scholarly journals IMPLICATIONS OF PLUME DISCHARGE FOR TIDAL CHANNELS MORPHODYNAMICS: A COUPLED ONSHORE AND OFFSHORE SYSTEM

2017 ◽  
pp. 12
Author(s):  
Alfonso Miguel Jiménez-Robles ◽  
Stefano Lanzoni ◽  
Miguel Ortega-Sánchez
Keyword(s):  
Sediment Concentration ◽  
Tidal Channel ◽  
Tidal Channels ◽  
Channel Dynamics ◽  
Sediment Bed ◽  
Load Transport ◽  
Bed Load Transport ◽  
Dynamical Coupling ◽  
Final Channel ◽  
Constant Slope

This contribution investigates the morphodynamic equilibrium of a funnel-shaped, well-mixed tidal channel taking into account the existing dynamical coupling between the tidal channel itself and the related offshore sediment-laden plume. We use a quasi two-dimensional numerical model that resolves the fully nonlinear unsteady shallow water, sediment bed load transport and suspended sediment advection-diffusion equations along with the Exner equation for the bathymetric changes. We close this model by including a dynamic boundary condition at the channel mouth that transfers the offshore plume sediment concentration to the channel dynamics. This model reveals that the offshore plume reduces the timescales to reach equilibrium of the channel and plays a crucial role on shaping it. At equilibrium, the non-plume influence case attains a quasi-linear profile of constant slope in the seaward part. However, the bottom profile in the case that includes the offshore plume tends to increase the concavity of the bottom profile, reducing the final channel mouth depth. Finally, numerical results suggest that the plume characteristics are altered as a consequence of tidal channel evolution.

scholarly journals SEDIMENT TRANSPORT UNDER SHEET FLOW CONDITION

1982 ◽  
Vol 1 (18) ◽  
pp. 82 ◽  
Author(s):  
Kiyoshi Horikawa ◽  
Akira Watanabe ◽  
Sadakazu Katori
Keyword(s):  
Sediment Transport ◽  
Flow Condition ◽  
Average Rate ◽  
Empirical Relationship ◽  
Sediment Concentration ◽  
Transport Rate ◽  
Sheet Flow ◽  
Load Transport ◽  
Bed Load Transport ◽  
Moving Layer

A series of laboratory experiments in an oscillatory tank was carried out to investigate the sheet flow of sediment. Objectives of the study were to determine the criterion for inception of sheet flow, and to evaluate the sediment transport rate under the sheet flow condition. In order to proceed with the investigation, it was necessary to develop devices appropriate for tracing the sediment particle movement, and for measuring the extremely dense sediment concentration in the moving layer of sheet flow. The chief results are: 1) the criteria for the inception of sheet flow given by Manohar C1955) and by Komar and Miller (1974) are both applicable to materials composed of spheroidal particles, and 2) the average rate of sediment transport for sheet flow is well described by an empirical relationship given by Madsen and Grant (1976) for the bed load transport rate on a plane bed in oscillatory flow.

scholarly journals Sediment Bed-Load Transport: A Standardized Notation

Geosciences ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 368
Author(s):  
Ulrich Zanke ◽  
Aron Roland
Keyword(s):  
Shear Stress ◽  
Critical Shear Stress ◽  
Basic Structure ◽  
Structural Formula ◽  
Bed Load ◽  
Viscous Effects ◽  
Data Set ◽  
Sediment Bed ◽  
Load Transport ◽  
Bed Load Transport

Morphodynamic processes on Earth are a result of sediment displacements by the flow of water or the action of wind. An essential part of sediment transport takes place with permanent or intermittent contact with the bed. In the past, numerous approaches for bed-load transport rates have been developed, based on various fundamental ideas. For the user, the question arises which transport function to choose and why just that one. Different transport approaches can be compared based on measured transport rates. However, this method has the disadvantage that any measured data contains inaccuracies that correlate in different ways with the transport functions under comparison. Unequal conditions also exist if the factors of transport functions under test are fitted to parts of the test data set during the development of the function, but others are not. Therefore, a structural formula comparison is made by transferring altogether 13 transport functions into a standardized notation. Although these formulas were developed from different perspectives and with different approaches, it is shown that these approaches lead to essentially the same basic formula for the main variables. These are shear stress and critical shear stress. However, despite the basic structure of these 13 formulas being the same, their coefficients vary significantly. The reason for that variation and the possible effect on the bandwidth of results is identified and discussed. A further result is the finding that not only shear stress affects bed-load transport rates as is expressed by many transport formulas. Transport rates are also significantly affected by the internal friction of the moving sediment as well as by the friction fluid-bed. In the case of not fully rough flow conditions, also viscous effects and thus the Reynolds number becomes of importance.

scholarly journals Impact of the regularity of the sediment bed on bed-load transport

PAMM ◽  
2016 ◽  
Vol 16 (1) ◽  
pp. 583-584
Author(s):  
Ramandeep Jain ◽  
Bernhard Vowinckel ◽  
Jochen Fröhlich
Keyword(s):  
Bed Load ◽  
Sediment Bed ◽  
Load Transport ◽  
Bed Load Transport

scholarly journals The Management of Sediment Transported by Glacial Melt-Water Streams and its Significance for the Estimation of Sediment Yield

1989 ◽  
Vol 13 ◽  
pp. 1-5 ◽  
Author(s):  
A. Bezinge ◽  
M.J. Clark ◽  
A.M. Gurnell ◽  
J. Warburton
Keyword(s):  
Suspended Sediment ◽  
Sediment Concentration ◽  
Sediment Traps ◽  
Bedload Transport ◽  
Sediment Volume ◽  
Melt Water ◽  
Load Transport ◽  
Bed Load Transport ◽  
The Mean ◽  
Annual Patterns

This paper describes the calibration of sediment traps in melt-water intake structures of the Grande Dixence hydro-electricity scheme for the purpose of generating medium-term estimates of suspended sediment and bedload transport by pro-glacial streams. The frequency of emptying/purging of sediment from traps in 17 glacier basins in the Val d’Hérens is combined with their design sediment volume to provide first approximations of the mean annual volume of sediment purged. This is followed by more detailed consideration of 11 years of records from three of the basins, to investigate mean seasonal and inter-annual patterns of purging. The difficulties of relating sediment purging to sediment transport are considered. A sediment calibration strategy based on 2 years of turbidity records, hand sampling of suspended sediment concentration, and monitoring of the accumulation of sediment in sediment traps is proposed for one of the glacier basins, and is checked using hourly and 4 h suspended sediment observations from two further ablation seasons. The calibration is applied to 10 years of discharge and purge records to establish estimates of mean seasonal and inter-annual patterns of suspended sediment and bed-load transport.

scholarly journals Comparison between Calculation and Measurement of Total Sediment Load: Application to Nestos River

2020 ◽  
Vol 2 (1) ◽  
pp. 19
Author(s):  
Loukas Avgeris ◽  
Konstantinos Kaffas ◽  
Vlassios Hrissanthou
Keyword(s):  
Suspended Sediment Concentration ◽  
Sediment Load ◽  
Sediment Concentration ◽  
Stream Discharge ◽  
Nestos River ◽  
Engineering Department ◽  
Load Transport ◽  
Bed Load Transport ◽  
Total Sediment ◽  
Statistical Criteria

Measurements of stream discharge, bed load transport rate and suspended sediment concentration in the Nestos River (northeastern Greece) were conducted by the Section of Hydraulic Engineering, of the Civil Engineering Department, Democritus University of Thrace. In addition to those measurements, the total sediment concentration was calculated by means of the formulas of Yang. The comparison between the calculated and measured total sediment concentration was achieved by means of several statistical criteria and the results were deemed satisfactory.

scholarly journals The Management of Sediment Transported by Glacial Melt-Water Streams and its Significance for the Estimation of Sediment Yield

1989 ◽  
Vol 13 ◽  
pp. 1-5 ◽  
Author(s):  
A. Bezinge ◽  
M.J. Clark ◽  
A.M. Gurnell ◽  
J. Warburton
Keyword(s):  
Suspended Sediment ◽  
Sediment Concentration ◽  
Sediment Traps ◽  
Bedload Transport ◽  
Sediment Volume ◽  
Melt Water ◽  
Load Transport ◽  
Bed Load Transport ◽  
The Mean ◽  
Annual Patterns

This paper describes the calibration of sediment traps in melt-water intake structures of the Grande Dixence hydro-electricity scheme for the purpose of generating medium-term estimates of suspended sediment and bedload transport by pro-glacial streams. The frequency of emptying/purging of sediment from traps in 17 glacier basins in the Val d’Hérens is combined with their design sediment volume to provide first approximations of the mean annual volume of sediment purged. This is followed by more detailed consideration of 11 years of records from three of the basins, to investigate mean seasonal and inter-annual patterns of purging. The difficulties of relating sediment purging to sediment transport are considered. A sediment calibration strategy based on 2 years of turbidity records, hand sampling of suspended sediment concentration, and monitoring of the accumulation of sediment in sediment traps is proposed for one of the glacier basins, and is checked using hourly and 4 h suspended sediment observations from two further ablation seasons. The calibration is applied to 10 years of discharge and purge records to establish estimates of mean seasonal and inter-annual patterns of suspended sediment and bed-load transport.

QUASI-THREE-DIMENSIONAL MATHEMATICAL MODELING OF MORPHOLOGICAL PROCESSES BASED ON EQUILIBRIUM SEDIMENT TRANSPORT

2000 ◽  
Vol 11 (07) ◽  
pp. 1425-1436 ◽  
Author(s):  
MY. M. CHARAFI ◽  
A. SADOK ◽  
A. KAMAL ◽  
A. MENAI
Keyword(s):  
Sediment Transport ◽  
Three Dimensional ◽  
Sediment Concentration ◽  
Suspended Load ◽  
Bed Load ◽  
Change Rate ◽  
Sediment Mass ◽  
Load Transport ◽  
Bed Load Transport ◽  
Morphological Processes

A quasi-three-dimensional mathematical model has been developed to study the morphological processes based on equilibrium sediment transport method. The flow velocities are computed by a two-dimensional horizontal depth-averaged flow model (H2D) in combination with logarithmic velocity profiles. The transport of sediment particles by a flow water has been considered in the form of bed load and suspended load. The bed load transport rate is defined as the transport of particles by rolling and saltating along the bed surface and is given by the Van Rijn relationship (1987). The equilibrium suspended load transport is described in terms of an equilibrium sediment concentration profile (ce) and a logarithmic velocity (u). Based on the equilibrium transport, the bed change rate is given by integration of the sediment mass-balance equation. The model results have been compared with a Van Rijn results (equilibrium approach) and good agreement has been found.

scholarly journals Hysteretic Implications for Graded Bed Load Sediment Transport in Symmetrical Hydrograph Flows

2021 ◽  
Vol 9 ◽  
Author(s):  
Le Wang ◽  
Dayu Wang ◽  
Alan Cuthbertson ◽  
Deyu Zhong ◽  
Gareth Pender
Keyword(s):  
Sediment Transport ◽  
Size Class ◽  
Yield Ratio ◽  
Bed Load ◽  
Size Classes ◽  
Sediment Bed ◽  
Load Transport ◽  
Bed Load Transport ◽  
Load Sediment ◽  
Clockwise Hysteresis

Differential parametric values associated with bed load sediment transport, that result at the same discharge levels on the rising and falling limbs of a flood hydrograph, are usually defined as bed load hysteresis. This hysteresis in bed load sediment transport rates is of considerable interest in the field of fluvial hydraulics. Within this study, a series of well-defined, symmetrical hydrograph flows are generated over a graded, mobile sediment bed to fully examine the hysteresis of the resulting bed load sediment transport in terms of the threshold of motion, and differential bed load transport rates and bed load yields during the hydrographs. The experiments are conducted in a titling flume without sediment supply specified at the upstream inlet, thereby representing typical river reach conditions immediately downstream of a dam that are exclusively subject to net in-channel bed degradation from sediment transport initiated during flood events. Our results show that the fractional bed load transport of defined fine, medium and coarse size classes within the graded sediment bed generally display clockwise, no/mixed and counter-clockwise hysteresis patterns, respectively, with clockwise hysteresis most commonly found for the coarse size class mobilised by hydrographs with long durations. By contrast, counter-clockwise hysteresis is usually observed for fine size class transported by hydrographs with short durations. Accordingly, the corresponding reference stresses for each size class vary between different hydrographs and are primarily controlled by the hydrograph flashiness (i.e. unsteadiness) and magnitude (i.e. total water work). Moreover, it is shown that the hysteresis effect, particularly for those size classes and hydrograph combinations that result in clockwise and counter-clockwise behaviour, should be fully accounted for when reproducing bed load transport rates using separate-limb based method. Finally, we investigate the relative fractions of the overall bed load yields generated during the rising and falling limbs of all symmetrical hydrographs (i.e. the bed load yield ratio), which are found to be primarily dependent on bed load transport hysteresis. Finally, the relationship between the bed load yield ratio and the ratio of reference stresses for the fractional sediment motion of each size class on both limbs is found to follow a power law.

NUMERICAL MODEL TO SIMULATE THE EROSION ON THE SLOPE DUE TO OVERTOPPING

2010 ◽  
Vol 13 (3) ◽  
pp. 78-87
Author(s):  
Hoai Cong Huynh
Keyword(s):  
Numerical Model ◽  
Flow Model ◽  
Bed Load ◽  
Experiment Data ◽  
Step Method ◽  
Morphological Model ◽  
Load Transport ◽  
Bed Load Transport ◽  
The Finite Difference Method ◽  
Good Agreement

The numerical model is developed consisting of a 1D flow model and the morphological model to simulate the erosion due to the water overtopping. The step method is applied to solve the water surface on the slope and the finite difference method of the modified Lax Scheme is applied for bed change equation. The Meyer-Peter and Muller formulae is used to determine the bed load transport rate. The model is calibrated and verified based on the data in experiment. It is found that the computed results and experiment data are good agreement.

Sign in / Sign up

Export Citation Format

Share Document