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In this paper, we propose an accurate Riemann-solver free method for a coupled system modeling shallow water flows, sediment transport and rapid bed erosion. The hydrodynamic model solving shallow water equations (SWEs) is coupled with the sediment transport equation and the morphodynamic model. A Godunov-type central-upwind scheme is proposed to numerically solve the resulting system based on the technique that using two different pairs of local wave speeds to estimate numerical fluxes for hydrodynamic and morphodynamic models, respectively. The proposed technique leads to accurate results for the computation of the morphodynamic model. The proposed scheme is based on computationally efficient techniques and do not require analytical expressions of the eingenstructure of the system. A well-balanced discretization of the bed-slope terms is developed in framework of the coupling approach. Finally, we demonstrate the robustness and accuracy of the proposed numerical scheme for the coupled system using several numerical tests. [ABSTRACT FROM AUTHOR]

Abstract: Unsealed roads and tracks are potentially significant sources of diffuse pollutants, particularly sediment. This paper describes the application and development of a road erosion and sediment transport model in the Moruya-Deua and Tuross River catchments of southeast Australia. An empirical model based on the Washington Road Surface Erosion Model (WARSEM) is applied using typically widely available spatial data sets and field-collected data. The results suggest that approximately 21kt and 35kt of sediment respectively are produced annually from road erosion in the Moruya-Deua and Tuross River catchments, but that less than 10% of the sediment is delivered to streams. Surprisingly, about half of the delivered sediment is derived from only 4% of the total road network. Testing of the model shows that the model outputs are likely to overestimate road erosion rates. To address this problem, catchment-specific testing of the factors of the model and improving knowledge of the processes of road to stream sediment transport are required. [Copyright &y& Elsevier]

Purpose - The aim is to investigate in detail the sensitivity of sediment transport and bed morphology with respect to some parameters including bed slope, non-hydrostatic pressure term, sand grain size, temperature, salinity and lower boundary conditions for suspended sand concentration on a regional scale through numerical simulations based on a mathematical model. Design/methodology/approach - The numerical model consists of a 3D hydrodynamic code amended by a sediment transport module. At the same time, the influence of wave action has been taken into account. The model is applied to the Sylt-Romo tidal bay covering approximately 20?×?30?km2 spanned by about 2.7?×?106 active grid points with the constant wind and wave fields. Findings - The computed results of seven different cases over 150?h show that the effect of bed slope correction is very strong, especially in case of largely changeable bathymetry and depends on the horizontal grid resolution. Sand grain size strongly influences the vertical distribution of suspended sediment and then sedimentation. The impact of sea water temperature is relatively clear despite being less powerful than two former parameters. Non-hydrostatic pressure perturbations of the flow field and the kind of the lower boundary condition as well as salinity are negligible allowing for considerable savings of CPU time when the numerical simulation is carried out for a large area and for a very long-time period. Originality/value - The results of the study demonstrate that the geometrical factor of coastal bed and the range of sand particle size on the bottom contribute to the tendency of bed evolution in some measure. Additionally, the increase of temperature of sea water due to global warming may also make a considerable change to the mechanism of sediment transport and sedimentation in future. Therefore, the human intervention in the process of natural evolution is possible through the behaviour to the nature. At the same time, this is also interesting and useful information and it can consolidate the idea for coastal engineering projects. [ABSTRACT FROM AUTHOR]

From March to November 2001, six current meters equipped with turbidimeters were moored 12 meters above the bottom inside the Palam6s submarine canyon and on the adjacent slope. Horizontal particle fluxes were calculated from current and suspended sediment concentration data. This work aims to evaluate the advective sediment fluxes taking place in the Palam6s canyon region, and to discern the nature and time-scales of the processes involved in the across-margin transfer of particles over the study period. Near-bottom currents inside the canyon were constrained by the local topography and displayed a high spatio-temporal variability. The net near-bottom transport of suspended matter in the canyon was largely driven by sharp increases of sediment load and current speed, most of them attributed to sediment gravity flows. These energetic events dominated over the current-driven sediment transport, which was relatively weak due to periodical up-canyon/down-canyon inversions along the canyon axis, and to complex current patterns and the presence of low sediment loads for most of the time at the other sites. During this 8-month experiment, the mid-canyon (> 1200 m depth) acted as a by-pass zone, while at the canyon head, net sediment transport was directed persistently up-canyon. These patterns were further heightened during a major storm in November 2001. However, in this particular submarine canyon, substantial sedimentary activity and offshore export of particulate matter also occur in the absence of significant external forcings (storms, river floods). Human activities (deep trawling) induced sediment gravity flows during the dry and calm season (spring-summer) and enhanced the offshore transfer of particles during this time period. [ABSTRACT FROM AUTHOR]

Sediment concentration measurement in high-concentration runoff waters is highly problematic. A novel device was developed for high-concentration measurements. This device was then used to measure sediment concentrations during monsoon runoff events at the USDA-ARS Walnut Gulch experimental watershed in southeast Arizona as an example application. Data were obtained using a 55 cm, three-prong, embedded time domain reflectometry probe and sediments in a range of size classes from the site under laboratory conditions. In the laboratory, the sensor's concentration output was calculated using a model and the empirical function describing pure water. Without sediment-specific calibration, laboratory validation indicated agreement with known concentrations within about 0.02 kg L-1 for sediment and water mixtures and within 0.2 kg L-1 when the probe was completely buried in 0 to 2.5 cm channel bed material. In the field application, the probe was installed in the base and center of a flume. Basal (0 to 2 cm depth) sediment concentrations were monitored during three flows with peak discharges of 5, 70, and 130 m³ s-1, representing small, intermediate, and large events. For the large and intermediate events, basal sediment concentrations rose from 0.4 to 1.2 kg L-1 to a plateau of 1.5 to 1.9 kg L-1 after the flow peak. The plateau extended through much of the tail of the hydrograph before falling to back to 0.4 to 1.2 kg L-1. The small event had a similar progression but lower overall concentrations of 0.2 to 0.8 kg L-1. These observations are consistent with a period of high sediment transport and channel erosion in the tail of monsoon runoff hydrographs. The dielectric method provides in-situ measurements in high-concentration environments where traditional methods fail. [ABSTRACT FROM AUTHOR]

We assessed the relative improvement to the sediment trapping effectiveness of a permanent-pool sediment retention pond due to the installation of baffles composed of different materials commonly used on construction sites. A suite of experiments was performed at the Sediment and Erosion Control Research and Education Facility (SECREF) at North Carolina State University in which an acoustic Doppler velocimeter was used to record steady-state flow velocity and signal-to-noise ratio data. The data was gathered at 25 grid points at two depths within the pond for three different fixed input flow rates. The free flow maximum mean velocity in the pond, averaged over all input flow rates, was reduced by roughly 75% due to the presence of baffles composed of jute germination biotextile backed by coir fiber. Baffles made from a standard tree-protection fence, folded and tied together into three layers to reduce pore size, reduced the free flow maximum mean velocity by 65%, while baffles made of standard silt fabric fence reduced the free flow maximum mean velocity by 55%. A similar trend in the reduction of the signal-to-noise ratio along the length of the pond confirmed that the jute/coir baffles most effectively reduced the concentration of turbulent density fronts over that of the tree-protection fence or silt fence baffles, or free flow. In addition, analysis of the transverse velocity variance and vertical velocity gradients for each experiment further demonstrated that the jute/coir baffles most effectively diffused inflow momentum along the width and depth of the pond. The results of our analysis were used to calculate a sediment trapping efficiency based on Stokes settling. The minimum grain size captured would range from 30 to 42 microns with jute/coir baffles, compared to 68 to 86 microns for free flow. [ABSTRACT FROM AUTHOR]

Crop furrow erosion is one of the main causes of land degradation in upland cropping areas. This study derived a method to assess amounts of furrow erosion. The study combines theory with both flume and field plot experiments. The flume experimental results rendered a method for calculating potential sediment transport from a log-log relationship of a logistic curve between sediment transport rate and stream power per unit area. Comparison of potential calculation results with field plot measurement data revealed that the field values were always less than the potential values. The relationship between laboratory and field data was linear in log-log scale. Crop furrow erosion, therefore, can be assessed by two steps: (1) using a logistic relationship to obtain potential values, and (2) using a linear log-log relationship to obtain field values. [ABSTRACT FROM AUTHOR]

Presents evidence for aquaous fluid-sediment transport and erosional processes on Venus. Details of the canali morphology; Interpretations of erosional features; Comparison with terrestrial channel-forming processes; Problems with canali-lava models.

• The RBVMS formulation is a good option to model sediment transport in fluid flows. • The model developed has shown good agreement with the experimental data. • Upwind sand-slide is a robust method and the mass is preserved when it is applied. • Adaptive mesh refinement has shown to be important to save computational effort. Moving sediments are intrinsic to several engineering and natural phenomena. Consequently, the study of sediment transport induced by fluid flows is critical. The transport of sediments in fluids encompasses the suspended load and the bed-load. In the suspended load turbulence carries the sediment particles. The particles near the bottom are moved by sliding, rolling or by saltation, due to shear stresses in the bed-load region. The bed-load transport implies morphological changes which are also induced by erosion as a consequence of sediment entrainment into suspension. In this work, we implement these phenomena as numerical models for 2D simulations in libMesh, an open finite element library that provides a framework for multiphysics, considering adaptive mesh refinement. Here, the mathematical model results from the incompressible Navier–Stokes equations combined with an advection-diffusion transport equation for suspended sediments using an Arbitrary Lagrangian–Eulerian description. Both equations are treated with the residual-based variational multiscale finite element formulation. Empirical models are used to represent the entrainment and the bed-load transport rate of sediments. Special boundary conditions at the bottom are introduced to take into account sediment entrainment, as well as deposition. After each time step, we update the mesh according to the morphological changes at the bottom due the bed-load transport and erosion, considering smoothing techniques to avoid numerical instabilities. We also introduce a new smoothing technique, called upwind sand-slide, in which we consider the flow direction combined with the slope angle to avoid elevations higher than the sediment angle of repose. We validate the algorithm with test cases where experimental and numerical data are available. Finally, we discuss the results, concluding that our model is very promising. [ABSTRACT FROM AUTHOR]

The article offers information on a study completed in Siberia regarding the formation of river deltas throughout the country. Scientists have found that after the last ice age, the land in Europe was covered in a sheet of ice that altered the structure of the land's mantels and sea level. In 2007, the land in certain areas of Siberia is still subsiding to its original level, making it impossible for sediment to build up and deltas to form.