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- I am a retired Research Scientist. I worked for the Government of Canada in the Department of Environment, at the Nat... moreI am a retired Research Scientist. I worked for the Government of Canada in the Department of Environment, at the National Water Research Institute located in Burlington, Ontario. Currently, I am continuing my Research in the capacity as an Emeritus Research Scientist in the field of Environmental Research.edit
Fine-grained cohesive sediment is the primary vector for nutrient and contaminant redistribution through aquatic systems and is a critical indicator of land disturbance. A critical limitation of most existing sediment transport models is... more
Fine-grained cohesive sediment is the primary vector for nutrient and contaminant redistribution through aquatic systems and is a critical indicator of land disturbance. A critical limitation of most existing sediment transport models is that they assume that the transport characteristics of fine sediment can be described using the same approaches that are used for coarse-grained non-cohesive sediment, thereby ignoring the tendency of fine sediment to flocculate. Here, a modelling framework to simulate flow and fine sediment transport in the Crowsnest River, the Castle River, the Oldman River and the Oldman Reservoir after the 2003 Lost Creek wildfire in Alberta, Canada was developed and validated. It is the first to include explicit description of fine sediment deposition/erosion processes as a function of bed shear stress and the flocculation process. This framework integrates four existing numerical models: MOBED, RIVFLOC, RMA2 and RMA4 using river geometry, flow, fine suspended ...
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Sampling programs for suspended sediment were carried out in the Usumacinta River and its tributary Grijalva River in Mexico during the years 2016 and 2017. Suspended sediment samples collected during these sampling programs were analyzed... more
Sampling programs for suspended sediment were carried out in the Usumacinta River and its tributary Grijalva River in Mexico during the years 2016 and 2017. Suspended sediment samples collected during these sampling programs were analyzed in the laboratory using a Rotating Annular Flume (RAF) fitted with a Particle Tracking Velocimetry (PTV) to obtain the 2D images of the suspended sediment particles as they were undergoing floc reconstruction, and subsequently using a glass settling column fitted with inline digital holography set up to obtain 3D holograms of the fully flocculated sediment particles. From these high-resolution hologram images, the fractal dimension of the flocculated sediment particles was obtained using the classical box-counting method and an improved Triangular box-counting method. The estimated fractal dimension of flocculated sediment, which is a measure of floc compactness and structure that control the settling velocity of flocculated sediment was used to validate two empirical models to estimate the fractal dimension in terms of the floc sizes of suspended sediments of these two rivers. It is shown in this study that the floc characteristic can be analyzed in laboratory experiments after floc reconstruction with the use of an RAF and it offers a viable alternative to the costly in-situ sampling that is often carried out in ocean research. The digital holography method employed in this research offers an efficient methodology to obtain the floc fractal dimension. Regarding the innovative aspects and new contribution to science, we can say that we have developed a laboratory protocol to test river waters to establish floc properties such as fractal dimensions of flocs in this research which will help to test river waters on a routine basis with manageable costs. We can also say that we have developed models to predict the relationship between floc fractal dimension and floc size, which did not exist before.
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Dimensional analysis shows that the commonly used dimensionless transverse dispersion coefficient, e sub z uda h, should depend on both the friction factor and the width-to-depth ratio of the flow. Results for e sub z lead to the... more
Dimensional analysis shows that the commonly used dimensionless transverse dispersion coefficient, e sub z uda h, should depend on both the friction factor and the width-to-depth ratio of the flow. Results for e sub z lead to the conclusion that secondary circulation, and not turbulent diffusion, is the dominant transport mechanism. These results help to explain the failure to find consistent trends in the variation of e sub z/uh and suggest that uh is not a good representation for e sub z. Two alternative dimensionless dispersion coefficients, e sub z and e sub z/uda W, are introduced. Both appear to account for secondary circulation effects more properly. The dimensionless parameter e sub z/uda W is a function of the width-to-depth ratio and appears to be affected only slightly by variations in the friction factor. The parameter e sub z/uW shows distinct dependence on both friction factor and width-to-depth ratio. Both of these are better dimenstionless transverse dispersion coefficients to use than e sub z/udah. /ASCE/
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Abstract Fine sediment is a key driver of water quality degradation in rivers globally and improved knowledge of its source and transport is required to interpret the impacts of current land management in the context of sediment budgets... more
Abstract Fine sediment is a key driver of water quality degradation in rivers globally and improved knowledge of its source and transport is required to interpret the impacts of current land management in the context of sediment budgets and hydro-sedimentological responsiveness to model the efficacy of alternative future sediment control plans. However, despite the importance of elucidating cohesive sediment behavior in a comprehensive manner, most existing work continues to interpret management outcomes without due consideration of the conveyance or routing properties of flocculated sediment and to model future scenarios using simplistic process-based tools simulating the mobilization and delivery of discrete primary, rather than flocculated, sediment particles. To address this knowledge gap, the deposition behaviour of cohesive channel bed sediment was studied experimentally in an annular flume to provide parameters for improved modelling of fine sediment in the upper River Taw observatory in southwest England. Deposition experiments were carried out using a sediment-water mixture in an annular flume and in-situ size distributions of sediment flocs were measured to assess flocculation and settling behavior. These data were used to calibrate and test a mathematical model of flocculation and settling (FLUME) and the resulting measured and modelled data were in good agreement. Sediment concentration decreased as a function of time and reached a steady state value for all test conditions. Results of the deposition experiment highlight the critical role of flocculation on the settling properties of fine sediment and indicates that flocs between 20 to 30 µm in diameter will have the greatest propensity to settle while smaller (>0 to 5 µm) and larger (50 to 400 µm) flocs are more likely to be propagated downstream even at conditions of low shear stress. The density and settling velocity of the cohesive sediments were sensitive to biological activity within the floc structure. Data from the flume experiments are necessary as input parameters to model fine sediment in the upper River Taw catchment and assess the efficacy of sediment control options as a component of finalizing future pathways to sustainable agriculture. The findings of the work reported herein identify critical size classes prone to deposition or transport in suspension within the channel system, which in turn, have implications related to the impact of current grass or arable land soil management in the study area. More specifically, the higher carbon content of soil water-stable aggregates under permanent grassland management are likely to promote the development of larger flocs with reduced density and a greater propensity for rapid transport in suspension rather than intermediate storage on the channel bed.
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Traditional CSO storage facilities can be environmentally upgraded by optimising their hydraulics and implementing chemically aided settling. In the case study presented for the North Toronto CSO facility, a number of structural measures... more
Traditional CSO storage facilities can be environmentally upgraded by optimising their hydraulics and implementing chemically aided settling. In the case study presented for the North Toronto CSO facility, a number of structural measures serving to enhance the facility treatment rate and inducing favourable settling conditions in the settling basins were addressed by means of physical and computer modelling. A physical
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Accounts by witnesses of spring ice breakup in rivers often mention violent ice runs with extreme water speeds and rapidly rising water levels. Such events are believed to follow the release of major ice jams. To gain preliminary... more
Accounts by witnesses of spring ice breakup in rivers often mention violent ice runs with extreme water speeds and rapidly rising water levels. Such events are believed to follow the release of major ice jams. To gain preliminary understanding of this problem, an attempt is made to reconstruct a partially documented ice jam release reported recently by others. The equations of the ice–water flow that occurs after the release of an ice jam are formulated. It is shown that the problem may be approximately treated as a one-dimensional, unsteady, water-only flow of total depth identical to that of the ice–water flow, and average velocity. The retarding effect of the frequently encountered intact ice cover below the jam is considered implicitly, that is, by adjusting the friction factor so as to make the predicted and observed downstream stages equal. The effects of jam length are considered next by assuming longer jams of the same maximum water depth. The duration of the surging velocities increases with jam length and so does the peak stage. Less than 2 h after the jam release the surge was arrested and a new jam formed, causing further stage increases. Present capabilities of modelling the reformation process are discussed and the major unknowns identified.
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An intensive field program was conducted just before river-ice breakup at the Hay River, Northwest Territories, Canada in April, 2000, followed by controlled laboratory experiments on Hay River water and sediments in a rotating circular... more
An intensive field program was conducted just before river-ice breakup at the Hay River, Northwest Territories, Canada in April, 2000, followed by controlled laboratory experiments on Hay River water and sediments in a rotating circular flume at Burlington, Ontario, Canada to better understand the nature of cohesive sediment transport in the Hay River. Results from these earlier studies have shown that the deposition of fine sediment is possible in the shallower portion of the river along the river banks, where the bed shear stress is lower than the critical shear stress for deposition of the Hay River sediment during the winter months. The remobilization and the transverse dispersion of the sediment across the width of the river are attributed as possible causes for the formation of sediment plume just prior to breakup when the bed shear stress exceed the critical shear stress for the erosion. This hypothesis will be tested using a new modelling strategy proposed in this paper. INT...
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This study was conducted to improve understanding about the performance of Rolled Erosion Control Products (RECPs) in protecting channel beds against erosion prior to the establishment of permanent vegetative lining. A set of laboratory... more
This study was conducted to improve understanding about the performance of Rolled Erosion Control Products (RECPs) in protecting channel beds against erosion prior to the establishment of permanent vegetative lining. A set of laboratory experiments was designed and completed to study the kinematics of flow and the dynamics of forces of flow on a selected liner and on the channel-bed underneath the liner in controlled flow conditions. It was found that RECPs are in general highly permeable products and small pressure gradients can generate significant fluid flows through the liners. The surface roughness of the channels lined with RECPs is affected not only by the surface roughness of the liner but also the three-dimensional wavy geometry of the liner, its vertical oscillations and permeability. The mean bed shear stress underneath an RECP is likely to increase with increasing depth of flow underneath the liner and with slope of the energy grade line. In general, RECPs are very effec...
Increasing use of subsurface tile drains in agricultural watersheds has created concern for sediment delivery to receiving waters and potential undesirable effects on surface and subsurface water quality. In this study, transport... more
Increasing use of subsurface tile drains in agricultural watersheds has created concern for sediment delivery to receiving waters and potential undesirable effects on surface and subsurface water quality. In this study, transport characteristics of sediment from tile drains in predominantly clayloam soils of a southern Ontario watershed were tested in a rotating circular flume located at the National Water Research Institute, Burlington, Ontario. Tile drain sediments were collected and mixed with river water at different speeds in the flume to study transport processes such as deposition, erosion and flocculation as a function of bed shear stress. Empirical relationships are developed to describe erosion and deposition processes of tile drain sediment. The relationships are in a form suitable for use in the fine sediment transport model developed by Krishnappan (1997) and can be used to predict transport characteristics of tile drain sediment in receiving streams.
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A large volume sample of river-bed cohesive sediment and water from Hay River, Northwest Territories, Canada was collected during a spring field program in 2000 as part of a study on under-ice movement of sediment just before breakup.... more
A large volume sample of river-bed cohesive sediment and water from Hay River, Northwest Territories, Canada was collected during a spring field program in 2000 as part of a study on under-ice movement of sediment just before breakup. Controlled laboratory experiments were subsequently conducted on the Hay River water/sediments in a rotating annular flume at Burlington, Ontario, Canada to better understand the deposition and erosion processes of cohesive sediment transport. The deposition experiments in the rotating flume confirmed that the Hay River sediment is cohesive and the critical shear stress for deposition and the rates of deposition are a function of bed shear stress and the initial concentration of the sediment in suspension. The erosion experiments provided quantitative data on the critical shear stress for erosion and the rates of erosion as a function of bed shear stress and the age of the sediment deposit. The erosion experiments also indicated that the growth of the biofilm had an influence on the erosion characteristics of the Hay River sediment. Based on the data from the rotating circular flume experiments, a modelling strategy is proposed for calculating the under-ice transport of the cohesive sediments in the Hay River.
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The erosion, transport and fate of sediments and associated contaminants are known to be influenced by both particle characteristics and the flow dynamics imparted onto the sediment. The influential role of bitumen containing hydrophobic... more
The erosion, transport and fate of sediments and associated contaminants are known to be influenced by both particle characteristics and the flow dynamics imparted onto the sediment. The influential role of bitumen containing hydrophobic sediments and the microbial community on sediment dynamics are however less understood. This study links an experimental evaluation of sediment erosion with measured sediment-associated contaminant concentrations and microbial community analysis to provide an estimate of the potential for sediment to control the erosion, transport and fate of contaminants. Specifically the paper addresses the unique behaviour of hydrophobic sediments and the role that the microbial community associated with hydrophobic sediment may play in the transport of contaminated sediment. Results demonstrate that the hydrophobic cohesive sediment demonstrates unique transport and particle characteristics (poor settling and small floc size). Biofilms were observed to increase with consolidation/biostabilization times and generated a unique microbial consortium relative to the eroded flocs. Natural oil associated with the flocs appeared to be preferentially associated with microbial derived extracellular polymeric substances. While PAHs and naphthenic acid increased with increasing shear (indicative of increasing loads), they tended to decrease with consolidation/biostabilization (CB) time at similar shears suggesting a chemical and/or biological degradation. PAH and napthenic acid degrading microbes decreased with time as well, which may suggest that there was a reduced pool of PAHs and naphthenic acids available resulting in their die off. This study emphasizes the importance that any management strategies and operational assessments for the protection of human and aquatic health incorporate the sediment (suspended and bed sediment) and biological (biofilm) compartments and the energy dynamics within the system in order to better predict contaminant transport.
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Runoff from agricultural watersheds can carry a number of agricultural pollutants and pathogens; often associated with the sediment fraction. Deposition of this sediment can impact water quality and the ecology of the river, and the... more
Runoff from agricultural watersheds can carry a number of agricultural pollutants and pathogens; often associated with the sediment fraction. Deposition of this sediment can impact water quality and the ecology of the river, and the re-suspension of such sediment can become sources of contamination for reaches downstream. In this paper a modelling framework to predict sediment and associated microbial erosion, transport and deposition is proposed for the South Nation River, Ontario, Canada. The modelling framework is based on empirical relationships (deposition and re-suspension fluxes), derived from laboratory experiments in a rotating circular flume using sediment collected from the river bed. The bed shear stress governing the deposition and re-suspension processes in the stream was predicted using a one dimensional mobile boundary flow model called MOBED. Counts of live bacteria associated with the suspended and bed sediments were used in conjunction with measured suspended sedi...
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Experiments on settling of cohesive sediments were carried out in turbulent flows in an annular flume using kaolinite clay as well as a natural river sediment. Results indicate that the finer fractions were able to deposit because they... more
Experiments on settling of cohesive sediments were carried out in turbulent flows in an annular flume using kaolinite clay as well as a natural river sediment. Results indicate that the finer fractions were able to deposit because they were settling as floes. Data on concentration and size distribution of dispersed samples were used to calculate the effective settling velocities for the different size fractions.
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... However, numerical models demand considerable insight and understanding of their limits of applicability and ... from fluvial beds, and ejection motions are responsible for maintaining sediments in suspension. ... a relatively high... more
... However, numerical models demand considerable insight and understanding of their limits of applicability and ... from fluvial beds, and ejection motions are responsible for maintaining sediments in suspension. ... a relatively high pressure zone on the front side of a wavy liner, and ...
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This report is intended as a reference for practising engineers. A description of the various physical processes involved in the spreading of a substance in river flows as well as the mathematical formulation of these processes is given.... more
This report is intended as a reference for practising engineers. A description of the various physical processes involved in the spreading of a substance in river flows as well as the mathematical formulation of these processes is given. These processes are combined in the mass balance equation to describe the mixing of substances released into rivers. The difficulties of solving three-dimensional mixing problems for real river situations are discussed. The simplification of the equation into two dimensions using depth averaging and the introduction of the stream-tube concept are described. Analytical and numerical solutions are recommended. The conventional Fickian description of one-dimensional mixing is given, followed by the description of a model that takes into account the non-Fickian behaviour often observed. Sample problems of one-dimensional and two-dimensional mixing are solved, using the recommended procedures. The effects of ice cover on mixing are discussed and cases of...
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Hydrobiologia 235/236: 177-187, 1992. BT Hart & PG Sly (eds), Sediment/Water Interactions. © 1992 Kluwer Academic Publishers. Printed in Belgium . ... Cohesive sediment transport: emerging issues for toxic chemical ... ED Ongley, BG... more
Hydrobiologia 235/236: 177-187, 1992. BT Hart & PG Sly (eds), Sediment/Water Interactions. © 1992 Kluwer Academic Publishers. Printed in Belgium . ... Cohesive sediment transport: emerging issues for toxic chemical ... ED Ongley, BG Krishnappan, I . G. ...
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... the authors. ISBN 1 84339 021 3 (set) Page 2. Advection-dispersion in open-channel flows 227 schemes with the Total Variation Diminishing (TVD) methods for eliminating the numerical oscillation and diffusion. The TVD scheme ...
Experiments on settling of kaolin‐distilled water suspensions are carried out in a 5‐m diameter rotating annular flume in which flows were generated by rotating the flume walls in one direction and a top ring in the opposite direction.... more
Experiments on settling of kaolin‐distilled water suspensions are carried out in a 5‐m diameter rotating annular flume in which flows were generated by rotating the flume walls in one direction and a top ring in the opposite direction. Suspensions with initial concentrations varying ...
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The state-of-the-art of sediment source identification is reviewed in this paper. Sediment “fingerprinting” techniques using different “fingerprint” properties were examined. With these techniques, it is possible to identify potential... more
The state-of-the-art of sediment source identification is reviewed in this paper. Sediment “fingerprinting” techniques using different “fingerprint” properties were examined. With these techniques, it is possible to identify potential sources of sediment transported in river systems. Such knowledge is useful for implementing sediment control strategies to limit sediment production from upland areas in a watershed as well as for developing guidelines for land use practices to minimize adverse impacts on surface and ground water resources in agricultural watersheds. Examples of sediment source identification techniques that were carried out in agricultural watersheds in different parts of the world were also included in the present review.
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In this short communication, the erosion process of the fine, cohesive sediment collected from the upper River Taw in South West England was studied in a rotating annular flume located in the National Water Research Institute in... more
In this short communication, the erosion process of the fine, cohesive sediment collected from the upper River Taw in South West England was studied in a rotating annular flume located in the National Water Research Institute in Burlington, Ontario, Canada. This study is part of a research project that is underway to model the transport of fine sediment and the associated nutrients in that river system. The erosion experimental data show that the critical shear stress for erosion of the upper River Taw sediment is about 0.09 Pa and it did not depend on the age of sediment deposit. The eroded sediment was transported in a flocculated form and the agent of flocculation for the upper River Taw sediment may be due to the presence of fibrils from microorganisms and organic material in the system. The experimental data were analysed using a curve fitting approach of Krone and a mathematical model of cohesive sediment transport in rotating circular flumes developed by Krishnappan. The mode...
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A numerical model to predict settling behaviour of fine sediment mixtures in a stagnant water column is described. Both single-grain settling mode and the floc settling mode are considered. The single-grain settling mode is analyzed by... more
A numerical model to predict settling behaviour of fine sediment mixtures in a stagnant water column is described. Both single-grain settling mode and the floc settling mode are considered. The single-grain settling mode is analyzed by solving the unsteady, one-dimensional diffusion–advection equation numerically and the floc settling mode is examined by solving a coagulation equation expressed as a discrete equation in logarithmic radius space considering the differential settling as the only collision mechanism. The model results are compared with the laboratory experimental data of K. Kranck for both modes of sediment settling. The agreement between the model predictions and the experimental data is good. The model can be used as a basis for such practical applications as predicting sedimentation rates in reservoirs and settling basins. Key words: sediment mixtures, settling, flocculation, advection, diffusion, floc size distribution, primary particles.
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Field and laboratory measurements of the transport of the suspended sediment from the Athabasca River near Hinton, Alberta, Canada are described. The objective of these measurements was to examine the influence of pulp mill effluent... more
Field and laboratory measurements of the transport of the suspended sediment from the Athabasca River near Hinton, Alberta, Canada are described. The objective of these measurements was to examine the influence of pulp mill effluent entering the river from a nearby pulp mill on suspended sediment. The results of the field measurement showed that the effluent had significant impact on the transport of the sediment. Specifically, the effluent increased the deposition rates of the sediment and caused a substantial reduction of sediment concentrations in reaches downstream of the effluent outfall. The reduction in sediment concentrations and the concomitant sediment loads can only be attributed to the pulp mill effluent as there were no abrupt changes in the hydraulic characteristics of the river in the reach of interest. These observations were confirmed by laboratory experiments that were carried out using a rotating circular flume located at the National Water Research Institute in Burlington, Ontario, Canada. The findings of this study have implications for modelling suspended sediment transport in rivers receiving bleached pulp mill effluents.
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Erosion characteristics of fine sediment deposits were studied experimentally using a rotating circular flume in the laboratory. The influence of the rate of application of bed shear stress and the structure of sediment beds was... more
Erosion characteristics of fine sediment deposits were studied experimentally using a rotating circular flume in the laboratory. The influence of the rate of application of bed shear stress and the structure of sediment beds was investigated. When the shear stress was applied suddenly on a bed formed by placing a thick slurry of kaolin in the flume, the concentration of the eroded sediment first increased to reach a maximum value, and then it started to decrease and finally attained a steady state value that was significantly lower than the maximum concentration (the steady state concentration value was one third of the maximum concentration value). When the shear stress was applied gradually, the behaviour was similar, but the difference between the values of the maximum concentration and steady state concentration was very small (<10%). When the shear stress was applied gradually on a bed formed by depositing a dilute suspension, the concentration increased monotonically and reached the steady state concentration without exhibiting the hump. Such a behaviour was attributed to the sorting of flocs in the settling of dilute suspension in which stronger flocs deposit first followed by weaker flocs in succession.Key words: kaolin, erosion rate, bed shear stress, bed structure, rotating circular flume, flocculation, size distribution.