Non-cohesive Sediment Transport Research Articles

Comparison of simplified physically based dam breach models

Three simplified physically based earthen embankment breach models, NWS BREACH (Revision 1), HR BREACH (Version 4.1) and DLBreach, are used to calculate the breaching of twelve dams, and the results are compared against the measured data and the predictions by three parametric breach models. It is found that NWS BREACH may have large errors for cohesive embankments, since it uses a noncohesive sediment transport model and does not consider headcut erosion as a typical mode of cohesive dam breach. HR BREACH considers headcut and surface erosion modes and adopts various surface erosion equations for noncohesive and cohesive soils. DLBreach adopts a nonequilibrium total-load sediment transport model and headcut erosion model for noncohesive and cohesive embankment breaching, respectively. All the three physically based models can handle overtopping failure of homogeneous and composite dams, as well as piping failure. HR BREACH and DLBreach consider both one- and two-sided widening, whereas only DLBreach allows subbase erosion. The comparison shows that DLBreach has best overall performance. Sensitivity studies show that sensitivity of these three models to soil erodibility is case dependent, but overall, DLBreach and HR BREACH are more sensitive than NWS BREACH. In addition, it is demonstrated that an adequate physically based breach model can perform better and provide more detailed results than a parametric model.

Application of a Neuro-Fuzzy GMDH Model for Predicting the Velocity at Limit of Deposition in Storm Sewers

AbstractThe velocity at limit of deposition, namely, the velocity below which the sediments start to form stationary deposits on the pipe invert, plays a key role in designing an effective storm sewer system. In fact, an accurate evaluation of the aforesaid velocity permits to prevent the formation of sediment deposits in the pipe, and, consequently, a decreasing of the hydraulic capacity of the same pipe. Nowadays, different methods based on artificial intelligence are applied to analyze and solve problems of scientific and practical interest, among which the analysis of sediment transport mechanism in clean storm sewer networks. In this study, neuro-fuzzy based group method of data handling (NF-GMDH), an adaptive learning network, has been utilized to predict the velocity at limit of deposition in partially-filled circular storm sewer networks under noncohesive bed load sediment transport and clean pipe conditions. The NF-GMDH network has been developed using the particle swarm optimization (PSO). Four ...

Impacts of wave and tidal forcing on 3D nearshore processes on natural beaches. Part II: Sediment transport

This is the second of two papers on the 3D numerical modeling of nearshore hydro- and morphodynamics. In Part I, the focus was on surf and swash zone hydrodynamics in the cross-shore and longshore directions. Here, we consider nearshore processes with an emphasis on the effects of oceanic forcing and beach characteristics on sediment transport in the cross- and longshore directions, as well as on foreshore bathymetry changes. The Delft3D and XBeach models were used with four turbulence closures (viz., k-e, k-L, ATM and H-LES) to solve the 3D Navier-Stokes equations for incompressible flow as well as the beach morphology. The sediment transport module simulates both bed load and suspended load transport of non-cohesive sediments. Twenty sets of numerical experiments combining nine control parameters under a range of bed characteristics and incident wave and tidal conditions were simulated. For each case, the general morphological response in shore-normal and shore-parallel directions was presented. Numerical results showed that the k-e and H-LES closure models yield similar results that are in better agreement with existing morphodynamic observations than the results of the other turbulence models. The simulations showed that wave forcing drives a sediment circulation pattern that results in bar and berm formation. However, together with wave forcing, tides modulate the predicted nearshore sediment dynamics. The combination of tides and wave action has a notable effect on longshore suspended sediment transport fluxes, relative to wave action alone. The model’s ability to predict sediment transport under propagation of obliquely incident wave conditions underscores its potential for understanding the evolution of beach morphology at field scale. For example, the results of the model confirmed that the wave characteristics have a considerable effect on the cumulative erosion/deposition, cross-shore distribution of longshore sediment transport and transport rate across and along the beach face. In addition, for the same type of oceanic forcing, the beach morphology exhibits different erosive characteristics depending on grain size (e.g., foreshore profile evolution is erosive or accretive on fine or coarse sand beaches, respectively). Decreasing wave height increases the proportion of onshore to offshore fluxes, almost reaching a neutral net balance.

Impacts of wave and tidal forcing on 3D nearshore processes on natural beaches. Part I: Flow and turbulence fields

The major objective of this study was to develop further understanding of 3D nearshore hydrodynamics under a variety of wave and tidal forcing conditions. The main tool used was a comprehensive 3D numerical model – combining the flow module of Delft3D with the WAVE solver of XBeach – of nearshore hydro- and morphodynamics that can simulate flow, sediment transport, and morphological evolution. Surf-swash zone hydrodynamics were modeled using the 3D Navier-Stokes equations, combined with various turbulence models (k-e, k-L, ATM and H-LES). Sediment transport and resulting foreshore profile changes were approximated using different sediment transport relations that consider both bed- and suspended-load transport of non-cohesive sediments. The numerical set-up was tested against field data, with good agreement found. Different numerical experiments under a range of bed characteristics and incident wave and tidal conditions were run to test the model’s capability to reproduce 3D flow, wave propagation, sediment transport and morphodynamics in the nearshore at the field scale. The results were interpreted according to existing understanding of surf and swash zone processes. Our numerical experiments confirm that the angle between the crest line of the approaching wave and the shoreline defines the direction and strength of the longshore current, while the longshore current velocity varies across the nearshore zone. The model simulates the undertow, hydraulic cell and rip-current patterns generated by radiation stresses and longshore variability in wave heights. Numerical results show that a non-uniform seabed is crucial for generation of rip currents in the nearshore (when bed slope is uniform, rips are not generated). Increasing the wave height increases the peaks of eddy viscosity and TKE (turbulent kinetic energy), while increasing the tidal amplitude reduces these peaks. Wave and tide interaction has most striking effects on the foreshore profile with the formation of the intertidal bar. High values of eddy viscosity, TKE and wave set-up are spread offshore for coarser grain sizes. Beach profile steepness modifies the nearshore circulation pattern, significantly enhancing the vertical component of the flow. The local recirculation within the longshore current in the inshore region causes a transient offshore shift and strengthening of the longshore current. Overall, the analysis shows that, with reasonable hypotheses, it is possible to simulate the nearshore hydrodynamics subjected to oceanic forcing, consistent with existing understanding of this area. Part II of this work presents 3D nearshore morphodynamics induced by the tides and waves.

Head Loss Modelling with Advanced Hydroinformatic Tool in Sprinkler Irrigation Facilities, Study Case: Sprinkler Irrigation Facilities on 400 ha in Iohanesfeld, Romania

In in the last 10-15 years, droughts in Banat Plain have imposed finding new sources of water for irrigation application on drained land. This paper presents irrigation facilities on 400 hectares on a private area using modern sprinkler irrigation installations, with Bega River being the water source. The installations use modern mobile watering devices: centred pivots and hose - drum irrigation, longitudinally propelled. The water intake for the irrigation application is taken from Bega River and transported over a distance of 12.9km through the existing network of drainage channels, accumulated in a storage pool from which it is pumped in the underground through a network of pipes and distributed to the crops by mobile sprinkler irrigation equipment. Thereby this sprinkler irrigation facility is using the existing drainage network to transport water from the source to landscaped area. The numeric modelling was performed using MIKE11 by DHI software, HD module. The Hydrodynamic (HD) module is the nucleus of the MIKE 11 modelling system and forms the basis for most of the modules including Flood Forecasting, Advection-Dispersion, Water Quality and Non-cohesive sediment transport modules [1].

Nearshore waves and longshore sediment transport along Rameshwaram Island off the east coast of India

ABSTRACT Wave-induced Longshore Sediment Transport (LST) play an important role in the dynamics of the Dhanushkodi sandspit located southeast of Rameshwaram. The LST along the Dhanushkodi coast is studied based on data collected simultaneously in Gulf of Mannar (GoM) and Palk Bay (PB) using directional waverider buoys. The numerical model REF/DIF1 was used to calculate the nearshore waves and the LST rate was estimated using three different formulae. The model validation was done based on the measured nearshore waves using InterOcean 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 (~0.01 × 106 m3) compared to the GoM region (0.3 × 106 m3) were due to the weak waves. Accretion in the region led to growth of the Dhanushkodi sandspit by 65 m during the period 2010-2015.

Conceptual Site Model for Newark Bay—Hydrodynamics and Sediment Transport

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.

An overview on the use of backscattered sound for measuring suspended particle size and concentration profiles in non-cohesive inorganic sediment transport studies

For over two decades, coastal marine scientists studying boundary layer sediment transport processes have been using, and developing, the application of sound for high temporal–spatial resolution measurements of suspended particle size and concentration profiles. To extract the suspended sediment parameters from the acoustic data requires an understanding of the interaction of sound with a suspension of sediments and an inversion methodology. This understanding is distributed around journals in a number of scientific fields and there is no single article that succinctly draws together the different components. In the present work the aim is to provide an overview on the acoustic approach to measuring suspended sediment parameters and assess its application in the study of non-cohesive inorganic suspended sediment transport processes.

A one-dimensional model of mixed cohesive and non-cohesive sediment transport in open channels

A one-dimensional model has been developed to simulate mixed cohesive and non-cohesive sediment transport in open channels. Flocculation is considered by determining the floc settling velocity as function of sediment size, concentration, and bed shear stress. The critical shear stress of cohesive sediment erosion is related to the dry bed density that varies with time due to consolidation, and the critical shear stress of non-cohesive sediments is corrected when the cohesive fraction exceeds a certain limit such as 10%. Cohesive and non-cohesive sediment transport, bed change and bed-material sorting equations are solved in a coupled form. The model is tested using two field cases of mixed sediment transport in the Lower Fox River in USA and the Three Gorges Reservoir in China. The calculated results agree generally well with measured data.

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

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.

Depth-Averaged Two-Dimensional Model of Unsteady Flow and Sediment Transport due to Noncohesive Embankment Break/Breaching

AbstractA depth-averaged two-dimensional model has been developed in this study to simulate the unsteady flow and noncohesive sediment transport due to embankment break and overtopping breaching. The model adopts the generalized shallow-water equations that consider the effects of sediment transport and bed change on the flow, thus leading to coupled calculations of these processes. It computes the non-equilibrium total-load sediment transport and considers the noncohesive embankment slope avalanching. The model solves the governing equations using an explicit finite-volume method on a rectangular grid, with the Harten, Lax and van Leer (HLL) approximate Riemann solver to handle the mixed-regime flows generated by embankment break/breaching and the monotonic upstream scheme for conservation laws (MUSCL) piecewise reconstruction method to reach second-order accuracy in space. It uses a varying time step length that satisfies both the Courant-Friedrichs-Lewy condition and the limitation that the bed change ...

Morphodynamic modeling using the Telemac finite-element system

The open-source finite-element system Telemac has been applied to simulate various complex hydrodynamic and morphodynamic situations including waterways, curved channels, recirculating flows and wave-induced littoral transport. In the applications presented here, the sediment transport model is mainly restricted to the transport of non-cohesive sediments, which relies on classical semi-empirical concepts including sand grading effects, parameterization of secondary currents and wave effects. In comparison with other comprehensive modeling systems (Delft-3D, Mike-21, etc.), the main originality lies in the efficiency and flexibility of the finite elements. Thanks to the optimization of numerical schemes, parallelism, as well as tremendous progress in the performance of computers, bed evolution can be calculated on basin scale (10–100km) and for the medium term (years to decades), without the use of hydrodynamic filtering methods. As a novelty in release 6.0, we present a method of feedback for the bed roughness, which reduces uncertainty in the prediction of both transport rates and flow velocities.

A numerical model of nearshore waves, currents, and sediment transport

A two-dimensional numerical model of nearshore waves, currents, and sediment transport was developed. The multi-directional random wave transformation model formulated by Mase [Mase, H., 2001. Multi-directional random wave transformation model based on energy balance equation. Coastal Engineering Journal 43(4), 317-337.] based on an energy balance equation was employed with an improved description of the energy dissipation due to breaking. In order to describe surface roller effects on the momentum transport, an energy balance equation for the roller was included following Dally and Brown [Dally, W.R., Brown, C.A., 1995. A modeling investigation of the breaking wave roller with application to cross-shore currents. Journal of Geophysical Research 100(C12), 24873-24883.]. Nearshore currents and mean water elevation were modeled using the continuity equation together with the depth-averaged momentum equations. Sediment transport rates in the offshore and surf zone were computed using the sediment transport formulation proposed by Camenen and Larson [Camenen, B., Larson, M., 2005. A general formula for non-cohesive bed load sediment transport. Estuarine, Coastal and Shelf Science 63, 249-260.; Camenen, B., Larson, M., 2007. A unified sediment transport formulation for coastal inlet application. Technical report ERDC/CHL CR-07-1, US Army Engineer Research and Development Center, Vicksburg, MS.; Camenen, B., Larson, M., 2008. A general formula for non-cohesive suspended sediment transport. Journal of Coastal Research 24(3), 615-627.] together with the advection–diffusion equation, whereas the swash zone transport rate was obtained from the formulas derived by Larson and Wamsley [Larson, M., Wamsley, T.V., 2007. A formula for longshore sediment transport in the swash. Proceedings Coastal Sediments '07, ASCE, New Orleans, pp. 1924–1937.]. Three high-quality data sets from the LSTF experimental facility at the Coastal and Hydraulics Laboratory in Vicksburg, USA, were used to evaluate the predictive capability of the model. Good agreement between computations and measurements was obtained with regard to the cross-shore variation in waves, currents, mean water elevation, and sediment transport in the nearshore and swash zone. The present model will form the basis for predicting morphological evolution in the nearshore due to waves and currents with special focus on coastal structures.

Review of Sedimentation Engineering—Processes, Measurements, Modeling, and Practice (ASCE Manuals and Reports on Engineering Practice No. 110) by Marcelo H. GarciaSedimentation Engineering—Processes, Measurements, Modeling, and Practice (ASCE Manuals and Reports on Engineering Practice No. 110)ASCE9780784408148$138.75

Sedimentation engineering is a very important subject that deals with sedimentation processes such as erosion, entrainment, transport, deposition, and compaction of sediment induced by water, wind, gravity, and ice and affected by human activities. The original ASCE Manual 54 Sedimentation Engineering, edited by Vito A. Vanoni 1975 and the ASCE Task Committee for the Preparation of a Manual on Sedimentation assembled state-ofthe-art information and knowledge on sedimentation engineering available at that time. Since then, the scientific and engineering understanding and knowledge of sedimentation processes have been greatly advanced and expanded. The recently published Manual 110, edited by Marcelo H. Garcia and his task team, updates selected topics in the original manual and presents recent advances and new topics in the field of sedimentation science and engineering as a complement to the original Manual 54. This update is timely and makes significant contributions to the literature. This comprehensive volume consists of 23 chapters and 6 appendices. Among them, Chapters 2–4 broadly cover fundamentals of sediment transport mechanics, and a section of Chapter 19 briefly presents the mechanics of hyperconcentrated sediment flows. The original Manual 54 gives a good understanding of sedimentation processes and well defines the scope of sediment transport mechanics, whereas the new volume presents in considerable detail many recently developed theories and methods for non-cohesive sediment transport in sand-bedded streams Chapter 2 and gravel-bedded streams Chapter 3 , as well as for cohesive sediment transport Chapter 4 . Chapter 2 also introduces turbidity currents, while Chapter 3 also presents the transport of multiple-sized nonuniform sediment mixtures, which has been extensively studied in the last three decades. Chapter 4 explains the effects of waves on cohesive sediment transport, but such effects on noncohesive sediment transport are omitted in this manual. Chapter 5 reviews technologies for measuring bed-material properties and suspended and bed-load discharges, while Appendix D describes methods for estimating sediment discharges in streams using direct measurement data and empirical relations developed between hydraulic parameters and sediment transport potential. Several new types of samplers are introduced, as well as some traditional ones developed in the mid-twentieth century but modified recently. The measurement of bed load

Two-dimensional, two-phase granular sediment transport model with applications to scouring downstream of an apron

We present a two-dimensional, two-phase model for non-cohesive sediment transport. This model solves concentration-weighted averaged equations of motion for both fluid and sediment phases. The model accounts for the interphase momentum transfer by considering drag forces. A collisional theory is used to compute the sediment stresses, while a two-equation ( k– ε) fluid turbulence closure is implemented. A benchmark sediment transport problem concerning the scouring downstream of an apron is carried out as an example and numerical results agree with existing experimental data.

GSTARS computer models and their applications, part I: theoretical development

GSTARS is a series of computer models developed by the U.S. Bureau of Reclamation for alluvial river and reservoir sedimentation studies while the authors were employed by that agency. The first version of GSTARS was released in 1986 using Fortran IV for mainframe computers. GSTARS 2.0 was released in 1998 for personal computer application with most of the code in the original GSTARS revised, improved, and expanded using Fortran IV/77. GSTARS 2.1 is an improved and revised GSTARS 2.0 with graphical user interface. The unique features of all GSTARS models are the conjunctive use of the stream tube concept and of the minimum stream power theory. The application of minimum stream power theory allows the determination of optimum channel geometry with variable channel width and cross-sectional shape. The use of the stream tube concept enables the simulation of river hydraulics using one-dimensional numerical solutions to obtain a semi-two- dimensional presentation of the hydraulic conditions along and across an alluvial channel. According to the stream tube concept, no water or sediment particles can cross the walls of stream tubes, which is valid for many natural rivers. At and near sharp bends, however, sediment particles may cross the boundaries of stream tubes. GSTARS3, based on FORTRAN 90/95, addresses this phenomenon and further expands the capabilities of GSTARS 2.1 for cohesive and non-cohesive sediment transport in rivers and reservoirs. This paper presents the concepts, methods, and techniques used to develop the GSTARS series of computer models, especially GSTARS3.

Suspended sediment transport in the offshore near Yangtze Estuary

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.

Sedtrans05: An improved sediment-transport model for continental shelves and coastal waters with a new algorithm for cohesive sediments

The one-dimensional (vertical) sediment-transport model SEDTRANS96 has been upgraded to predict more accurately both cohesive and non-cohesive sediment transport. Sedtrans05 computes the bed shear stress for a given set of flow and seabed conditions using combined wave-current bottom boundary layer theory. Sediment transport (bedload and total load) is evaluated using one of five methods. The main modifications to the original version of the model are: (1) a reorganization of the code so that the computation routines can be easily accessed from different user interfaces, or may be called from other programs; (2) the addition of the Van Rijn method to the options for non-cohesive sediment transport; (3) the computation of density and viscosity of water from temperature and salinity inputs; and (4) the addition of a new cohesive sediment algorithm. This latter algorithm introduces variations of sediment properties with depth, represents the suspended sediment as a spectrum of settling velocities (i.e. size classes), includes the flocculation process, and models multiple erosion–deposition cycles. The new model matches slightly better the field measurements of non-cohesive sediment transport, than does the predictions by SEDTRANS96. The sand-transport calibration has been extended to high transport rates. The cohesive sediment algorithm reproduced well experimental data from annular flume experiments.

Advances in the Study of Moving Sediments and Evolving Seabeds

Sands and mud are continually being transported around the world’s coastal seas due to the action of tides, wind and waves. The transport of these sediments modifies the boundary between the land and the sea, changing and reshaping its form. Sometimes the nearshore bathymetry evolves slowly over long time periods, at other times more rapidly due to natural episodic events or the introduction of manmade structures at the shoreline. For over half a century we have been trying to understand the physics of sediment transport processes and formulate predictive models. Although significant progress has been made, our capability to forecast the future behaviour of the coastal zone from basic principles is still relatively poor. However, innovative acoustic techniques for studying the fundamentals of sediment movement experimentally are now providing new insights, and it is expected that such observations, coupled with developing theoretical works, will allow us to take further steps towards the goal of predicting the evolution of coastlines and coastal bathymetry. This paper presents an overview of our existing predictive capabilities, primarily in the field of non-cohesive sediment transport, and highlights how new acoustic techniques are enabling our modelling efforts to achieve greater sophistication and accuracy. The paper is aimed at coastal scientists and managers seeking to understand how detailed physical studies can contribute to the improvement of coastal area models and, hence, inform coastal zone management strategies.

Sediment Dynamics in the Meghna Estuary, Bangladesh: A Model Study

A depth integrated two-dimensional numerical modeling was carried out to study the sediment dynamics within the Meghna estuary. The sediment–water dynamics within this estuary are very complex due to its irregular shape, wide seasonal variation, and the changing role of the tide. Both cohesive and noncohesive sediment transport formulations were used to estimate the total transport. An interactive morphological computation was also used to verify the bed level changes over 2years. Sediment transports of both monsoon and dry seasons (the two most hydrologically pronounced periods in this region) were modeled, and a large seasonal variation in sediment transport pattern was observed. Land reclamation dams were tested by the model and found to be effective in enhancing the accretion in its vicinity.