scholarly journals Morphodynamic Evolution of a Nourished Beach with Artificial Sandbars: Field Observations and Numerical Modeling

2021 ◽  
Vol 9 (3) ◽  
pp. 245
Author(s):  
Cuiping Kuang ◽  
Xuejian Han ◽  
Jiabo Zhang ◽  
Qingping Zou ◽  
Boling Dong
Keyword(s):  
Sediment Transport ◽  
Tidal Current ◽  
Model Simulation ◽  
Morphological Changes ◽  
Current Model ◽  
Beach Nourishment ◽  
Tidal Range ◽  
Coastal Protection ◽  
Field Observations ◽  
One Year

Beach nourishment, a common practice to replenish an eroded beach face with filling sand, has become increasingly popular as an environmentally friendly soft engineering measure to tackle coastal erosion. In this study, three 200 m long offshore submerged sandbars were placed about 200 m from the shore in August 2017 for both coastal protection and beach nourishment at Shanhai Pass, Bohai Sea, northeastern China. A series of 21 beach profiles were collected from August 2017 to July 2018 to monitor the morphological changes of the nourished beach. Field observations of wave and tide levels were conducted for one year and tidal current for 25 h, respectively. To investigate the spatial-temporal responses of hydrodynamics, sediment transport, and morphology to the presence of three artificial submerged sandbars, a two-dimensional depth-averaged (2DH) multi-fraction sediment transport and morphological model were coupled with wave and current model and implemented over a spatially varying nested grid. The model results compare well with the field observations of hydrodynamics and morphological changes. The tidal range was around 1.0 m and the waves predominately came from the south-south-east (SSE) direction in the study area. The observed and predicted beach profiles indicate that the sandbars moved onshore and the morphology experienced drastic changes immediately after the introduction of sandbars and reached an equilibrium state in about one year. The morphological change was mainly driven by waves. Under the influences of the prevailing waves and the longshore drift toward the northeast, the coastline on the leeside of the sandbars advanced seaward by 35 m maximally while the rest adjacent coastline retreated severely by 44 m maximally within August 2017–July 2018. The model results demonstrate that the three sandbars have little effect on the tidal current but attenuate the incoming wave significantly. As a result, the medium-coarse sand of sandbars is transported onshore and the background silt is mainly transported offshore and partly in the longshore direction toward the northeast. The 2- and 5-year model simulation results further indicate that shoreline salient may form behind the sandbars and protrude offshore enough to reach the sandbars, similar to the tombolo behind the breakwater.

scholarly journals DEVELOPMENT OF A THREE DIMENSIONAL NUMERICAL MODEL OF SEDIMENT TRANSPORT AND MORPHOLOGICAL EVOLUTION ON SANDY BEACH

2020 ◽  
pp. 41
Author(s):  
Qinghe Zhang ◽  
Chao Ji ◽  
Jinfeng Zhang ◽  
Yuefeng Wu
Keyword(s):  
Sediment Transport ◽  
Numerical Model ◽  
Hydrodynamic Model ◽  
Information Exchange ◽  
Sandy Beach ◽  
Morphological Evolution ◽  
Current Model ◽  
Three Dimensional ◽  
Circulation Model ◽  
Coastal Protection

In recent years, sandy coasts are suffering from erosion. It is of great importance to evaluate the state of coasts and assure the achievement of coastal protection measures. Therefore, a three-dimensional numerical model of sandy beach response was developed based on unstructured grids and with capability of describing nearshore hydrodynamics and sediment transports. A three-dimensional hydrodynamic model was first developed based on a coupled wave-current model system that included the Simulating Waves Nearshore (SWAN) wave model and the Finite Volume Community Ocean Model (FVCOM) circulation model. Information exchange between the two models used Model-Coupling Toolkit (MCT) software following Chen et al. (2018). The new three-dimensional radiation stress including the bottom slope effects was employed (Ji et al. 2017). Based on the hydrodynamic model, a numerical model of sediment transport and morphological evolution on sandy beach was developed.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/BVVn1kfViH0

scholarly journals APPLICABILITY OF SUSPENDED SEDIMENT CONCENTRATION FORMULAE TO LARGE-SCALE BEACH MORPHOLOGICAL CHANGES

2012 ◽  
Vol 1 (33) ◽  
pp. 57 ◽  
Author(s):  
Ravindra Jayaratne ◽  
Yasufumi Takayama ◽  
Tomoya Shibayama
Keyword(s):  
Sediment Transport ◽  
Large Scale ◽  
Surf Zone ◽  
Morphological Changes ◽  
Current Model ◽  
Sediment Concentration ◽  
Sandy Beaches ◽  
Propagation Model ◽  
Deformation Model ◽  
Seabed Sediment

Study of beach morphological changes under storm conditions and its prediction capability are of paramount importance in coastal zone management. Seabed sediment is picked up violently in and outside the surf zone due to suspension mechanisms, therefore a considerable amount of sand is transported in coastal waters due to such mechanisms. For the construction of an accurate beach morphological model, it is necessary to elucidate the sediment suspension and to introduce it properly into the modelling of sediment transport. Jayaratne and Shibayama (2007) developed a complete set of explicit theoretical formulae to predict the time-averaged concentration on sandy beaches due to three suspension mechanisms: a) vortical motion over wave-generated sand ripples, b) from sheet flow, and c) turbulent motion under breaking waves. The present paper focuses on the development of a quasi-3D beach deformation model using the sediment concentration models of Jayaratne and Shibayama (2007), the bed load model of Watanabe (1982), the wave propagation model of Onaka et al. (1988), the nearshore current model of Philips (1977) and the undertow model of Okayasu et al. (1990) to predict the large-scale morphodynamics of sandy beaches. The predicted beach profiles and total sediment transport rates were compared with two sets of large-scale laboratory experimental data [Kajima et al. (1983); Kraus and Larson (1988)] and Seisho beach at Kanagawa Prefecture, Japan. It can be concluded that the present numerical model is capable of predicting sediment transport direction, on-offshore sand bar formation and the general trend of the beach profiles of large-scale erosive- and accretive-type sandy beaches to a satisfactory level.

scholarly journals Impact of coastal forcing and groundwater recharge on the growth of fresh groundwater resources in a mega-scale beach nourishment

2017 ◽  
Author(s):  
Sebastian Huizer ◽  
Max Radermacher ◽  
Sierd de Vries ◽  
Gualbert H. P. Oude Essink ◽  
Marc F. P. Bierkens
Keyword(s):  
Groundwater Recharge ◽  
Land Surface ◽  
Morphological Changes ◽  
Groundwater Resources ◽  
Beach Nourishment ◽  
Coastal Protection ◽  
Tidal Dynamics ◽  
Fresh Groundwater ◽  
Protection Measures ◽  
The Impact

Abstract. Large concentrated sand replenishments or nourishments are one of the few coastal protection measures that can simultaneously result in an increase of local fresh groundwater resources. For a large beach nourishment called the Sand Engine – constructed in 2011 at the Dutch coast – we have examined the impact of groundwater recharge and coastal forcing (i.e. natural processes that drive coastal hydro- and morphodynamics) on the growth of the fresh groundwater resources between 2011 and 2016. Measurements of the morphological change and the tidal dynamics were incorporated in a calibrated three-dimensional and variable-density groundwater model of the study area. Simulations with this model showed that the detailed incorporation of the local hydro- and morphodynamics and the actual recharge rate can result in a reliable reconstruction of the growth in fresh groundwater resources. Similarly, the neglect of tidal dynamics, land-surface inundations and morphological changes in model simulations can result in considerable overestimations of the volume of fresh groundwater. In particular wave run-up and coinciding coastal erosion during storm surges limit the growth in fresh groundwater resources in dynamic coastal environments, and should be considered at potential nourishment sites to delineate the area that is vulnerable to salinization.

Effect of Tidal Current and Wave-Current Interaction on the Sediment Transport and Morphological Change in the Channel Water Intake

2017 ◽  
Vol 862 ◽  
pp. 16-20
Author(s):  
Suntoyo ◽  
Made Mustika Wijaya ◽  
Silvianita ◽  
Hasan Ikhwani
Keyword(s):  
Sediment Transport ◽  
Morphological Change ◽  
Water Intake ◽  
Tidal Current ◽  
Morphological Changes ◽  
Measurement Data ◽  
Transport Rate ◽  
Sediment Transport Rate ◽  
Channel Water ◽  
Current Interaction

Investigation of sediment transport rate induced by tidal current and wave-current interaction are very important to explain the sediment transport mechanics, sedimentation and erosion process, and also the coastal morphological changes. The understanding of sediment transport caused by wave and current interaction in detail should be known well in order to predict it, accurately. This paper aim to investigate the characteristics of sediment transport rate due to tidal current and wave-currents interaction motion in the the channel water intake by using numerical modelling. The performance of the modelling results indicated by the Root Mean Square (RMSE) with error of 0.5 % by means validating the model water surface elevation from the fields measurement data and the modelling results. The result showed that sediment transport caused by wave-current interaction give more the amount of total sediment transport than caused by tidal current only. It can be concluded that the wave has dominant effect than tidal current to conduct sedimentation and morphological change in the canal water intake.

scholarly journals Modeling of solid sediment transport in mountain rivers

2020 ◽  
Vol 175 ◽  
pp. 12002 ◽  
Author(s):  
Issam Boukhanef ◽  
Anna Khadzhidi ◽  
Lyudmila Kravchenko ◽  
Zeroual Ayoub ◽  
Kastali Abdennour
Keyword(s):  
Sediment Transport ◽  
Fine Particles ◽  
Agricultural Soils ◽  
Suspended Sediments ◽  
High Water ◽  
The Other ◽  
Concentration Data ◽  
Solid Transport ◽  
One Year ◽  
The One

In Algeria, the problems of erosion and sediment transport are critical, since they have the most dramatic consequences of the degradation of agricultural soils on the one hand and the siltation of the dam on the other .The sediment transport in the Algerian basins is very important especially during the periods of floods, It is in this sense that this study, which consists of estimating the sediment transport in suspension and determining the models of relation linking the liquid discharge and the sediment discharge in order to estimate the solid transport in the absence of suspended sediments concentration data at the Sidi Akkacha station at the outlet of the basin of Oued Allala which is subject to a high water erosion, it degrades from one year to the other under the effect of this phenomenon especially during the floods which drain high amounts of fine particles exceeding in general, the concentration of 150 g/l, the results obtained from the application of the models are very encouraging since the correlation between liquid and solid discharge exceeds 80 %.

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 Modelling of sediment transport and morphological evolution under the combined action of waves and currents

Ocean Science ◽  
2017 ◽  
Vol 13 (5) ◽  
pp. 673-690 ◽  
Author(s):  
Guilherme Franz ◽  
Matthias T. Delpey ◽  
David Brito ◽  
Lígia Pinto ◽  
Paulo Leitão ◽  
...  
Keyword(s):  
Sediment Transport ◽  
Morphological Changes ◽  
Morphological Evolution ◽  
Research Effort ◽  
Beach Erosion ◽  
Model Complexity ◽  
Invariant Equilibrium ◽  
Waves And Currents ◽  
Combined Action ◽  
Modelling System

Abstract. Coastal defence structures are often constructed to prevent beach erosion. However, poorly designed structures may cause serious erosion problems in the downdrift direction. Morphological models are useful tools to predict such impacts and assess the efficiency of defence structures for different scenarios. Nevertheless, morphological modelling is still a topic under intense research effort. The processes simulated by a morphological model depend on model complexity. For instance, undertow currents are neglected in coastal area models (2DH), which is a limitation for simulating the evolution of beach profiles for long periods. Model limitations are generally overcome by predefining invariant equilibrium profiles that are allowed to shift offshore or onshore. A more flexible approach is described in this paper, which can be generalised to 3-D models. The present work is based on the coupling of the MOHID modelling system and the SWAN wave model. The impacts of different designs of detached breakwaters and groynes were simulated in a schematic beach configuration following a 2DH approach. The results of bathymetry evolution are in agreement with the patterns found in the literature for several existing structures. The model was also tested in a 3-D test case to simulate the formation of sandbars by undertow currents. The findings of this work confirmed the applicability of the MOHID modelling system to study sediment transport and morphological changes in coastal zones under the combined action of waves and currents. The same modelling methodology was applied to a coastal zone (Costa da Caparica) located at the mouth of a mesotidal estuary (Tagus Estuary, Portugal) to evaluate the hydrodynamics and sediment transport both in calm water conditions and during events of highly energetic waves. The MOHID code is available in the GitHub repository.

scholarly journals Major Aortic Reconstruction with the Replacement of Supra-Aortic Branches: Successful Surgical Treatment of Takayasu Arteritis Initially Presented as Congestive Heart Failure

Diagnostics ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 216
Author(s):  
Maja Stojanovic ◽  
Sanvila Raskovic ◽  
Marija Boricic-Kostic ◽  
Vesna Bozic ◽  
Maja Vuckovic ◽  
...  
Keyword(s):  
Heart Failure ◽  
Congestive Heart Failure ◽  
Takayasu Arteritis ◽  
Morphological Changes ◽  
Pulmonary Arteries ◽  
Uneventful Recovery ◽  
Severe Aortic Regurgitation ◽  
Bentall Procedure ◽  
One Year ◽  
Arch Reconstruction

Takayasu arteritis (TA) is a rare, large vessel vasculitis that affects aorta, its major branches, and occasionally pulmonary arteries. Patients with TA can present with constitutional features and/or various symptoms and signs caused by morphological changes in the blood vessels affected by the inflammatory process. Corticosteroids (CS) and immunosuppressives (IS) are the first line treatment for active TA. Open surgery remains a treatment of choice for TA patients with moderate-to-severe aortic regurgitation (AR) and ascending aortic aneurysm (AAA). We present a 26-year-old female diagnosed with an advanced stage of TA, initially presented as congestive heart failure. Due to a progressive course of the disease (AR 3+, AAA 5.5 cm), surgery of the Aortic valve and root (Bentall procedure), with total arch reconstruction and replacement of supra-aortic branches was performed. The patient has had an uneventful recovery during the postoperative course with no complications at one year follow-up. Normal left ventricle (LV) diameter, LV ejection fraction 67%, and a trace of AR were seen on the last echocardiography.

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