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

2017 ◽  
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 3D models. The present work is based on the coupling of the MOHID modelling system and 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 3D 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 in calm water conditions and during events of highly energetic waves.

Sediment transport by waves and currents

1983 ◽  
Vol 10 (1) ◽  
pp. 142-149 ◽  
Author(s):  
Michael C. Quick
Keyword(s):  
Sediment Transport ◽  
Mass Transport ◽  
Power Relationship ◽  
Zero Current ◽  
Transport Direction ◽  
Transport Velocity ◽  
Waves And Currents ◽  
Mass Transport Velocity ◽  
Combined Action ◽  
The Waves

Sediment transport is measured under the combined action of waves and currents. Measurements are made with currents in the direction of wave advance and with currents opposing the wave motion. Theoretical relationships are considered that predict the wave velocity field and the mass transport velocity for zero current and for steady currents.Following Bagnold's approach, a transport power relationship is developed to predict the sediment transport rate. Making assumptions for the mass transport velocity, the transport power is shown to agree with the measured sediment transport rates. It is particularly noted that the sediment transport direction is mainly determined by the direction of wave movement, even for adverse currents, until the waves start to break. Keywords: sediment transport, waves and currents, coastal engineering.

scholarly journals Coastal Processes and Longshore Sediment Transport along Zemmouri Bay, Central East Coast of Algeria

2019 ◽  
Vol 21 (1) ◽  
pp. 7-15
Author(s):  
Khoudir Mezouar ◽  
Romeo Ciortan
Keyword(s):  
Sediment Transport ◽  
Morphological Changes ◽  
Shoreline Change ◽  
Spatial And Temporal Scales ◽  
Wave Refraction ◽  
Shoreline Evolution ◽  
Longshore Sediment Transport ◽  
Western Area ◽  
Waves And Currents ◽  
Comprehensive Study

Abstract The coastline of Zemmouri Bay on the northeast coast of Algeria with about 50 km of shoreline has been eroding since 1970. Changes of the sandy shoreline are continuous and occur at diverse spatial and temporal scales. This erosion is a major crisis and it potentially impacts the coastal population and natural environment. In order to understand and predict these morphological changes, an accurate description of sediment transport by waves and currents and shoreline change is important. This paper presents a comprehensive study of wave refraction, current-driven sediment transport and shoreline change. Results show that the study area exhibits a great variety of shoreline evolution trends, with erosion prevailing in the eastern and central sectors and stability or even accretion in the Western area.

scholarly journals WAVE-CURRENT INTERACTION, SEDIMENT TRANSPORT AND SEABED EVOLUTION IN THE PIRAQUÊ-AÇU/PIRAQUÊ MIRIM ESTUARY (BRAZIL)

2017 ◽  
pp. 32
Author(s):  
Thais Nunes Coutinho ◽  
Leonardo Carvalho De Jesus ◽  
Julio Tomás Aquije Chacaltana
Keyword(s):  
Sediment Transport ◽  
Gravity Waves ◽  
Morphological Changes ◽  
Morphological Evolution ◽  
Seabed Sediment ◽  
Estuary Mouth ◽  
Sediment Mass ◽  
Current Interaction ◽  
Bedload Sediment ◽  
Seabed Evolution

The medium-term seabed evolution of Piraquê-Açú/Piraquê-Mirim estuary (ES/Brazil) is studied numerically in this work. The hydrodynamics is induced by the tide, the river discharges, and the incident water wave. The wave-tide-current interactions are obtained by coupling the shallow water equations with the radiation stress tensor introduced by Longuet-Higgins & Stewart (1960). In this way, the influence of both the tidal current and the current induced by gravity waves on the sediment transport are taken into account. We utilized the Exner (1925) equation, based on the conservation of seabed sediment mass, to calculate the morphological evolution. Seabed morphological changes are accelerated by introducing a time scale factor. Four bedload sediment transport formulations were tested and compared. We found an excellent agreement when numerical results are compared with currents measured in the upper estuary and with sediment transport rates measured at the river’s mouth when using the Engelund and Hansen (1967) sediment transport formulation. We also found that the main morphological changes occurring at the estuary mouth are due to the action of gravity waves. Between the head and mouth of the estuary, the sediment transport rate and morphological seabed changes are controlled exclusively by the tidal currents and the river discharge. In this latter case, we found that the large sandbank located at the estuary mouth is responsible for the absence of wave.

scholarly journals A Numerical Investigation on Tidally Induced Sediment Transport and Morphological Changes with Changing Sea Level in South-East England

Geosciences ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 140
Author(s):  
Nicoletta Leonardi ◽  
Xiaorong Li ◽  
Iacopo Carnacina
Keyword(s):  
Sediment Transport ◽  
Sea Level Rise ◽  
Water Level ◽  
Sea Level ◽  
Large Scale ◽  
Morphological Changes ◽  
Morphological Evolution ◽  
Morphodynamic Equilibrium ◽  
South East England

The impact of tide-induced morphological changes and water level variations on the sediment transport in a tidally dominated system has been investigated using the numerical model Delft3D and South-East England as a test case. The goal of this manuscript is to explore the long-term changes in morphology due to sea level rise and the large-scale morphodynamic equilibrium of the South-East England. Our results suggest that the long term (century scale) tidally-induced morphological evolution of the seabed slows down in time and promotes a vanishing net transport across the large scale system. Century-scale morphologically updated simulations show that both morphological changes and net transport values tend to decrease in time as the system attains a dynamic equilibrium configuration. Results further suggest that the presence of a gradual increase in mean sea level accelerates the initial morphological evolution of the system whose morphological rate of change gradually attains, however, same plateau values as in the absence of sea level rise. Given the same base morphology, increasing water levels enhance residual currents and the net transport near the coastline; and vice-versa, decreasing sea levels minimize both residuals and net transport near the coastline. The areas that are more affected by, water level and morphological changes, are the ones where the net transport is the highest. This manuscript explores and allows extending the idea of morphodynamic equilibrium at a regional scale, larger than the one for which this concept has been generally explored i.e., estuarine scale.

Advances in sediment transport under combined action of waves and currents

2015 ◽  
Vol 30 (4) ◽  
pp. 351-360 ◽  
Author(s):  
Yongjun Lu ◽  
Shouqian Li ◽  
Liqin Zuo ◽  
Huaixiang Liu ◽  
J.A. Roelvink
Keyword(s):  
Sediment Transport ◽  
Waves And Currents ◽  
Combined Action

scholarly journals USE OF A RADIO-ACTIVE TRACER FOR THE MEASUREMENT OF SEDIMENT TRANSPORT IN THE NETHERLANDS

2011 ◽  
Vol 1 (7) ◽  
pp. 25
Author(s):  
J.N. Svasek ◽  
H. Engel
Keyword(s):  
Sediment Transport ◽  
Sea Bottom ◽  
Sea Bed ◽  
Continuous Registration ◽  
Waves And Currents ◽  
Combined Action ◽  
Active Isotope ◽  
Working Out ◽  
The Vertical Distribution ◽  
Specific Radio

The "Rijkswaterstaat" has developed a method based on the use of radio-active tracers for the evaluation of sediment transport due to the combined action of waves and currents. The results of preparatory studies and a laboratory test were published in a previous report by J.J. Arlman, P. Santema and J.N. Svasek [1]. The main principles of the method were 1. Detection by a sledge-mounted unit towed by a survey vessel and continuous registration on board of the radio-activity measured on the sea bottom. 2. Employment of low specific radio-activity of tracer material and a large quantity thereof. 5> Use of a long-life isotope and high radio-activity. k. Measurement of the vertical distribution of radioactivity in core samples or if possible by discrimination. In March 1958 the first lot of tracer material was placed on the sea bed. The tracer material consisted of the radio-active isotope Scandium^" emitting 2 curies incorporated in 100 kg "greensand". Scandium^" has a half-life of 8^ days and emits strong gramma radiations with energies of 0.89 and 1.12 MeV. Afterwards, in 1959, two series of measurements were taken near the entrance to the Rotterdam Waterway. Four droppings formed one series; they were generally carried out in the following manner: 50 kg greensand labeled with 2 Curies Scandium was dropped in k places at a safe distance from each other. 2 of the 8 portions consisted of smaller quantities of both radio-activity and greensand. In the following paragraphs the preparation, dropping and detection of the tracer, the working out of the registrations and the interpretation of the results of the 1959 measurements are discussed.

scholarly journals AEOLIAN SEDIMENT TRANSPORT AT A MAN-MADE DUNE SYSTEM; BUILDING WITH NATURE AT THE HONDSBOSSCHE DUNES

2018 ◽  
pp. 83 ◽  
Author(s):  
Marloes Wittebrood ◽  
Sierd De Vries ◽  
Petra Goessen ◽  
Stefan Aarninkhof
Keyword(s):  
Sediment Transport ◽  
Transport Model ◽  
Morphological Changes ◽  
Morphological Evolution ◽  
Sediment Supply ◽  
Dune System ◽  
Morphological Response ◽  
Profile Type ◽  
Building With Nature ◽  
Aeolian Sediment

This paper presents the influence of aeolian sediment transport on the initial morphological evolution of beach and dunes at the man-made dune system ‘Hondsbossche Dunes’ at the Dutch coast. In total 35 million m^3 dredged material was used for the construction of a beach, dune and foreshore system. This study focused on differences in morphological response within the five different realized dune profile types. A conceptual framework was developed, based on the assessment of (1) environmental forcing, (2) sediment supply from aeolian and marine sources and (3) dune types. These three components were quantified from an analysis of measured profile evolution and the application of an aeolian sediment transport model for the first 19 months since the project delivery date in May 2015. Morphological changes were most pronounced in the first seven months after construction. Dune growth of a profile type at this location is determined by a temporal and alongshore variability in local processes that determines the aeolian sediment supply towards the dunes and the dune geometry that determines the capacity of the profile type to capture the sediments. The model simulations managed to qualitatively reproduce alongshore variations in dune growth as a result of spatial variations in sediment availability, grain size, profile shape and interaction with vegetation. Overall, this study shows the relevance of both marine and aeolian processes in such man-made dynamic systems that are comparable to natural systems. Continuing the monitoring and modelling of this system will improve the quantitative knowledge for design optimization of the Building with Nature philosophy.

scholarly journals MODELLING OF THE IMPACT OF A WAVE FARM ON NEARSHORE SEDIMENT TRANSPORT

2012 ◽  
Vol 1 (33) ◽  
pp. 66 ◽  
Author(s):  
Raul Gonzalez ◽  
Qingping Zou ◽  
Shunqi Pan
Keyword(s):  
Sediment Transport ◽  
Large Scale ◽  
Morphological Changes ◽  
Field Measurements ◽  
Integrated Modelling ◽  
Shear Stresses ◽  
Nearshore Sediment Transport ◽  
Wave Farm ◽  
The Impact ◽  
Modelling System

This paper presents the results from an integrated modelling system investigating the effects of a wave farm on nearshore sediment transport. Wave Hub project is a large scale demonstration site for the development of the operation of arrays of wave energy generation devices located at the southwest coast of the UK where multiple field measurements took place. The two-way coupled SWAN and ROMS models with nested modelling system were set up at the Wave Hub site and run with and without a wave farm. The model results show that the presence of the wave farm has significant impacts on the nearshore circulation, bed shear stresses and sediment transport. The morphological changes are also altered by the wave farm. The study is the key element for the wave resource characterization and environmental impact assessment of the wave farm.

Sign in / Sign up

Export Citation Format

Share Document