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Opening of the Arctic Ocean has been the subject of much debate, and the placement of terranes in the Early Mesozoic remains a crucial part of this important discussion. Several continental terranes complicate the palaeogeographical reconstruction. One such terrane is Crockerland, which has been inferred to explain sediment distribution in the Arctic throughout the Mesozoic. However, Triassic successions throughout the Arctic basins bear many similarities, and a common sedimentary source could offer a simpler explanation with fewer complications for the past configuration of the Arctic. The study's goal is to test the hypothesis of long-distance sediment transport from a common source in present-day Russia to all Arctic basins in the Triassic, and to demonstrate how estimates of sediment routing distances can improve pre-break-up plate-tectonic reconstructions. Results confirm that (1) the Arctic basins were closely connected prior to break-up in the Mesozoic, (2) based on regional facies distribution, sediment budgets, sediment modelling and detrital zircon age spectra, the Crockerland terrane is unlikely to have existed as a major sediment supplying area, (3) the reconstructed Arctic sediment routing system can help to constrain plate-tectonic models, and (4) statistical estimation of sediment transport is a novel and potentially important tool for improving plate-tectonic and palaeogeographical reconstructions. Supplementary material: A database for provenance study, detrital zircon age spectra and the sedimentary length calculations method are available at https://doi.org/10.6084/m9.figshare.c.6086468 [ABSTRACT FROM AUTHOR]

When disturbed, dynamic emergent systems, such as tectonics on Earth, may transition from one stable state to another if the perturbation is sufficiently large. Here, we identify such state shifts through examination of statistically significant change points in the time series of metamorphic pressure–temperature and cooling rate data. Change points occur in the mid-Paleoproterozoic, the Mesoproterozoic, the early and late Paleozoic and the Cenozoic. To compare the timing of change points with mantle geodynamics, we interrogate the time series of calculated mantle potential temperature, which yields a statistically significant drop of >130°C in the mid-Paleoproterozoic, indicating a change in the mechanism of mantle cooling. We interpret changes in the mid-Paleoproterozoic to relate to the global emergence of stable subduction, orogenesis associated with the formation of the Nuna megacontinent, and slab breakoff, consistent with the operation of a distinctive style of Proterozoic plate tectonics. By contrast, changes from the dawn of the Cambrian onward may relate to the large volume of sediments supplied to trenches following multiple Cryogenian and Paleozoic glaciations. Sediments acted as a lubricant, allowing deeper subduction, transport of lower continental plates to mantle depths and faster metamorphic cooling rates, features characteristic of modern plate tectonics. Supplementary material: A dataset of metamorphic cooling rates is available at https://doi.org/10.6084/m9.figshare.c.5943418 [ABSTRACT FROM AUTHOR]

The main goal of this work is the resolution of the two-dimensional shallow water equations of water–sediment mixture coupled to the transport diffusion equation for the total sediment load, and bed change rate equation by Roe scheme with a new discretization of the source term. The proposed discretization is well-balanced with the flux gradient and uses data right and left on the interfaces between two control volumes and satisfies the C-property. The numerical method uses unstructured meshes and incorporates minmod limiter and Runge–Kutta method to reach second order spatial and temporal accuracy. We also use an adaptive mesh based on gradient concentration of sediments to refine the study domain with a lower computational cost. We present some numerical results in order to verify and validate the performance of the numerical scheme, particular attention is given to the treatment of the dam-break problem over mobile beds. The numerical scheme demonstrates the intended accuracy and robustness to modelize dam-break flows over erodible bed. [ABSTRACT FROM AUTHOR]

Wetlands play an important role in maintaining many natural cycles and supporting a wide range of biodiversity. In the current world, the transport of solute in a wetland with vegetation is an essential issue in environmental, biological, geophysical, and concerned applications. Specially, floating vegetated wetland which is a buoyant platform enveloped by plants, playing a pivotal role in filtering and purifying water in aquatic ecosystems The main focus of the present research is to investigate the transport of sediment particles in a depth-dominated tidal floating vegetated wetland (FVW) flow. The characteristics of floating vegetation absorption and vegetation parameter in FVW are explained to explore the transport of sediment particles. This work's model relies on an advection-diffusion equation, the solution of which discloses the concentration of settling particles in the water phase. Utilizing the method of moments, a set of moment equations is derived from the governing equation. The equations of moment are then solved using a finite difference implicit scheme. Further, the four moments and Hermite polynomial illustration is adopted to derive the vertical mean concentration distribution profile. The effective dispersivity and the concentration distributions of the sediment particles are illustrated for three different situations of fluid flow: steady, purely oscillatory, and periodic flow with non-zero-mean for all time. The effects of the vegetation factor, settling velocity, absorption due to floating vegetation, and other important factors on sediment transport in FVW are discussed for three different cases separately. Result shows as settling velocity (ω) increases, the influence of vegetation absorption (β) on dispersion coefficient diminishes in the steady state, and its effect on mean concentration becomes less pronounced due to the downward movement of particles. This is because vegetation absorption is stronger near the upper surface, but higher ω values lead to particle downward, reducing β ′ s impact. The results are described in the context of some real-world situations, as the free surface of a tidal wetland is naturally covered with plants; FVW serve as a natural water purification filter for polluted estuaries, contaminated crude oil wastewater, and so on. This study has potential to aid in water purification efforts as well as for the protection and conservation of coastal environments to limit sea level rise. [ABSTRACT FROM AUTHOR]

The article explores how experimental floods in Spöl, an excellent open-air laboratory for researching transport processes and dealing with the ecological effects of dams. Topics include diverse ecosystem, alpine rivers sustain life and offer important ecosystem services such as drinking water and recreation; and observations of artificial floods with negative effects of riverregulation with the monitoring program focused on the biological and ecological features of the morphological changes.

When reconstructing sediment provenance, the challenge posed by multiple univariate (i.e., age-only) detrital geochronology data sets with similar one-dimensional distributions can be mitigated by incorporation of a second variable such as Hf isotopic data. However, there is no commonly applied method of sample intercomparison, much less forward or inverse modeling of these bivariate data sets. In this paper we explore application of non-negative matrix factorization (NMF) to bivariate data sets. Factorization of univariate mixed (a.k.a., sink or daughter) data sets has been demonstrated to successfully recover both the one-dimensional endmember (a.k.a., source or parent) distributions and their mixture weightings. We show that NMF can successfully recover both the two-dimensional distributions and mixing weights in synthetic data sets. Application of the method to 24 published Neoproterozoic–Triassic samples from western Laurentia yields six two-dimensional endmember distributions that are a close match to empirical sediment sources on the southern, eastern, and northern margin of Laurentia. The results are broadly consistent with previous interpretations and confirm that the method can characterize unknown sediment sources based on data from analyzed sink samples. Correlating between factorized endmembers and empirical sources indicates that the Transcontinental Arch was not a barrier to east–west sediment transport until the late Cambrian. Quantitative comparison also shows that the closest known match for a factorized endmember with highly evolved Permo-Triassic zircons is from northern South America and suggests northward transport of this detritus following assembly of Pangea. Recognizing these empirical sources and their distribution into strata that would later be incorporated into the North American Cordillera sets the stage for interpreting sediment provenance records in the Jurassic–Paleogene Cordilleran retroarc foreland basin. Supplementary material: The open-source software (DZnmf2D) and a user manual is available in public repositories: https://doi.org/10.5281/zenodo.4460336. All other supplemental files are available at https://doi.org/10.6084/m9.figshare.c.5280320 Thematic collection: This article is part of the Fold-and-thrust belts and associated basins collection available at: https://www.lyellcollection.org/cc/fold-and-thrust-belts [ABSTRACT FROM AUTHOR]

Early foredeep successions can yield insight into tectonic processes operating adjacent to and ahead of fledgling orogenic belts but are commonly deformed by the same orogens. We develop a workflow towards stratigraphic understanding of these deformed basins, applied to the Eastern Champsaur Basin of the French Alps. This contains a down-system correlative of the southern-sourced (Eocene–Oligocene) Annot turbidites. These strata are deformed by arrays of west-facing folds that developed beneath the Embrunais–Ubaye tectonic allochthon. The folds vary in geometry through the stratigraphic multilayer. Total shortening in the basin is around 4 km and the restored (un-decompacted) stratal thickness exceeds 980 m. The turbidites are generally sand-rich and bed-sets can be correlated through the entire fold train. The succession shows onlap and differential thickening indicating deposition across palaeobathymetry that evolved during active basement deformation, before being overridden by the allochthon. The sand system originally continued over what is now the Ecrins basement massif that, although contributing to basin floor structure, served only to confine and potentially focus further sediment transport to the north. Deformation ahead of the main Alpine orogen appears to have continued progressively, and the past definition of distinct 'phases' ('pre-' and 'post-Nummulitic') is an artefact of the stratigraphic record. [ABSTRACT FROM AUTHOR]

The article discusses the westward stream known as the African Easterly Jet and how it triggers the hurricane. Topics mention including the combination of Earth's rotation converge, warm ocean temperature and moist air, extraction of sediment cores from the seafloor and measuring the radioactive isotope of carbon.

We present a numerical model for the simulation of 3D poly-dispersed sediment transport in a Newtonian flow with free surfaces. The physical model is based on a mixture model for multiphase flows. The Navier–Stokes equations are coupled with the transport and deposition of the particle concentrations, and a volume-of-fluid approach to track the free surface between water and air. The numerical algorithm relies on operator-splitting to decouple advection and diffusion phenomena. Two grids are used, based on unstructured finite elements for diffusion and an appropriate combination of the characteristics method with Godunov’s method for advection on a structured grid. The numerical model is validated through numerical experiments. Simulation results are compared with experimental results in various situations for mono-disperse and bi-disperse sediments, and the calibration of the model is performed using, in particular, erosion experiments. [ABSTRACT FROM AUTHOR]

The burial and scour of objects at the bottom of the ocean is governed by a range of different factors and is thus a complex system to simulate with numerical methods. In this work, we present a sediment transport model based on the lattice Boltzmann method which is capable of predicting the influence of a unidirectional flow field on the development of the sand bed in the vicinity of arbitrarily shaped objects, even under turbulent conditions and relatively low resolution. The underlying lattice Boltzmann method for the fluid phase of the simulation is governed by the three-dimensional entropic multi-relaxation time collision model and further makes use of appropriate three-dimensional grid refinement and off-lattice boundaries. The corresponding framework was implemented in the open-source Palabos library and enables accurate turbulent flow simulations around arbitrarily shaped objects without the need to tune any specific model parameters. For the simulation of the sediment transport, the advection–diffusion equation is solved via the lattice Boltzmann method with an adapted version of the entropic multi-relaxation time collision model for a three-dimensional lattice with seven discrete lattice velocities (D3Q7). The presented sediment transport model thus inherits the unconditional numerical stability and the simplicity of the entropic multi-relaxation time collision model. Furthermore, erosion and sedimentation processes are included based on the critical Shields parameter, i.e. on the wall shear stress. An initial simulation of the flow and sediment transport around a horizontally bedded finite cylinder shows that the presented model is generally able to capture the major sediment processes which govern the development of the sand bed. [ABSTRACT FROM AUTHOR]

In this paper we present the results of the numerical simulation of a three-dimensional current-driven sediment transport process. In detail, the temporal evolution of a barchanoid dune is studied. Two phenomena are treated in this context. First, the three-dimensional flow of a single phase fluid is considered. Second, the interaction of the flow and the sediment bed with its morphological change of the sediment surface is taken into account. We numerically solve the instationary incompressible Navier–Stokes equations, an advection diffusion equation and Exner’s bed level equation to update the sediment bed morphology. Here, Exner’s equation determines the change of the bed level due to the bed load. The suspended material is treated as a sediment concentration and its movement is modelled by an advection-diffusion equation. To secure the continuous interchange between bed load and the suspension load sink and source terms are used. Both equations are discretised and explicitly coupled to the discrete fluid model. The typical sedimentary processes and the sedimentary form of a prototypical barchanoid dune are well captured by our numerical simulation, which is supported by a qualitative comparison with examples from the literature. [ABSTRACT FROM AUTHOR]

Effects of roughness on the near-bed turbulence characteristics in oscillatory flows are studied by means of particle-resolved direct numerical simulations (DNS). Two particle sizes of diameter 375 and 125 in wall units in a very rough turbulent flow regime are studied. A double-averaging technique is employed to study the nature of the wake field, i.e., the spatial inhomogeneity at the roughness length scale. This introduced dispersive stresses along with additional production and transport terms in the double-averaged Reynolds stress budget, indicating alternate pathways of turbulent energy transfer mechanisms. While overall nature of the elementary processes responsible for energy transport in both flow cases remains identical, there are some discernible differences with regards to the near-bed turbulence structure. It is shown that the roughness modulates the near-bed turbulence, distorts and breaks the streamwise horseshoe structures, and therefore reduces the large-scale anisotropy; a result of redistribution of energy from streamwise component to other two components of the Reynolds stress and is illustrated by studying their individual budgets. In comparison to the small diameter, such effects are found to be significant in the case of large diameter particle-bed. In addition, redistribution of energy in the large diameter particle case shows reduced dependence on the flow oscillations, while for the small diameter particle it is more pronounced towards the end of an acceleration cycle. [ABSTRACT FROM AUTHOR]

We perform a simulation-based study on the suspension and transport of sediment under a plunging wave breaker. Navier–Stokes equations for a multi-phase incompressible flow are solved using an in-house finite-difference code. The air–water interface is captured by using the coupled level-set and volume-of-fluid method. The convection–diffusion equation with a settling term for a passive scalar is solved to describe the transport of the sediment concentration. The pick-up function is used to address the sediment flux at the bottom. Five cases with different water depth and wave steepness have been simulated. Both instantaneous and statistical results on the sediment concentration are analyzed to investigate the processes of sediment suspension and transport. It is observed from the simulation results that during wave breaking, sediment is suspended due to the high shear stress at the water bottom. The wave breaking also induces an upward motion of water between two large scale counter-rotating vortices, which in turn transports the suspended sediment towards the water surface. Based on the analysis of the mass center of suspended sediment, the process of sediment transport under the plunging breaking wave is divided into the erosion stage, suspension stage, and transport stage. The effects of water depth and wave steepness on the bulk concentration of suspended sediment, bottom erosion and deposition fluxes, and the mass center of sediment are discussed. As the water depth decreases and as the wave steepness increases, more sediment is picked up during the wave breaking. The bed deformation is also predicted based on the transport equation of the bed elevation. [ABSTRACT FROM AUTHOR]

This study aims to develop a three-dimensional (3-D) numerical model for shallow water flows over mobile topography, which is capable of simulating morphological evolution under shock waves, e.g. dam-break flows. The hydrodynamic model solves the three-dimensional shallow water equations (SWEs) using a finite volume method on prismatic cells in σ -coordinates. The morphodynamic model solves an Exner equation consisting of bed-load sediment transportation. Using a relaxation approach, a hyperbolic system is built for hydrodynamic system, which allows for using a Godunov-type central-upwind method to capture the shocks and approximate the numerical fluxes. Consequently, the 3D-SWEs-Exner model proposed in the present study can stably and accurately solve the dam-break flows over mobile beds. A spatially and temporally second-order “prismatic” central-upwind method is used to approximate the numerical fluxes through cell interfaces. The Exner equation is solved using an upwind method. Using spatially linear reconstruction and explicit two-stage Runge–Kutta time discretization, second order accuracy is achieved in space and time. The proposed model can preserve the well-balanced property due to the special discretization of bed-slope source terms. The proposed model is validated by several tests with experimental measurements, and is compared with the simulated results using reported two-dimensional (2-D) models. [ABSTRACT FROM AUTHOR]

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]

Significant advances in the modeling of nearshore processes have occurred over recent decades as a result of developments in both computational approaches and theoretical understanding. This review examines the present state of progress primarily from a hydrodynamics standpoint, followed by a brief discussion of applications to sediment transport and morphological evolution. Wave-averaged formulations of the wave-current interaction problem and resulting models for wave-induced currents are reviewed in order to compare and contrast radiation stress and vortex force approaches. Waveresolving approaches are then discussed, with an emphasis on the recent rapid development of 3D nonhydrostatic models and their application to a wide range of physical problems. The recently developed understanding of the importance of vorticity generation mechanisms at wave-resolved scales, and their contribution to transport and mixing processes, are discussed. [ABSTRACT FROM AUTHOR]

Langmuir circulation cells extending through entire water columns exert a profound influence on sediment transport on shallow shelves, hence their designation as "Langmuir Supercells" (LSs) upon discovery in 2004 in water of 15 m depth at the Long-Term Ecosystem Observatory (LEO) off New Jersey (United States). Until now, similar high-frequency, full water column measurements of turbulent velocities and density fields have not been reported from significantly deeper continental shelf environments. Such deeper measurements are needed to determine whether LSs exist to influence sediment transport outside the inner shelf. In this article, that deficiency is addressed, using measurements from a midshelf location in the South Atlantic Bight. These data indicate that LSs form during high wind and wave forcing in water of 26 m depth and are thus capable of affecting sediment transport over more than about half of the area of this wide, shallow shelf. Relative to those at LEO, the LSs reported here are less organized and more temporally variable despite similar magnitude forcing. Possible causes of cell weakness and variability are considered. [ABSTRACT FROM AUTHOR]

We employ a numerical simulation of the three-dimensional fluid flow and the simultaneous transport of sediment to reproduce current-driven sediment transport processes. In particular, the scouring at a rectangular obstacle is investigated. To solve the instationary incompressible Navier–Stokes equations we use the code NaSt3D. The morphological change of the sediment bed is modeled by Exner’s bed level equation, which is discretized and coupled to the discrete fluid model, i.e., to the NaSt3D code. A large eddy turbulence approach using a Smagorinsky subgrid scale tensor is applied. For our purposes, we only consider bed load transport under clear water conditions. Furthermore, we demonstrate mass conservation and convergence of our approach for a test case. We compare the results of our numerical simulations for a scour mark with those obtained in a laboratory flume. The typical sedimentary processes and the sedimentary form of a scour mark are well captured by our numerical simulation. [ABSTRACT FROM AUTHOR]

This paper describes the numerical scheme of the one-dimensional Exner - shallow water equations for sediment modeling. Here, our novel numerical scheme is called hydrostatic relaxation scheme which is a robust and straightforward scheme. This scheme is given as the hydrostatic reconstruction of the relaxation solver. Some numerical tests are presented such as analytical solution, transcritical flow over a granular bump, and erodible bottom due to dam-break. The comparisons of numerical and data experiments are also given in dam-break over granular bed simulation. The results of our simulation have a good agreement with analytical solution and the data experiments. Moreover, satisfactory convergence rate in L 1 -norm is obtained. [ABSTRACT FROM AUTHOR]

Calculation of the coastal sediment budget involves estimation of the timing and intensity of processes of erosion, transport, and deposition, as well as an understanding of local and regional sediment dynamics. The modern sedimentary deposits present in the coastal zone constitute the physical basis of coastal ecosystems. Knowledge of the dynamics of these sediments from the source to sink area, through regional sediment management, is critical to understanding the long-term stability of the coastal zone and the fate of these important natural resources. In this article, the littoral cell concept has been applied to the midcoast of Rio Grande do Sul, a wave-dominated and dissipativeintermediate sandy coast in southern Brazil. To analyze littoral drift variations along the 275 km long study area, the shoreline was divided into 12 cells. Littoral drift rates were estimated and compared using the energy flux method. Wave parameters were obtained from WAVEWATCH III. The sand volume of the coastal dune field (4.20 billion m³) was quantified using satellite imagery and the aeolian transport rates estimated utilizing the sediment budget residual. The net annual longshore transport rates obtained with the Coastal Engineering Research Center equation range from 0.60 to 2.63 million m³ per year. The littoral drift rates obtained with the Van Rijn (2001) and Kamphuis (1991) equations range between 0.15 and 1.00 million m³ per year. Based on the sediment budget and dune field age, the CERC formula seems more appropriate to estimate longshore transport. [ABSTRACT FROM AUTHOR]

A numerical model was built to study the mechanism of sedimentary bedform development in hydraulically smooth turbulent flows. The model consisted of a module for flows, a module for sediment transport, and a module for bed surface evolution. The flow was unsteady, three-dimensional and modeled by a Large-Eddy-Simulation (LES) method coupled with an Immersed-Boundary-Method (IBM). Governing equations were discretized on a fixed Cartesian grid by Finite Difference Method. Sediment (bedload) transport was estimated by Van Rijn formula corresponding to bed shear stress distribution obtained from the flow solution. The bed surface evolution was adapted to the sediment flux and described by the Exner–Polya equation. Updated bed surface was then used as the boundary for solving the flow field in the next time step. Time-advancement was discretized by the Adams–Bashforth method. The model was first validated by two test cases of bed shear stress and turbulence statistics over fixed sinusoidal bed surfaces. It was then employed to study initiation and development of bedforms from an initially flat bed to fully developed forms. Formation of newly and successively formed bedforms, growing and downstream propagating process of existing bedforms were very close to experimental observations. Instantaneous bed shear stress and corresponding sediment flux around evolving bedforms, which were difficult to observe in experiments, were also well produced by this model. [ABSTRACT FROM AUTHOR]

Langmuir supercells (LS), which are Langmuir circulations (LC) extending over full water column depth during storms and revealed by high water column backscatter from surface-origin microbubbles and bottom-origin sediment, were discovered in 2003 during several months of measurements in 15 m of water near the coast of New Jersey. Both the structures themselves and the specific forcing conditions under which they occur have been documented elsewhere. This paper provides an account of the broader oceanographic setting of supercell events, focusing on conditions at the start and end. The start of events is associated with the presence of surface waves of intermediate type that "feel bottom" with amplitudes sufficiently large to resuspend sediment and achievement of three conditions for full-depth LC: an unstratified water column, La < ~0.3 and ∣Ra∣ < 105, where Ra and La are dimensionless parameters derived from scaling of the wave-averaged momentum equation. Event cessation is associated with failure of one of the latter two conditions or the reappearance of stratification. There is no fixed order in which conditions necessary for full-depth LC are met or fail. Comparison with data from a deeper site off Georgia suggests that coherent full-depth Langmuir circulations will not generally be observed in unstratified water columns much deeper than 25-30 m, a depth determined primarily by the wavelength of surface waves generated by typical storms. We also document two features of LC acting in the surface layer of the stratified water column that existed prior to onset of the prototype LS event. First, LC confined to the surface layer generated first mode internalwaves with frequency that of the stratified interior. Secondly, active surface layer LC did not act efficiently as direct agents of mixed layer deepening, which occurred primarily in two separate episodes of Richardson number lowered by increased shear. Instead, as a result of quasi-organized structure and enhanced vertical penetration relative to stress-driven turbulence, the primary role of LC may be to increase efficiency of momentum transfer to the surface layer, enhancing surface layer acceleration and contributing to onset of the shear instability that does deepen the surface layer. [ABSTRACT FROM AUTHOR]

Abstract: A simple solver is proposed for the numerical solution of density-driven multi-layer shallow water flows. The governing equations consist on coupling the multi-layer shallow water equations for the hydraulic variables with suspended sediment transport equations for the concentration variables. The layers can be formed in the shallow water model based on the variation of water density which may depend on the water temperature and salinity. At each time step, the method consists of two stages to update the numerical solution. In the first stage, the multi-layer shallow water equations are rewritten in a non-conservative form and the intermediate solutions are calculated using the modified method of characteristics. In the second stage, the numerical fluxes are reconstructed from the intermediate solutions in the first stage and used in the conservative form of the multi-layer shallow water equations. The proposed method avoids Riemann problem solvers and it is suitable for multi-layer shallow water equations on non-flat topography. Several numerical results are presented to illustrate the performance of the proposed finite volume method. The computed results confirm its capability to solve multi-layer shallow water equations for density-driven flows over flat and non-flat bottom topography. [Copyright &y& Elsevier]

Before railroad and lorry traffic became common, many canals were built for transportation purposes. Water quality in canals has become a major concern as maintenance of these historically active canals has declined. A generic canal model has been developed to simulate the hydro-environmental processes specifically relevant to inland navigational canals, namely lockage, weir overflow, boat traffic, and algal growth. Apart from the movement of water, three types of particulate matter are tracked: algae (chlorophyll-a), inorganic non-cohesive sediment, and inorganic cohesive sediment. The newly developed model was applied to the Kennet and Avon Canal in southern England. The method of determining the input parameters for the model was documented herein, including setting up a Hydrological Simulation Program - Fortran model to obtain the landscape flow and sediment runoff to the canal. The model predictions were compared with the observed hydrological, sediment, and chlorophyll-a data at monitoring locations along the canal, and favourable agreements were achieved. [ABSTRACT FROM AUTHOR]

Highlights: [•] We propose a modified general definition for bedload transport. [•] It takes into account the thickness of the sediment layer. [•] It coincides with a classical bedload transport formula in the case of uniform flows. [•] Mathematical properties (hyperbolicity) are preserved but eigenvalues can differ. [•] Numerical simulations show a more realistic behavior in the case of an advancing dune. [Copyright &y& Elsevier]

Remnants of fluvial sediments and their paleovalleys may map out a late Oligocene-early Miocene "super-river" from headwaters in the southern Colorado Plateau, through a proto-Grand Canyon to the Labrador Sea, where delta deposits contain microfossils that may have been derived from the southwestern United States. The delta may explain the fate of sediment that was denuded from the southern Colorado Plateau during late Oligocene-early Miocene time. I propose the following model: 1. Uplift of the Rio Grande Rift cut the southern Colorado Plateau out of the Great Plains at 26 Ma and tilted it to the southwest. 2. The upper Colorado River and its tributaries began as consequent streams that flowed down the structural plunge of the basin toward the southwest corner of the Colorado Plateau, where the river passed through a Paleogene canyon. 3. The river turned north in the Lake Mead region to enter Paleogene rifts of the eastern Great Basin. 4. NE-trending grabens across the Idaho and Montana Rockies provided the final link to the Great Plains, where the Miocene drainage joined the "Bell River" of Canada, which drained to the Labrador Sea. 5. Faulting and volcanism began to segment the paleo-river by ca. 16 Ma. 6. Faulting dammed Miocene Grand Canyon, creating a large ephemeral lake that persisted until after 6 Ma, when the Colorado River was captured by the Gulf of California. 7. The resulting shortcut to sea level greatly increased the gradient of the Colorado River, leading to headward incision of the Inner Gorge of Grand Canyon along the trace of the Miocene bedrock valley f loor and renewed late Miocene-Holocene erosion of the Colorado Plateau. 8. The Yellowstone hotspot cut the river off in Idaho after 6 Ma. 9. Pleistocene continental glaciation destroyed the Canadian Bell River and diverted Montana's drainage into the modern Missouri River. [ABSTRACT FROM AUTHOR]

The Chile Trench of the convergent continental margin of Central Chile is a sediment-filled basin that stretches over 1500 km in a north-south direction. The sediment fill reflects latitudinal variations in climate as well as in the morphology and geology of Chile, but also of sediment transport processes to the trench and within the trench. We try to untangle these signals by calculating the total volume and the latitudinal volume distribution of trench sediments and by relating this distribution to a number of factors that affect this pattern. The volume calculation is based on a model geometry of the top of the subducting oceanic plate that is buried beneath trench sediments and the sea floor as measured by swath bathymetry. We obtain the model geometry of the subducting plate by interpolating between depth-converted seismic reflection profiles that cross the trench. The total volume of the trench fill between 32 and 46°S is calculated to be 46000 ± 500 km³. The resulting latitudinal volume distribution is best explained by a sedimentation model that alternates between (1) glacial phases of high sediment flux from Southern Chile combined with active latitudinal sediment transport within the trench and (2) interglacial phases over which sediment input is dominated by local factors. [ABSTRACT FROM AUTHOR]

Highlights: [•] Model the transport/deposition of the ocean sediments in a coastal water system. [•] Examine the sediment deposition pattern on the lake bed and channel bottom. [•] Validate the deposition pattern with measurement data. [•] Examine the regular tidal effect and flood effect on the sediment deposition. [Copyright &y& Elsevier]

Abstract: As high performance computing (HPC) systems become more accessible, numerical simulations of various physical systems has become a popular research tool. These methods usually require the solution of a large system of coupled equations which, to take advantage of parallel processing, are usually solved by decomposing the domain. A particularly challenging problem in the area of computational fluid dynamics (CFD) is free surface phenomena which requires a moving domain and with the inclusion of the relevant dynamic boundary conditions, thin boundary layers on the rigid bottom boundary and free surface, which scale with the Reynolds number as Re −1/2. To capture the flow in near wall regions at higher Reynolds numbers requires the solution of ever larger systems of equations. The implementation of these CFD codes to run efficiently on HPC systems is not trivial. This work couples together various computational techniques to be able to simulate high Reynolds number two dimensional free surface flows. This is accomplished through a simple manual domain decomposition technique and by linking to external high performance libraries for parallel vectors/matrices and system solution. The code was tested on UCL’s supercomputer Legion and demonstrated linear weak scaling in tests carried out with up to 60m nodes and up to 256 cores. The laminar boundary layer under a solitary wave was investigated to highlight the codes ability to resolve the thin boundary layers present. The technique was then applied to analyse sediment transport under a solitary wave. [Copyright &y& Elsevier]

Abstract: The numerical simulation of sediment transport problems is considered in this paper. The physical problem is modeled through the shallow-water equations coupled with the Exner equation to describe the time evolution of the bed profile. The spatial discretization of the governing equations is carried out by a finite-volume method and a modified Roe scheme designed for non-conservative systems. As for the time advancing, starting from an explicit method, a linearized implicit scheme is generated, in which the flux Jacobian is computed through automatic differentiation. Second-order accuracy in space is then obtained through MUSCL reconstruction and in time through a backward differentiation formula associated with a defect-correction approach. The implicit time advancing is compared in terms of accuracy and computational time with the explicit approach for one-dimensional and two-dimensional sediment transport problems, characterized by different time scales for the evolution of the bed and of the water flow. It is shown that, whenever the use of large time steps is compatible with the capture of the water flow dynamics and of the bedload evolution, the implicit scheme is far more efficient than its explicit counterpart with a CPU reduction up to more than two orders of magnitude. This makes implicit time differencing an attractive option for complex real life applications in this area. [Copyright &y& Elsevier]

The scouring effect of the flowing water around bridge piers may undermine the stability of the structure, leading to extremely high direct and indirect costs and, in extreme cases, the loss of human lives. The use of Artificial Neural Network (ANN) models has been recently proposed in the literature for estimating the maximum scour depth around bridge piers: this study aims at further investigating the potentiality of the ANN approach and, in particular, at analysing the influence of the experimental setting (laboratory or field data) and of the sediment transport mode (clear water or live bed) on the prediction performances. A large database of both field and laboratory observations has been collected from the literature for predicting the maximum local scour depth as a function of a parsimonious set of variables characterizing the flow, the sediments and the pier. Neural networks with an increasing degree of specialization have been implemented -- using different subsets of the calibration data in the training phase -- and validated over an external validation dataset. The results confirm that the ANN scour depths' predictions outperform the estimates obtained by empirical formulae conventionally used in the literature and in the current engineering practice, and demonstrate the importance of taking into account the differences in the type of available data -- laboratory or field data -- and the sediment transport mode -- clear water or live bed conditions. [ABSTRACT FROM AUTHOR]

Few studies describe and compare the transport mechanisms operating to disperse mud in different parts of basins. Instead, the physical processes operating to disperse mud in offshore environments, where storm and tidal processes are interpreted to dominate, are generally considered in isolation from those occurring in basinal settings where changes in bottom-water anoxia and suspension settling from buoyant plumes are mostly interpreted to dominate. Using microtextural, mineralogical and geochemical data derived from the analyses of 151 thin sections obtained from the Lower Jurassic mudstone-dominated succession exposed on the coast of NE England, we investigate how varying sediment dispersal mechanisms, bioturbation and early diagenesis operated to produce the lithofacies variability observed. In particular, we consider the processes of sediment delivery while bottom waters were interpreted to be euxinic. Analyses of these samples reveal that the succession is highly variable at millimetre to centimetre scales. Six main lithofacies were observed: (1) sand- and clay-bearing, silt-rich mudstones; (2) silt-bearing, clay-rich mudstones; (3) clay-rich mudstones; (4) clay-, calcareous nannoplankton-, and organic carbon-bearing mudstones; (5) fine-grained muddy sandstones; (6) cement-rich mudstones. These units are organized typically into stacked successions of sharp-based, normally graded, thin (,10 mm) beds. Single beds exhibit a variety of sedimentary structures. Specifically tempestites, wave-enhanced sediment gravity flows of fluid mud, ripples and gutter casts are common in the coarser-grained mudstone facies. In contrast, thin siltstone lags, compacted ripples and organomineralic aggregates are common in the finer grained mudstone facies and those with significant primary production-derived components. Bioturbation is common throughout. These data indicate that sediment was transported by density flows and traction currents operating at the sediment-water interface in all parts of the studied succession. Bioturbation has overprinted depositional fabrics in the majority of samples. The extent to which persistent bottom-water anoxia and low-energy suspension settling influenced lithofacies variability in the basinal parts of the succession has been overstated; these environments were more dynamic than most researchers have previously concluded. [ABSTRACT FROM AUTHOR]

Abstract: We propose a new numerical method for solving the equations of coupled sediment transport and bed morphology by free-surface water flows. The mathematical formulation of these models consists of the shallow water equations for the hydraulics, an advection equation for the transport of sediment species, and an Exner equation for the bedload transport. The coupled problem forms a one-dimensional hyperbolic system of conservation laws with geometric source terms. The proposed numerical method combines the method of characteristics with a finite volume discretization of the system. The combined method is simple to implement and accurately resolves the governing equations without relying on Riemann problem solvers. Numerical results are presented for several test examples on sediment transport and bed morphology by free-surface water flows. [Copyright &y& Elsevier]

Abstract: Unstructured finite volume methods are receiving increased attention mainly because of their ability to provide a flexible spatial discretization. Hence, some areas can be resolved in great detail while not over-resolving other areas. Development of these models is an ongoing process with significant longstanding issues with adaptive grids, efficiency, well-balanced flux-gradient and source-term approximations, and so forth. However, many of these problems have been solved with the current generation of models which have much promise for morphodynamic models in contracting channel flows. Our purpose is to compare a class of unstructured finite volume morphodynamic models in contracting channel flows. The proposed adaptive finite volume method has important advantages in the discretization of the gradient fluxes and source terms and can handle complex topography using unstructured grids and satisfies the conservation property. The adaptation criteria is based on monitoring the bedload in the computational domain during its transport process. The comparison is illustrated with a simple test case of contracting channel flow. [Copyright &y& Elsevier]

This paper presents the geologic and hydrogeologic features of the Ojo de Agua zone in the southern basin of Guatemala City where a battery of water wells produces around 72% of the groundwater extracted from the aquifers of the central valley. The exploited outflow at Ojo de Agua represents 20% of the total production of Guatemala City. Therefore, Ojo de Agua is of essential importance for the water supply of the city making it is necessary to be exploit in a sustainable manner. This research is necessary to determine a conceptual hydrologic model and to establish new sites for water wells. The geology is conformed by lava flows, pyroclasts and sediments of variable permeability. An upper aquifer and lower aquifer have been established. The upper aquifer is conformed by pyroclasts and lake and fluvial sediments, with primary permeability and unconfined type. The aquifer has transmisivity values of 50 to 750 m²/day for the pyroclastic materials, and 150 to 2000 m²/day for the sediment materials. The storage coefficient is 0,09 and 0.20 respectively. The lower aquifer is confined and has secondary permeability; transmisivity varies from 1600 to 9500 m²day and the volcanic rocks have a storage coefficient of 0,014. The static levels of the water wells of Ojo de Agua have been fell down an average of 9 m in a period of over 20 years; the maximum drop registered is 13,2 m. The actual groundwater level depth is 12 to 14 m below ground level. Surging springs were reported in the area before the groundwater exploitation. The outflow of the main water wells varies from 134 to 232 1/s, for a total of 1675 1/s. The direction of groundwater flow is mainly north-south, controlled by a fault system with the same orientation that has developed horst and graben structures nearby. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, nonlinear time series modeling techniques are applied to analyze suspended sediment data. The data are collected from the Yellow River basin at Tongguan, Shanxi, China during January 1980–December 2002. The phase space, which describes the evolution of the behavior of a nonlinear system, is reconstructed using the delay embedding theorem suggested by TAKENS. The delay time used for the reconstruction is chosen after examining the first zero-crossing of the autocorrelation function and the first minimum of the average mutual information (AMI) of the data. It is found that both methods yield a delay time of 7 days and 9 days, respectively, for the suspended sediment time series. The sufficient embedding dimension is estimated using the false nearest neighbor algorithm which has a value of 12. Based on these embedding parameters we calculate the correlation dimension of the resulting attractor, as well as the average divergence rate of nearby orbits given by the largest Lyapunov exponent. The correlation dimension 6.6 and largest Lyapunov exponent 0.065 are estimated. Finally, the phase space embedding based weight predictor algorithm (PSEWPA) is employed to make a short-term prediction of the chaotic time series for which the governing equations of the system may be unknown. The predicted values are, in general, in good agreement with the observed ones within 15 days, but they appear much less accurate beyond the limits of 20 days. These results indicate that chaotic characteristics obviously exist in the sediment transport phenomenon; techniques based on phase space dynamics can be used to analyze and predict the suspended sediment concentration. [Copyright &y& Elsevier]

This work examines various methods for creating empirical equations on the basis of data while taking advantage of knowledge about the problem domain. It is demonstrated that the use of high level concepts aid in evolving equations that are easier to interpret by domain specialists. The application of the approach to real-world problems reveals that the utilization of such concepts results in equations with performance equal or superior to that of human experts. Finally, it is argued that the algorithm is best used as a hypothesis generator assisting scientists in the discovery process. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a framework for synchronously coupling wave, current, sediment transport, and seabed morphology for the accurate simulation of multi-physics coastal ocean processes. The governing equations, which represent models that are commonly adopted in practical simulations, are discretized using finite-difference methods. The resulting system is validated against analytical solutions. In order to test the performance of the proposed framework and the numerical methods, dam-break flow over a mobile-bed and evolution of a wave-driven sand dune are simulated. The interactions among waves, currents, and seabed morphology are illustrated. [Copyright &y& Elsevier]

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]

Based on previous work on the transport-transformation model of heavy metal pollutants in fluvial rivers, this paper presents the formulation of a two-dimensional model to describe chemical transport-transformation in fluvial rivers by considering basic principles of environmental chemistry, hydraulics and mechanics of sediment transport and recent developments along with three very simplified test cases. The model consists of water flow governing equations, sediment transport governing equations, transport-transformation equation of chemicals and convection- diffusion equations of sorption-desorption kinetics of particulate chemical concentrations on suspended load, bed load and bed sediment. The chemical transport-transformation equation is basically a mass balance equation. It demonstrates how sediment transport affects transport- transformation of chemicals in fluvial rivers. The convection-diffusion equations of sorption- desorption kinetics of chemicals, being an extension of batch reactor experimental results, take both physical transport, i.e. convection and diffusion, and chemical reactions, i.e. sorption- desorption into account. The effects of sediment transport on chemical transport-transformation were clarified through three simple examples. Specifically, the transport-transformation of chemicals in a steady, uniform and equilibrium sediment-laden flow was calculated by applying this model, and results were shown to be rational. Both theoretical analysis and numerical simulation indicated that the transport-transformation of chemicals in sediment-laden flows with a clay-enriched riverbed possesses not only the generality of common tracer pollutants, but also characteristics of transport-transformation induced by sediment motion. Future work will be conducted to present the validation/application of the model with available data. [ABSTRACT FROM AUTHOR]

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]

Abstract: This paper is concerned with the numerical approximation of bedload sediment transport due to water evolution. For the hydrodynamical component we consider Shallow Water equations. The morphodynamical component is defined by a continuity equation, which is defined in function of the solid transport discharge. We present several deterministic models, such as Meyer-Peter & Müller, Van Rijn or Grass model. We also present an unified definition for the solid transport discharge, and we compare with Grass model. Both components define a coupled system of equations that can be rewrite as a non-conservative hyperbolic system. To discretize it, we consider finite volume methods with or without flux limiters and high order state reconstructions. Finally we present several tests, where we observe numerically the order of the numerical schemes. Comparisons with analytical solutions and experimental data are also presented. [Copyright &y& Elsevier]

The article discusses efforts underway to restore the ecosystem of the Platte River in Colorado, Wyoming, and Nebraska. The governors of those three states and U.S. Secretary of the Interior Dirk Kempthorne signed an agreement in late 2006 creating the Platte River Recovery Program. The Platte, which drains large portions of the Great Plains, has always been a marginalized river because it moves slowly and doesn't carry much water. It has, however, been instrumental in carrying sediment from its northern headwaters to the Great Plains, which has provided valuable fertile soil for agriculture. The Platte has been so diverted and damned that sections of the river run dry in summer months.

This review provides an assessment of sediment trap accuracy issues by gathering data to address trap hydrodynamics, the problem of zooplankton ‘swimmers,’ and the solubilization of material after collection. For each topic, the problem is identified, its magnitude and causes reviewed using selected examples, and an update on methods to correct for the potential bias or minimize the problem using new technologies is presented. To minimize hydrodynamic biases due to flow over the trap mouth, the use of neutrally buoyant sediment traps is encouraged. The influence of swimmers is best minimized using traps that limit zooplankton access to the sample collection chamber. New data on the impact of different swimmer removal protocols at the US time-series sites HOT and BATS are compared and shown to be important. Recent data on solubilization are compiled and assessed suggesting selective losses from sinking particles to the trap supernatant after collection, which may alter both fluxes and ratios of elements in long term and typically deeper trap deployments. Different methods are needed to assess shallow and short- term trap solubilization effects, but thus far new incubation experiments suggest these impacts to be small for most elements. A discussion of trap calibration methods reviews independent assessments of flux, including elemental budgets, particle abundance and flux modeling, and emphasizes the utility of U-Th radionuclide calibration methods. [ABSTRACT FROM AUTHOR]

The drilling of hydrocarbon exploration wells in the Faroe-Shetland Basin has provided an expanding sample resource that provides material for testing recently developed palynology-based sediment transport analysis. This technique has been verified by comparison with heavy mineral analysis; both approaches have been used to identify sediment sources and input points along the strike of the Palaeocene West Shetland Platform. Integration of heavy mineral and palynological data has provided a basis for understanding arenaceous and argillaceous sediment distribution and sourcing. In addition to a source from the western, Greenland side of the basin, four argillaceous and four arenaceous sedimentary sources have been identified along the strike of the West Shetland Platform. These vary in temporal and spatial distribution, and thus provide a history of sediment source evolution. This analysis supports a persistent difference in source between the Corona Basin and the Flett and Judd Sub-basins. Although source variation and overlap between basins is evident, transfer zones represent both conduits for and barriers to effective sediment transport. Both palynological and heavy mineral evidence identifies the former presence of Late Namurian-Westphalian strata on the West Shetland Platform, which were removed by subsequent erosion. [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]

Burrowing benthic animals ventilate their burrow networks, and this enhances the transport of solutes in the sediment and exchange with the overlying water column, a process referred to as bio-irrigation. Various models have been proposed to model bio-irrigation, with different levels of sophistication related to model dimensionality and parameter numbers. Here we address the issue of model complexity for bio-irrigation in permeable sediments. To this end, we simulated flowline patterns and tracer signals using (1) a full 3D model that explicitly models the J-shaped geometry of the burrow in a suitable microenvironment surrounding the burrow, (2) a simplified 2D axi- symmetric analogue, which neglects the burrow shaft and only models the location of burrow water injection, (3) a highly simplified 1D model obtained by laterally averaging the microenvironment. Simulation of two separate inert tracer experiments shows that the 2D pocket injection model includes essential features (downward advective transport, spatial heterogeneity of pore water velocity, mechanistic specification of the seepage area) that are lost upon averaging to the corresponding ID model. This loss of model detail must be compensated for by the introduction of additional, non-mechanistic fitting parameters in the ID description. Similarly, the extension of the 2D model to a full sophisticated 3D description requires a major increase in computational resources, but only leads to a marginal improvement in the data simulation. Accordingly, we conclude that the 2D description provides an optional balance between model simplicity and predictive capacity. [ABSTRACT FROM AUTHOR]

Abstract: The purpose of the present study is to investigate the presence of fractal behaviors in the sediment transport phenomenon to consider the possibility of using a fractal approach for suspended sediment characterization. Suspended sediment concentration data collected from the Yellow River basin at Tongguan, Shanxi, China are studied. The power spectrum, the empirical probability distribution function, the statistical moment scaling function and the autocorrelation function are used as indicators to investigate the presence of fractal. The results from the fractal identification methods indicate that the sediment data exhibit fractal behavior. [Copyright &y& Elsevier]