the

  11. Analysis of sediment transport pattern along the coastal line of the Curonian Spit

    Science.gov (United States)

    Kovaleva, Olga; Chubarenko, Boris

    2016-04-01

    Among a wide range of approaches for determination of long-shore sediment transport direction changes in grain-size parameters (mean, sorting, skewness) of beach deposits use not so often. There are two trends in alongshore distributions of surface sediments grain-size parameters which may indicate an alongshore transport (McLaren, Bowles, 1985): (a) sediments become finer, sorting and skewness decreases; (b) sediments become coarser, sorting decreases and skewness increases. Over all more than 150 sand samples were collected along the coastline of the Curonian Spit during 2011, 2014 and 2015 summer seasons. The grain-size analysis of the samples were carried out and mentioned above grain-size parameters were calculated. Shore segments with different trends were identified using a running 9-nodes window, level of significance of trend analysis was estimated. Results of the method testing reflected different sediment transportation patterns for different years. However for other areas such as embayed coasts at the Gulf of Finland this method showed presence of one-directed longshore sediment flow. As a result it is possible to say that for straightened coasts such as the Curonian Spit the method allows to determine the alongshore flux pattern formed by the last significant storm event, i.e. to estimate an actual consequence of winds and waves influence in the studied area and can not be used for describing multiannual longshore sediment transport. The work was financed by the Russian Scientific Fund (grant 14-37-00047) and by the Russian Foundation for Basic Research, research projects No. 14-35-50130 and No. 15-35-50613.

  12. Physical Modeling of the Cross-Shore Sediment Transport on a Sand-Gravel Beach

    Science.gov (United States)

    Xharde, Regis; Brunelle, Corinne; Frandsen, Jannette

    2014-11-01

    The aim of the study is to investigate the cross-shore evolution of a nourished beach profile under storm wave conditions with specific emphasis on sediment transport within the breaking zone. To investigate the underlying mechanisms of the coastal transport processes, a physical model of the beach was built at scale 1:3 in the new Quebec Coastal Physics Laboratory (QCPL), Canada. The modeled beach is 4.2 m high, 5 m wide and 40 m long with a mean slope of 1:10. The beach is formed of a mixture of sediment with grain sizes ranging from 0.65 mm up to 20 mm. The stability of the beach is tested for operational and storm waves. We report on run-up and run-down processes via wave gages, video records of waves and ultrasonic water level measurements. Sediment transport processes within the surf zone and on the beach face are monitored using acoustic Doppler profilers and optical backscattering sensors. The beach profile is surveyed prior and after each test series using a topographic laser scanner. Initial results show that sand is transported off-shore to a breaker bar while cobbles are pushed on the upper beach by run-up. Details of the underlying mechanism of different breaker types and impact on sediment transport will be presented.

  13. Flow and sediment transport induced by a plunging solitary wave

    DEFF Research Database (Denmark)

    Sumer, B. Mutlu; Sen, M.Berke; Karagali, Ioanna

    2011-01-01

    , and for observation of the morphological changes. The two experimental conditions were maintained as similar as possible. The experiments showed that the complete sequence of the plunging solitary wave involves the following processes: Shoaling and wave breaking; Runup; Rundown and hydraulic jump; and Trailing wave...... affected, by as much as a factor of 2, in the runup and hydraulic jump stages. The pore-water pressure measurements showed that the sediment at (or near) the surface of the bed experiences upward-directed pressure gradient forces during the downrush phase. The magnitude of this force can reach values...

  14. Deschutes estuary feasibility study: hydrodynamics and sediment transport modeling

    Science.gov (United States)

    George, Douglas A.; Gelfenbaum, Guy; Lesser, Giles; Stevens, Andrew W.

    2006-01-01

    Continual sediment accumulation in Capitol Lake since the damming of the Deschutes River in 1951 has altered the initial morphology of the basin. As part of the Deschutes River Estuary Feasibility Study (DEFS), the United States Geological Survey (USGS) was tasked to model how tidal and storm processes will influence the river, lake and lower Budd Inlet should estuary restoration occur. Understanding these mechanisms will assist in developing a scientifically sound assessment on the feasibility of restoring the estuary. The goals of the DEFS are as follows. - Increase understanding of the estuary alternative to the same level as managing the lake environment.

  15. Winter-time circulation and sediment transport in the Hudson Shelf Valley

    Science.gov (United States)

    Harris, C.K.; Butman, B.; Traykovski, P.

    2003-01-01

    The Hudson Shelf Valley is a bathymetric low that extends across the continental shelf offshore of New York and New Jersey. From December 1999 to April 2000 a field experiment was carried out to investigate the transport of sediment in the shelf and valley system. Near-bed tripods and water-column moorings were deployed at water depths from 38 to 75 m in the axis of the shelf valley and at about 26 m on the adjacent shelves offshore of New Jersey and Long Island, New York. These measured suspended sediment concentrations, current velocities, waves, and water column properties. This paper analyzes observations made during December 1999 and January 2000, and presents the first direct near-bed measurements of suspended sediment concentration and sediment flux from the region. Sediment transport within the Hudson Shelf Valley was coherent over tens of kilometers, and usually aligned with the axis of the shelf valley. Down-valley (off-shore) transport was associated with energetic waves, winds from the east, moderate current velocities (5-10 cm/s), and sea level setup at Sandy Hook, NJ. Up-valley (shoreward) transport occurred frequently, and was associated with winds from the west, low wave energy, high current velocities (20-40 cm/s), and sea level set-down at the coast. Within the shelf valley, net sediment flux (the product of near-bed concentration and velocity) was directed shoreward, up the axis of the valley. Current velocities and suspended sediment fluxes on the New York and New Jersey continental shelves were lower than within the shelf valley, and exhibited greater variability in alignment. Longer term meteorological data indicate that wind, setup, and wave conditions during the study period were more conducive to up-valley transport than seasonal data suggest as average. To relate the observed up-valley sediment flux to observed accumulation of contaminants within the Hudson Shelf Valley requires consideration of transport over longer timescales than those

  16. Wave forecasting and longshore sediment transport gradients along a transgressive barrier island: Chandeleur Islands, Louisiana

    Science.gov (United States)

    Georgiou, Ioannis Y.; Schindler, Jennifer K.

    2009-12-01

    Louisiana barrier islands, such as the chain surrounding the southeast region of the state, are experiencing rapid loss of land area, shoreline erosion, and landward migration due to transgression and in-place drowning, and the landfall of several major hurricanes in the last decade. Observations of migration rates and overall impacts to these barrier islands are poorly understood since they do not respond in a traditional way, such as barrier rollover. This paper aims to verify how wave energy and potential longshore sediment transport trends have influenced the recent evolution of the Chandeleur Islands, by direct comparison with recent observations of migration and erosion trends. The Chandeleur Islands are characterized by a bidirectional transport system, with material moving from the central arc to the flanks. The longshore sediment transport along the barrier islands was calculated after propagation and transformation of waves to breaking (generated using observed winds), and through the use of a common longshore sediment transport formula. Seasonal variations in wind climate produced changes in the transport trends and gradients that agree with migration and rotation patterns observed for this barrier island system. Results suggest that wind dominance produces seasonal oscillations that cause an imbalance in the resulting transport gradients that over time are responsible for higher rates of transport in the northward direction. These results and data from other works verify the evolutionary model previously suggested, and qualitatively confirm the recent observations in asymmetric shoreline erosion.

  17. Suspended sediment transport in distributary channel networks and its implication on the evolution of delta

    Science.gov (United States)

    Suying, Ou; hao, Yang

    2016-04-01

    Suspended sediment (SS) transport in distributary channels play an important role on the evolution of deltas and estuaries. Under the interactions between river discharge, tide, and bathymetry of Pearl River delta (PRD) in south China, the spatial and temporal characteristics of suspended sediment transport are investigated by using the field data of July 16 to 25, 1999 and February 7 to 15, 2001. The PRD, as one of the most complex tributary system in the world and composed of 324 transversal and longitudinal tributaries, with eight outlets to the three sub-estuaries, has higher suspended sediment load in middle delta including six outlets than in right and left tidal dominant channels of PRD, that is Humen channel and Yamen channel system. Under large river discharge of one flood in summer, the tidal averaged SS transport from channel to the estuaries, the SS concentration of middle delta is 10~20 times and the transport rate is 100~500 times of dry season. But the transport rate changes little between flood season and dry season in the upper channel system of Yamen and Humen, and in dry season the tidal averaged transport change direction from estuary to these channel systems. About 70~85% of total Pearl River SS load transport along the main channel of West River, then transport about 45~55% into the lower West river delta, about 30% of total SS load flushed into the Modaomen outlets. Under the bathymetry of branched channels, SS load which advected from the Pearl River and resuspended from bed, redistributed 4~8 times in the PRD and then cause the different changes of channels. It found that in flood season, the suspended sediment load from Pearl River including East, West, North River and Tanjiang, Liuxi River into the PRD is less than that discharged into the estuaries through eight outlets, which indicated the erosion in the channels of PRD especially in the lower part of PRD. Suspended sediment budget in dry season during neap-spring cycle indicated that

  18. Lack of cross-shelf transport of sediments on the western margin of India: Evidence from clay mineralogy

    Digital Repository Service at National Institute of Oceanography (India)

    Ramaswamy, V.; Nair, R.R.

    transported long distances along the shelf, cross-shelf transport appears to be minimal. Confirmatory evidence of qualitative differences in outer and inner shelf clays is provided by sediment trap clay mineralogy on the outer shelf. Clay bound pollutant...

  19. Simulating Landscape Sediment Transport Capacity by Using a Modified SWAT Model.

    Science.gov (United States)

    Bonumá, Nadia B; Rossi, Colleen G; Arnold, Jeffrey G; Reichert, José M; Minella, Jean P; Allen, Peter M; Volk, Martin

    2014-01-01

    Sediment delivery from hillslopes to rivers is spatially variable and may lead to long-term delays between initial erosion and related sediment yield at the watershed outlet. Consideration of spatial variability is important for developing sound strategies for water quality improvement and soil protection at the watershed scale. Hence, the Soil and Water Assessment Tool (SWAT) was modified and tested in this study to simulate the landscape transport capacity of sediment. The study area was the steeply sloped Arroio Lino watershed in southern Brazil. Observed sediment yield data at the watershed outlet were used to calibrate and validate a modified SWAT model. For the calibration period, the modified model performed better than the unaltered SWAT2009 version; the models achieved Nash-Sutcliffe efficiency (NSE) values of 0.7 and -0.1, respectively. Nash-Sutcliffe efficiencies were less for the validation period, but the modified model's NSE was higher than the unaltered model (-1.4 and -12.1, respectively). Despite the relatively low NSE values, the results of this first test are promising because the model modifications lowered the percent bias in sediment yield from 73 to 18%. Simulation results for the modified model indicated that approximately 60% of the mobilized soil is deposited along the landscape before it reaches the river channels. This research demonstrates the modified model's ability to simulate sediment yield in watersheds with steep slopes. The results suggest that integration of the sediment deposition routine in SWAT increases accuracy in steeper areas while significantly improving its ability to predict the spatial distribution of sediment deposition areas. Further work is needed regarding (i) improved strategies for spatially distributed sediment transport measurements (for improving process knowledge and model evaluation) and (ii) extensive model tests in other well instrumented experimental watersheds with differing topographic configurations

  20. Development of a three-dimensional, regional, coupled wave, current, and sediment-transport model

    Science.gov (United States)

    Warner, J.C.; Sherwood, C.R.; Signell, R.P.; Harris, C.K.; Arango, H.G.

    2008-01-01

    We are developing a three-dimensional numerical model that implements algorithms for sediment transport and evolution of bottom morphology in the coastal-circulation model Regional Ocean Modeling System (ROMS v3.0), and provides a two-way link between ROMS and the wave model Simulating Waves in the Nearshore (SWAN) via the Model-Coupling Toolkit. The coupled model is applicable for fluvial, estuarine, shelf, and nearshore (surfzone) environments. Three-dimensional radiation-stress terms have been included in the momentum equations, along with effects of a surface wave roller model. The sediment-transport algorithms are implemented for an unlimited number of user-defined non-cohesive sediment classes. Each class has attributes of grain diameter, density, settling velocity, critical stress threshold for erosion, and erodibility constant. Suspended-sediment transport in the water column is computed with the same advection-diffusion algorithm used for all passive tracers and an additional algorithm for vertical settling that is not limited by the CFL criterion. Erosion and deposition are based on flux formulations. A multi-level bed framework tracks the distribution of every size class in each layer and stores bulk properties including layer thickness, porosity, and mass, allowing computation of bed morphology and stratigraphy. Also tracked are bed-surface properties including active-layer thickness, ripple geometry, and bed roughness. Bedload transport is calculated for mobile sediment classes in the top layer. Bottom-boundary layer submodels parameterize wave-current interactions that enhance bottom stresses and thereby facilitate sediment transport and increase bottom drag, creating a feedback to the circulation. The model is demonstrated in a series of simple test cases and a realistic application in Massachusetts Bay. ?? 2008 Elsevier Ltd. All rights reserved.

  1. Sediment Yields Revealed and Fluid Modelling by Twice LiDAR Surveys in Active Tectonics Area

    Science.gov (United States)

    Hsieh, Y.; Chan, Y.; Hu, J.; Lin, C.

    2010-12-01

    LiDAR technique allows rapid acquisition of high resolution and high precision topographic data. The technique has found considerable use in the earth sciences, for example for fluvial morphology and flood modelling. These developments have offered new opportunities for investigating spatial and temporal patterns of morphological change in gravel-bed river and have contributed to develop in two points: (1)morphometric estimates of sediment transport and sediment yields ;(2)boundary conditions for numerical models, including computational fluid dynamics and modelling. This topographic research funded by the Taiwan Central Geological Survey, surveyed the terrain of the Lanyang River before and after the typhoon season using Airborne LiDAR technique, and computed the terrain variations. The Lanyang River is one of main rivers in Taiwan and often suffers the influence of typhoon during summer. Most of sediments generated from slump and soil erosion into river were transported from the upstream watershed and resulted in the riverbed changes during the typhoon season. In 2008, there are four significant typhoon events influencing this area, including the Kalmaegi, Fung-wong, Sinlaku, and Jangmi typhoons. At present, sediment yield calculation often used empirical or theoretical formula as well as data collected at hydrological stations, and rarely had the actual measured value through high-resolution topography. The variations of the terrain on the riverbed may be regarded as the sediment yield of the bed load transported during the typhoon season. This research used high-resolution terrain models to compute sediment yield of the bed load, and further discussed volumes of sediment yield in watershed during the typhoon season. In the Lanyang River we discovered that the upstream and midstream channel still had the characteristics of erosion and transportation during the typhoon season. The results imply significant sediment yield and transportation from the upstream

  2. Sediment Transport Dynamic in a Meandering Fluvial System: Case Study of Chini River

    Science.gov (United States)

    Nazir, M. H. M.; Awang, S.; Shaaban, A. J.; Yahaya, N. K. E. M.; Jusoh, A. M.; Arumugam, M. A. R. M. A.; Ghani, A. A.

    2016-07-01

    Sedimentation in river reduces the flood carrying capacity which lead to the increasing of inundation area in the river basin. Basic sediment transport can predict the fluvial processes in natural rivers and stream through modeling approaches. However, the sediment transport dynamic in a small meandering and low-lying fluvial system is considered scarce in Malaysia. The aim of this study was to analyze the current riverbed erosion and sedimentation scenarios along the Chini River, Pekan, Pahang. The present study revealed that silt and clay has potentially been eroded several parts of the river. Sinuosity index (1.98) indicates that Chini River is very unstable and continuous erosion process in waterways has increase the riverbank instability due to the meandering factors. The riverbed erosional and depositional process in the Chini River is a sluggish process since the lake reduces the flow velocity and causes the deposited particles into the silt and clay soil at the bed of the lake. Besides, the bed layer of the lake comprised of cohesive silt and clayey composition that tend to attach the larger grain size of sediment. The present study estimated the total sediment accumulated along the Chini River is 1.72 ton. The HEC-RAS was employed in the simulations and in general the model performed well, once all parameters were set within their effective ranges.

  3. Sediments as tracers for transport and deposition processes in peri-alpine lakes: A case study

    Science.gov (United States)

    Righetti, Maurizio; Toffolon, Marco; Lucarelli, Corrado; Serafini, Michele

    2011-12-01

    SummaryThe benthic sediment fingerprint is analysed in the small peri-alpine lake Levico (Trentino, Italy) to identify the causes of recurrent phenomena of turbidity peaks, particularly evident in a littoral region of the water body. In order to study the sediment transport processes, we exploit the fact that the sediment supply from the major tributary has a specific chemical composition, which differs from that of the nearby lake basin. Three elements (Fe, Al, K) have been used as tracers to identify the source and the deposition patterns of tributary sediments, and another typical element, Si, has been critically analysed because of its dual (allochthonous and autochthonous) origin. Several samples of the benthic material have been analysed using SEM-EDS, and the results of the sedimentological characterisation have been compared with the patterns of sediment accumulation at the bed of the lake obtained using a three-dimensional numerical model, in response to the tributary supply under different external forcing and stratification conditions. The coupled use of field measurements and numerical results suggests that the turbidity phenomena are strongly related to the deposition of the sediments supplied by the tributary stream, and shows that it is possible to reconstruct the process of local transport when the tributary inflow is chemically specific.

  4. Soil erosion and sediment transport in the gullied Loess Plateau:Scale effects and their mechanisms

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Scale effects exist in the whole process of rainfall―runoff―soil erosion―sediment transport in river basins.The differences of hydrographs and sediment graphs in different positions in a river basin are treated as basic scale effects,which are more complex in the gullied Loess Plateau,a region notorious for high intensity soil erosion and hyper-concentrated sediment-laden flow.The up-scaling method of direct extrapolation that maintains dynamical mechanism effective in large scale application was cho-sen as the methodology of this paper.Firstly,scale effects of hydrographs and sediment graphs were analyzed by using field data,and key sub-processes and their mechanisms contributing to scale effects were clearly defined.Then,the Digital Yellow River Model that integrates sub-models for the sub-processes was used with high resolution to simulate rainfall―runoff―soil erosion―sediment transport response in Chabagou watershed,and the distributed results representing scale effects were obtained.Finally,analysis on the simulation results was carried out.It was shown that gravitational erosion and hyper-concentrated flow contribute most to the spatial variation of hydrographs and sediment graphs in the spatial scale.Different spatial scale distributions and superposition of different sub-processes are the mechanisms of scale effects.

  5. Soil erosion and sediment transport in the gullied Loess Plateau: Scale effects and their mechanisms

    Institute of Scientific and Technical Information of China (English)

    LI TieJian; WANG GuangQian; XUE Hai; WANG Kai

    2009-01-01

    Scale effects exist in the whole process of rainfall--runoff--soil erosion--sediment transport in river basins. The differences of hydrographa and sediment graphs in different positions in a river basin are treated as basic scale effects, which are more complex in the gullied Loess Plateau, a region notorious for high intensity soil erosion and hyper-concentrated sediment-laden flow. The up-scaling method of direct extrapolation that maintains dynamical mechanism effective in large scale application was cho-sen as the methodology of this paper. Firstly, scale effects of hydrographa and sediment graphs were analyzed by using field data, and key sub-processes and their mechanisms contributing to scale effects were clearly defined. Then, the Digital Yellow River Model that integrates sub-models for the sub-processes was used with high resolution to simulate rainfall--runoff--soil erosion--sediment transport response in Chabagou watershed, and the distributed results representing scale effects were obtained.Finally, analysis on the simulation results was carried out. It was shown that gravitational erosion and hyper-concentrated flow contribute most to the spatial variation of hydrographs and sediment graphs in the spatial scale. Different spatial scale distributions and superposition of different sub-processes are the mechanisms of scale effects.

  6. Control factors and scale analysis of annual river water, sediments and carbon transport in China

    Science.gov (United States)

    Song, Chunlin; Wang, Genxu; Sun, Xiangyang; Chang, Ruiying; Mao, Tianxu

    2016-05-01

    Under the context of dramatic human disturbances on river system, the processes that control the transport of water, sediment, and carbon from river basins to coastal seas are not completely understood. Here we performed a quantitative synthesis for 121 sites across China to find control factors of annual river exports (Rc: runoff coefficient; TSSC: total suspended sediment concentration; TSSL: total suspended sediment loads; TOCL: total organic carbon loads) at different spatial scales. The results indicated that human activities such as dam construction and vegetation restoration might have a greater influence than climate on the transport of river sediment and carbon, although climate was a major driver of Rc. Multiple spatial scale analyses indicated that Rc increased from the small to medium scale by 20% and then decreased at the sizable scale by 20%. TSSC decreased from the small to sizeable scale but increase from the sizeable to large scales; however, TSSL significantly decreased from small (768 g·m‑2·a‑1) to medium spatial scale basins (258 g·m‑2·a‑1), and TOCL decreased from the medium to large scale. Our results will improve the understanding of water, sediment and carbon transport processes and contribute better water and land resources management strategies from different spatial scales.

  7. Transport and deposition of sediment-associated Escherichia coli in natural streams.

    Science.gov (United States)

    Jamieson, Rob; Joy, Doug M; Lee, Hung; Kostaschuk, Ray; Gordon, Robert

    2005-07-01

    The association of microorganisms with sediment particles is one of the primary complicating factors in assessing microbial fate in aquatic systems. The literature indicates that the majority of enteric bacteria in aquatic systems are associated with sediments and that these associations influence their survival and transport characteristics. Yet, the nature of these associations has not been fully characterized. In this study, a combination of field experiments and mathematical modeling were used to better understand the processes which control the fate and transport of enteric bacteria in alluvial streams. An experimental procedure, involving the use of a tracer-bacteria, was developed to simulate the transport and deposition of bacteria-laden bed sediments in a small alluvial stream during steady flow conditions. The experimental data and mathematical model were used to determine dispersion coefficients, deposition rates, and partitioning coefficients for sediment-associated bacteria in two natural streams. The results provided evidence that bacterial adsorption can be modeled as an irreversible process in freshwater environments. Net settling velocities of fine sediments and associated bacteria were typically two orders of magnitude lower than those predicted from Stokes equation, due to re-entrainment of settled particles. The information presented in this study will further the development of representative microbial water quality models.

  8. Well-balanced numerical modelling of non-uniform sediment transport in alluvial rivers

    Institute of Scientific and Technical Information of China (English)

    Honglu Qian; Zhixian Cao; Gareth Pender; Huaihan Liu; Peng Hu

    2015-01-01

    abstract The last two decades have witnessed the development and application of well-balanced numerical models for shallow flows in natural rivers. However, until now there have been no such models for flows with non-uniform sediment transport. This paper presents a 1D well-balanced model to simulate flows and non-capacity transport of non-uniform sediment in alluvial rivers. The active layer formulation is adopted to resolve the change of bed sediment composition. In the framework of the finite volume Slope LImiter Centred (SLIC) scheme, a surface gradient method is incorporated to attain well-balanced solutions to the governing equations. The proposed model is tested against typical cases with irregular topography, including the refilling of dredged trenches, aggradation due to sediment overloading and flood flow due to landslide dam failure. The agreement between the computed results and measured data is encouraging. Compared to a non-well-balanced model, the well-balanced model features improved performance in reproducing stage, velocity and bed deformation. It should find general applications for non-uniform sediment transport modelling in alluvial rivers, especially in mountain areas where the bed topography is mostly irregular.

  9. Sediment Transportation Induced by Deep-Seated Landslides in a Debris Flow Basin in Taiwan

    Science.gov (United States)

    Lin, Meei Ling; Chen, Te Wei; Chen, Yong Sheng; Sin Jhuang, Han

    2016-04-01

    Typhoon Morakot brought huge amount of rainfall to the southern Taiwan in 2009 and caused severe landslides and debris flow hazard. After Typhoon Morakot, it was found that the volume of sediment transported by the debris flow and its effects on the affected area were much more significant compared to previous case history, which may due to the huge amount of rainfall causing significant deep-seated landslides in the basin. In this study, the effects and tendency of the sediment transportation in a river basin following deep-seated landslides caused by typhoon Morakot were evaluated. We used LiDAR, DEM, and aerial photo to identify characteristics of deep-seated landslides in a debris flow river basin, KSDF079 in Liuoguey District, Kaohsiung City, Taiwan. Eight deep-seated landslides were identified in the basin. To estimate the potential landslide volume associated with the deep-seated landslides, the stability analysis was conducted to locate the critical sliding surface, and the potential landside volume was estimated based on the estimation equation proposed by the International Geotechnical Societies' UNESCO Working Party on World Landslide Inventory (WP/WLI, 1990). The total potential landslide volume of the eight deep-seated landslides in KSDF079 basin was about 28,906,856 m3. Topographic analysis was performed by using DEM before and LiDAR derived DEM after typhoon Morakot to calculate the landslide volume transported. The result of erosion volume and deposition volume lead to a run out volume of 5,832,433 m3. The results appeared to consist well with the field condition and aerial photo. Comparing the potential landslide volume and run out volume of eight deep-seated landslides, it was found that the remaining potential landslide volume was about 80%. Field investigation and topographic analysis of the KSDF079 debris flow revealed that a significant amount of sediment deposition remained in the river channel ranging from the middle to the downstream

  10. RANS-based simulation of wave-induced sheet-flow transport of graded sediments

    DEFF Research Database (Denmark)

    Calistan, Ugur; Fuhrman, David R.

    2017-01-01

    for each grain fraction, includingeffects associated with increased exposure of larger particles within a mixture. The suspended sedimenttransport model also makes use of modified reference concentration approach, wherein reference concentrationscomputed individually for each fraction are translated....... The sediment transport model is validated against sheet-flow experimentaloscillatory tunnel measurements beneath velocity-skewed wave signals, and demonstrates similar accuracy(transport rates generally within a factor of two) for both graded and uniform sands. The model is likewisevalidated against...

  11. Numerical Modelling of Suspended Transport and Deposition of Highway Deposited Sediments

    DEFF Research Database (Denmark)

    Bentzen, Thomas Ruby; Larsen, Torben; Bach, Christine;

    Good data for calibration and validation of numerical models are of high importance. In the natural environment data can be hard to archive and the stochastic nature have governing influence on the data archived. Hence for modelling of suspended transport and deposition of particles, originating...... from the highway surfaces, in highway detention ponds, four experiments are carried out. To simplify the complexity of a real pond and for easy control and measurement the sediment transports where carried out in two rectangular channels....

  12. Spatially distributed modeling of sediment and associated heavy metal transport on regional and catchment scale

    Science.gov (United States)

    Schindewolf, Marcus; Schmidt, Jürgen; Käpermann, Philipp

    2013-04-01

    Achievements of new legislations, as EU-Water Framework Directive (EU-WFD), require great efforts in order to reduce the yields of sediment and sediment attached heavy metals of surface water bodies. In this regard planning authorities strongly need comparable assessments on regional scale, which enables predictions on the level of measures. The study aims to identify the main sediment delivery areas in the German federal state of Saxony (18400 km²) and to locate pass over points of sediment and associated heavy metals into surface waters. Applying the process based EROSION 3D simulation model spatially distributed (20 m grid cell) estimates of sediment and particle attached heavy metal inputs are realized on regional and catchment scale related to three land use scenarios and a 10years rainfall event. Concerning these calculations it has to be considered, that this substances are predominantly attached to the fine-grained soil particles. The selective nature of soil erosion causes a preferentially transport of this fine particles while less contaminated larger particles remain on site. Consequently heavy metals are enriched in the eroded sediment compared to the origin soil. Hence it is essential that EROSION 3D provides the particle size distribution (clay, silt and sand) of transported sediments. Regarding heavy metal input calculations from sediment inputs, heavy metal contents of particle size classes has to be known. For this purpose particle size separates of erosion susceptible soils are analyzed. Comprehensive heavy metal contents of origin top soils are interpolated via kriging using available monitoring data. The regional scaled simulations identify the Saxon loess belt as the main affected region of sediment inputs. Since particle attached heavy metal transport to surface waters is strongly related to sediment delivery, the streams of this region suffer from considerable inputs. Compared to empirical estimates, the results of this study suggest that

  13. Hydrodynamic and Sediment Transport Processes in Long Bay of the Carolinas

    Science.gov (United States)

    Ma, Y.; Xu, K.; He, R.; Wren, P. A.; Gong, Y.; Quigley, B.; Tarpley, D.

    2010-12-01

    The coastline along Long Bay of the Carolinas is a fast-growing and heavily-developed area supporting local populations, infrastructure, and a large tourism industry. Myrtle Beach and its adjacent sandy beaches are popular tourist destinations that attract millions of visitors each year, representing one of the state’s most essential natural resources. The economy of this region is closely related to the stability of the sandy beaches, which are vulnerable to coastal erosion during severe storm events. Quantifying the sediment transport processes in the nearshore and inner continental shelf regions is thus critical for both understanding the regional sediment budget and implementing effective coastal management. As a first step toward investigating the sediment transport processes, a three-dimensional coupled hydrodynamic-sediment transport model for Long Bay in the Carolinas has been developed. The model, based on the Regional Ocean Modeling System (ROMS), spans from Cape Fear estuary in NC to Winyah Bay estuary in SC. It considers the delivery of fluvial sediment from the Cape Fear and Pee Dee Rivers, resuspension from seabed, and transport of suspended sediment by ambient currents and waves calculated using Simulating WAve Nearshore model (SWAN). Our model simulations are driven by observed wind fields, which were collected at nearby meteorological stations maintained by National Data Buoy Center as well as at six buoys by the Palmetto Wind Research Project at Coastal Carolina University. Spatially varying sea bed conditions consisting of both hard bottoms and sandy bodies are applied in the calculation. The model is one-way nested inside a large-scale coastal circulation model that covers both the Middle Atlantic Bight and the South Atlantic Bight and provides dynamically consistent and numerically accurate circulation open boundary conditions. Modeling results indicate both wind-driven currents and storm-induced waves are capable of resuspending sandy

  14. Predicting Coarse Sediment Transport from Patchy Beds in Ephemeral Channels

    Science.gov (United States)

    2012-04-01

    into a Holocene alluvial veneer covering the Whetstone Pediment, a gentle transport slope composed of Gleeson Road Conglomerate, underlying much of...north-central Walnut Gulch (Gilluly 1956; Osterkamp 2008). The Gleeson Road Conglomerate near the Lucky Hills region is a poorly to well cemented

  15. Aeolian Sediment Transport through Large Patches of Roughness in the Atmospheric Inertial Sublayer

    Science.gov (United States)

    Gillies, John A.; Nickling, Willilam G.; King, James

    2006-01-01

    Roughness influences the flux of wind driven sand transport. In this paper, we report on sediment transport measurements for four different surface roughness configurations composed of the same size (solid) roughness elements in the atmospheric inertial sublayer (ISL). Results of these tests indicate that sediment transport rates through patches of roughness in the atmospheric inertial sublayer are to a large extent controlled and scale proportionally with the roughness density (lambda = n b h/S, where n is number of elements of breadth b and height h in area S) of the surface. However, element size apparently increases the magnitude of the reduction beyond that attributable to lambda. A sediment transport model that incorporates the effect of shear stress partitioning appears to predict reasonably well the effect of roughness on sand transport in the cases where the roughness elements are less than or equal to 0.10 m in height. However, when the dimensions of the roughness itself are equivalent to or are greater than the range of saltation lengths (vertical and horizontal), additional interactions of the elements with the saltation cloud appear to reduce the transport efficiency.

  16. Sediment transport modelling in a distributed physically based hydrological catchment model

    Directory of Open Access Journals (Sweden)

    M. Konz

    2011-09-01

    Full Text Available Bedload sediment transport and erosion processes in channels are important components of water induced natural hazards in alpine environments. A raster based distributed hydrological model, TOPKAPI, has been further developed to support continuous simulations of river bed erosion and deposition processes. The hydrological model simulates all relevant components of the water cycle and non-linear reservoir methods are applied for water fluxes in the soil, on the ground surface and in the channel. The sediment transport simulations are performed on a sub-grid level, which allows for a better discretization of the channel geometry, whereas water fluxes are calculated on the grid level in order to be CPU efficient. Several transport equations as well as the effects of an armour layer on the transport threshold discharge are considered. Flow resistance due to macro roughness is also considered. The advantage of this approach is the integrated simulation of the entire basin runoff response combined with hillslope-channel coupled erosion and transport simulation. The comparison with the modelling tool SETRAC demonstrates the reliability of the modelling concept. The devised technique is very fast and of comparable accuracy to the more specialised sediment transport model SETRAC.

  17. Modeling of soil erosion and sediment transport in the East River Basin in southern China.

    Science.gov (United States)

    Wu, Yiping; Chen, Ji

    2012-12-15

    Soil erosion is a major global environmental problem that has caused many issues involving land degradation, sedimentation of waterways, ecological degradation, and nonpoint source pollution. Therefore, it is significant to understand the processes of soil erosion and sediment transport along rivers, and this can help identify the erosion prone areas and find potential measures to alleviate the environmental effects. In this study, we investigated soil erosion and identified the most seriously eroded areas in the East River Basin in southern China using a physically-based model, Soil and Water Assessment Tool (SWAT). We also introduced a classical sediment transport method (Zhang) into SWAT and compared it with the built-in Bagnold method in simulating sediment transport process along the river. The derived spatial soil erosion map and land use based erosion levels can explicitly illustrate the identification and prioritization of the critical soil erosion areas in this basin. Our results also indicate that erosion is quite sensitive to soil properties and slope. Comparison of Bagnold and Zhang methods shows that the latter can give an overall better performance especially in tracking the peak and low sediment concentrations along the river. We also found that the East River is mainly characterized by sediment deposition in most of the segments and at most times of a year. Overall, the results presented in this paper can provide decision support for watershed managers about where the best management practices (conservation measures) can be implemented effectively and at low cost. The methods we used in this study can also be of interest in sediment modeling for other basins worldwide.

  18. Modeling of soil erosion and sediment transport in the East River Basin in southern China

    Science.gov (United States)

    Wu, Yping; Chen, Ji

    2012-01-01

    Soil erosion is a major global environmental problem that has caused many issues involving land degradation, sedimentation of waterways, ecological degradation, and nonpoint source pollution. Therefore, it is significant to understand the processes of soil erosion and sediment transport along rivers, and this can help identify the erosion prone areas and find potential measures to alleviate the environmental effects. In this study, we investigated soil erosion and identified the most seriously eroded areas in the East River Basin in southern China using a physically-based model, Soil and Water Assessment Tool (SWAT). We also introduced a classical sediment transport method (Zhang) into SWAT and compared it with the built-in Bagnold method in simulating sediment transport process along the river. The derived spatial soil erosion map and land use based erosion levels can explicitly illustrate the identification and prioritization of the critical soil erosion areas in this basin. Our results also indicate that erosion is quite sensitive to soil properties and slope. Comparison of Bagnold and Zhang methods shows that the latter can give an overall better performance especially in tracking the peak and low sediment concentrations along the river. We also found that the East River is mainly characterized by sediment deposition in most of the segments and at most times of a year. Overall, the results presented in this paper can provide decision support for watershed managers about where the best management practices (conservation measures) can be implemented effectively and at low cost. The methods we used in this study can also be of interest in sediment modeling for other basins worldwide.

  19. Numerical modeling of subglacial erosion and sediment transport beneath the Laurentide Ice Sheet

    Science.gov (United States)

    Melanson, A.; Bell, T.; Tarasov, L.

    2012-04-01

    Present-day sediment distribution offers a potentially strong constraint on past ice sheet evolution. However, glacial system models (GSMs) cannot address this while lacking physically-based representations of subglacial sediment generation and transport. Incorporation of these elements in GSMs is also required in order to understand the impact of changing sediment cover on glacial cycle dynamics. Towards this goal, we present a subglacial process model that incorporates mechanisms for sediment production, entrainment, transport, and deposition. An abrasion law based on Hallet's model and a quarrying law dependent on basal water pressure and bed roughness are used to calculate bedrock erosion. The incorporation of loose debris in the basal ice is modeled by regelation intrusion and basal freeze-on, depending on the thermal condition and the availability of water at the base. The entrained debris is subsequently transported along the ice sheet's internal velocity field and vertically mixed through a diffusion equation that accounts for folding and thrust faulting. The inclusion of vertical mixing lowers the basal debris concentration and allows more regelation entrainment. Soft bed deformation is included as an advective component within the subglacial sediment, the rheology of which is assumed to be weakly non-linear. Deposition occurs whenever the basal ice is debris-laden and the melting rate exceeds the entrainment rate. The model is coupled to the MUN 3D GSM, which includes a newly developed subglacial hydrology module. The GSM itself has been subject to Bayesian calibration for North American and Eurasian deglaciation and thus a probabilistic ensemble of deglacial chronologies is available. With this calibrated ensemble, we compare the range of calculated sediment thickness fields and cumulative erosion over the last glacial cycle against the present-day pattern of glacigenic sediment and the geological estimates of glacial erosion over North America

  20. Effect of Different Forcing Processes on the Longshore Sediment Transport at the Sand Motor, The Netherlands

    NARCIS (Netherlands)

    Kaji, A.O.; Luijendijk, A.P.; van Thiel de Vries, J.S.M.; De Schipper, M.A.; Stive, M.J.F.

    2014-01-01

    The Sand Motor is a pilot project of a ‘mega-nourishment’ built in the Dutch coast in 2011. In order to understand which conditions reshape those mega-nourishments the influence of different types of forcing on the longshore sediment transport along the Sand Motor has been assessed in this paper usi

  1. Modeling of Sediment Transport and Self-Cleansing in Sea Outfalls

    DEFF Research Database (Denmark)

    Larsen, Torben; Ibro, I.

    2011-01-01

    The paper describes an on-going project on modeling of sediment transport in outfalls with special focus on the self-cleansing problem occurring due to the daily flow variations seen in outfalls. The two central elements of the project is the development of the numerical model and a matching phys...

  2. Variation of longshore current and sediment transport along the south Maharashtra coast, west coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Chandramohan, P.; SanilKumar, V.; Nayak, B.U.; Pathak, K.C.

    on the field measurements, the estimated longshore sediment transport rates at Ratnagiri, Ambolgarh and Vengurla were 1.19 x 10 super(5), 1.9 x 10 super(5) and 0.53 x 10 super(5) m super(3) y/1 respectively and the direction was southward. Significance of field...

  3. Nearshore waves and longshore sediment transport along Rameshwaram Island off the east coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Gowthaman, R.; SanilKumar, V.; Dwarakish, G.S.; Shanas, P.R.; Jena, B.K.; Singh, J.

    nearshore waves using Inter Ocean S4DW. Numerical model LITPACK was also used for simulating non-cohesive sediment transport and the LITLINE module was used to study the shoreline evolution over 5 years. Low net annual LST along PB (~.01×106 m...

  4. A Non-Equilibrium Sediment Transport Model for Coastal Inlets and Navigation Channels

    Science.gov (United States)

    2011-01-01

    Navigation Channels Alejandro Sánchez† and Weiming Wu‡ ABSTRACT SANCHEZ, A. and WU, W., 2011. A Non-Equilibrium Sediment Transport Model...2009; accessed January 20, 2009). Nicholson, J.; Brøker, I.; Roelvink, J. A.; Price, D.; Tanguy, J. M., and Moreno , L., 1997. Intercomparison of

  5. A seepage erosion sediment transport function and geometric headcut relationships for predicting seepage erosion undercutting

    Science.gov (United States)

    Seepage erosion is an important factor in hillslope instability and failure. However, predicting erosion by subsurface flow or seepage and incorporating its effects into stability models remain a challenge. Limitations exist with all existing seepage erosion sediment transport functions, including n...

  6. Sediment texture, distribution and transport on the Ayeyarwady continental shelf, Andaman Sea

    Digital Repository Service at National Institute of Oceanography (India)

    Rao, P.S.; Ramaswamy, V.; Thwin, S.

    resulting in shoaling of its water depths. Part of the sediment discharge reaches the deep Andaman Sea via the Martaban Canyon and the rest is transported westward into the Bay of Bengal by the counter-clockwise flowing NE monsoon currents....

  7. Modeling of Breaching Due to Overtopping Flow and Waves Based on Coupled Flow and Sediment Transport

    CERN Document Server

    He, Zhiguo; Zhao, Liang; Wu, Ganfeng; Pähtz, Thomas

    2015-01-01

    Breaching of earthen or sandy dams/dunes by overtopping flow and waves is a complicated process with strong, unsteady flow, high sediment transport, and rapid bed changes in which the interactions between flow and morphology should not be ignored. This study presents a depth-averaged two-dimensional (2D) coupled flow and sediment transport model to investigate the flow and breaching processes with and without waves. Bed change and variable flow density are included in the flow continuity and momentum equations to consider the impacts of sediment transport. The model adopts the non-equilibrium approach for total-load sediment transport and specifies different repose angles to handle non-cohesive embankment slope avalanching. The equations are solved using an explicit finite volume method on a rectangular grid with the improved Godunov-type central upwind scheme and the nonnegative reconstruction of the water depth method to handle mixed-regime flows near the breach. The model has been tested against two sets o...

  8. Diffuser Design For Marine Outfalls in Areas With Strong Currents, High Waves and Sediment Transport

    DEFF Research Database (Denmark)

    Larsen, Torben

    1995-01-01

    of this uncompromising accept of environmental demands. Two examples of unconventional design are given in the paper. Both cases involved risk of blockage of the diffuser section because of wave and current induced sediment transport. The paper also discusses how acceptable far field dilution conditions can be achieved...

  9. A review and re-assessment of sediment transport along the Goa Coast, India

    Digital Repository Service at National Institute of Oceanography (India)

    Kunte, P.D.; Wagle, B.G.; Yasuhiro Sugimori

    Although, a variety of methods have been employed to determine sediment transport along Goa coast, India, the results differ in some sections. Fifteen studies have been reviewed, compared, re-assessed and a corrected shore drift map of the Goa coast...

  10. Long-distance electron transport by cable bacteria in mangrove sediments

    NARCIS (Netherlands)

    Burdorf, L.D.; Hidalgo-Martinez, S.; Cook, P.L.M.C.; Meysman, F.

    2016-01-01

    Cable bacteria are long, filamentoussulphur-oxidizing bacteria that induce long-distanceelectron transport in aquatic sediments. They turnthe seafloor into an electro-active environment, characterizedby currents and electrical fields, and whenpresent, they exert a strong impact on the geochemicalcyc

  11. Effect of Different Forcing Processes on the Longshore Sediment Transport at the Sand Motor, The Netherlands

    NARCIS (Netherlands)

    Kaji, A.O.; Luijendijk, A.P.; van Thiel de Vries, J.S.M.; De Schipper, M.A.; Stive, M.J.F.

    2014-01-01

    The Sand Motor is a pilot project of a ‘mega-nourishment’ built in the Dutch coast in 2011. In order to understand which conditions reshape those mega-nourishments the influence of different types of forcing on the longshore sediment transport along the Sand Motor has been assessed in this paper

  12. High Resolution Numerical Modeling of Cohesive Sediment Transport

    Science.gov (United States)

    2011-01-01

    Transport Tian-Jian Hsu Civil and Environmental Engineering Center for Applied Coastal Research University of Delaware, Newark, DE 19716...ORGANIZATION NAME(S) AND ADDRESS(ES) Civil and Environmental Engineering Center for Applied Coastal Research University of Delaware, Newark, DE 19716 8...Hence, there exists a competition between direct mud dissipation and shoaling process at muddy shelf. This problem is not only dependent on mud rheology

  13. The South Carolina Coastal Erosion Study: Integrated Circulation and Sediment Transport Studies. A Project Overview.

    Science.gov (United States)

    Voulgaris, G.; Warner, J. C.; Work, P. A.; Hanes, D. M.; Haas, K. A.

    2004-12-01

    The South Carolina Coastal Erosion Study (SCCES) is a cooperative research program funded by the U.S. Geological Survey Coastal and Marine Geology Program and managed by the South Carolina Sea Grant Consortium. The main objective of the study is to understand the factors and processes that control coastal sediment movement along the northern part of the South Carolina coast while at the same time advance our basic understanding of circulation, wave propagation and sediment transport processes. Earlier geological framework studies carried out by the same program provided detailed data on bathymetry, bottom sediment thickness and grain size distribution. They identified an extensive (10km long, 2km wide) sand body deposit located in the inner shelf that has potential use for beach nourishment. The main objectives are to: (1) identify the role of wind-driven circulation in controlling regional sediment distribution on the SC shelf; (2) examine the hypothesis that the shoal is of the "fair-weather type" with bedload being the dominant sediment transport mode and the tidally-averaged flow being at different directions at the two flanks of the shoal; (3) investigate the possibility that the sediment source for the shoal is derived from the nearshore as the result of the convergence of the longshore sediment transport; and finally, (4) quantify the control that the shoal exerts on the nearshore conditions through changes on the wave energy propagation characteristics. Field measurements and numerical modeling techniques are utilized in this project. Two deployments of oceanographic and sediment transport systems took place for a period of 6 months (October 2003 to April 2004) measuring wind forcing, vertical distribution of currents, stratification, and wave spectral characteristics. Further, bed-flow interactions were measured at two locations, with instrumented tripods equipped with pairs of ADVs for measuring turbulence, PC-ADPs for measuring vertical current profiles

  14. Modeling of Breaching Due to Overtopping Flow and Waves Based on Coupled Flow and Sediment Transport

    Directory of Open Access Journals (Sweden)

    Zhiguo He

    2015-08-01

    Full Text Available Breaching of earthen or sandy dams/dunes by overtopping flow and waves is a complicated process with strong, unsteady flow, high sediment transport, and rapid bed changes in which the interactions between flow and morphology should not be ignored. This study presents a depth-averaged two-dimensional (2D coupled flow and sediment transport model to investigate the flow and breaching processes with and without waves. Bed change and variable flow density are included in the flow continuity and momentum equations to consider the impacts of sediment transport. The model adopts the non-equilibrium approach for total-load sediment transport and specifies different repose angles to handle non-cohesive embankment slope avalanching. The equations are solved using an explicit finite volume method on a rectangular grid with the improved Godunov-type central upwind scheme and the nonnegative reconstruction of the water depth method to handle mixed-regime flows near the breach. The model has been tested against two sets of experimental data which show that it well simulates the flow characteristics, bed changes, and sediment transport. It is then applied to analyze flow and morphologic changes by overtopping flow with and without waves. The simulated bed change and breach cross-section shape show a significant difference if waves are considered. Erosion by flow without waves mainly occurs at the breach and is dominated by vertical erosion at the initial stage followed by the lateral erosion. With waves, the flow overtops the entire length of the dune to cause faster erosion along the entire length. Erosion mainly takes place at the upper layer at the initial stage and gradually accelerates as the height of the dune reduces and flow discharge increases, which indicates the simulated results with waves shall be further verified by physical experimental evidence.

  15. The timing of sediment transport down Monterey Submarine Canyon, offshore California

    Science.gov (United States)

    Stevens, Thomas; Paull, Charles K.; Ussler, William III; McGann, Mary; Buylaert, Jan-Pieter; Lundsten, Eve M

    2013-01-01

    While submarine canyons are the major conduits through which sediments are transported from the continents out into the deep sea, the time it takes for sediment to pass down through a submarine canyon system is poorly constrained. Here we report on the first study to couple optically stimulated luminescence (OSL) ages of quartz sand deposits and accelerator mass spectrometry 14C ages measured on benthic foraminifera to examine the timing of sediment transport through the axial channel of Monterey Submarine Canyon and Fan, offshore California. The OSL ages date the timing of sediment entry into the canyon head while the 14C ages of benthic foraminifera record the deposition of hemipelagic sediments that bound the sand horizons. We use both single-grain and small (∼2 mm area) single-aliquot regeneration approaches on vibracore samples from fining-upward sequences at various water depths to demonstrate relatively rapid, decadal-scale sand transport to at least 1.1 km depth and more variable decadal- to millennial-scale transport to a least 3.5 km depth on the fan. Significant differences between the time sand was last exposed at the canyon head (OSL age) and the timing of deposition of the sand (from 14C ages of benthic foraminifera in bracketing hemipelagic sediments) are interpreted as indicating that the sand does not pass through the entire canyon instantly in large individual events, but rather moves multiple times before emerging onto the fan. The increased spread in single-grain OSL dates with water depth provides evidence of mixing and temporary storage of sediment as it moves through the canyon system. The ages also indicate that the frequency of sediment transport events decreases with distance down the canyon channel system. The amalgamated sands near the canyon head yield OSL ages that are consistent with a sub-decadal recurrence frequency while the fining-upward sand sequences on the fan indicate that the channel is still experiencing events with a 150

  16. Sediment transport in grassed swales during simulated runoff events.

    Science.gov (United States)

    Bäckström, M

    2002-01-01

    Particle trapping in nine different grassed swales was measured successfully with a standardised runoff event simulation procedure. The percentage of total suspe