WAVE-CURRENT INTERACTION, SEDIMENT TRANSPORT AND SEABED EVOLUTION IN THE PIRAQUÃŠ-AÃ‡U/PIRAQUÃŠ MIRIM ESTUARY (BRAZIL)

The medium-term seabed evolution of PiraquÃª-AÃ§Ãº/PiraquÃª-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 riverâ€™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.

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

Ocean Science ◽

10.5194/os-13-673-2017 ◽

2017 ◽

Vol 13 (5) ◽

pp. 673-690 ◽

Cited By ~ 5

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.

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

10.5194/os-2017-8 ◽

2017 ◽

Cited By ~ 1

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.

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

Geosciences ◽

10.3390/geosciences9030140 ◽

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.

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

Coastal Engineering Proceedings ◽

10.9753/icce.v33.sediment.57 ◽

2012 ◽

Vol 1 (33) ◽

pp. 57 ◽

Cited By ~ 1

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.

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

Coastal Engineering Proceedings ◽

10.9753/icce.v36.papers.83 ◽

2018 ◽

pp. 83 ◽

Cited By ~ 1

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 â€˜Hondsbossche Dunesâ€™ 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.

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Sand spit morphological evolution at tidal inlets by using satellite images analysis: Two case studies in Vietnam

Journal of Science and Technology in Civil Engineering (STCE) - NUCE ◽

10.31814/stce.nuce2020-14(2)-02 ◽

2020 ◽

Vol 14 (2) ◽

pp. 17-27

Author(s):

Nguyen Quang Duc Anh ◽

Hitoshi Tanaka ◽

Nguyen Xuan Tinh ◽

Nguyen Trung Viet

Keyword(s):

Sediment Transport ◽

Satellite Images ◽

Morphological Changes ◽

Morphological Evolution ◽

Google Earth ◽

Sluice Gate ◽

Landsat Images ◽

Longshore Sediment Transport ◽

Sand Spit

This paper presents the long-term morphological changes of the sand spits at the Ken Inlet in Ha Tinh Province and Phan Inlet in Binh Thuan Province, Vietnam. The analysis results show that the sand spit morphology at Ken Inlet was drastically changed before the completion of the Da Bac sluice gate construction in 1992, after that the sand spit elongation rate became stable at a rate of about 68 meters per year. Meanwhile, the sand spit at Phan Inlet was breached three times during the winter months of 1990-1991, 1998-1999 and 2014-2015. Moreover, the results of remote sensing image analysis also show that after the sand spit have been breached, it continued elongating at a relatively stable rate of 170÷200 meters per year. Based on the analytical model by Kraus (1999) for predicting the sand spit elongation, the estimated long-shore sediment transport rates of Phan Inlet and Ken Inlet are 145,000 m3/year and 133,500 m3/year, respectively. These longshore sediment transport rates are a main contribution for the sand spit elongation in these study areas. Keywords: sand spits; tidal Inlet; breaching; elongation; Landsat images; Google Earth images.

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

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.862.16 ◽

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.

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