Search Results (118)

Marine and underwater structures, such as seawalls, piers, breakwaters, and pipelines, are particularly susceptible to seismic events. These events can directly damage the structures or destabilize their supporting soil through phenomena like liquefaction. This review examines advanced numerical modeling approaches, including CFD, FEM, DEM, FVM, and BEM, to assess the impacts of earthquakes on these structures. These methods provide cost-effective and reliable simulations, demonstrating strong alignment with experimental and theoretical data. However, challenges persist in areas such as computational efficiency and algorithmic limitations. Key findings highlight the ability of these models to accurately simulate primary forces during seismic events and secondary effects, such as wave-induced loads. Nonetheless, discrepancies remain, particularly in capturing energy dissipation processes in existing models. Future advancements in computational capabilities and techniques, such as high-resolution DNS for wave–structure interactions and improved near-field seismoacoustic modeling show potential for enhancing simulation accuracy. Furthermore, integrating laboratory and field data into unified frameworks will significantly improve the precision and practicality of these models, offering robust tools for predicting earthquake and wave impacts on marine environments. Full article

The beneficial or detrimental effects of human-built marine structures (piers, breakwaters, and seawalls) on macrozoobenthic assemblages and diversities are currently underexplored. The present study investigated the enhancement of β-diversity of oysterbed-associated species on breakwaters constructed along sandy beaches. We compared habitat complexities and species assemblages among artificial breakwater shores (ABS), a natural rocky shore (NS), and an embayment shore (ES). Oysterbed habitat complexity was found to be greatest on the ABS due to the successional colonization of the reef-forming estuarine oyster, Saccostrea echinata, followed by the colonization of boring bivalves and burrowing annelids. High-resolution taxonomic data revealed that the ABS supports the greatest species richness, including 48.1% unique species and 33.3% species shared with the embayment shore. The other shores uniquely or in combination with ABS support up to 11.1% of the total species richness associated with the oysterbeds (n = 81). Taxonomic dominance in terms of species number was Mollusca > Annelida > Arthropoda. This study reveals that ABS enhances β-diversity by ~91% (Jaccard dissimilarity index), which is driven by the sequential cascading events of (1) sheltering of shores, (2) colonization of novel habitat-forming oysters, (3) novel macrozoobenthic species recruitment from adjacent shores and sheltered embayments, including habitat-forming bivalves and annelids, and (4) the recruitment of macrozoobenthic species to boreholes. ABS habitat complexity derives from a spatially distinct, three-tiered ecological engineering system, involving (1) breakwater construction (100 m), (2) reef-forming oysters (10 m), and (3) boring bivalves and burrowing annelids (<10 cm). Irrespective of the purpose of their construction, breakwaters along extended sandy shores can potentially increase the resilience (β-diversity) and regional interconnectivity of hard surface macrozoobenthic species. Full article

As part of an investigation into downfall impacts from violent overtopping waves, experimental data are presented for the impact pressures and forces generated by regular and focused waves breaking onto a vertical wall and impacting a landward horizontal deck at a scale of 1:38. Particular attention is given to the wave-by-wave uprush and impact downfall events. By selecting regular and focused wave conditions that produce impacts, new trends are identified for violent downfall phenomena that could easily be underestimated in current practice. The characteristics of the downfall impacts are investigated and three different types of downfall impact are identified and discussed. Using a Wavelet Filter to denoise the signal from pressure probes without losing the peak impact pressures or introducing a phase shift, the distinctive features and dynamic behaviours of the white-water impacts are considered, and it is shown that downfall pressure magnitudes of $30–40 \rho gH$ are regularly achieved. Dynamic impulse times of the events are also presented with higher-impact events generally relating to shorter impulse times, highlighting the dynamic character of these impacts. The largest downfall pressures are found to occur further from the vertical wall than previously measured. Importantly, the spray travelling furthest from the point of the initial wave impact on the vertical wall causes some of the largest downfall pressures on the deck. The paper concludes that, while the dataset is small, there are strong indications that the effects of these types of impacts are structurally significant and present a risk to infrastructure located landward of seawalls. Full article

It is crucial for reef revetments to respond dynamically to rigorous wave actions for structural stability and safety. A comprehensive analysis of the interaction between the wave force and wave overtopping in a reef revetment project was conducted based on wave flume experiments. This study explored how wave conditions, the water depth along the reef flat, and the proximity of the reef edge to the revetment project influenced wave overtopping and wave force patterns. The results indicate that as the incident wave height, period, and water depth along the reef flat increased, the average wave overtopping within the revetment project also increased. Additionally, higher levels of average wave overtopping occurred with the decrease in the distance between the revetment project and the reef edge. The peak wave force on the seawall of the revetment project was studied in response to various factors, including wave period, wave height, water depth along the reef flat, and distance to the reef edge. The changes in the maximum wave force reflected those of the average wave overtopping, with a strong linear correlation. The quantitative relationship between these variables was determined, and the wave forces on the seawall could be indirectly estimated using the average wave overtopping volume. This study provides an efficient methodology for assessing the dynamic attributes of revetment projects and the disaster risk of these structures. Full article

The preservation of the ancient seawall site is a focal point and challenge in the protection of historical relics along Hangzhou’s Grand Canal in China. This endeavor holds significant historical and contemporary value in uncovering and perpetuating Hangzhou’s cultural heritage. Researchers investigating the Linping section of the seawall site aimed to address soil site deterioration by selecting environmentally friendly alkali-activated slag cementitious materials and applying the response surface method (RSM) to conduct solidification experiments on the seawall soil. Researchers used the results of unconfined compressive strength tests and microscopic electron microscopy analysis, considering the comprehensive performance of soil solidification mechanisms and mechanical properties, to establish a least-squares regression fitting model to optimize the solidification material process parameters. The experimental results indicate that the optimal mass ratio of lime, gypsum, and slag for achieving the best solidification process parameters for the seawall soil, with a 28-day curing period, is 1:1.9:6.2. This ratio was subsequently applied to the restoration and reconstruction of the seawall site, with parts of the restored seawall exhibited in a museum to promote the sustainable conservation of urban cultural heritage. This study provides theoretical support and practical guidance for the protection and restoration of soil sites. Full article

Beach erosion and coastal protection are complex and interconnected phenomena that have a substantial impact on coastal environments worldwide. Among the various coastal protection measures, seawalls have been widely implemented to mitigate erosion and protect coastal assets. However, the interrelationship between beach erosion and seawalls remains a critical topic for investigation to ensure effective and sustainable coastal management strategies. Seawalls impact the shoreline, particularly through the “end effect”, where the seawall functions similarly to a groin, causing erosion on the downdrift side relative to the direction of wave approach. This study provides a detailed analysis of the interplay between beach erosion and seawall structures in Loc An, Vietnam, employing both remote sensing and numerical approaches. Sentinel-2 images were employed together with an analytical solution to observe the shoreline change at the Loc An sand spit and to determine input values for the numerical model. Based on the shoreline dynamics, a numerical scheme was employed to study the shoreline evolution after the construction of a seawall. Our findings show that the shoreline evolution can be divided into three stages: (1) The first stage corresponds to the elongation of the sand spit without interference from coastal structures. (2) The second stage shows the effect of jetties on the shoreline, as signaled by the buildup of sand updrift of the jetties. (3) The third stage shows the effectiveness of the seawall, where the shoreline reaches its equilibrium condition. The study provides a quick and simple method for estimating shoreline diffusivity (ε) in situations where measured data is scarce. Full article

The protection against a storm event provided by nourishment to Costa da Caparica beaches near Lisbon, Portugal, is investigated numerically with a two-dimensional-horizontal morphodynamic model able to generate and propagate the longer infragravity waves. The beach has a groyne field and a multi-typology backshore. The nourishment of 10⁶ m³ of sand was placed at the beach face and backshore. Pre- and post-nourishment topo-bathymetric surveys of the beach, which suffers from chronic erosion, were performed under a monitoring program. The morphodynamics of the pre- and post-nourished beach when exposed to a simulated historically damaging storm event and the post-storm morphologies were compared to evaluate the efficacy of the nourishment. Results indicate that the lower surface level of the beach face and backshore of the pre-nourished beach induces a larger erosion volume. The nourishment prevented the extreme retreat of the shoreline that occurred during the storm in the pre-nourished beach and reduced the storm-induced erosion volume by 20%, thus protecting the beach effectively against the storm. The beach backshore typology (seawall vs. dune) exerts differential influences on the sandy bottom. As a result, multi-typology backshores induce alongshore variability in cross-shore dynamics. The backshore seawalls exposed to direct wave action cause higher erosion volumes and a larger cross-shore extension of the active zone. The most vulnerable alongshore sectors of the beach were identified and related to the mechanisms responsible for the erosion phenomenon. These findings strengthen the importance of sand nourishment for the protection and sustainability of beaches, particularly those with a seawall at the backshore, where storm events cause higher erosion. Full article

In response to the incident of tourists falling into the sea due to waves on the seawall berm at Macau Road, Qingdao, during the passage of Typhoon “Songda” in 2022, a combination of numerical simulations and physical model experiments was performed to investigate the mechanics of the event, with emphasis on the wave flow characteristics and the flow evolution process on the seawall berm as well as the force exerted on a human body-equivalent cylinder model. The study found that the thickness of the return flow was significantly greater than that of the overtopping flow on the landward part of the berm. The recoil forces applied to the model on the berm were larger than the impact forces, and the ratio tended towards 1 as the wave height increased. In addition, the stability of pedestrians on the seawall berm was analyzed. The instability conditions for pedestrians in cross-wave flows differed slightly from those in floods. Full article

Wave overtopping occurring in offshore wind renewable energy structures such as tension leg platforms (TLPs) or semi-submersible platforms is a phenomenon that is worth studying and preventing in order to extend the remaining useful life of the corresponding facilities. The behaviour of this phenomenon has been extensively reported for linear coastal defences like seawalls. However, no referenced study has treated the case of cylindrical structures typical of these applications to a similar extent. The aim of the present study is to define an empirical expression that portrays the relative overtopping rate over a vertical cylinder including a variety of bull-nose type mitigation structures to reduce the overtopping rate in the same fashion as for the linear structures characteristic of shoreline defences. Hydrodynamic interaction was studied by means of an experimentally validated numerical model applied to a non-impulsive regular wave regime and the results were compared with the case of a plain cylinder to evaluate the expected improvement in the overtopping performance. Four different types of parapets were added to the crest of the base cylinder, with different parapet height and horizontal extension, to see the influence of the geometry on the mitigation efficiency. Computational results confirmed the effectivity of the proposed solution in the overtopping reduction, though the singularity of each parapet geometry did not lead to an outstanding difference between the analysed options. Consequently, the resulting overtopping decrease in all the proposed geometries could be modelled by a unique specific Weibull-type function of the relative freeboard, which governed the phenomenon, showing a net reduction in comparison with the cylinder without the geometric modifications. In addition, the relationship between the reduced relative overtopping rate and the mean flow thickness over the vertical cylinder crest was studied as an alternative methodology to assess the potential damage caused by overtopping in real structures without complex volumetric measurements. The collection of computational results was fitted to a useful function, allowing for the definition of the overtopping discharge once the mean flow thickness was known. Full article

The purpose of this research is to develop a new method for automatically optimizing the seawall cross-section with composite slopes and a berm, considering both overtopping discharge and construction cost. Minimizing these competing multi-objectives is highly challenging due to the intricate geometry of seawalls. In this study, the surrogate model optimization algorithm DYCORS (Dynamic COordinate search using Response Surface models) is employed to search for the optimal seawall geometry, coupled with the ANN (Artificial Neural Network) model for determining the overtopping discharge. A total of 20 trials have been run to evaluate the performance of our methodology. Even the worst-performing Trial 7 among these 20 trials shows a satisfactory performance, with a reduction of 17.67% in overtopping discharge and a 12.1% decrease in cost compared to the original solution. Furthermore, compared to other optimization schemes using GAs (Genetic Algorithms) with the same decision vectors, constraints, and multi-objective functions, the methodology has been proven to be more effective and robust. Additionally, when facing different combinations of wave conditions and water levels, there was a 27.8% reduction in objective function value compared to the original solution. The optimal results indicate that this method can still be effectively applied for optimizing the seawall cross-section as it is a general method. Full article

Settlement prediction based on monitoring data holds significant importance for engineering maintenance of seawalls. In practical engineering, the volume of the collected monitoring data is often limited due to the restrictions of devices and engineering budgets. Previous studies have applied the fractional-order grey model to time series prediction under the situation of limited data volume. However, the performance of the fractional-order grey model is easily affected by the inappropriate settings of fractional order. Also, the model cannot make dynamic predictions due to the characteristic of fixed step size. To solve the above problems, in this paper, the genetic algorithm with enhanced search capabilities was employed to solve the premature convergence problem. Additionally, to solve the problem of the fractional-order grey model associated with fixed step size, the real-time tracing algorithm was introduced to conduct equal-dimensionally recursive calculation. The proposed model was validated using monitoring data of four monitoring points at Haiyan seawall in Zhejiang province, China. The prediction performance of the proposed model was then compared with those of the fractional-order GM(1,1), integer-order GM(1,1), and fractal theory model. Results indicate that the proposed model significantly improves the prediction performance compared to other models. Full article

Storm surge is the most serious marine disaster in China, and the inundation characteristics of storm surge are the key indicators of disaster severity. Especially in the context of relative sea level rise (RSLR), it is very important to rapidly and accurately estimate the inundation characteristics of storm surge for the risk assessment and emergency management of storm surge disasters. Taking Taizhou city, Zhejiang Province, as the study area, this paper constructed an RSLR scenario library considering absolute sea level rise, land subsidence and storm surge water increase. The scenario library includes 72 scenarios, consisting of a combination of four absolute sea level rise scenarios, three land subsidence scenarios, three timescales (2030, 2050 and 2100) and two storm surge water increase scenarios. Then, an improved passive inundation method was used to predict and analyze the inundation characteristics of storm surge under each scenario. This improved method combines the advantages of the accurate active inundation method and the rapid passive inundation method, and is suitable for rapid and accurate estimation of the storm surge inundation characteristics, which can meet the needs of a storm surge disaster risk assessment and emergency response. The prediction and analysis results show that a minor RSLR can also cause a large-scale inundation in coastal areas of Taizhou. When the value of RSLR exceeds the critical value (0.6 m), it may significantly increase the expansion of the inundation area of storm surge. At a relative sea level rise of 1.57 m (extreme scenario in 2100), the inland storm surge inundation of low-risk areas may become high-risk areas. Finally, the quantitative measures for preventing storm surge disasters were put forward according to the current situation of the coast in Taizhou. Without considering storm surge and superimposed general surge, the existing 20-year return period standard seawall can effectively protect against storm surge under various scenarios. In the case of maximum water increase, it is expected that effective protection will remain until 2030, but the standard of the seawall defense will need to be improved in 2050 and 2100. Full article

By comparing different settlement forecast methods, eight methods were selected considering the creep of marine soft soils in this case study, including the Hyperbolic Method (HM), Exponential Curve Method (ECM), Pearl Growth Curve Modeling (PGCM), Gompertz Growth Curve Modeling (GGCM), Grey (1, 1) Model (GM), Grey Verhulst Model (GVM), Back Propagation of Artificial Neural Network (BPANN) with Levenberg–Marquardt Algorithm (BPLM), and BPANN with Gradient Descent of Momentum and Adaptive Learning Rate (BPGD). Taking Lingni Seawall soil ground improved with prefabricated vertical drain-assisted staged riprap filling as an example, forecasts of the short-term, medium-term, long-term, and final settlements at different locations of the soft ground were performed with the eight selected methods. The forecasting values were compared with each other and with the monitored data. When relative errors were between 0 and −1%, both the forecasting accuracy and engineering safety were appropriate and reliable. It was concluded that the appropriate forecast methods were different not only due to the time periods during the settlement process, but also the locations of soft ground. Among these methods, only BPGD was appropriate for all the time periods and locations, such as at the edge of the berm, and at the center of the berm and embankment. Full article

Artificial coastal structures, such as seawalls, breakwaters, and groins, can exert various impacts on the fish communities in the nearby regions. This study focuses on assessing the ecological effects of coastal infrastructure on marine environments, by comparing, at different seasons, the habitat complexity and heterogeneity, as well as their effects on fish assemblages, between the artificial habitat created with the intention of constructing a marina (Puerto Amor) and the natural habitats surrounding the Cabo de la Huerta area in Alicante (Spain). Employing an asymmetric design and examining two temporal and spatial scales, we utilized visual censuses in snorkeling to gauge the abundance and size of fish species, alongside various parameters related to habitat complexity and heterogeneity. The overarching hypothesis is that fish populations associated with artificial habitats will differ in terms of abundance, biomass, species richness, and diversity compared to fish populations associated with natural habitats, due to changes in complexity and heterogeneity. The findings indicate a shift in fish assemblages; for example, the family Labridae showed differences between the two habitat types for several species. These changes were due to the influences of the Posidonia oceanica meadow and algae like Jania rubens; being influenced by biological variables such as Ellisolandia elongata, Oculina patagonica, and Sarcotragus spinosulus; as well as physical variables such as stones, gravel, and blocks. While there is evidence of alteration in fish assemblages due to changes in habitat structure, there is also an increase in richness (9 species/m²) and total abundance and biomass (1000 ind./m² and 1700 g/m², respectively) in the artificial habitat. Multivariate analyses reveal that the fish community in Puerto Amor is less homogeneous than the one in the natural habitat. However, these analyses also indicate an overlap between the communities of both habitats, suggesting substantial similarity despite the noted differences. Consequently, although the habitat alteration has impacted fish populations, it has not diminished abundance, biomass, or species richness. In conclusion, the artificial rocky habitat resulting from the construction attempt at Puerto Amor harbor has fish populations with ecological significance and its removal could lead to undesirable impacts in the area, as the fish assemblages have become well established. Full article

Hurricanes Ian and Nicole caused devastating destruction across Florida in September and November 2022, leaving widespread damage in their wakes. This study focuses on the assessment of barrier islands’ shorelines, encompassing natural sand dunes and dune vegetation as well as armored dunes with man-made infrastructure such as seawalls. High-resolution satellite imagery from Planet was used to assess the impacts of these hurricanes on the beach shorelines of Volusia, Flagler, and St. Johns Counties on the Florida Central East Coast. Shorefront vegetation was classified into two classes. Normalized Difference Vegetation Index (NDVI) values were calculated before the hurricanes, one month after Hurricane Ian, one month after Hurricane Nicole, and one-year post landfall. LiDAR (Light Detection and Ranging) was incorporated to calculate vertical changes in the shorelines before and after the hurricanes. The results suggest that natural sand dunes were more resilient as they experienced less impact to vegetation and elevation and more substantial recovery than armored dunes. Moreover, the close timeframe of the storm events suggests a compound effect on the weakened dune systems. This study highlights the importance of understanding natural dune resilience to facilitate future adaptive management efforts because armored dunes may have long-term detrimental effects on hurricane-prone barrier islands. Full article