Journal of Waterway, Port, Coastal, and Ocean Engineering

The coastal stretch between Vagueira and Praia de Mira, northern Portugal, is subject to high-energy wave conditions. At the same time, the shoreline is a main contributor to the local economy, extensively due to tourism. Despite the shoreline being currently protected by groynes, a better understanding of the hydrodynamics and the morphodynamics in the area is crucial for coastal managers and planners. In this work, it is intended to use a process-based model, COAST2D, to predict the beach morphological changes of the said sandy beach as the study site. The model is applied to simulate the morphological changes over a 4-month period between October 2013 and February 2014 to the study site, during which a series of high-intensity storm events occurred along the west coasts of Europe. Model results are compared with the measurements from topobathymetric fieldwork campaigns. The model results show the effect of the groynes on the nearshore coastal processes under the combined wave and tide conditions. The predicted morphological changes agree well with the field measurements. The model results also show the shoreline sensibility at the study site to high-energy waves during storms, where the shoreline changed its slope to adapt to the more energetic conditions. The results clearly demonstrate the capability of COAST2D in modeling the complex hydrodynamics and morphodynamics at the study site in a seasonal scale.

Gravity wharf (GW) structures are gaining popularity in new port constructions, as well as expanding existing ports. When such structures are located on saturated alluvial seabed, their seismic performance needs to be established, particularly from a liquefaction point of view. In this paper, time domain finite element (FE) analyses were carried out on a typical GW structure cross section located on a 10-m-thick saturated sand bed. In addition, the same cross section was tested in a geotechnical centrifuge and subjected to earthquake loading. The results from the FE analyses were directly compared with the centrifuge test data. Firstly, the settlement and rotation of the GW structure when subjected to a series of earthquake loadings were compared. It was shown that the FE analyses were able to capture the level of settlements quite accurately. Similarly, the dynamic responses of the GW structure observed during the centrifuge testing were compared with the results from the FE analyses. Finally, the excess pore pressures generated in the sand bed were compared with the experimental data. In addition to the centrifuge testing, the FE analysis was able to provide the spatial redistribution of the vertical effective stresses with the onset of excess pore pressure generation. Similarly, the excess pore pressure ratio contours could be constructed at any given time point. In combination, the results from the FE analyses and the centrifuge data concluded that the GW structures could perform well, even under strong earthquake loading with acceptable settlements.

A large-scale physical model was constructed in the Large Wave Flume of Hinsdale Wave Research Laboratory (HWRL) at Oregon State University to develop a dataset of measured pressures and forces acting on an elevated, coastal structure, representing a two-story building with an elevated foundation, due to tsunami-like wave impacts. Two wave cases, unbroken and broken long waves, were investigated by changing the still water level, resulting in cases without and with an air gap between the still water level and the bottom of the test specimen, while maintaining the base of the test specimen at the same elevation. Horizontal and vertical pressures and forces were measured on the faces of the test specimen and between the test specimen and its supports, respectively. Three pressure gauge layouts were used to measure the distribution of pressures around the test specimen for each wave case. Regression surfaces of the pressure gauge measurements illustrate the shape of the pressure distributions on the test specimen. The maximum vertical forces were measured during the unbroken-wave case. However, the streamwise, horizontal force was maximized when the structure was subjected to the broken wave. The findings and data presented here are intended for use by numerical modelers for future validation analyses that can be used toward enabling tsunami-resistant designs of coastal elevated building structures.

Longshore sediment transport (LST) prediction is still a challenging task in coastal engineering, due to complexity in affecting physical processes. There have been studies to develop tools to predict the LST rate, but there is still room to revisit methods and data previously collected to achieve a more robust formula. In this study, an extensive sediment data set including sand, gravel, and shingle was collected and used to evaluate the performance of existing LST volumetric rate prediction formulas and to derive two new formulas (based on dimensional and nondimensional approaches). Both formulas are based on commonly available parameters, that is, significant wave height at breaker point (H_sb), peak wave period (T_P), wave angle at breaker point (α_b), and sediment size (D₅₀). The benefits of the formulas are: (1) minimum required input parameters; (2) easy to comprehend, physically justifiable functional forms, free from making any assumptions or using any other equation; and (3) a wide range of applicability. Eventually, the formula derived based on nondimensional parameters is suggested, owing to its homogeneity and accuracy using an independent field data set.

Floating silt screens are widely applied to confine and control turbidity plumes and sedimentation due to dredging activities. Their efficient deployment requires detailed knowledge of the ambient hydrodynamic conditions. Incorrect deployment may lead to confinement deficiencies, screen burial, or damage. One aspect of deployment efficiency is the sediment transport rate beneath the silt screen. The sediment transport between the sides of a floating silt screen is mostly affected by ambient currents. In addition, gravity currents and shear-stress–induced screen motion also affect the sediment transport. The gravity current is governed by the suspended sediment concentration, whereas the shear-stress–inflicted flow scales with the ambient current. This study is concerned with the evaluation of the sediment transport, in terms of the effective screen depth, the suspended sediment concentration, and the ambient parallel current. Two computational models for density gradient and screen motion inflicted sediment transport are presented for the analyses of these transport mechanisms. Based on the generated data, a scaling law dependence for the water transport in dependence of the effective screen depth, the ambient current, and the suspended sediment concentration is proposed.

Breakwaters are effective structures for mitigating tsunami-induced damage. However, pieces of the breakwater can be displaced by the turbulent tsunami flow, which undermines the stability of the breakwater and reduces its mitigation effectiveness. Assessing the damage to breakwaters in tsunami-prone coasts is, therefore, valuable for the port authority, cargo owners, and coastal residents. Physical experiments were conducted to assess potential damage to a typical composite breakwater in New Zealand due to tsunamis. Higher breakwaters can resist a stronger bore impact and experience delayed initiation of the same damage. A new parameter is proposed to assess the damage in the armor layer, which takes into account the size and density of armor units, the height of the breakwater, and the tsunami bore depth.

An advanced fully hydro- and morphodynamic two-dimensional horizontal (2DH) numerical model, describing the processes of nonlinear wave propagation, sediment transport, and morphological changes and being suitable for the design of structures for coastal protection against erosion, has been developed and tested here. The Boussinesq-type equations, including nonlinear higher-order terms, which can enhance a model's behavior regarding highly nonlinear wave propagation in the nearshore region, including the swash zone, are used. The bed load and sheet flow transport rate are estimated using a quasi-steady formulation for waves and currents. Both phase-lag and acceleration effects are included in the formula. The suspended sediment transport rate is estimated by solving the depth-integrated transport equation for suspended sediment. Model predictions are compared with laboratory data and field measurements (breaking wave-induced current field and morphological changes associated with emerged and submerged detached breakwaters). Numerical results and data are in satisfactory agreement. In the case of emerged detached breakwaters, the well-known criteria for tombolo or salient formation (based on empirical design guidelines) agree with the model predictions. The methodology is also applied to simulate the morphological changes behind submerged breakwaters, resulting in useful conclusions concerning the role of the transmission coefficient and the net mass influx over the breakwater. The developed model can be used for the design of emerged and submerged detached breakwaters.

To give high performance over a broader wave frequency range and enable the multipurpose utilization of marine structures, an asymmetric offshore-stationary oscillating water column device with an outstretched bottom plate is considered theoretically. Through solving boundary value problems by means of the matched eigenfunction expansion method, the effects of the geometric parameters, including drafts of the front and back walls, air chamber height and width, and length of the bottom plate, on hydrodynamic performance, such as optimum conversion efficiency (E_opt), reflection (C_r) and transmission (C_t) coefficients, radiation conductance ($\tilde{B}$) and susceptance ($\tilde{C}$), and diffraction flux factor ($\widetilde{\mathrm{{\rm Y}}}$), are explored in detail. The results show that a draft of d₂/h = 3/8 is favorable to improve the extraction efficiency of the system. The air compressibility (increasing the chamber height) significantly influences the extraction efficiency for the intermediate- and short-wave regimes. Moreover, the presence of the bottom plate can provide another resonance mechanism, which can be tuned to provide a wider bandwidth of high performance.

This paper describes an investigation of the interaction of breaking solitary wave runup with a two-dimensional semipermeable (vegetated) obstacle and the resulting wave loading on a downstream cylinder. The OpenFOAM model, together with an IHFOAM module for mangrove–fluid interaction, are used for 276 numerical experiments, performed for a wide range of damping coefficients. In general, wave heights inside and just downstream of the obstacle were found to increase, compared with the bare earth case, with reflection from and inside the obstacle as the major factor. By contrast, wave loads decreased strongly when sheltered by the obstacle, with increasing damping coefficients leading to lower loads, but with considerable scatter. This paper provides several different methods to estimate wave runup loads behind semipermeable obstacles, with results presented in forms that may prove useful for design.

An artificial neural network (ANN) tool trained using a backpropagation algorithm was developed to predict the overtopping rate of impermeable vertical seawalls on coral reefs. The training database was produced from simulations of a nonhydrostatic wave model calibrated using a subset of experimental overtopping data and covered a wide range of hydrological conditions, reef morphologies, and seawall heights. The ANN configuration was optimized through sensitivity analysis and overfitting was prevented using the k-fold cross-validation technique. The generalization ability of the ANN tool was tested against the remaining subset of the experimental data. The ANN tool provided reliable predictions using deep water wave parameters as input rather than parameters for waves at the toes of structures. This made it a practical predictor for use in the preliminary design of vertical seawalls and real time forecasting of wave-induced flooding in coral reef environments.

A series of laboratory experiments and high-fidelity numerical modeling were conducted to study the effects of the lowest floor elevation on the flow and loading patterns resulting from the overland propagation of a solitary wave among an array of idealized beachfront buildings. Although the uplift force is found to be nearly independent of the building position within the array, it significantly varies with the elevation of the lowest floor. The analyses show that the wave-induced uplift force reaches its peak as the lowest floor elevation is positioned at the still water level. The position of the building within the array and the elevation of the lowest floor are found to be the two most influential factors on the lateral force. The lateral and uplift forces varied with the lowest floor elevation by an inverse linear and a third-order polynomial relationship, respectively. The collective maximum force on the array estimated using the concept of momentum flux demonstrated a confidence level of more than 70%.

Various unsteady Reynolds-averaged Navier–Stokes (URANS) modeling techniques to predict container ship squat in confined water are investigated and compared in this study to assess the suitability of each modeling technique. Five methods are compared, among which three are quasi-statical estimations of squat from computational fluid dynamics (CFD)-computed hydrodynamic forces and moment (QS), and two are based on directly computed squat utilizing dynamic overset meshing (OV) technique. In addition, the effect of self-propulsion on the squat is investigated by comparing different methods of propulsion, i.e., the hull is either towed (T) or self-propelled by means of body-force propulsion virtual disc (VD) model or a fully discretized propeller (DP). The investigation shows that the QS methods tend to be superior in terms of computation efficiency, range of applicability, and trim prediction accuracy. It is also shown that the effect of self-propulsion is significant and should be accounted for to provide accurate results, especially at relatively high speeds. Moreover, virtual disc modeling is more computationally economical while also providing a degree of accuracy similar to that of a discretized propeller. Thus, the most suitable method is the quasi-static method with virtual disc self-propulsion (QS-VD). However, for very shallow cases where h/T < 1.14, the towed quasi-static squat model (QS-T) is recommended due to better accuracy.

New approximate analytic solutions are developed to study wave propagation through collections of coastal features. Solutions are developed for circular shoals formed by a submerged cylinder with water depth shallower than the surrounding sea, and for bathymetric depressions formed by a circular pit deeper than the surrounding sea. Classic solutions for monochromatic wave propagation through a single isolated coastal feature are extended using the analytic element method to achieve analytic solutions for a number of coastal features that collectively shape the wave field. Each element is formulated as a Riemann–Hilbert interface problem, where the wave amplitude and phase are continuous between the element and its surroundings; however, a discontinuity in the normal derivative of the wave field occurs as a result of the change in water depth across the interface. Interface conditions are satisfied nearly exactly for typical problems, as demonstrated by normalized root mean square errors of the order of 10⁻¹⁶. This article contributes new mathematical and computational methods that shed insight into wave amplification and dissipation generated within collections of coastal features, with potential applications including the study of trapped waves and tsunamis near coastal features, and of waves traveling through aquatic vegetation.

Seaports are particularly vulnerable to coastal hazards such as hurricanes and flooding due to their location. Sea level change (SLC) can magnify the impacts of these coastal hazards, threatening the resilience of ports. Engineers must design port infrastructure that is adequately prepared for the amount of SLC expected within the design life of the structure. However, the uncertainty of SLC projections coupled with the long service lives of port infrastructure presents unique challenges to do so. Through an online survey of 85 US port and maritime infrastructure engineers, this research reflects the US engineering community's attitude and approach to planning for SLC for maritime infrastructure projects. Only 29% of respondents indicated that their organization had an internal SLC policy, design, or planning document. Furthermore, results show that the lack of regulatory design standards in this area leads to engineers and their clients disregarding SLC more frequently. There is a clear need for collaboration among stakeholders to develop practical design methods for designing resilient port infrastructure.

Ship waves and ship-induced flows are the main hydrodynamic loads on waterway beds and embankments. However, the underlying physical processes are not yet understood fully. Recent field measurements, conducted in the Kiel Canal, Germany, allow a better understanding of these loads and the resulting (ship-induced) sediment transport. The measurements include high-resolution time series of pressure, three-dimensional flow velocities, and turbidity, collected using stationary as well as vessel-mounted sensors. The focus of this paper is on two aspects. First, existing drawdown estimation approaches are reviewed and validated against field measurements. Based on this, a new approach is derived to improve the general description of ship waves in confined waters. Second, a new approach to estimate the ship-induced sediment transport in the Kiel Canal is developed using turbidity and flow measurements and validated against dredging volumes. Our results show that about 10% of the total transported sediment volume in the Kiel Canal can be attributed to ship traffic, whereas the remaining volume is mainly transported during regular dewatering periods. This paper provides an empirical-based method to estimate ship-induced sediment transport in artificial waterways as basis for future canal management strategies.

During a tsunami event, neighboring structures can significantly influence the forces experienced by an individual structure within an urban community. To assess the effects of adjacent structures on the resulting fluid flow, and the corresponding pressures and forces exerted on a structure, two tsunami-like waves were generated in the Large Wave Flume at the Hinsdale Wave Research Laboratory (HWRL) at Oregon State University. The forces and pressures on an elevated structure were measured for a reference geometry without neighboring structures, as well as for five structure configurations that included one or two neighboring structures arranged in layouts meant to be representative of prototypical rectangular buildings in subsections of a coastal community. Results showed that adjacent structures can shield a structure from the flow, causing decreased total forces with increasing blockage ratios. However, local channelization of the flow was found to increase local pressures, increasing the demands on structural components. Comparisons with ASCE 7-16 methods for determining force increase ratios due to channeling showed strong agreement for channeling-dominated configurations and bore-like waves that broke before impacting the elevated structure. In contrast, shielding-dominated configurations and waves that were unbroken on impacting the elevated structure showed that the ASCE 7-16 methods would overestimate force increase ratios.

The tidally influenced shipyard Elsflether Werft, Germany, has experienced a large increase in siltation and short periods of refilling since the 2000s. Its navigational depth was reduced by over 2 m in 2017 and by 0.5 m within only 4 months in 2014. A comprehensive field study was conducted in 2016 employing a time-lapse camera, multiparameter probes, sediment traps, vessel-based measurements, and unmanned aerial observations. Measurements show a strong shear flow along the dock entrance, as well as distinct turbidity signal spikes during regular and neap tides, which are drowned during spring tides. Deploying an unmanned aerial system (UAS), sediment plumes entering the dock were observed. Introducing a biodegradable tracer into the dock, a vortex structure was monitored by the UAS and orthophoto sequences processed by particle image velocimetry yielding time-averaged surface flow patterns and magnitudes, which correlate well with other measurements. Contextual data revealed a cross-sectional widening and river-bed geometry changes, which indicate increased siltation rates attributable to a retention basin effect.

In this study, the dynamic behavior of bed-load sediments under unsteady flow conditions is experimentally investigated and discussed. A series of experiments were conducted in a 6-m-long laboratory flume with naturally shaped hydrographs, and a video technique was applied to simultaneously monitor the bed-load motion and variations in the water level. Analysis of the experimental results demonstrated that the flow unsteadiness contributes to easier entrainment of the bed load, and the effect on the bed-load behavior decreases with an increase in the hydrograph duration. A further analysis revealed that the time lag between the occurrence of the peak discharge and that of the peak sediment transport rate is related to the base flow, and the bed-shear-stress peak triggers the bed-load transport peak. An unsteadiness parameter is proposed to account for the influence of the bed-load incipient. The regression analysis indicates a strong linear relationship between the bed-load transport and the unsteadiness parameters, which can be used for the estimation of the bed-load motion in the unsteady flow.