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J. Mar. Sci. Eng., Volume 9, Issue 1 (January 2021) – 101 articles

Cover Story (view full-size image): The “Sand Engine” mega feeder nourishment, which is installed in the Netherlands, consists of 20 Mm³ sediment in the shape of a sandy peninsula with an initial size of 2.2 by 1.2 km. Natural processes, such as wind and waves, spread sediments from the initial peninsula further along the coast. In the first five years after construction (2011–2016), over 4 Mm³ of sand were redistributed, feeding adjacent coastal sections with sediment. As a result of the spreading of these large volumes of sediments, the peninsula’s shape changed dramatically during these five years. The top photo shows the situation just after construction in August 2011; the bottom photo was taken in February 2016. View this paper.
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Open AccessArticle
Structural Analysis of a Barge Midship Section Considering the Still Water and Wave Load Effects
J. Mar. Sci. Eng. 2021, 9(1), 99; https://0-doi-org.brum.beds.ac.uk/10.3390/jmse9010099 - 19 Jan 2021
Viewed by 748
Abstract
Structural failures in the barge midship sections can cause operational delay, sinking, cargo loss and environmental damage. These failures can be generated by the barge and cargo weights, and wave load effects on the midships sections. These load types must be considered in [...] Read more.
Structural failures in the barge midship sections can cause operational delay, sinking, cargo loss and environmental damage. These failures can be generated by the barge and cargo weights, and wave load effects on the midships sections. These load types must be considered in the design of the barge midship sections. Here, we present the structural analysis of a barge midship section that has decreased up to 36.4% of its deck thickness caused by corrosion. This analysis is developed using finite element method (FEM) models that include the barge and cargo weights, and wave load effects. The FEM models regarded three cargo tanks in the midship section, containing the main longitudinal and transverse structural elements. In addition, the hull girder section modulus and the required deck thickness of the barge were calculated using Lloyd’s Register rules. These rules were applied to estimate the permissible bending stresses at deck and bottom plates under sagging and hogging conditions, which agreed well with those of the FEM models. Based on FEM models, the maximum compressive normal stress and von Mises stress of the hull girder structure were 175.54 MPa and 215.53 MPa, respectively. These stress values do not overcome the yield strength (250 MPa) of the barge material, allowing a safe structural behavior of the barge. The structural modeling of the barge midship section can predict its structural behavior under different sagging and hogging conditions, considering the cargo, weight and wave loads. Full article
(This article belongs to the Section Ocean Engineering)
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Open AccessArticle
3D FE-Informed Laboratory Soil Testing for the Design of Offshore Wind Turbine Monopiles
J. Mar. Sci. Eng. 2021, 9(1), 101; https://0-doi-org.brum.beds.ac.uk/10.3390/jmse9010101 - 19 Jan 2021
Viewed by 329
Abstract
Based on advanced 3D finite element modelling, this paper analyses the stress paths experienced by soil elements in the vicinity of a monopile foundation for offshore wind turbines subjected to cyclic loading with the aim of informing soil laboratory testing in support of [...] Read more.
Based on advanced 3D finite element modelling, this paper analyses the stress paths experienced by soil elements in the vicinity of a monopile foundation for offshore wind turbines subjected to cyclic loading with the aim of informing soil laboratory testing in support of monopile foundation design. It is shown that the soil elements in front of the laterally loaded monopile are subjected to complex stress variations, which gradually evolve towards steady stress cycles as the cyclic lateral pile loading proceeds. The amplitude, direction and average value of such steady stress cycles are dependent on the depth and radial distance from the pile of the soil element, but it also invariably involves the cyclic rotation of principal stress axes. Complementary laboratory testing using the hollow-cylinder torsional apparatus was carried out on granular soil samples imposing cyclic stress paths (with up to about 3 × 104 cycles) which resemble those determined after 3D finite element analysis. The importance of considering the cyclic rotation of principal stress axes when investigating the response of soil elements under stress conditions mimicking those around a monopile foundation subjected to cyclic lateral loading is emphasised. Full article
(This article belongs to the Special Issue Selected Papers from the 7th PRIMaRE Conference 2020)
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Open AccessArticle
Relationship Between Tree Size, Sediment Mud Content, Oxygen Levels, and Pneumatophore Abundance in the Mangrove Tree Species Avicennia Marina (Forssk.) Vierh
J. Mar. Sci. Eng. 2021, 9(1), 100; https://0-doi-org.brum.beds.ac.uk/10.3390/jmse9010100 - 19 Jan 2021
Viewed by 368
Abstract
Mangroves are important in protecting and stabilizing coastal zones. Pneumatophores of the mangrove species Avicennia marina can form a large aboveground complex of aerial roots, which are important in supporting mangrove growth in low-oxygen environments. We examined the relationship between mangrove tree height, [...] Read more.
Mangroves are important in protecting and stabilizing coastal zones. Pneumatophores of the mangrove species Avicennia marina can form a large aboveground complex of aerial roots, which are important in supporting mangrove growth in low-oxygen environments. We examined the relationship between mangrove tree height, tree girth, sediment mud content, and oxygen levels with pneumatophore abundance. As sediments with higher mud content have more anaerobic conditions due to their lower porosity, we hypothesized that pneumatophore abundance would be positively correlated with sediment mud content and negatively correlated with sediment oxygen levels. Pneumatophore abundance of A. marina ranged from 14 to 516 per m2 (mean 171.8 ± 0.61 per m2), pneumatophore height from 6.6 to 27.5 cm (14.1 ± 0.86 cm), and maximum pneumatophore diameter from 8.5–12.7 mm (8.5 ± 0.24 mm). Pneumatophore abundance was positively correlated with tree height and tree girth. As hypothesized, pneumatophore abundance was positively correlated with percentage of mud content in sediment and negatively correlated with oxygen percentage. This suggests that mangrove trees can adapt to anaerobic and water-logged conditions by increasing their number of pneumatophores, hence providing greater surface area for gas exchange. In addition, there was a significant effect of mangrove (natural and planted), tidal position, and their interaction. With natural mangrove having higher abundance of pneumatophores compared to the planted mangrove, with the highest number closest to the sea. While pneumatophore abundance did not differ among tidal zones in planted mangrove. Full article
(This article belongs to the Section Marine Biology)
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Open AccessFeature PaperReview
Microplastics in Mediterranean Coastal Countries: A Recent Overview
J. Mar. Sci. Eng. 2021, 9(1), 98; https://0-doi-org.brum.beds.ac.uk/10.3390/jmse9010098 - 18 Jan 2021
Viewed by 396
Abstract
The aim of this paper is to present information gathered from studies regarding the current status and challenges of microplastics (MPs) in Mediterranean coastal counties. MPs are considered emerging pollutants, and their effect on fish and on the final consumer through the trophic [...] Read more.
The aim of this paper is to present information gathered from studies regarding the current status and challenges of microplastics (MPs) in Mediterranean coastal counties. MPs are considered emerging pollutants, and their effect on fish and on the final consumer through the trophic food chain are of great concern. Studies from almost all of the Mediterranean coastal countries are gathered and discussed. The source of MPs, as well as their transfer and accumulation are reviewed. In addition, the laboratory techniques for sampling, analysis and characterization of MPs are presented. Moreover, the current regulations for MPs restrictions in Europe will be discussed. Finally, the authors present the current challenges on the topic and provide recommendations for future work. Full article
(This article belongs to the Special Issue Marine Microplastics Pollution)
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Open AccessReview
Visual Appearance of Oil on the Sea
J. Mar. Sci. Eng. 2021, 9(1), 97; https://0-doi-org.brum.beds.ac.uk/10.3390/jmse9010097 - 18 Jan 2021
Viewed by 322
Abstract
The visual appearance of oil spills at sea is often used as an indicator of spilled oil properties, state and slick thickness. These appearances and the oil properties that are associated with them are reviewed in this paper. The appearance of oil spills [...] Read more.
The visual appearance of oil spills at sea is often used as an indicator of spilled oil properties, state and slick thickness. These appearances and the oil properties that are associated with them are reviewed in this paper. The appearance of oil spills is an estimator of thickness of thin oil slicks, thinner than a rainbow sheen (<3 µm). Rainbow sheens have a strong physical explanation. Thicker oil slicks (e.g., >3 µm) are not correlated with a given oil appearance. At one time, the appearance of surface discharges from ships was thought to be correlated with discharge rate and vessel speed; however, this approach is now known to be incorrect. Oil on the sea can sometimes form water-in-oil emulsions, dependent on the properties of the oil, and these are often reddish in color. These can be detected visually, providing useful information on the state of the oil. Oil-in-water emulsions can be seen as a coffee-colored cloud below the water surface. Other information gleaned from the oil appearance includes coverage and distribution on the surface. Full article
(This article belongs to the Special Issue Marine Oil Spills 2020)
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Open AccessArticle
Comparative Analysis of Environmental Contour Approaches to Estimating Extreme Waves for Offshore Installations for the Baltic Sea and the North Sea
J. Mar. Sci. Eng. 2021, 9(1), 96; https://0-doi-org.brum.beds.ac.uk/10.3390/jmse9010096 - 18 Jan 2021
Viewed by 474
Abstract
At the stage of design load analysis for offshore installations such as wave energy systems, a critical step is the determination of environmental cases to be evaluated for the definition of the characteristic design load. A commonly used methodology for load case selection, [...] Read more.
At the stage of design load analysis for offshore installations such as wave energy systems, a critical step is the determination of environmental cases to be evaluated for the definition of the characteristic design load. A commonly used methodology for load case selection, applied in multiple studies and recommended by technical specifications and guidelines, is the environmental contour approach. Here, 50-year environmental contours were generated for four study sites located in the North Sea, Skagerrak and the Baltic Sea by considering both observations and hindcast (model) data. For the construction of the contours, the well-established inverse first-order method (I-FORM) and a modified version using principal component analysis (PCA) were both examined. Furthermore, a 2-dimensional peaks-over-threshold (2D POT) method was evaluated. It was found that a version of the regular I-FORM was able to produce satisfactory contours which properly accounted for the highest waves. When using PCA, the dependency in the data was not properly captured by the probability functions under consideration. The 2D POT method, where applicable, was found to underestimate the extreme sea states. Comparisons between contours obtained from observations and hindcast data showed that the contours may differ substantially depending on the site and method, and thus care must be exercised when using hindcast data for such purposes. Full article
(This article belongs to the Section Ocean Engineering)
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Open AccessArticle
Evolution Process of Liquefied Natural Gas from Stratification to Rollover in Tanks of Coastal Engineering with the Influence of Baffle Structure
J. Mar. Sci. Eng. 2021, 9(1), 95; https://0-doi-org.brum.beds.ac.uk/10.3390/jmse9010095 - 17 Jan 2021
Viewed by 360
Abstract
During the storage process, liquefied natural gas (LNG) may undergo severe evaporation, stratification, and rollover in large storage tanks due to heat leakage, aging, or charging, causing major safety risks. Therefore, this article theoretically analyzes the causes and inducing factors of the LNG [...] Read more.
During the storage process, liquefied natural gas (LNG) may undergo severe evaporation, stratification, and rollover in large storage tanks due to heat leakage, aging, or charging, causing major safety risks. Therefore, this article theoretically analyzes the causes and inducing factors of the LNG stratification and rollover phenomenon in the storage tank of coastal engineering. The computational fluid dynamics was used to establish a numerical model for the heat and mass transfer of LNG multicomponent materials in the imaginary layered interface of the storage tank, and the evolution process of LNG from spontaneous stratification to rollover was simulated. The accuracy of the mathematical model is verified by comparing numerical results with experimental data from open literature. The effects of the density difference between upper and lower layers, layering parameters, heat leakage parameters, and the baffles structure on the rollover process were studied. The effects of the interfacial surface variations are not included in this study. The results show that different baffle structures will form different boundary velocity fields, which will only affect the severity of the rollover, not the occurrence time. The larger the layering density difference, the earlier the rollover occurs. Under current conditions, the baffle structure that has the best suppression of rollover and the minimum boundary velocity is at 0.5 m above the stratified interface with the installation of the baffle at 5 degrees. Full article
(This article belongs to the Section Coastal Engineering)
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Open AccessArticle
Hydrodynamic Efficiency of a Wave Energy Converter in Front of an Orthogonal Breakwater
J. Mar. Sci. Eng. 2021, 9(1), 94; https://0-doi-org.brum.beds.ac.uk/10.3390/jmse9010094 - 17 Jan 2021
Viewed by 285
Abstract
In the present study, the hydrodynamic efficiency of a cylindrical wave energy converter (WEC) of vertical symmetry axis and arranged in front of a reflecting orthogonal breakwater is explored. The idea is based on exploiting the anticipated amplification of the scattered and the [...] Read more.
In the present study, the hydrodynamic efficiency of a cylindrical wave energy converter (WEC) of vertical symmetry axis and arranged in front of a reflecting orthogonal breakwater is explored. The idea is based on exploiting the anticipated amplification of the scattered and the reflected wave fields originating from the presence of the vertical walls, towards increasing the WEC’s wave power absorption due to the walls’ wave reflections. Two types of converters are examined, namely the heaving device and the oscillating water column (OWC) device, assuming linear potential theory. The associated diffraction-, motion-, and pressure-radiation problems are solved using axisymmetric eigenfunction expansions for the velocity potential around the WECs by properly accounting for the wave field’s modification due to the walls’ presence. To this end, a theoretical formulation dealing with the evaluation of the converter’s performance is presented accounting for the coupling between the WEC and the reflecting vertical walls. The results depict that the amount of the harvested wave power by the WEC in front of an orthogonal wall is amplified compared to the absorbed wave power by the same WEC in the open sea. Full article
(This article belongs to the Special Issue Breakwater Behaviour)
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Open AccessEditor’s ChoiceArticle
Analysis and Trends of Global Research on Nautical, Maritime and Marine Tourism
J. Mar. Sci. Eng. 2021, 9(1), 93; https://0-doi-org.brum.beds.ac.uk/10.3390/jmse9010093 - 17 Jan 2021
Viewed by 324
Abstract
Tourism related to the sea and boating activities is becoming increasingly popular and revolves around a range of leisure, water sports, nautical or other maritime activities. This article studies the main scientific contributions in this area, bearing in mind the complexity of finding [...] Read more.
Tourism related to the sea and boating activities is becoming increasingly popular and revolves around a range of leisure, water sports, nautical or other maritime activities. This article studies the main scientific contributions in this area, bearing in mind the complexity of finding a suitable definition of this concept. Hence, the aim of this paper is to analyze the scientific production from 1986 to 2020 in impact journals of the terms “nautical tourism”, “maritime tourism” and “marine tourism” considering the following variables: number of documents, number of articles, period being studied, Hirsch citations and index. The results show an increasing trend in terms of both the number of published articles and citations publications from 2007 onwards and the review of the literature raises the need to define a new concept: “blue tourism”. Future trends in research include terms such as tourist ports, quality of websites and blue economy. Full article
(This article belongs to the Section Ocean Engineering)
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Open AccessCommunication
New Marine Geoheritage from the Russian Altai
J. Mar. Sci. Eng. 2021, 9(1), 92; https://0-doi-org.brum.beds.ac.uk/10.3390/jmse9010092 - 16 Jan 2021
Viewed by 283
Abstract
Marine geoheritage comprises unique geological features of modern and ancient seas and oceans. The Russian Altai (southern Siberia) is a vast and geologically rich area, which was covered by a marginal sea of the Panthalassa Ocean in the Devonian. New geosites representing shallow- [...] Read more.
Marine geoheritage comprises unique geological features of modern and ancient seas and oceans. The Russian Altai (southern Siberia) is a vast and geologically rich area, which was covered by a marginal sea of the Panthalassa Ocean in the Devonian. New geosites representing shallow- and deep-marine depositional environments and palaeoecosystems of submarine volcano slopes are proposed, namely, Melnichnye Sopki and Zavodskie Sopki. They are located near the town of Zmeinogorsk (Altai Region of the Russian Federation). These pieces of marine geoheritage are valuable on an international scale. Special geoconservation procedures are recommended to manage the proposed geosites efficiently. They can be included in a geopark, which is reasonable to create due to the concentration of geological and mining heritage in the study area. Full article
(This article belongs to the Section Geological Oceanography)
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Open AccessFeature PaperArticle
Modeling Dynamic Processes of Mondego Estuary and Óbidos Lagoon Using Delft3D
J. Mar. Sci. Eng. 2021, 9(1), 91; https://0-doi-org.brum.beds.ac.uk/10.3390/jmse9010091 - 15 Jan 2021
Viewed by 397
Abstract
Estuarine systems currently face increasing pressure due to population growth, rapid economic development, and the effect of climate change, which threatens the deterioration of their water quality. This study uses an open-source model of high transferability (Delft3D), to investigate the physics and water [...] Read more.
Estuarine systems currently face increasing pressure due to population growth, rapid economic development, and the effect of climate change, which threatens the deterioration of their water quality. This study uses an open-source model of high transferability (Delft3D), to investigate the physics and water quality dynamics, spatial variability, and interrelation of two estuarine systems of the Portuguese west coast: Mondego Estuary and Óbidos Lagoon. In this context, the Delft3D was successfully implemented and validated for both systems through model-observation comparisons and further explored using realistically forced and process-oriented experiments. Model results show (1) high accuracy to predict the local hydrodynamics and fair accuracy to predict the transport and water quality of both systems; (2) the importance of the local geomorphology and estuary dimensions in the tidal propagation and asymmetry; (3) Mondego Estuary (except for the south arm) has a higher water volume exchange with the adjacent ocean when compared to Óbidos Lagoon, resulting from the highest fluvial discharge that contributes to a better water renewal; (4) the dissolved oxygen (DO) varies with water temperature and salinity differently for both systems. On the one hand, for Mondego Estuary during winter the DO levels mainly fluctuate with salinity. On the other hand, for Óbidos Lagoon, DO distribution is determined by both water temperature and salinity. During summer, the high residence time and water temperature limit the DO levels in both systems. The high transferability and superior stability of Delft3D make this model a foundation for realistic simulation and research of distinct estuarine systems, giving support to their maintenance and restoration. Full article
(This article belongs to the Section Physical Oceanography)
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Open AccessArticle
Study on Reactive Power Compensation Strategies for Long Distance Submarine Cables Considering Electrothermal Coordination
J. Mar. Sci. Eng. 2021, 9(1), 90; https://0-doi-org.brum.beds.ac.uk/10.3390/jmse9010090 - 15 Jan 2021
Viewed by 307
Abstract
Long-distance high voltage alternating current (AC) submarine cables are widely used to connect offshore wind farms and land power grids. However, the transmission capacity of the submarine cable is limited by the capacitive charging current. This paper analyzes the impacts of reactive power [...] Read more.
Long-distance high voltage alternating current (AC) submarine cables are widely used to connect offshore wind farms and land power grids. However, the transmission capacity of the submarine cable is limited by the capacitive charging current. This paper analyzes the impacts of reactive power compensation in different positions on the current distribution on long-distance submarine cable transmission lines, and tests the rationality of the existing reactive power compensation schemes based on electrothermal coordination (ETC). Research shows that compensation at the sending end has obvious impacts on current distribution along the cable, and the maximum current occurs at the sending or receiving end. Moreover, the reactive power compensation at sending end will reduce the current at receiving end of the line. On the contrary, it will increase the current at sending end. Compared with the directly buried laying method of the submarine cable in the landing section, the cable trench laying method can increase the cable ampacity of the landing section and reduce the reactive power compensation capacity at the sending end. The ampacity is the current representation of the thermal limits of the cable. ETC exploits the cable ampacity to coordinate current distribution on transmission lines under existing reactive power compensation schemes, thus optimizing the reactive power compensation schemes and avoiding the bottleneck point of cable ampacity. Full article
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Open AccessArticle
L2-Gain Based Adaptive Robust Heel/Roll Reduction Control Using Fin Stabilizer during Ship Turns
J. Mar. Sci. Eng. 2021, 9(1), 89; https://0-doi-org.brum.beds.ac.uk/10.3390/jmse9010089 - 15 Jan 2021
Viewed by 256
Abstract
The rolling and heeling experienced by a ship during turning will be more severe under the interference of winds and waves, which will seriously affect the navigation safety of the ship. The fin stabilizer is currently the best active anti-rolling device, which is [...] Read more.
The rolling and heeling experienced by a ship during turning will be more severe under the interference of winds and waves, which will seriously affect the navigation safety of the ship. The fin stabilizer is currently the best active anti-rolling device, which is usually used to reduce the roll of the ship during straight-line sailing. The purpose of this work is to study the use of fin stabilizers to reduce the rolling and heeling during ship turning, considering the non-linearity and uncertainty during the rotation. The 4 degrees of freedom (4-DOF) nonlinear motion model of a multi-purpose naval vessel is established. The forces and moments produced by fin stabilizers, rudders, propellers, and waves are also considered. The nonlinear control model of rotation and roll is derived and established. Given the non-linearity and uncertainty in the ship turning process, an L2-gain based robust adaptive control is proposed to control the fin stabilizers to reduce the turning heel and roll motion. The proof of the stability and the detailed design process of the controller are also given. Simulations are carried out to verify the effectiveness of the proposed control strategy. For comparison purposes, the simulation results under a well-tuned PID controller are also given. The simulation results show that the developed control strategy can effectively reduce the heel and roll during ship turns, and it has good robustness against uncertainty and internal and external interference. Full article
(This article belongs to the Special Issue Automatic Control and Routing of Marine Vessels)
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Open AccessFeature PaperArticle
On the Tidal Prism: The Roles of Basin Extension, Bottom Friction and Inlet Cross-Section
J. Mar. Sci. Eng. 2021, 9(1), 88; https://0-doi-org.brum.beds.ac.uk/10.3390/jmse9010088 - 15 Jan 2021
Viewed by 298
Abstract
The prism of the Lignano tidal inlet was approximately constant over the last forty years, although the section width has halved. This has led to questions concerning the factors that most influence the tidal prism, and on the applicability of the well-known A–P [...] Read more.
The prism of the Lignano tidal inlet was approximately constant over the last forty years, although the section width has halved. This has led to questions concerning the factors that most influence the tidal prism, and on the applicability of the well-known A–P relationship. A conceptual scheme of the sea–channel–lagoon system has been used to perform a sensitivity analysis of different parameters that characterize both the basin and the inlet cross-section. A 2D hydrodynamic model has been applied to evaluate the prism and compare it to the one derived by a static method, which is the basis of the analytical derivation of the A–P linkage. Three regimes have been found in the prism variability as a function of the basin extension: a linear static regime between prism and basin area; an asymptotic regime in which the prism depends only on the basin bottom friction; and an intermediate one. In addition, the roles of the inlet and channel sizes on the prism value have been investigated. The results, compared to the empirical relationships between the prism and the inlet cross-section, show that a variation in the cross-sectional area does not always corresponds to a change in tidal prism. Full article
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Open AccessArticle
Hydrodynamic Analysis and Motions of Ship with Forward Speed via a Three-Dimensional Time-Domain Panel Method
J. Mar. Sci. Eng. 2021, 9(1), 87; https://0-doi-org.brum.beds.ac.uk/10.3390/jmse9010087 - 15 Jan 2021
Viewed by 265
Abstract
A new three-dimensional (3D) time-domain panel method is developed to solve the ship hydrodynamic problem and motions. For an advancing ship with a constant forward speed in regular waves, the ship’s hull can be discretized and processed into a number of quadrilateral panels. [...] Read more.
A new three-dimensional (3D) time-domain panel method is developed to solve the ship hydrodynamic problem and motions. For an advancing ship with a constant forward speed in regular waves, the ship’s hull can be discretized and processed into a number of quadrilateral panels. Based on Green’s theorem, an analytical expression for Froude–Krylov (F–K) forces evaluation on the quadrilateral panels is derived without accuracy loss. Within the linear potential theory, the transient free surface Green function (TFSGF) is applied to solve the boundary value problem. To improve the efficiency and numerical stability of TFSGF evaluation, a precise integration method with variable parameters setting for extended identity matrix is developed to compute the TFSGF in the computation domain. Then, radiation and diffraction forces can be evaluated by means of the impulse response function method. The Wigley I hull form is taken as a study case, and the computed hydrodynamic coefficients, wave exciting forces, and motions by the present method are compared with previous literature experimental data and prior published results. It manifests that the three-dimensional time-domain panel method proposed in this paper has good accuracy. Full article
(This article belongs to the Section Ocean Engineering)
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Open AccessArticle
Simulating Destructive and Constructive Morphodynamic Processes in Steep Beaches
J. Mar. Sci. Eng. 2021, 9(1), 86; https://0-doi-org.brum.beds.ac.uk/10.3390/jmse9010086 - 15 Jan 2021
Viewed by 720
Abstract
Short-term beach morphodynamics are typically modelled solely through storm-induced erosion, disregarding post-storm recovery. Yet, the full cycle of beach profile response is critical to simulating and understanding morphodynamics over longer temporal scales. The XBeach model is calibrated using topographic profiles from a reflective [...] Read more.
Short-term beach morphodynamics are typically modelled solely through storm-induced erosion, disregarding post-storm recovery. Yet, the full cycle of beach profile response is critical to simulating and understanding morphodynamics over longer temporal scales. The XBeach model is calibrated using topographic profiles from a reflective beach (Faro Beach, in S. Portugal) during and after the incidence of a fierce storm (Emma) that impacted the area in early 2018. Recovery in all three profiles showed rapid steepening of the beachface and significant recovery of eroded volumes (68–92%) within 45 days after the storm, while berm heights reached 4.5–5 m. Two calibration parameters were used (facua and bermslope), considering two sets of values, one for erosive (Hm0 ≥ 3 m) and one for accretive (Hm0 < 3 m) conditions. A correction of the runup height underestimation by the model in surfbeat mode was necessary to reproduce the measured berm elevation and morphology during recovery. Simulated profiles effectively capture storm erosion, but also berm growth and gradual recovery of the profiles, showing good skill in all three profiles and recovery phases. These experiments will be the basis to formulate event-scale simulations using schematized wave forcing that will allow to calibrate the model for longer-term changes. Full article
(This article belongs to the Special Issue Monitoring and Modelling of Coastal Environment)
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Open AccessArticle
Preventive Maintenance of a k-out-of-n System with Applications in Subsea Pipeline Monitoring
J. Mar. Sci. Eng. 2021, 9(1), 85; https://0-doi-org.brum.beds.ac.uk/10.3390/jmse9010085 - 15 Jan 2021
Viewed by 340
Abstract
Environmental safety issues are of particular importance when we design and operate underwater transport systems. To ensure the transport systems function safely, special systems to monitor their condition are being created. Underwater pipeline monitoring systems should continuously operate to detect and prevent emergency [...] Read more.
Environmental safety issues are of particular importance when we design and operate underwater transport systems. To ensure the transport systems function safely, special systems to monitor their condition are being created. Underwater pipeline monitoring systems should continuously operate to detect and prevent emergency and pre-emergency situations in a timely manner. The purpose of this article is to demonstrate the possibility of using a mathematical model of a k-out-of-n system to support decision-making in the preventive maintenance of an unmanned underwater vehicle to monitor the condition of a subsea pipeline. The novelty and feature of this study are that we investigate a strategy of preventive maintenance for a model of a k-out-of-n system, where failures depend not only on the number but also on the location of the failed components in the system. The method to solve this problem, based on the distribution of the members of the variational series of the failing components, is also new. Since the distributions of the system component lifetimes are usually known with an accuracy of only one or two moments, we paid special attention to how sensitive the decision making about preventive maintenance is to the shape of the distributions. Numerical examples are conducted in order to support the theoretical investigations of the paper. The results of the study are applied to specific equipment to monitor the state of the outer surface of the pipeline. Full article
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Open AccessEditorial
Storm Tide and Wave Simulations and Assessment
J. Mar. Sci. Eng. 2021, 9(1), 84; https://0-doi-org.brum.beds.ac.uk/10.3390/jmse9010084 - 14 Jan 2021
Viewed by 356
Abstract
Storm tides, surges, and waves associated with typhoons/tropical cyclones/hurricanes are among the most severe threats to coastal zones, nearshore waters, and navigational safety [...] Full article
(This article belongs to the Special Issue Storm Tide and Wave Simulations and Assessment)
Open AccessArticle
A Comparative Study of Computational Methods for Wave-Induced Motions and Loads
J. Mar. Sci. Eng. 2021, 9(1), 83; https://0-doi-org.brum.beds.ac.uk/10.3390/jmse9010083 - 14 Jan 2021
Cited by 1 | Viewed by 359
Abstract
Ship hull structural damages are often caused by extreme wave-induced loads. Reliable load predictions are required to minimize the risk of structural failures. One conceivable approach relies on direct computations of extreme events with appropriate numerical methods. In this perspective, we present a [...] Read more.
Ship hull structural damages are often caused by extreme wave-induced loads. Reliable load predictions are required to minimize the risk of structural failures. One conceivable approach relies on direct computations of extreme events with appropriate numerical methods. In this perspective, we present a systematic study comparing results obtained with different computational methods for wave-induced loads and motions of different ship types in regular and random irregular long-crested extremes waves. Significant wave heights between 10.5 and 12.5 m were analyzed. The numerical methods differ in complexity and are based on strip theory, boundary element methods (BEM) and unsteady Reynolds-Averaged Navier–Stokes (URANS) equations. In advance to the comparative study, the codes applied have been enhanced by different researchers to account for relevant nonlinearities related to wave excitations and corresponding ship responses in extreme waves. The sea states investigated were identified based on the Coefficient of Contribution (CoC) method. Computed time histories, response amplitude operators and short-term statistics of ship responses and wave elevation were systematically compared against experimental data. While the results of the numerical methods, based on potential theory, in small and moderate waves agreed favorably with the experiments, they deviated considerably from the measurements in higher waves. The URANS-based predictions compared fairly well to experimental measurements with the drawback of significantly higher computation times. Full article
(This article belongs to the Special Issue Ship Dynamics for Performance Based Design and Risk Averse Operations)
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Open AccessArticle
Experimental Assessment of a Conducting Polymer (PEDOT) and Microbial Biofilms as Deterrents and Facilitators of Macro-Biofouling: Larval Settlement of the Barnacle Notobalanus flosculus (Darwin, 1854) from Central Chile
J. Mar. Sci. Eng. 2021, 9(1), 82; https://0-doi-org.brum.beds.ac.uk/10.3390/jmse9010082 - 14 Jan 2021
Viewed by 283
Abstract
Maritime enterprises have long sought solutions to reduce the negative consequences of the settlement and growth of marine biofouling (micro- and macro-organisms) on virtually all surfaces and materials deployed at sea. The development of biofouling control strategies requires solutions that are cost-effective and [...] Read more.
Maritime enterprises have long sought solutions to reduce the negative consequences of the settlement and growth of marine biofouling (micro- and macro-organisms) on virtually all surfaces and materials deployed at sea. The development of biofouling control strategies requires solutions that are cost-effective and environmentally friendly. Polymer-based coatings, such as the poly (3,4-ethylenedioxythiophene) (PEDOT) and its potential applications, have blossomed over the last decade thanks to their low cost, nontoxicity, and high versatility. Here, using multiple-choice larval settlement experiments, we assessed the efficacy of PEDOT against the balanoid barnacle Notobalanus flosculus one of the most common biofouling species in Southeastern Pacific shores, and compared results against a commercially available antifouling (AF) coating, and biofilms at different stages of succession (1, 2, 4 and 8 weeks). We show that larval settlement on PEDOT-coated surfaces was similar to the settlement on AF-coated surfaces, while larvae settled abundantly on roughened acrylic and on early-to-intermediate stages of biofilm (one to four weeks old). These results are promising and suggest that PEDOT is a good candidate for fouling-resistant coating for specific applications at sea. Further studies to improve our understanding of the mechanisms of barnacle larval deterrence, as well as exposure to field conditions, are encouraged. Full article
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Open AccessArticle
Study on the Rheological Behavior of a Model Clay Sediment
J. Mar. Sci. Eng. 2021, 9(1), 81; https://0-doi-org.brum.beds.ac.uk/10.3390/jmse9010081 - 14 Jan 2021
Viewed by 325
Abstract
Clay sediments are the main component of seabed sediment. Interactions between the nano-sized, disk-shaped and charged clay particles are complicated, as they control the sediment’s rheology. In this study, we studied the rheological behavior of the clay sediment modeled by laponite and bentonite [...] Read more.
Clay sediments are the main component of seabed sediment. Interactions between the nano-sized, disk-shaped and charged clay particles are complicated, as they control the sediment’s rheology. In this study, we studied the rheological behavior of the clay sediment modeled by laponite and bentonite suspensions experimentally using a rotational rheometer. The yield stress decreased when water content increased. Meanwhile, the yield stress of the laponite suspension first increased and then decreased with increasing salinity. It is considered that the face-to-face repulsive electrostatic interaction between clay platelets dominated the yield behavior. A yield stress model was developed to describe the change of the yield stress with both the water content and the salinity. When the system started to flow, the viscosity decreased with increasing shear. A master curve of viscosity is was from the viscosity-stress curves at different water contents if the applied shear stress was normalized by the yield stress and the viscosity normalized by a characteristic viscosity. This study provides a preliminary understanding of the clay sediment rheology and its mechanism for the investigation on the flowing of the sediment systems with strong interparticle interaction. Full article
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Open AccessArticle
Improvement of the Welding Process for Fillet Air Test for the Biggest Taiwan Shipyard
J. Mar. Sci. Eng. 2021, 9(1), 80; https://0-doi-org.brum.beds.ac.uk/10.3390/jmse9010080 - 13 Jan 2021
Viewed by 301
Abstract
During ship block construction, watertight bulkheads weld of every cabin of ships need to undergo stress testing according to the tanks’ test plan. Every incomplete bulkhead cannot be sprayed in order to protect them after sandblasting; this seriously affects the process of construction. [...] Read more.
During ship block construction, watertight bulkheads weld of every cabin of ships need to undergo stress testing according to the tanks’ test plan. Every incomplete bulkhead cannot be sprayed in order to protect them after sandblasting; this seriously affects the process of construction. Therefore, the issue of this study is to maintain the integrity of the painting quality and reduce the destruction of the paint, ship-building personnel seek how best to complete the block operation. The aim of this project is to improve the recent watertight bulkheads fillet air test operations in the construction stage using TRIZ (theory of inventive problem solving), promote the ground painting session integrity of every ship, improve the tanks’ test plan in the dock, and reduce the time spent on dismantling operations and the painting operation. Through the TRIZ, this study proposed lots of improvements, some of which are: the watertight cabins can finish the tanks test plan completely, and the integrity of the ground painting can be promoted to reduce the range of cabin test in the dock and reduce watertight bulkheads’ dismantling time. Moreover, because of the considerate reduction of the destruction of the coating, the painting operation is of good quality. The results demonstrate that the TRIZ successfully controls the production quality during construction, reduces working time, and promotes full efficiency. This study saved more than US$1 million of the outsourcing fee. Full article
(This article belongs to the Special Issue Advances in Marine Structures)
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Open AccessArticle
ROV Navigation in a Fish Cage with Laser-Camera Triangulation
J. Mar. Sci. Eng. 2021, 9(1), 79; https://0-doi-org.brum.beds.ac.uk/10.3390/jmse9010079 - 13 Jan 2021
Viewed by 395
Abstract
Aquaculture net cage inspection and maintenance is a central issue in fish farming. Inspection using autonomous underwater vehicles is a promising solution. This paper proposes laser-camera triangulation for pose estimation to enable autonomous net following for an autonomous vehicle. The laser triangulation 3D [...] Read more.
Aquaculture net cage inspection and maintenance is a central issue in fish farming. Inspection using autonomous underwater vehicles is a promising solution. This paper proposes laser-camera triangulation for pose estimation to enable autonomous net following for an autonomous vehicle. The laser triangulation 3D data is experimentally compared to a doppler velocity log (DVL) in an active fish farm. We show that our system is comparable in performance to a DVL for distance and angular pose measurements. Laser triangulation is promising as a short distance ranging sensor for autonomous vehicles at a low cost compared to acoustic sensors. Full article
(This article belongs to the Special Issue Localization, Mapping and SLAM in Marine and Underwater Environments)
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Open AccessFeature PaperArticle
Acoustic Presence of Dolphins through Whistles Detection in Mediterranean Shallow Waters
J. Mar. Sci. Eng. 2021, 9(1), 78; https://0-doi-org.brum.beds.ac.uk/10.3390/jmse9010078 - 13 Jan 2021
Viewed by 368
Abstract
The evaluation of acoustic temporal rhythms in wide-ranging cetaceans can reveal patterns in animal spatial presence and the occurrence of periodical phenomena. Here, we aimed at assessing the temporal patterns of dolphin’s acoustic presence in a shallow-water area in the Sicily Strait (Mediterranean [...] Read more.
The evaluation of acoustic temporal rhythms in wide-ranging cetaceans can reveal patterns in animal spatial presence and the occurrence of periodical phenomena. Here, we aimed at assessing the temporal patterns of dolphin’s acoustic presence in a shallow-water area in the Sicily Strait (Mediterranean Sea). Whistles were collected continuously for 14 months from an acoustic monitoring station installed aboard of an elastic seamark. Over a total of 6955 h of recording, 14,048 signals were identified using both automatic and visual methods. Three parameters were analyzed: hourly presence (HP), used as a proxy of the presence of dolphins in the area; detection rate (DR), indicating the acoustic activity rate of dolphins measured per hour in the entire dataset; and detection rate in presence of dolphins (DRD), indicating the acoustic activity rate of dolphins considering only the hours when whistles were recorded. The highest values of both HP and DR were reached during the night, and the Autumn and Winter months, suggesting an increase in the dolphin’s occurrence and a possible moving away and towards the monitoring station potentially following prey. DRD, instead, showed an almost uniform distribution throughout the day implying that when the animals are close to the monitoring station, the acoustic activity does not show any pattern. However, possible changes in the communication exchange along the seasons were suggested. This study complements other work on this subject, improving the knowledge of dolphins’ acoustic activity in the area. Full article
(This article belongs to the Special Issue Passive Acoustics to Study Marine and Freshwater Ecosystems)
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Open AccessArticle
Radioactivity Monitoring at North Aegean Sea Integrating In-Situ Sensor in an Ocean Observing Platform
J. Mar. Sci. Eng. 2021, 9(1), 77; https://0-doi-org.brum.beds.ac.uk/10.3390/jmse9010077 - 13 Jan 2021
Viewed by 292
Abstract
The integration of the radioactivity spectrometer KATERINA II in a fixed station (buoy) of the POSEIDON network at the North Aegean Sea within the framework of MARRE Project is presented. The acquisition period lasted from 20 November 2019 till 22 February 2020. An [...] Read more.
The integration of the radioactivity spectrometer KATERINA II in a fixed station (buoy) of the POSEIDON network at the North Aegean Sea within the framework of MARRE Project is presented. The acquisition period lasted from 20 November 2019 till 22 February 2020. An intense increment of the activity concentration of radon progenies (up to an order of magnitude) was recorded during rainfall. More specifically, the 214Bi activity concentration varied from 0.09 to 0.53 Bq L−1 without rainfall and the 214Pb activity concentration varied from 0.14 to 0.81 Bq L−1. The 214Bi activity concentration during rainfall ranged from 0.4 to 5.4 Bq L−1 and of 214Pb from 0.3 to 5.3 Bq L−1. The minimum detectable activity of the KATERINA II detection system for measuring low level activities of 137Cs is optimized applying background subtraction and the full spectrum analysis technique. Full article
(This article belongs to the Special Issue Application of Coastal/Ocean Sensors and Systems)
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Open AccessArticle
Development and Validation of Quasi-Eulerian Mean Three-Dimensional Equations of Motion Using the Generalized Lagrangian Mean Method
J. Mar. Sci. Eng. 2021, 9(1), 76; https://0-doi-org.brum.beds.ac.uk/10.3390/jmse9010076 - 13 Jan 2021
Viewed by 579
Abstract
This study aims at developing a new set of equations of mean motion in the presence of surface waves, which is practically applicable from deep water to the coastal zone, estuaries, and outflow areas. The generalized Lagrangian mean (GLM) method is employed to [...] Read more.
This study aims at developing a new set of equations of mean motion in the presence of surface waves, which is practically applicable from deep water to the coastal zone, estuaries, and outflow areas. The generalized Lagrangian mean (GLM) method is employed to derive a set of quasi-Eulerian mean three-dimensional equations of motion, where effects of the waves are included through source terms. The obtained equations are expressed to the second-order of wave amplitude. Whereas the classical Eulerian-mean equations of motion are only applicable below the wave trough, the new equations are valid until the mean water surface even in the presence of finite-amplitude surface waves. A two-dimensional numerical model (2DV model) is developed to validate the new set of equations of motion. The 2DV model passes the test of steady monochromatic waves propagating over a slope without dissipation (adiabatic condition). This is a primary test for equations of mean motion with a known analytical solution. In addition to this, experimental data for the interaction between random waves and a mean current in both non-breaking and breaking waves are employed to validate the 2DV model. As shown by this successful implementation and validation, the implementation of these equations in any 3D model code is straightforward and may be expected to provide consistent results from deep water to the surf zone, under both weak and strong ambient currents. Full article
(This article belongs to the Section Ocean Engineering)
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Open AccessArticle
Verification and Validation of CFD Based Form Factors as a Combined CFD/EFD Method
J. Mar. Sci. Eng. 2021, 9(1), 75; https://0-doi-org.brum.beds.ac.uk/10.3390/jmse9010075 - 13 Jan 2021
Viewed by 366
Abstract
Predicting the propulsive power of ships with high accuracy still remains a challenge. Well established practices in the 1978 ITTC Power Prediction method have been questioned such as the form factor approach and its determination method. This paper investigates the possibility to improve [...] Read more.
Predicting the propulsive power of ships with high accuracy still remains a challenge. Well established practices in the 1978 ITTC Power Prediction method have been questioned such as the form factor approach and its determination method. This paper investigates the possibility to improve the power predictions by the introduction of a combined CFD/EFD Method where the experimental determination of form factor is replaced by double body RANS computations. Following the Quality Assurance Procedure proposed by ITTC, a best practice guideline has been derived for the CFD based form factor determination method by applying systematic variations to the CFD set-ups. Following the verification and validation of the CFD based form factor method in model scale, the full scale speed-power-rpm relations between large number of speed trials and full scale predictions using the CFD based form factors in combination with ITTC-57 line and numerical friction lines are investigated. It is observed that the usage of CFD based form factors improves the predictions in general and no deterioration is noted within the limits of this study. Therefore, the combination of EFD and CFD is expected to provide immediate improvements to the 1978 ITTC Performance Prediction Method. Full article
(This article belongs to the Special Issue CFD Simulations of Marine Hydrodynamics)
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Open AccessArticle
Social, Economic and Environmental Sustainability of Port Regions: MCDM Approach in Composite Index Creation
J. Mar. Sci. Eng. 2021, 9(1), 74; https://0-doi-org.brum.beds.ac.uk/10.3390/jmse9010074 - 13 Jan 2021
Viewed by 279
Abstract
Maritime transport and ports are among the most important linkages between global economies, handling more than 90% of internationally traded goods. Economic importance of maritime transport imposes significant implications on the social and environmental performance of port regions. The paper aims to create [...] Read more.
Maritime transport and ports are among the most important linkages between global economies, handling more than 90% of internationally traded goods. Economic importance of maritime transport imposes significant implications on the social and environmental performance of port regions. The paper aims to create composite indices as relevant, scientific-based tools used in comparing and monitoring various aspects of sustainability across 37 sea port regions in seven countries on the European side of the Mediterranean, covering a five-year period from 2014 to 2018. The model encompasses Eurostat and OECD annual NUTS2 level data covering economic, social and environmental dimensions of sustainability. Two important indicators of maritime transport activity, maritime transport of freight and maritime transport of passengers, are included within the group of economic indicators. To create composite indices, the multicriteria decision making (MCDM) framework was used as an integrated approach of entropy in the weighting segment, and the Preference Ranking Organization METHod for Enrichment of Evaluations (PROMETHEE) as an aggregation method. The results highlight GDP per capita and population density as indicators of the greatest relative importance when it comes to port regions sustainability. The ranking results indicate that, despite the fact that Attica is the best ranked region in terms of overall sustainability, the largest number of top rated port regions are in Italy, Spain and France. Full article
(This article belongs to the Special Issue Maritime Transport and Its Impact on Regional Economic Development)
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Open AccessArticle
An Ecological Risk Assessment of Sediments in a Developing Environment—Batticaloa Lagoon, Sri Lanka
J. Mar. Sci. Eng. 2021, 9(1), 73; https://0-doi-org.brum.beds.ac.uk/10.3390/jmse9010073 - 13 Jan 2021
Viewed by 384
Abstract
The land-sea interface is considered as a threatening environment due to anthropogenic development activities. Unplanned developments can cause effects on important ecosystems, water and human health as well. In this study, the influence of rapid regional development on the accumulation of trace elements [...] Read more.
The land-sea interface is considered as a threatening environment due to anthropogenic development activities. Unplanned developments can cause effects on important ecosystems, water and human health as well. In this study, the influence of rapid regional development on the accumulation of trace elements to the sediments of an important ecosystem, Batticaloa lagoon, Sri Lanka was examined. Surface sediment pollution status and ecological risk was compared with that of the recent sedimentary history of about 1 m depth. Sediment core samples were collected and analyzed for grain size, organic matter and carbonate contents and trace elements (As, Pb, Zn, Cu, Ni and Cr) by the X-Ray Fluorescence (XRF) technique. The chemical results of core samples and recently published data of surface sediments of the same project were evaluated by pollution load index (PLI), potential ecological risk index (PERI) and sediment quality guidelines (SQG). Except for Cr, all other elements in cores show lower concentrations than the SQGs confirming the high Cr contents as recorded in the most of other Sri Lankan sediments. The sediment cores indicate an unpolluted, low ecological risk sedimentary history for all core sampling locations, whereas most of the surface sediments of the lagoon are less polluted with low potential ecological risk. Present anthropogenic practices and illiteracy of this rapid developing region can damage the green environment and hence environmental management planning is suggested for a sustainable future. Full article
(This article belongs to the Special Issue Coastal Lagoon Ecology)
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Open AccessReview
Coastal Sensitivity/Vulnerability Characterization and Adaptation Strategies: A Review
J. Mar. Sci. Eng. 2021, 9(1), 72; https://0-doi-org.brum.beds.ac.uk/10.3390/jmse9010072 - 12 Jan 2021
Cited by 1 | Viewed by 398
Abstract
Coastal area constitutes a vulnerable environment and requires special attention to preserve ecosystems and human activities therein. To this aim, many studies have been devoted both in past and recent years to analyzing the main factors affecting coastal vulnerability and susceptibility. Among the [...] Read more.
Coastal area constitutes a vulnerable environment and requires special attention to preserve ecosystems and human activities therein. To this aim, many studies have been devoted both in past and recent years to analyzing the main factors affecting coastal vulnerability and susceptibility. Among the most used approaches, the Coastal Vulnerability Index (CVI) accounts for all relevant variables that characterize the coastal environment dealing with: (i) forcing actions (waves, tidal range, sea-level rise, etc.), (ii) morphological characteristics (geomorphology, foreshore slope, dune features, etc.), (iii) socio-economic, ecological and cultural aspects (tourism activities, natural habitats, etc.). Each variable is evaluated at each portion of the investigated coast, and associated with a vulnerability level which usually ranges from 1 (very low vulnerability), to 5 (very high vulnerability). Following a susceptibility/vulnerability analysis of a coastal stretch, specific strategies must be chosen and implemented to favor coastal resilience and adaptation, spanning from hard solutions (e.g., groins, breakwaters, etc.) to soft solutions (e.g., beach and dune nourishment projects), to the relocation option and the establishment of accommodation strategies (e.g., emergency preparedness). Full article
(This article belongs to the Special Issue Feature Reviews in Marine Science and Engineering)
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