The Experts below are selected from a list of 318 Experts worldwide ranked by ideXlab platform
Scott Katz - One of the best experts on this subject based on the ideXlab platform.
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A bed Load Transport equation based on the spatial distribution of shear stress – Oak Creek revisited
Earth Surface Dynamics, 2020Co-Authors: Angel Monsalve, Catalina Segura, Nicole Hucke, Scott KatzAbstract:Abstract. Bed Load Transport formulations for gravel-bed rivers are often based on reach-averaged shear stress values. However, the complexity of the flow field in these systems results in wide distributions of shear stress, whose effects on bed Load Transport are not well captured by the frequently used equations, leading to inaccurate estimates of sediment Transport. Here, we modified a subsurface-based bed Load Transport equation to include the complete distributions of shear stress generated by a given flow within a reach. The equation was calibrated and verified using bed Load data measured at Oak Creek, OR. The spatially variable flow field characterization was obtained using a two-dimensional flow model calibrated over a wide range of flows between 0.1 and 1.0 of bankfull discharge. The shape of the distributions of shear stress was remarkably similar across different discharge levels, which allowed it to be parameterized in terms of discharge using a gamma function. When discharge is high enough to mobilize the pavement layer (1.0 m3 s−1 in Oak Creek), the proposed Transport equation had a similar performance to the original formulation based on reach-averaged shear stress values. In addition, the proposed equation predicts bed Load Transport rates for lower flows when the pavement layer is still present because it accounts for bed Load Transport occurring in a small fraction of the channel bed that experiences high values of shear stress. This is an improvement over the original equation, which fails to estimate this bed Load flux by relying solely on reach-average shear stress values.
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A bed Load Transport equation based on the spatial distribution of shear stress – Oak Creek revisit
2020Co-Authors: Angel Monsalve, Catalina Segura, Nicole Hucke, Scott KatzAbstract:Abstract. Bed Load Transport formulations for gravel bed-rivers are often based on reach-averaged shear stress values. However, the complexity of the flow field in these systems results in wide distributions of shear stress, whose effects on bed Load Transport are not well captured by the frequently used bed Load Transport equations, leading to inaccurate estimates of sediment Transport. Here, we modified a subsurface-based bed Load Transport equation to include the complete distributions of shear stress generated by a given flow within a reach. The equation was calibrated and verified using bed Load data measured at Oak Creek, OR. The spatially variable flow field characterization was obtained using a two-dimensional flow model calibrated over a wide range of flows between 0.1 and 1.0 of bankfull discharge. The shape of the distributions of shear stress was remarkably similar across different discharge levels which allowed it to be parameterized in terms of discharge using a Gamma function. When discharge is high enough to mobilize the pavement layer (1.0 m3/s in Oak Creek), the proposed Transport equation had a similar performance to the original formulation based on reach-averaged shear stress values. In addition, the proposed equation predicts bed Load Transport rates for lower flows when the pavement layer is still present because it accounts for bed Load Transport occurring in a small fraction of the channel bed that experience high values of shear stress. This is an improvement over the original equation, which fails to estimate this bed Load flux by relying solely on reach-average shear stress values.
Angel Monsalve - One of the best experts on this subject based on the ideXlab platform.
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A bed Load Transport equation based on the spatial distribution of shear stress – Oak Creek revisited
Earth Surface Dynamics, 2020Co-Authors: Angel Monsalve, Catalina Segura, Nicole Hucke, Scott KatzAbstract:Abstract. Bed Load Transport formulations for gravel-bed rivers are often based on reach-averaged shear stress values. However, the complexity of the flow field in these systems results in wide distributions of shear stress, whose effects on bed Load Transport are not well captured by the frequently used equations, leading to inaccurate estimates of sediment Transport. Here, we modified a subsurface-based bed Load Transport equation to include the complete distributions of shear stress generated by a given flow within a reach. The equation was calibrated and verified using bed Load data measured at Oak Creek, OR. The spatially variable flow field characterization was obtained using a two-dimensional flow model calibrated over a wide range of flows between 0.1 and 1.0 of bankfull discharge. The shape of the distributions of shear stress was remarkably similar across different discharge levels, which allowed it to be parameterized in terms of discharge using a gamma function. When discharge is high enough to mobilize the pavement layer (1.0 m3 s−1 in Oak Creek), the proposed Transport equation had a similar performance to the original formulation based on reach-averaged shear stress values. In addition, the proposed equation predicts bed Load Transport rates for lower flows when the pavement layer is still present because it accounts for bed Load Transport occurring in a small fraction of the channel bed that experiences high values of shear stress. This is an improvement over the original equation, which fails to estimate this bed Load flux by relying solely on reach-average shear stress values.
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A bed Load Transport equation based on the spatial distribution of shear stress – Oak Creek revisit
2020Co-Authors: Angel Monsalve, Catalina Segura, Nicole Hucke, Scott KatzAbstract:Abstract. Bed Load Transport formulations for gravel bed-rivers are often based on reach-averaged shear stress values. However, the complexity of the flow field in these systems results in wide distributions of shear stress, whose effects on bed Load Transport are not well captured by the frequently used bed Load Transport equations, leading to inaccurate estimates of sediment Transport. Here, we modified a subsurface-based bed Load Transport equation to include the complete distributions of shear stress generated by a given flow within a reach. The equation was calibrated and verified using bed Load data measured at Oak Creek, OR. The spatially variable flow field characterization was obtained using a two-dimensional flow model calibrated over a wide range of flows between 0.1 and 1.0 of bankfull discharge. The shape of the distributions of shear stress was remarkably similar across different discharge levels which allowed it to be parameterized in terms of discharge using a Gamma function. When discharge is high enough to mobilize the pavement layer (1.0 m3/s in Oak Creek), the proposed Transport equation had a similar performance to the original formulation based on reach-averaged shear stress values. In addition, the proposed equation predicts bed Load Transport rates for lower flows when the pavement layer is still present because it accounts for bed Load Transport occurring in a small fraction of the channel bed that experience high values of shear stress. This is an improvement over the original equation, which fails to estimate this bed Load flux by relying solely on reach-average shear stress values.
Lauren Schmied - One of the best experts on this subject based on the ideXlab platform.
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Cross‐shore suspended sand and bed Load Transport on beaches
Journal of Geophysical Research, 2008Co-Authors: Nobuhisa Kobayashi, Andres Payo, Lauren SchmiedAbstract:Simple formulas are developed to predict the time-averaged rates of cross-shore suspended sand and bed Load Transport. The net suspended sand Transport rate is expressed as the product of the depth-averaged current and the suspended sediment volume per unit bottom area with a reduction factor that accounts for the correlation between the time-varying fluid velocity and sediment concentration. The net bed Load Transport rate under nonlinear waves is assumed to be onshore and proportional to ?U3 where ?U is the standard deviation of the horizontal velocity. The probabilities of sediment movement and suspension are introduced to account for the initiation of sediment movement and suspension. Simple functions are proposed to account for the effects of a steep bottom slope on the bed Load and suspended sediment Transport rates. The proposed formulas are found to be in agreement with three data sets within a factor of about 2. The proposed formulas are shown to be consistent with existing simple formulas. The formulas are incorporated into a time-averaged wave model and the continuity equation of bottom sediment to predict the beach profile evolution. The numerical model is compared with seven small-scale tests including berm erosion tests and seven large-scale tests including dune erosion tests. The numerical model predicts the overall beach profile evolution including the berm and dune erosion but does not always predict the fairly subtle profile changes including bar migration accurately.
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cross shore suspended sand and bed Load Transport on beaches
Journal of Geophysical Research, 2008Co-Authors: Nobuhisa Kobayashi, Andres Payo, Lauren SchmiedAbstract:Simple formulas are developed to predict the time-averaged rates of cross-shore suspended sand and bed Load Transport. The net suspended sand Transport rate is expressed as the product of the depth-averaged current and the suspended sediment volume per unit bottom area with a reduction factor that accounts for the correlation between the time-varying fluid velocity and sediment concentration. The net bed Load Transport rate under nonlinear waves is assumed to be onshore and proportional to ?U3 where ?U is the standard deviation of the horizontal velocity. The probabilities of sediment movement and suspension are introduced to account for the initiation of sediment movement and suspension. Simple functions are proposed to account for the effects of a steep bottom slope on the bed Load and suspended sediment Transport rates. The proposed formulas are found to be in agreement with three data sets within a factor of about 2. The proposed formulas are shown to be consistent with existing simple formulas. The formulas are incorporated into a time-averaged wave model and the continuity equation of bottom sediment to predict the beach profile evolution. The numerical model is compared with seven small-scale tests including berm erosion tests and seven large-scale tests including dune erosion tests. The numerical model predicts the overall beach profile evolution including the berm and dune erosion but does not always predict the fairly subtle profile changes including bar migration accurately.
Alain Recking - One of the best experts on this subject based on the ideXlab platform.
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Simple Method for Calculating Reach-Averaged Bed-Load Transport
Journal of Hydraulic Engineering, 2013Co-Authors: Alain ReckingAbstract:AbstractA simple and robust method is proposed for calculating reach-averaged bed-Load Transport in sand- and gravel-bed rivers with no calibration. The data required are the bed surface D50 and D84 measured with the nontruncated pebble-count technique, the slope, the width, and the flow depth or discharge. The method is illustrated by comparison with bed-Load samples measured in 15 river reaches.
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a comparison between flume and field bed Load Transport data and consequences for surface based bed Load Transport prediction
Water Resources Research, 2010Co-Authors: Alain ReckingAbstract:[1] The ability of simple equations to predict bed Load Transport with limited knowledge of the bed surface material was investigated. This was done using a data set consisting of 7,636 bed Load Transport values from the flume (1,317 data) and from 84 river reaches (6,319 field data). It was possible to collapse field and flume data by correcting the ratio between the Shields number and its critical value with a very simple hiding function proposed as a power law of the D84/D50 ratio. In so doing, a surface-based bed Load Transport formula was proposed. It was successfully tested on an independent data set (comprising sand and gravel bed rivers with slope in the range 0.0002–0.08), with 86% of the values predicted within a precision of 1 order of magnitude. Moreover, the formula reproduced the low Transport rates well, contrary to the usual surface-based formulas also tested, and is particularly well suited for estimating low Transport rates associated with near-bankfull flow discharge. This new formula is neither time consuming (no fractionwise calculation) nor data consuming (the required parameters are the flow discharge, the active width, the slope, and the surface grain diameters D50 and D84).
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Bed-Load Transport Flume Experiments on Steep Slopes
Journal of Hydraulic Engineering, 2008Co-Authors: Alain Recking, Philippe Frey, Andre Paquier, Philippe Belleudy, Jean-yves ChampagneAbstract:Experiments were conducted over uniform gravel bed materials to obtain 143 friction factor values under bed-Load equilibrium flow conditions in an attempt to add to the scarce data available on slopes between 1 and 9% for Shields numbers between 0.08 and 0.29. Analyses showed that when only flows over flat beds are considered, a distinction must be made between flows with and without bed Load. More particularly, fitting flow resistance equations indicated that the roughness parameter increases by a factor of 2.5 from clear water flow to intense bed-Load Transport. Between these two states, the flow resistance can be approximated by a constant for a given slope.
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Bed-Load Transport Flume Experiments on Steep Slopes
Journal of Hydraulic Engineering, 2008Co-Authors: Alain Recking, Philippe Frey, Andre Paquier, Philippe Belleudy, Jean-yves ChampagneAbstract:International audienceExperiments were conducted over uniform gravel bed materials to obtain 143 friction factor values under bed-Load equilibrium flow conditions in an attempt to add to the scarce data available on slopes between 1 and 9% for Shields numbers between 0.08 and 0.29. Analyses showed that when only flows over flat beds are considered, a distinction must be made between flows with and without bed Load. More particularly, fitting flow resistance equations indicated that the roughness parameter increases by a factor of 2.5 from clear water flow to intense bed-Load Transport. Between these two states, the flow resistance can be approximated by a constant for a given slope
Catalina Segura - One of the best experts on this subject based on the ideXlab platform.
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A bed Load Transport equation based on the spatial distribution of shear stress – Oak Creek revisited
Earth Surface Dynamics, 2020Co-Authors: Angel Monsalve, Catalina Segura, Nicole Hucke, Scott KatzAbstract:Abstract. Bed Load Transport formulations for gravel-bed rivers are often based on reach-averaged shear stress values. However, the complexity of the flow field in these systems results in wide distributions of shear stress, whose effects on bed Load Transport are not well captured by the frequently used equations, leading to inaccurate estimates of sediment Transport. Here, we modified a subsurface-based bed Load Transport equation to include the complete distributions of shear stress generated by a given flow within a reach. The equation was calibrated and verified using bed Load data measured at Oak Creek, OR. The spatially variable flow field characterization was obtained using a two-dimensional flow model calibrated over a wide range of flows between 0.1 and 1.0 of bankfull discharge. The shape of the distributions of shear stress was remarkably similar across different discharge levels, which allowed it to be parameterized in terms of discharge using a gamma function. When discharge is high enough to mobilize the pavement layer (1.0 m3 s−1 in Oak Creek), the proposed Transport equation had a similar performance to the original formulation based on reach-averaged shear stress values. In addition, the proposed equation predicts bed Load Transport rates for lower flows when the pavement layer is still present because it accounts for bed Load Transport occurring in a small fraction of the channel bed that experiences high values of shear stress. This is an improvement over the original equation, which fails to estimate this bed Load flux by relying solely on reach-average shear stress values.
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A bed Load Transport equation based on the spatial distribution of shear stress – Oak Creek revisit
2020Co-Authors: Angel Monsalve, Catalina Segura, Nicole Hucke, Scott KatzAbstract:Abstract. Bed Load Transport formulations for gravel bed-rivers are often based on reach-averaged shear stress values. However, the complexity of the flow field in these systems results in wide distributions of shear stress, whose effects on bed Load Transport are not well captured by the frequently used bed Load Transport equations, leading to inaccurate estimates of sediment Transport. Here, we modified a subsurface-based bed Load Transport equation to include the complete distributions of shear stress generated by a given flow within a reach. The equation was calibrated and verified using bed Load data measured at Oak Creek, OR. The spatially variable flow field characterization was obtained using a two-dimensional flow model calibrated over a wide range of flows between 0.1 and 1.0 of bankfull discharge. The shape of the distributions of shear stress was remarkably similar across different discharge levels which allowed it to be parameterized in terms of discharge using a Gamma function. When discharge is high enough to mobilize the pavement layer (1.0 m3/s in Oak Creek), the proposed Transport equation had a similar performance to the original formulation based on reach-averaged shear stress values. In addition, the proposed equation predicts bed Load Transport rates for lower flows when the pavement layer is still present because it accounts for bed Load Transport occurring in a small fraction of the channel bed that experience high values of shear stress. This is an improvement over the original equation, which fails to estimate this bed Load flux by relying solely on reach-average shear stress values.