Sedimentation and equilibrium in wave-formed bars: a review and case study

1979 ◽  
Vol 16 (2) ◽  
pp. 312-332 ◽  
Author(s):  
Brian Greenwood ◽  
Robin G. D. Davidson-Arnott
Keyword(s):  
Sediment Transport ◽  
Hydrodynamic Instability ◽  
Field Measurements ◽  
Theoretical Models ◽  
Break Point ◽  
Rip Currents ◽  
Group Vi ◽  
Process Factors ◽  
Incident Waves ◽  
Bar Formation

A tentative classification of wave-formed bars is presented based on available evidence of both morphological and process factors. One specific group of bars (group VI), which has been described by numerous studies in the Great Lakes, the Mediterranean, and the Gulf of St. Lawrence, is examined in detail; models of bar formation and equilibrium, which may be relevant to this group, are reviewed and evaluated. These include (1) vortex action under plunging breakers; (2) interaction of incident waves with standing waves generated by reflection; (3) interaction of incident waves with standing edge waves; and (4) hydrodynamic instability of a uniformly long wave setup produced by incident waves.Results of field measurements of one set of crescentic group VI bars in Kouchibouguac Bay, New Brunswick, indicate that none of the theoretical models adequately explains the characteristics of these bars: (a) the stability of the bar form in an area of high longshore sediment transport; (b) sediment transport patterns, which reveal a continuous circulation of sediment through the bar; and (c) the occurrence of spilling rather than plunging breakers. A conceptual model of bar formation and equilibrium is proposed based upon: (a) landward sediment transport by shoaling waves, increasing towards the break point; (b) gradual reduction of transport rates associated with spilling breakers leading to a buildup of the bar; (c) maintenance of the trough through removal of sediments by longshore and rip current circulation; (d) seaward transport of sediment by rip currents; and (e) landward transport of sediments under reformed waves landward of the trough. The application of this model to other group VI bars, particularly straight bars, is discussed.

scholarly journals NEARSHORE SEDIMENT TRANSPORT: ESTIMATES FROM DETAILED MEASUREMENTS OF THE NEARSHORE VELOCITY FIELD

1984 ◽  
Vol 1 (19) ◽  
pp. 115
Author(s):  
A.J. Bowen ◽  
J.C. Doering
Keyword(s):  
Sediment Transport ◽  
Velocity Field ◽  
Conceptual Models ◽  
Relative Importance ◽  
Rip Currents ◽  
Velocity Measurements ◽  
Wave Drift ◽  
Nearshore Sediment Transport ◽  
Incident Waves

A very wide variety of conceptual models has been used to explain the movement of sediment in the nearshore region. While there is general agreement that the incident waves are primarily responsible for the mobilisation of sediment, many processes have been proposed as the transport agents, for example, wave drift velocities, wave assymetry, longshore and rip currents, undertow, the downslope component of gravity. As it is currently difficult to make reliable point measurements of sediment transport, many of these ideas can not be tested directly. However, in many cases, detailed measurements of the velocity field in the water can be used to examine at least the relative importance of these possible processes. The situation is complicated by the lack of accepted formulae for sediment transport. The result is that the velocity measurements are also being used to examine the 'reasonability' of the various formulations.

Sediment transport under dry weather conditions in a small sewer system

1998 ◽  
Vol 37 (1) ◽  
pp. 155-162
Author(s):  
Flemming Schlütter ◽  
Kjeld Schaarup-Jensen
Keyword(s):  
Sediment Transport ◽  
Field Data ◽  
Field Measurements ◽  
Weather Conditions ◽  
Sewer System ◽  
Transport Models ◽  
Sewer Systems ◽  
Combined Sewer ◽  
Initial Results

Increased knowledge of the processes which govern the transport of solids in sewers is necessary in order to develop more reliable and applicable sediment transport models for sewer systems. Proper validation of these are essential. For that purpose thorough field measurements are imperative. This paper renders initial results obtained in an ongoing case study of a Danish combined sewer system in Frejlev, a small town southwest of Aalborg, Denmark. Field data are presented concerning estimation of the sediment transport during dry weather. Finally, considerations on how to approach numerical modelling is made based on numerical simulations using MOUSE TRAP (DHI 1993).

scholarly journals Artificial Intelligence Application on Sediment Transport

2021 ◽  
Vol 9 (6) ◽  
pp. 600
Author(s):  
Hyun Dong Kim ◽  
Shin-ichi Aoki
Keyword(s):  
Sediment Transport ◽  
Numerical Models ◽  
Beach Nourishment ◽  
Hydraulic Model ◽  
Alternative Methods ◽  
Cross Sectional ◽  
Sand And Gravel ◽  
Incident Waves ◽  
Artificial Intelligence Application ◽  
Deep Learning Model

When erosion occurs, sand beaches cannot maintain sufficient sand width, foreshore slopes become steeper due to frequent erosion effects, and beaches are trapped in a vicious cycle of vulnerability due to incident waves. Accordingly, beach nourishment can be used as a countermeasure to simultaneously minimize environmental impacts. However, beach nourishment is not a permanent solution and requires periodic renourishment after several years. To address this problem, minimizing the period of renourishment is an economical alternative. In the present study, using the Tuvaluan coast with its cross-sectional gravel nourishment site, four different test cases were selected for the hydraulic model experiment aimed at discovering an effective nourishment strategy to determine effective alternative methods. Numerical simulations were performed to reproduce gravel nourishment; however, none of these models simultaneously simulated the sediment transport of gravel and sand. Thus, an artificial neural network, a deep learning model, was developed using hydraulic model experiments as training datasets to analyze the possibility of simultaneously accomplishing the sediment transport of sand and gravel and supplement the shortcomings of the numerical models.

scholarly journals Sediment Transport and Water Flow Resistance in Alluvial River Channels: Modified Model of Transport of Non-Uniform Grain-Size Sediments

Water ◽  
2021 ◽  
Vol 13 (15) ◽  
pp. 2038
Author(s):  
Gennady Gladkov ◽  
Michał Habel ◽  
Zygmunt Babiński ◽  
Pakhom Belyakov
Keyword(s):  
Sediment Transport ◽  
Water Flow ◽  
Transport Model ◽  
Flow Characteristics ◽  
Field Measurements ◽  
Field Investigation ◽  
Empirical Modeling ◽  
River Channels ◽  
Channel Deformations ◽  
East European

The paper presents recommendations for using the results obtained in sediment transport simulation and modeling of channel deformations in rivers. This work relates to the issues of empirical modeling of the water flow characteristics in natural riverbeds with a movable bottom (alluvial channels) which are extremely complex. The study shows that in the simulation of sediment transport and calculation of channel deformations in the rivers, it is expedient to use the calculation dependences of Chézy’s coefficient for assessing the roughness of the bottom sediment mixture, or the dependences of the form based on the field investigation data. Three models are most commonly used and based on the original formulas of Meyer-Peter and Müller (1948), Einstein (1950) and van Rijn (1984). This work deals with assessing the hydraulic resistance of the channel and improving the river sediment transport model in a simulation of riverbed transformation on the basis of previous research to verify it based on 296 field measurements on the Central-East European lowland rivers. The performed test calculations show that the modified van Rijn formula gives the best results from all the considered variants.

scholarly journals Rip currents in the non-tidal surf zone with sandbars: numerical analysis versus field measurements

Oceanologia ◽  
2020 ◽  
Vol 62 (3) ◽  
pp. 291-308
Author(s):  
Aleksandra Dudkowska ◽  
Aleksandra Boruń ◽  
Jakub Malicki ◽  
Jan Schönhofer ◽  
Gabriela Gic-Grusza
Keyword(s):  
Numerical Analysis ◽  
Surf Zone ◽  
Field Measurements ◽  
Rip Currents

scholarly journals One-dimensional sediment transport modelling with Engelund–Hansen and Ackers–White transport equations for the Lower Danube River

2021 ◽  
pp. 103-117
Author(s):  
Davor Kvočka
Keyword(s):  
Sediment Transport ◽  
Negative Impact ◽  
Statistical Tests ◽  
Field Measurements ◽  
River Basin Management ◽  
Transport Equations ◽  
Danube River ◽  
Transport Modelling ◽  
1D Modelling ◽  
Sediment Transport Modelling

Sediment transport can have a negative impact on riparian environments, as it can lead to the deterioration of ecological diversity and increase flood risks. Sediment transport modelling is thus a key tool in river basin management and the development of river training structures. In this study, we examined the appropriateness of 1D modelling for total sediment transport loads using the Engelund–Hansen and Ackers–White transport equations for the Lower Danube River. The study evaluated the effect of sediment grading on the accuracy of 1D model results, the appropriateness of 1D sediment transport modelling within technical or engineering projects, and the appropriateness of the Engelund–Hansen and Ackers–White equations for estimating sediment yield in the area of the Lower Danube River. The model results have been compared to field measurements, with the accuracy of the modelling results being evaluated with statistical tests. The obtained results show: (i) the sediment grading does not have a significant impact on the 1D modelling results, (ii) 1D sediment transport modelling gives sufficiently accurate results for practical engineering use (e.g. the estimation of dredging activities), and (iii) the Engelund–Hansen equation is generally better for sediment transport modelling in the Lower Danube River.

scholarly journals GROIN LENGTH AND THE GENERATION OF EDGE WAVES

1976 ◽  
Vol 1 (15) ◽  
pp. 85 ◽  
Author(s):  
Michael K. Gaughan ◽  
Paul D. Komar
Keyword(s):  
Incident Wave ◽  
Wave Length ◽  
Critical Length ◽  
Beach Erosion ◽  
Rip Currents ◽  
Edge Waves ◽  
Normal Waves ◽  
Wave Basin ◽  
Incident Waves ◽  
Selection Of

A series of wave basin experiments were undertaken to better understand the selection of groin spacings and lengths. Rather than obtaining edge waves with the same period as the normal incident waves, subharmonic edge waves were produced with a period twice that of the incoming waves and a wave length equal to the groin spacing. Rip currents were therefore not formed by the interactions of the synchronous edge waves and normal waves as proposed by Bowen and Inman (1969). Rips were present in the wave basin but their origin is uncertain and they were never strong enough to cause beach erosion. The generation of strong subharmonic edge waves conforms with the work of Guza and Davis (1974) and Guza and Inman (1975). The subharmonic edge waves interacted with the incoming waves to give an alternating sequence of surging and collapsing breakers along the beach. Their effects on the swash were sufficient to erode the beach in some places and cause deposition in other places. Thus major rearrangements of the sand were produced between the groins, but significant erosion did not occur as had been anticipated when the study began. By progressively decreasing the length of the submerged portions of the groins, it was found that the strength (amplitude) of the edge waves decreases. A critical submerged groin length was determined whereby the normally incident wave field could not generate resonant subharmonic edge waves of mode zero with a wavelength equal to the groin spacing. The ratio of this critical length to the spacing of the groins was found in the experiments to be approximately 0.15 to 0.20, and did not vary with the steepness of the normal incident waves.

scholarly journals River flow and sediment transport simulation based on a curvilinear and rectilinear grid modelling approach – a comparison study

2017 ◽  
Vol 17 (5) ◽  
pp. 1325-1334 ◽  
Author(s):  
G. G. Morianou ◽  
N. N. Kourgialas ◽  
G. P. Karatzas ◽  
N. P. Nikolaidis
Keyword(s):  
Sediment Transport ◽  
River Flow ◽  
Morphological Changes ◽  
Field Measurements ◽  
Grid Model ◽  
Curvilinear Grid ◽  
Saint Venant Equations ◽  
Flow And Sediment Transport ◽  
Downstream Section ◽  
The Difference

In the present work, a two-dimensional (2D) hydraulic model was used for the simulation of river flow and sediment transport in the downstream section of the Koiliaris River Basin in Crete, Greece, based on two different structured grids. Specifically, an important goal of the present study was the comparison of a curvilinear grid model with a rectilinear grid model. The MIKE 21C model has been developed to simulate 2D flows and morphological changes in rivers by using either an orthogonal curvilinear grid or a rectilinear grid. The MIKE 21C model comprises two parts: (a) the hydrodynamic part that is based on the Saint-Venant equations and (b) the morphological change part for the simulation of bank erosion and sediment transport. The difference between the curvilinear and the rectilinear grid is that the curvilinear grid lines follow the bank lines of the river, providing a better resolution of the flow near the boundaries. The water depth and sediment results obtained from the simulations for the two different grids were compared with field observations and a series of statistical indicators. It was concluded that the curvilinear grid model results were in better agreement with the field measurements.

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