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Erosion of sediment deposition in storm sewers is dominated by the bed shear stress and the deposition characteristics. A laboratory study investigated the critical shear stress and erosion processes for different types of deposition in storm sewers. The critical shear stress increased from 0.19 to 0.41 N/m2 for the 0.4-mm sand when the weight content of silt-clay changed from 0% to 20%, whereas the critical shear stress increased from 0.98 to 1.98 N/m2 for the 1.8-mm sand deposition. A prediction method for the critical shear stress was developed based on the particle size and silt-clay content. The erosion patterns can be classified as ripple surface, dune surface, flat surface, and rugged surface, mainly determined by the cohesive effect, particle size, and bed shear stress. The erosion rate is a function of the sediment transport rate per unit width and particle transport distance. A field sampling program was conducted to obtain sediment deposition characteristics in a storm trunk sewer. Based on the sediment characteristics and estimated flow rate, the predicted deposition profile using the method developed in this study compared well with the field measurements. [ABSTRACT FROM AUTHOR]

Sediment depositions in storm sewer systems have received significant attention due to their implications for urban flooding and environmental impacts. However, only limited attention has been paid to sediment deposition in submerged storm sewers. In this study, a laboratory model was used to study the sediment transport and deposition processes in a submerged storm sewer. The growth of the deposition can be divided into two stages: rapid growth (both deposition height and length increase) and equilibrium growth (only deposition length increases). The sediment loading rate determines the duration of the rapid growth stage, and the equilibrium height increases for larger sediment size and higher sediment concentration. The bed shear stress at the equilibrium stage varies from 1.8 to 8.7 N/m2 corresponding to the variation of the bed friction factor from 0.058 to 0.185, which is about 2–4 times that caused by the sediment roughness height alone. This increase in the bed shear stress is mainly due to the significant amount of momentum needed to transport the required sediment loading. A prediction method and its applications are also presented. [ABSTRACT FROM AUTHOR]

This paper reviews the application of computational fluid dynamics (CFD) to numerically model the two-phase flow of water and sediment in the complex environment of a stormwater retention pond. The review is intended to draw the attention of the hydraulic engineering community, specifically those involved in pond design, to the recent advancements in computational modeling of sediment transport in ponds. It provides an up-to-date survey of current simulation capability, focusing on the potential of fully three-dimensional methods for solving sediment transport in complex pond flows. An additional goal of this paper is to alert new researchers engaged in stormwater retention pond design to the research opportunities presented by CFD. Even though pond configurations have become more complex to improve their performance, many studies have continued to rely solely on single-phase models. At the present time, unsteady three-dimensional two-phase models are becoming available to study these problems. Of the multiphase models that might be considered, the particle tracking (Eulerian-Lagrangian) method and two-fluid (Eulerian-Eulerian) method both are potentially applicable to modeling sediment transport in pond-type flows. To date, only the particle-tracking method has been applied to stormwater retention ponds. The two-fluid method is capable of simulating sediment transport in retention ponds. It would be advantageous for a simulation of large-scale ponds in which the number of particles required for particle-tracking becomes excessive. Currently, fully three-dimensional CFD methods are being successfully used to model a variety of multiphase flows in mechanical and chemical engineering, as well as some specific applications in hydraulic engineering. Its application to predict sediment transport in a retention pond shows significant promise, especially when the effect of turbulence becomes challenging to model. [ABSTRACT FROM AUTHOR]

The study of sediment transport in water natural bodies is a challenging task. There have been several attempts to describe sediment mathematically using hydraulic characteristics of water bodies. Most researchers who developed empirical formulas to describe sediment transport performed laboratory experiments with assumptions that did not take into account variations of hydraulic parameters and the fine sediment sizes that are part of this phenomenon. Recently, new approaches for studying sediment transport have been developed involving the use of machine-learning algorithms that have proven accuracy and efficiency in predicting sediment transport. A novel machine-learning method, the Multivariate Relevance Vector Machine (MVRVM), has yet to be tested to model sediment transport and water quality in estuaries and lakes. The selection of the MVRVM is suggested by the limited field observations that present challenges for alternative statistical learning machines, and by the promise of using the MVRVM approach to inform future data-collection efforts. This paper tests the success of calibrating the MVRVM model to predict suspended fine-sediment transport and other environmental measures in Mud Lake, southeastern Idaho, United States. In addition, the authors introduce and explain the technique that can be used to arrange the data which will allow the model to work. Training and validation results for turbidity, total suspended solids (TSS), pH, dissolved oxygen (DO), and water temperature are presented. These results emphasize that modeling the water-quality constituents and sediment transport with few observations is possible using the MVRVM. [ABSTRACT FROM AUTHOR]

Time-variable (periodic) flow over a lake bed, and the associated boundary layer development, have the potential to control or at least influence rates of mass transfer across the sediment/water interface. An analysis for instantaneous and time averaged flux of a material across the sediment/water interface for infinite supply in the water and infinite sink in the sediment is presented. The water flow above the interface is characterized by the shear velocity ([U.sub.*]) which is a periodic function of time with a maximum amplitude of ([U.sub.*o]) as may be typical of an internal seiche (internal standing wave) motion in a density stratified lake. The relationship between the shear velocity on the lake bed and the wind shear on the lake surface is illustrated for an extremely simplified two-layered lake of constant depth. For a less restrictive analysis, shear velocities on a lake bed have to be obtained either from field measurements or from a three-dimensional lake circulation model driven by atmospheric forcing including wind. Smaller and wind-sheltered lakes will have lower ([U.sub.*0]) and periodicities (T). The response of the diffusive boundary layer was related to the period of the periodic motion (T), Schmidt number (Sc), and shear velocity ([U.sub.*]). The vertical diffusive flux at the sediment/water interface was expressed by a Sherwood number (Sh), either instantaneous or time averaged. The mean Sherwood number ([Sh.sub.ave]) varies with shear velocity of the wave motion over the sediment bed, Schmidt number (Sc) and the period (T) due to the response of the diffusive boundary layer to the time variable water velocity. Effective diffusive boundary layers develop only at low shear velocities. Where they do, maximum and minimum boundary layer thickness depends on all three independent variables (T, Sc, and [U.sub.*0]). The diffusive boundary layer strongly affects sediment/water mass transfer, i.e., Sherwood numbers. Mass transfer averaged over a period can be substantially less than that produced by steady-state flow at the same [U.sub.*0] and Sc. At Sc=500, typical for dissolved oxygen, the mass transfer ratio can be reduced to 60% of steady state, depending on the internal wave period (T). CE Database subject headings: Diffusion; Mass transfer; Boundary layer; Dissolved oxygen; Sediment; Oxygen demand; Turbulence.

It has been a challenge to couple a stream channel system with adjacent wetlands and to simulate their interactions and the dynamic processes associated with water flow, sediment movement, and contaminant transport. In this study, a physically based model was developed for simulating metal and sediment transport in a coupled stream-wetland system that consisted of the water column, the underlying active bed, and the adjacent wetland subsystems. The model simulated the dynamic interactions and mass exchanges (water, sediment, and metal) between subsystems and accounted for a set of processes related to the two-phase (dissolved and adsorbed phases) metal and sediment transport, including advection, dispersion/diffusion, sorption, settling, resuspension, and sedimentation. The integrated metal-sediment transport model was solved by using a semidiscrete method. Model simulations of cadmium fate and transport were tested against field data from Little Black Creek (LBC) in western Michigan, which was heavily impacted by historic discharges of cadmium originated from metal plating operations. The preliminary modeling results emphasized the important roles of the cadmium-contaminated sediments in cadmium transport in the stream-wetland system (e.g., accumulation in streambed sediments and release through resuspension) and the potential of heavy metal accumulation in Mona Lake, which received discharge from LBC and the adjacent wetlands. [ABSTRACT FROM AUTHOR]

Sediment oxygen demand (SOD) can be a significant oxygen sink in various types of water bodies, particularly slow-moving waters with substantial organic sediment accumulation. In most settings in which SOD is a concern, the prevailing hydraulic conditions are such that the impact of sediment resuspension on SOD is not considered. However, in the case of Bubbly Creek in Chicago, the prevailing slack water conditions are interrupted by infrequent intervals of very high flow rates associated with pumped combined sewer overflow (CSO) during intense hydrologic events. These events can cause resuspension of the highly organic, nutrient-rich bottom sediments, resulting in precipitous drawdown of dissolved oxygen (DO) in the water column. To address this issue, a new in situ experimental apparatus designed to achieve high flow velocities was implemented to characterize SOD, both with and without sediment resuspension. In the case of resuspension, the suspended sediment concentration was analyzed as a function of bed shear stress, and a formulation was developed to characterize resuspended-sediment oxygen demand (SODR) as a function of suspended sediment concentration in a form similar to first-order biochemical oxygen demand (BOD) kinetics with the DO term in the form of Monod kinetics. The results obtained can be implemented into a model containing hydrodynamic, sediment transport, and water-quality components to yield oxygen demand varying in both space and time for specific flow events. The results are used to evaluate water quality improvement alternatives that take into account the impact of SOD under various flow conditions. [ABSTRACT FROM AUTHOR]

A numerical model for Type I circular sedimentation tanks (center feed) has been developed to provide useful information for circular tank operation. The unsteady flow process in circular sedimentation tanks is divided by numerous time intervals in which flow and sediment transport are considered to be steady. The other feature for this model is that particle size distribution of raw water is nonuniform. A numerical experiment based on the proposed model is carried out, and the results were compared with results from other models. The comparison shows that this model can provide more information, such as variations of water elevation, overall removal efficiency, bottom sludge thickness, and particle size distribution at outlet. In addition, this model had the advantage of optimizing the tank dimensions based on the sludge raking frequency and preferred removal efficiency. After simplification of the model, this model is practical in determining the overall removal efficiency and dimension of the tank based on different inflow situations for tank design. [ABSTRACT FROM AUTHOR]

Sediment fingerprinting has been developed by researchers over the past three decades for watershed sediment transport research. Sediment fingerprinting is a method to allocate sediment nonpoint source pollutants in a watershed through the use of natural tracer technology with a combination of field data collection, laboratory analyses of sediments, and statistical modeling techniques. The method offers a valuable tool for total maximum daily load assessment to aid in developing efficient remediation strategies for pollution in watersheds. We review the methodological steps of sediment fingerprinting including classification of sediment sources in a watershed, identification of unique tracers for each sediment source, representation of sediment sources and sinks using field sampling, accounting for sediment and tracer fate during transport from source to sink, and utilization of an unmixing model to allocate sediment sources. This review places additional emphasis upon tracers used to discriminate sediment sources during past studies performed on different continents and across different physiogeographic regions. Review and analysis of tracer dependence upon watershed variables provides an additional resource for tracer selection to the community. Finally, future improvements needed for sediment fingerprinting are discussed in order to practically apply the technology for sediment nonpoint source pollution allocation within the context of total maximum daily load assessments. [ABSTRACT FROM AUTHOR]

The performance of four sedimentation basins (SBs) at a Pennsylvania Department of Transportation I-99 highway construction site was evaluated based on their particle removal ability. Suspended solids data from the basins indicated poor particle removal, peaks in suspended solid concentration that correlated with rainfall peaks and possibility of sediment resuspension. The current Pennsylvania Department of Environmental Protection basis for basin design is the allocation of 28 m3(1,000 ft3) of sediment storage zone and 140 m3(5,000 ft3) of drainage zone per disturbed acre of the drainage basin. Overflow rate, which is a scientific basis for particle removal, is currently not considered in the design of basins. This paper presents a methodology for developing an integrated design for SBs, applying rainfall probability plots to determine an appropriate basin settling volume. The revised universal soil loss equation is used to identify sediment zone volume, and an overflow rate is determined to design basin surface area. The method presented is a comprehensive procedure for designing SBs with flexibility to choose the extent of particle removal and runoff capture, and to vary construction costs. [ABSTRACT FROM AUTHOR]

The interactions between acid mine drainage (AMD) and three tropical clayey soils have been studied through hydraulic conductivity and batch sorption/dissolution testing. After 19–24 pore volumes of AMD flow through the soils, the measured final hydraulic conductivity ranged between 1.1×10-11 and 3.3×10-11 m/s. The pH, electrical conductivity, and solute breakthrough curves obtained suggested the soils had low acid-buffering capacities. Also, several chemical species were released from the soils due to AMD attack of soil grains and mineral. The batch tests revealed high dissolution of species such as sodium, cobalt, and sulfate from the soils by AMD. The results also indicated dissolution of metals from soil constituents, desorption of chemical species, and transformation and dissolution of soil minerals due to AMD attack. The results of the study showed that, in general, the soils were not effective in attenuating contaminants present in the AMD. Thus, they may not be used alone to construct liners for acid-generating waste mine containment facilities. [ABSTRACT FROM AUTHOR]

The river inflow in a natural lake with important suspended sediment load during floods, can impact water quality by mobilizing dissolved matters like phosphorous from deep to surface waters. Generally due to thermal stratification in prealpine lakes, the water column is stable. It does not mix vertically unless acted on by outside forces, for example, currents or winds. Since Lake Lugano has a strong thermal stratification, river inflow exhibits different modes of density currents, from surface flows and thermocline intrusion to bottom currents. Turbidity currents are the direct cause of the downward water flow, and at the same time at the origin of upward directed flow. In this study, the impact of river born turbidity currents in Lake Lugano under varying ambient conditions was investigated using field measurements at the inflow river and inside the lake, together with a full three-dimensional numerical model of the entire lake. The paper characterizes the induced circulation of the turbidity plume and gives some indications on the relevance of turbidity currents on the lake. [ABSTRACT FROM AUTHOR]

Lake Okeechobee is a large and shallow freshwater body in south Florida. Due to the shallowness of Lake Okeechobee, the nutrient dynamics are strongly influenced by hydrodynamic processes (circulation and wind-induced waves) and sediment transport processes. To study water quality and the effects of hydrodynamic and sediment transport processes on nutrient dynamics in the lake, a three-dimensional simulation system that closely couples hydrodynamic and sediment transport processes with nutrient dynamics was developed and used. In this paper, we present a three-dimensional, coupled hydrodynamics-sediment-nutrient model for Lake Okeechobee. The coupled model was used to simulate a four-week survey conducted in spring 1989 in Lake Okeechobee. By comparing model results to measured field data, it is shown that the coupled model system is able to simulate weekly sediment and phosphorus dynamics in Lake Okeechobee. Model applications demonstrated that the resuspension flux of phosphorus from the lake bottom is significantly higher than the molecular flux during resuspension events and can cause increases of phosphorus concentrations in the water column. Sensitivity runs of the model show that both the advective/diffusive transport and the algal uptake promote the release of phosphorus from suspended sediments and thus affect the phosphorus budget in the lake and the net resuspension flux of phosphorus from the lake bottom. [ABSTRACT FROM AUTHOR]

A marina was constructed in the Great Barrier Reef World Heritage Area in close proximity to coral reefs that could be damaged by excess turbidity generated during construction. Since there was uncertainty about both the fate of suspended sediments and their effect on corals, initial water quality constraints were set very conservatively. In order to better understand the movement of suspended sediment during construction, a numerical model study was commissioned using three-dimensional, numerical, hydrodynamic, and Lagrangian particle tracking models. The study was successful in: (1) increasing the understanding of and reducing the uncertainty of sediment dispersal patterns under a range of common forcing conditions; (2) testing the variation in suspended sediment concentrations over sensitive areas for two different outfall locations; (3) offering evidence that a good choice in outfall locations will reduce the threat to corals; and importantly (4) presenting the results in a way that enhanced understanding by nontechnical reef managers. This final result was achieved by creating movies of sediment movement that clearly demonstrated the complex hydrodynamic processes involved with near-coastal water currents. Specific model results showed: (1) that a more seaward outfall increases effluent dispersal away from sensitive areas; (2) the highest concentrations of effluent over sensitive sites occur during no wind and neap tide conditions; and (3) prevailing southeast winds advect effluent offshore, away from sensitive sites. [ABSTRACT FROM AUTHOR]

While very fine sediments (colloids) are normally assumed to be readily transported downstream without deposition, recent evidence suggests that these particles will often deposit into streambeds due to a combination of physical and chemical mechanisms. This study investigates a regime of particle deposition where settling is unimportant and thus where particle deposition can only result from advective stream–subsurface exchange followed by deep-bed filtration. Laboratory flume experiments were conducted to examine the deposition of 0.45 μm diameter silica colloids into a silica sand bed. This system was selected for study because submicron sized colloids will not settle and silica colloid filtration by silica sand is generally quite low. Despite the lack of settling and the weak particle–particle interactions, the ongoing interfacial flux of colloids to the subsurface still produced significant filtration of silica colloids over the course of the experiments. Variation of the background ionic strength caused significant modification of filtration behavior and silica colloid deposition. In addition, cleaning the sand surface with mild acid and base washes reduced both filtration and net colloid exchange. These experimental results are interpreted in terms of a fundamentally based physicochemical model which predicts net particle deposition based on stream and subsurface hydrodynamic conditions and subsurface filtration. These results show that both particle surface chemical conditions and background water chemistry play a critical role in controlling the net transport and deposition of fine sediments. It is important to recognize the effects of physicochemical processes both when designing laboratory experiments and when analyzing environmental particle transport. [ABSTRACT FROM AUTHOR]

In this case study, a harmonized optimal postreclamation coastline is determined from a set of proposed options for Deep Bay in South China, where large-scale reclamation work is under consideration. Within the framework of the integrated approach presented in the companion paper, hydrodynamic, sediment transport, and water quality models are calibrated, validated, and then used to predict reclamation impacts on tidal flow, sediment deposition and erosion, and water quality under different scenarios. The ecological impact due to reclamation is qualitatively interpreted in terms of changes in deposition and erosion rate, in addition to professional judgement. The analytical hierarchy process method is applied to determine weights for the various primary issues and control factors, and thus an integrated mark calculated for each option. A sensitivity analysis indicates that the priority order of three proposed options does not change for certain fluctuations in the values of assigned weights and grades. Hence, the choice of postreclamation coastline for Deep Bay may be regarded as reliable. [ABSTRACT FROM AUTHOR]

Presents a study which proposed a method to predict analytically the concentration profile and transport of fine suspended sediment from a sediment-covered bed to an open-work gravel bed. Mathematical formulation of problem; Results; Conclusions.

Presents information on a study of the wash-off algorithm in the Storm Management Model used to stimulate the wash-off of sediment and pollutants from impervious areas. Exponential wash-off model; Analytical determination of the two parameters; Discussion; Summary and conclusions.

Focuses on a study which presented the transport-morphology link and the implication of this linkage in filter modeling, prediction of sediment characteristics, and membrane fouling. Mechanisms of particle deposition; Results from simple models of particle deposition on flat surface; Evidence for transport-morphology link in porous media; Morphology of deposits formed under influence of tangential flow.

Provides information on a study which examined the use of differential-turbulence column (DTC) as a tool for evaluating the transport of non-cohesive particles in a stratified estuary. Discussion on DTC; Characterization of turbulence decay below an operating grid; Results of the study; Conclusions.

Evaluates a series of box models to determine the extent to which streamflow separation was capable of reproducing the observed variability in metal transport for the Aberjona River near Boston, Massachusetts. Inclusion in the model of subunits for sub-basins draining directly toward the Aberjona River; Sub-basin draining a major tributary; Ground-water withdrawal.

A non–point source pollution management model, ANSWERS-2000, was developed to simulate long-term average annual runoff and sediment yield from agricultural watersheds. The model is based on the event-based ANSWERS model and is intended for use without calibration. The physically based Green-Ampt infiltration equation was incorporated into ANSWERS-2000 to improve estimates of infiltration. An evapotranspiration submodel was added to permit long-term, continuous simulation. The model was validated without calibration using data from the field-sized P2 and P4 watersheds in Watkinsville, Ga. Additional validation with limited calibration was done on the Owl Run watershed in Virginia. Model predictions of cumulative sediment yield were within 12% and 68% of observed values. Predicted cumulative runoff volumes ranged from 3% to 35% of observed values. Predictions of sediment yield and runoff volume for individual storms were less accurate, but generally within 200% of observed values. In a practical application, the use of the model in agricultural non–point-source pollution control planning was demonstrated. [ABSTRACT FROM AUTHOR]

The in-place pollutant export model (IPX) is a screening-level model for estimating contaminant export from tributaries with contaminated sediments to receiving waterbodies. IPX is a modified version of the USEPA's WASP4 modeling framework. IPX synthesizes sediment transport processes for sediment aging, decreased sediment resuspendability with increasing age, and resuspension of freshly deposited sediments as a function of water velocity, into an expanded WASP4 contaminant transport and fate chassis while retaining the computational flexibility of the original framework. These process descriptions are needed to accurately simulate contaminant transport and substantially improve the framework for application to tributary systems subject to significant deposition and resuspension events. The potential for applying IPX is broad; water quality impairments attributable to contaminated sediments are widespread due to discharges from industry, agriculture, and mining and ore processing. IPX has been successfully applied to the upper and lower Fox River in Wisconsin, and the Buffalo and Oswego Rivers in New York, all impaired by contaminated sediments. [ABSTRACT FROM AUTHOR]

The development of monitoring programs for water quality and habitat assessment in surface waters is an ongoing challenge because of inherent difficulties in determining the effective spatial and temporal distribution of sites and trips. Recent advances in statistical learning theory, in which system characteristics are learned from data, point to the possibility of using the information content of data to shed light on monitoring results that provide sensitive and independent results. One of those techniques, multivariate relevance vector machines (MVRVM), creates as part of its algorithm subsets of a data set, called relevant vectors (RVs), that are most relevant for building an empirical model of a process, thereby revealing the information-rich portions of the data and potentially providing unambiguous information for management decision making. In this paper, we explore this concept in the context of a shallow lake, Mud Lake in SE Idaho, used as a sediment trap and as a wildlife refuge that is suffering from excessive sediment deposition and lack of data for water quality constituents that might affect the habitat for resident species. Data collected extensively in the lake over a 2-year period were used to train the MVRVM model and revealed that more than 40% of the observations contained little or no model-relevant or, by extension, management-relevant information. It is further demonstrated how RVs can help decision makers understand the practical problems of how much data are sufficient to support this class of model in order to tailor monitoring programs to efficiently maximize information. [ABSTRACT FROM AUTHOR]

Discusses the article by Dennis D. Truax, Adnan Shindala and Hunter Sartain in the September 1995 issue of `Journal of Environmental Engineering' about rates of sediment oxygen demand. In-situ measurements made by the US Environmental Protection Agency; Impact of overlying water velocity fluctuations.