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J. Mar. Sci. Eng., Volume 7, Issue 9 (September 2019)

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Cover Story (view full-size image) Short text: Cnidarians are one of the most problematical groups in marine finfish aquaculture, [...] Read more.
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Open AccessArticle
Inter-Annual Variability of the Seawater Light Absorption in Surface Layer of the Northeastern Black Sea in Connection with Hydrometeorological Factors
J. Mar. Sci. Eng. 2019, 7(9), 326; https://doi.org/10.3390/jmse7090326 - 19 Sep 2019
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Abstract
Data on the light absorption by seawater and its components are needed in many theoretical and practical aspects of marine science and engineering. However, up to now, there is a lack of such data for the northeastern part of the Black Sea. This [...] Read more.
Data on the light absorption by seawater and its components are needed in many theoretical and practical aspects of marine science and engineering. However, up to now, there is a lack of such data for the northeastern part of the Black Sea. This article presents the data on light absorption measured by a portable integrated cavity absorption meter (ICAM) spectrophotometer in the Gelendzhik region of the Black Sea during field studies in June 2017 and 2018, together with other bio-optical and oceanographic data from in situ measurements and satellite observations. In 2018, the elevated values of the colored dissolved organic matter (CDOM) absorption in the surface layer were observed concurrently with high values of salinity, contradicting the idea of river runoff being the main CDOM source. The vertical profiles of salinity differed in 2017 and 2018, especially in shallow waters; in the upper layer, the salinity increased from 17.1 psu in 2017 to 17.8 psu in 2018, while the values of CDOM absorption increased from 0.10 to 0.16 m−1. The analysis of available hydrometeorological data pointed to intensive vertical mixing due to the strong wind forcing as a main factor in increasing values of both salinity and the CDOM absorption in the surface layer in 2018. Full article
(This article belongs to the Section Physical Oceanography)
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Open AccessArticle
Combining Numerical Simulations and Normalized Scalar Product Strategy: A New Tool for Predicting Beach Inundation
J. Mar. Sci. Eng. 2019, 7(9), 325; https://doi.org/10.3390/jmse7090325 - 19 Sep 2019
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Abstract
The skills of the Normalized Scalar Product (NSP) strategy, commonly used to estimate the wave field, as well as bathymetry and sea-surface current, from X-band radar images, are investigated with the aim to better understand coastal inundation during extreme events. Numerical simulations performed [...] Read more.
The skills of the Normalized Scalar Product (NSP) strategy, commonly used to estimate the wave field, as well as bathymetry and sea-surface current, from X-band radar images, are investigated with the aim to better understand coastal inundation during extreme events. Numerical simulations performed using a Nonlinear Shallow-Water Equations (NSWE) solver are run over a real-world barred beach (baseline tests). Both bathymetry and wave fields, induced by reproducing specific storm conditions, are estimated in the offshore portion of the domain exploiting the capabilities of the NSP approach. Such estimates are then used as input conditions for additional NSWE simulations aimed at propagating waves up to the coast (flood simulations). Two different wave spectra, which mimic the actual storm conditions occurring along the coast of Senigallia (Adriatic Sea, central Italy), have been simulated. The beach inundations obtained from baseline and flood tests related to both storm conditions are compared. The results confirm that good predictions can be obtained using the combined NSP–NSWE approach. Such findings demonstrate that for practical purposes, the combined use of an X-band radar and NSWE simulations provides suitable beach-inundation predictions and may represent a useful tool for public authorities dealing with the coastal environment, e.g., for hazard mapping or warning purposes. Full article
(This article belongs to the Special Issue Dynamics of the Coastal Zone)
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Open AccessArticle
A Rational Method for the Design of Sand Dike/Dune Systems at Sheltered Sites; Wadden Sea Coast of Texel, The Netherlands
J. Mar. Sci. Eng. 2019, 7(9), 324; https://doi.org/10.3390/jmse7090324 - 18 Sep 2019
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Abstract
A rational method for the design of sand dike/dune systems at sheltered sites is presented, focussing on the cross-shore dimensions of the sand dike in relation to the local wave climate, tidal regime and available sandy materials. The example case is the new [...] Read more.
A rational method for the design of sand dike/dune systems at sheltered sites is presented, focussing on the cross-shore dimensions of the sand dike in relation to the local wave climate, tidal regime and available sandy materials. The example case is the new sand dike/dune system along the south-east coast of Texel, The Netherlands. The old dike protecting the island was not sufficiently strong to withstand an extreme storm event and has been strengthened by a new sand dune/dike. Various empirical and numerical models have been used, compared and validated to determine the erosion volumes during annual conditions and extreme storm events. Potential wind-induced (aeolian) sediment transport and erosion is also studied using the modified Bagnold-equation including the effects of grain size, moisture content and vegetation. The overall design method resulted into an innovative design solution, guarantying a naturally integrated and resilient sand protection as well as optimal coastal safety. Full article
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Open AccessArticle
The Flow Noise Calculation for an Axisymmetric Body in a Complex Underwater Environment
J. Mar. Sci. Eng. 2019, 7(9), 323; https://doi.org/10.3390/jmse7090323 - 17 Sep 2019
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Abstract
The flow noise of a sonar platform is one of the main background interferences for sonar applications. This paper focuses on the flow noise of an axisymmetric body in a complex oceanic environment. Under the condition of a constant stream velocity which comes [...] Read more.
The flow noise of a sonar platform is one of the main background interferences for sonar applications. This paper focuses on the flow noise of an axisymmetric body in a complex oceanic environment. Under the condition of a constant stream velocity which comes from the axial direction, an analytical method for computing the flow noise power spectrum in the transition region of the axisymmetric body is given in detail. The flow noise power spectrum computed by the analytical method is in agreement with the numerical simulation result. Then the flow noise physical features of the axisymmetric body in different incoming stream directions and velocity states caused by the complex oceanic environment are computed and analyzed by the numerical method. The results show that as the incoming stream direction changes, the transition region will migrate and the flow noise radiation direction of the axisymmetric body will also rotate at an angle which equals the stream direction variation. The flow noise energy generated by other directional incoming streams is slightly larger than that generated by the stream coming from an axial direction. When the incoming stream velocity is time-varying, the vorticity change on the axisymmetric body surface is obviously stronger than that under a constant stream, and the generated flow noise energy is also significantly larger. In addition, it indicates that there is a significant correlation between the intensity of flow noise energy and the magnitude of flow velocity. Full article
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Open AccessFeature PaperReview
Life Cycle Assessment of Ocean Energy Technologies: A Systematic Review
J. Mar. Sci. Eng. 2019, 7(9), 322; https://doi.org/10.3390/jmse7090322 - 17 Sep 2019
Viewed by 276
Abstract
The increase of greenhouse gases (GHG) generated by the burning of fossil fuels has been recognized as one of the main causes of climate change (CC). Different countries of the world have developed new policies on national energy security directed to the use [...] Read more.
The increase of greenhouse gases (GHG) generated by the burning of fossil fuels has been recognized as one of the main causes of climate change (CC). Different countries of the world have developed new policies on national energy security directed to the use of renewable energies mainly, ocean energy being one of them. The implementation of ocean energy is increasing worldwide. However, the use of these technologies is not exempt from the generation of potential environmental impacts throughout their life cycle. In this context, life cycle assessment (LCA) is a holistic approach used to evaluate the environmental impacts of a product or system throughout its entire life cycle. LCA studies need to be conducted to foster the development of ocean energy technologies (OET) in sustainable management. In this paper, a systematic review was conducted and 18 LCA studies of OET were analyzed. Most of the LCA studies are focused on wave and tidal energy. CC is the most relevant impact category evaluated, which is generated mostly by raw material extraction, manufacturing stage and shipping operations. Finally, the critical stages of the systems evaluated were identified, together with, the opportunity areas to promote an environmental management for ocean energy developers. Full article
(This article belongs to the Special Issue The Development of Marine Energy Extraction)
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Open AccessArticle
Hydro-Acoustic and Hydrodynamic Optimization of a Marine Propeller Using Genetic Algorithm, Boundary Element Method, and FW-H Equations
J. Mar. Sci. Eng. 2019, 7(9), 321; https://doi.org/10.3390/jmse7090321 - 16 Sep 2019
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Abstract
Noise generated by ships is one of the most significant noises in seas, and the propeller has a significant impact on the noise of ships, which reducing it can significantly lower the noise of vessels. In this study, a genetic algorithm was used [...] Read more.
Noise generated by ships is one of the most significant noises in seas, and the propeller has a significant impact on the noise of ships, which reducing it can significantly lower the noise of vessels. In this study, a genetic algorithm was used to optimize the hydro-acoustic and hydrodynamic performance of propellers. The main objectives of this optimization were to reduce the propeller noise and increase its hydrodynamic efficiency. Modifying the propeller geometry is one of the most effective methods for optimizing a propeller performance. One of the numerical methods for calculating propeller noise is the Ffowcs Williams and Hawkings (FW-H) Model. A numerical code was developed by authors which solved these equations using the velocity and pressure distribution around the propeller and calculated its noise. To obtain flow quantities and to investigate the hydrodynamic performance of the propeller, a code was developed using a Boundary Element Method, the panel method. The geometry of DTMB 4119 propeller was selected for optimization, where geometric modifications included skew angle, rake angle, pitch to diameter (P/D) distribution, and chord to diameter (c/D) distribution. Finally, the results of geometric optimization were presented as Pareto optimal solutions. The results indicated that the optimum geometries had rake angles between 8.14 and 12.05 degrees and skew angles between 31.52 and 39.74 degrees. It was also observed that the increase in the chord up to a specific limit enhanced the efficiency and reduced the noise of the propeller. Full article
(This article belongs to the Special Issue Marine Propellers and Ship Propulsion)
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Open AccessArticle
Model-Based Evaluation of Hydroelectric Dam’s Impact on the Seasonal Variabilities of POC in Coastal Ocean: A Case Study of Three Gorges Project
J. Mar. Sci. Eng. 2019, 7(9), 320; https://doi.org/10.3390/jmse7090320 - 14 Sep 2019
Viewed by 280
Abstract
Particulate organic carbon (POC) plays an important role in the global carbon cycle. The POC in the Changjiang Estuary and adjacent coastal region of the East China Sea (ECS) is dominated by riverine input and marine production and is significantly influenced by the [...] Read more.
Particulate organic carbon (POC) plays an important role in the global carbon cycle. The POC in the Changjiang Estuary and adjacent coastal region of the East China Sea (ECS) is dominated by riverine input and marine production and is significantly influenced by the three gorges project (TGP). A coupled physical-biogeochemical model was used to evaluate TGP’s impact on POC. The results demonstrate that TGP regulates the area influenced by diluted water and POC through direct river and sediment discharge and affects the ecosystem. From the early to later TGP construction periods, the surface region with high-POC concentration (>40 μmol L−1) decreases by 20.5% in area and 11.5% in concentration. Meanwhile, POC in the whole water column decreases from 19.5 to 17.8 μmol L−1. By contrast, the concentrations of chlorophyll-a (Chl-a) and related nutrients increase. A three end-member mixing model based on quasi-conservative temperature and salinity is used to quantify relative contributions of different water sources to POC in our research area. We also estimate the biological POC production by the difference between the physical-biogeochemical model predicted POC and three end-member model mixing POC. The result demonstrate that under the regulation of TGP in the later period, the decrease of sediment load increases water transparency, which favors photosynthesis and oceanic biological produced POC. In addition, over 70% of the areas have C/Chl-a > 200 and high C/N ratios, which are circumstantial evidences that organic detritus and terrestrial input sources still dominate in the Changjiang Estuary and adjacent coastal ECS but are influenced by TGP’s regulation. Full article
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Open AccessEditorial
Tsunami Science and Engineering II
J. Mar. Sci. Eng. 2019, 7(9), 319; https://doi.org/10.3390/jmse7090319 - 13 Sep 2019
Viewed by 269
Abstract
Earthquake-tsunamis, including the 2004 Indian Ocean Tsunami, with approximately 227,898 casualties, and the 2011 Tōhoku Tsunami in Japan, with 18,550 people missing or dead [...] Full article
(This article belongs to the Special Issue Tsunami Science and Engineering II)
Open AccessArticle
Extracting Typhoon Disaster Information from VGI Based on Machine Learning
J. Mar. Sci. Eng. 2019, 7(9), 318; https://doi.org/10.3390/jmse7090318 - 12 Sep 2019
Viewed by 288
Abstract
The southeastern coast of China suffers many typhoon disasters every year, causing huge casualties and economic losses. In addition, collecting statistics on typhoon disaster situations is hard work for the government. At the same time, near-real-time disaster-related information can be obtained on developed [...] Read more.
The southeastern coast of China suffers many typhoon disasters every year, causing huge casualties and economic losses. In addition, collecting statistics on typhoon disaster situations is hard work for the government. At the same time, near-real-time disaster-related information can be obtained on developed social media platforms like Twitter and Weibo. Many cases have proved that citizens are able to organize themselves promptly on the spot, and begin to share disaster information when a disaster strikes, producing massive VGI (volunteered geographic information) about the disaster situation, which could be valuable for disaster response if this VGI could be exploited efficiently and properly. However, this social media information has features such as large quantity, high noise, and unofficial modes of expression that make it difficult to obtain useful information. In order to solve this problem, we first designed a new classification system based on the characteristics of social medial data like Sina Weibo data, and made a microblogging dataset of typhoon damage with according category labels. Secondly, we used this social medial dataset to train the deep learning model, and constructed a typhoon disaster mining model based on a deep learning network, which could automatically extract information about the disaster situation. The model is different from the general classification system in that it automatically selected microblogs related to disasters from a large number of microblog data, and further subdivided them into different types of disasters to facilitate subsequent emergency response and loss estimation. The advantages of the model included a wide application range, high reliability, strong pertinence and fast speed. The research results of this thesis provide a new approach to typhoon disaster assessment in the southeastern coastal areas of China, and provide the necessary information for the authoritative information acquisition channel. Full article
(This article belongs to the Special Issue Intelligent Marine Robotics Modelling, Simulation and Applications)
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Open AccessArticle
Contribution of Pumping Action of Wave-Induced Pore-Pressure Response to Development of Fluid Mud Layer
J. Mar. Sci. Eng. 2019, 7(9), 317; https://doi.org/10.3390/jmse7090317 - 12 Sep 2019
Viewed by 226
Abstract
To investigate the vertical migration response of fine sediments, the pore pressure response of the silty seabed under the action of waves was tested. Under the action of waves, there is an obvious pumping phenomenon in the sludge accumulated by pore pressure. The [...] Read more.
To investigate the vertical migration response of fine sediments, the pore pressure response of the silty seabed under the action of waves was tested. Under the action of waves, there is an obvious pumping phenomenon in the sludge accumulated by pore pressure. The excess pore water pressure caused by the waves in the seabed is unevenly distributed with respect to depth and there is an extreme value of up to 1.19 kPa. The pressure affects the liquefaction properties of the sludge. According to instantaneous-liquefaction judgment, the liquefaction of surface soil occurs, but the soil is not completely liquefied. Using theoretical calculations, the vertical source supply of floating mud development was analyzed. The pumping effect of the wave-induced excess pore pressure manifests in two aspects, as follows: (1) The centralized migration of splitting channels, which is visible to the naked eye, and (2) the general migration of fine particles between particle gaps at the mesoscopic level, which accounts for up to 22.2% of the migration of fine particles. Full article
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Open AccessArticle
Application of Sentinel-2 Multispectral Data for Habitat Mapping of Pacific Islands: Palau Republic (Micronesia, Pacific Ocean)
J. Mar. Sci. Eng. 2019, 7(9), 316; https://doi.org/10.3390/jmse7090316 - 12 Sep 2019
Viewed by 225
Abstract
Sustainable and ecosystem-based marine spatial planning is a priority of Pacific Island countries basing their economy on marine resources. The urgency of management coral reef systems and associated coastal environments, threatened by the effects of climate change, require a detailed habitat mapping of [...] Read more.
Sustainable and ecosystem-based marine spatial planning is a priority of Pacific Island countries basing their economy on marine resources. The urgency of management coral reef systems and associated coastal environments, threatened by the effects of climate change, require a detailed habitat mapping of the present status and a future monitoring of changes over time. Here, we present a remote sensing study using free available Sentinel-2 imagery for mapping at large scale the most sensible and high value habitats (corals, seagrasses, mangroves) of Palau Republic (Micronesia, Pacific Ocean), carried out without any sea truth validation. Remote sensing ‘supervised’ and ‘unsupervised’ classification methods applied to 2017 Sentinel-2 imagery with 10 m resolution together with comparisons with free ancillary data on web platform and available scientific literature were used to map mangrove, coral, and seagrass communities in the Palau Archipelago. This paper addresses the challenge of multispectral benthic mapping estimation using commercial software for preprocessing steps (ERDAS ATCOR) and for benthic classification (ENVI) on the base of satellite image analysis. The accuracy of the methods was tested comparing results with reference NOAA (National Oceanic and Atmospheric Administration, Silver Spring, MD, USA) habitat maps achieved through Ikonos and Quickbird imagery interpretation and sea-truth validations. Results showed how the proposed approach allowed an overall good classification of marine habitats, namely a good concordance of mangroves cover around Palau Archipelago with previous literature and a good identification of coastal habitats in two sites (barrier reef and coastal reef) with an accuracy of 39.8–56.8%, suitable for survey and monitoring of most sensible habitats in tropical remote islands. Full article
(This article belongs to the Special Issue Remote Sensing in Coastline Detection)
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Open AccessFeature PaperArticle
Testing A Methodology to Assess Fluctuations of Coastal Rocks Surface Temperature
J. Mar. Sci. Eng. 2019, 7(9), 315; https://doi.org/10.3390/jmse7090315 - 12 Sep 2019
Viewed by 178
Abstract
The aim of this work is testing a cheap and user-friendly methodology suitable for studying temperature fluctuations of coastal rocks’ surfaces. An infrared thermometer was used, that permits a contactless measurement of the average surface temperature of a patch around a measuring point. [...] Read more.
The aim of this work is testing a cheap and user-friendly methodology suitable for studying temperature fluctuations of coastal rocks’ surfaces. An infrared thermometer was used, that permits a contactless measurement of the average surface temperature of a patch around a measuring point. Temperature was measured in an array of selected plots every 45 min from dawn to sunset in a 20 m2 study area along the rocky coast of Calafuria (NW Italy). During the experiment daily temperature in all plots was minimum at dawn and quickly reached its peak value shortly after sun culmination; subsequently, it underwent a small-gradient decrease until sunset. In connection with temporary sun-shading and wind gusts relevant short-term rock surface temperature fluctuations were recorded. Considering mean daily temperature in each plot, it proved to be positively correlated with distance from the shoreline. As regards daily temperature range, its amplitude progressively increased moving farther from the shoreline. The measuring points located where the rock is extensively covered by barnacles experience a temperature magnification effect, possibly due to a micro-greenhouse effect triggered by the production of carbon dioxide by this biota. The entity of measured daily temperature fluctuations is ca. one order of magnitude greater than air temperature fluctuations measured at the same elevation in the closest meteorological station. The results of this work highlight that the infrared thermometer is an effective tool to measure rock surface temperature along rocky coasts, capable of detecting temperature fluctuations more effectively than traditionally employed data loggers. Moreover, this work emphasizes the relevance of temporary sun-shading and wind gusts in triggering short-term rock surface temperature fluctuations, potentially capable of enhancing thermal fatigue and foster surface rock breakdown. Full article
(This article belongs to the Special Issue Coastal Morphodynamics II)
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Open AccessArticle
An Integrated Web-Based System for the Monitoring and Forecasting of Coastal Harmful Algae Blooms: Application to Shenzhen City, China
J. Mar. Sci. Eng. 2019, 7(9), 314; https://doi.org/10.3390/jmse7090314 - 09 Sep 2019
Viewed by 290
Abstract
Harmful algal blooms (HABs) cause environmental problems worldwide. Continuous monitoring and forecasting of harmful algal blooms are necessary for marine resources managers to detect the intensity and spatial extent of HABs and provide early warnings to the public. In this study, we introduce [...] Read more.
Harmful algal blooms (HABs) cause environmental problems worldwide. Continuous monitoring and forecasting of harmful algal blooms are necessary for marine resources managers to detect the intensity and spatial extent of HABs and provide early warnings to the public. In this study, we introduce an integrated web-based system for the monitoring and forecasting of coastal HABs. The system is named the Harmful Algal Blooms Monitoring and Forecasting System (HMFS). HMFS integrates in situ observations, a remote-sensing-based model, hydrodynamic and water quality model and Web-Based Geographic Information System (GIS) techniques into one environment. The in situ sensors and remote sensing model provide automatic and continuous monitoring of the coastal water conditions. The numerical models provide short-term prediction and early warning of HAB of up to 5 days. The overall forecast accuracy is more than or equal to 50% for the major coastal areas of Shenzhen in 2018. By leveraging a web-based GIS technique and Service-Oriented Architecture (SOA), the web portal of HMFS provides a graphic interface for users and mangers to view real-time in situ measurements and remote sensing maps, explore numerical model forecasts and get early warning information. HMFS was applied to Shenzhen, which is a rising megacity in Southern China. The application study demonstrated the applicability and effectiveness of HMFS for monitoring and predicting HABs. Full article
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Open AccessArticle
Load Transfer of Offshore Open-Ended Pipe Piles Considering the Effect of Soil Plugging
J. Mar. Sci. Eng. 2019, 7(9), 313; https://doi.org/10.3390/jmse7090313 - 08 Sep 2019
Viewed by 251
Abstract
Open-ended pipe piles have been increasingly used as the foundations for offshore structures. Considering the soil plugging effect, a novel analytical model is proposed in this paper to study the load transfer mechanism of open-ended pipe piles. A trilinear model for the external [...] Read more.
Open-ended pipe piles have been increasingly used as the foundations for offshore structures. Considering the soil plugging effect, a novel analytical model is proposed in this paper to study the load transfer mechanism of open-ended pipe piles. A trilinear model for the external shaft friction was introduced, while a rigid plastic model was adopted to describe the load transfer at the pile-plug interface. Furthermore, an equilibrium equation of the soil plug was proposed, based on the hypothesis of a trilinear distribution of lateral earth pressure. The pile end resistance was analyzed by dividing it into two parts, i.e., the soil plug and pile annulus, the behaviors of which were described by the double broken line model. A calculation example was carried out to analyze the load transfer properties of the open-ended pipe piles. As a validation, similar load transfer processes of the open-ended pile were also captured in a newly built discrete element method model, mimicking the 100g centrifuge testing conditions. Full article
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Open AccessArticle
Stability Assessment of Rubble Mound Breakwaters Using Extreme Learning Machine Models
J. Mar. Sci. Eng. 2019, 7(9), 312; https://doi.org/10.3390/jmse7090312 - 07 Sep 2019
Viewed by 288
Abstract
The stability number of a breakwater can determine the armor unit’s weight, which is an important parameter in the breakwater design process. In this paper, a novel and simple machine learning approach is proposed to evaluate the stability of rubble-mound breakwaters by using [...] Read more.
The stability number of a breakwater can determine the armor unit’s weight, which is an important parameter in the breakwater design process. In this paper, a novel and simple machine learning approach is proposed to evaluate the stability of rubble-mound breakwaters by using Extreme Learning Machine (ELM) models. The data-driven stability assessment models were built based on a small size of training samples with a simple establishment procedure. By comparing them with other approaches, the simulation results showed that the proposed models had good assessment performances. The least user intervention and the good generalization ability could be seen as the advantages of using the stability assessment models. Full article
(This article belongs to the Special Issue Modelling of Harbour and Coastal Structures)
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Open AccessArticle
Coral Resilience at Malauka`a Fringing Reef, Kāneʻohe Bay, Oʻahu after 18 years
J. Mar. Sci. Eng. 2019, 7(9), 311; https://doi.org/10.3390/jmse7090311 - 06 Sep 2019
Viewed by 542
Abstract
Globally, coral reefs are under threat from climate change and increasingly frequent bleaching events. However, corals in Kāneʻohe Bay, Hawaiʻi have demonstrated the ability to acclimatize and resist increasing temperatures. Benthic cover (i.e., coral, algae, other) was compared over an 18 year period [...] Read more.
Globally, coral reefs are under threat from climate change and increasingly frequent bleaching events. However, corals in Kāneʻohe Bay, Hawaiʻi have demonstrated the ability to acclimatize and resist increasing temperatures. Benthic cover (i.e., coral, algae, other) was compared over an 18 year period (2000 vs. 2018) to estimate species composition changes. Despite a climate change induced 0.96 °C temperature increase and two major bleaching events within the 18-year period, the fringing reef saw no significant change in total coral cover (%) or relative coral species composition in the two dominant reef-building corals, Porites compressa and Montipora capitata. However, the loss of two coral species (Pocillopora meandrina and Porites lobata) and the addition of one new coral species (Leptastrea purpurea) between surveys indicates that while the fringing reef remains intact, a shift in species composition has occurred. While total non-coral substrate cover (%) increased from 2000 to 2018, two species of algae (Gracilaria salicornia and Kappaphycus alvarezii) present in the original survey were absent in 2018. The previously dominant algae Dictyosphaeria spp. significantly decreased in percent cover between surveys. The survival of the studied fringing reef indicates resilience and suggests these Hawaiian corals are capable of acclimatization to climate change and bleaching events. Full article
(This article belongs to the Special Issue Coral Reef Resilience)
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Open AccessFeature PaperArticle
Microparticles in Table Salt: Levels and Chemical Composition of the Smallest Dimensional Fraction
J. Mar. Sci. Eng. 2019, 7(9), 310; https://doi.org/10.3390/jmse7090310 - 06 Sep 2019
Viewed by 274
Abstract
This study evaluates the chemical composition of microplastic materials (MPs) and non-synthetic particles in different table salts of marine origin by the µFT-IR technique. This research focuses on the microparticles fraction within 10–150 µm of size. Eleven commercial trademarks coming from Italy (IT [...] Read more.
This study evaluates the chemical composition of microplastic materials (MPs) and non-synthetic particles in different table salts of marine origin by the µFT-IR technique. This research focuses on the microparticles fraction within 10–150 µm of size. Eleven commercial trademarks coming from Italy (IT = 6) and Croatia (CRO = 5) were grouped in two different cost ranges, cheap (n = 5) and expensive (n = 6) and were analysed in replicates (n = 3). Levels and chemical composition of microparticles measured in commercial products were correlated on a statistical basis to some factors of variability of potential scientific interest (geographical origin of marine salt, cost of commercial products, etc.). Results of analyses performed on the tested size fraction of microparticles (10–150 µm) evidence that: (i) levels of MPs are within 0.17–0.32 items/g (IT) and 0.07–0.20 items/g (CRO); (ii) non-synthetic particles detected are mostly made by fibres made of cellulose acetate; (iii) Nations show a different chemical composition of MPs recovered in analysed trademarks (PET and PVC from Italy; PA, PP, and nylon from Croatia); (iv) the annual amount ingested by humans from marine salt consumption ranges between 131.4–372.3 items/y (CRO) and 306.6–580.35 items/y (IT) considering a dose of 5 g of salt per day; (v) statistics performed on factors of interest evidenced that the geographical origin of marine salt do not affect neither levels nor chemical composition of MPs in tested trademarks; while slight correlations are recorded with non-synthetic particles. Further studies are needed to better explore on statistical basis if both levels and chemical composition of MPs in table salts of marine origin can be used or not as good indicators of marine pollution. Full article
(This article belongs to the Special Issue Marine Litter)
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Open AccessArticle
Numerical Modelling of a Mussel Line System by Means of Lumped-Mass Approach
J. Mar. Sci. Eng. 2019, 7(9), 309; https://doi.org/10.3390/jmse7090309 - 05 Sep 2019
Viewed by 414
Abstract
This paper describes a numerical model to simulate the behavior of a mussel longline system, subjected to environmental loads such as waves and current. The mussel line system consists of an anchor, a mooring chain, a long backbone line, mussel collector lines and [...] Read more.
This paper describes a numerical model to simulate the behavior of a mussel longline system, subjected to environmental loads such as waves and current. The mussel line system consists of an anchor, a mooring chain, a long backbone line, mussel collector lines and buoys. The lumped-mass open-source code MoorDyn is modified for the current application. Waves are modelled as a directional spectrum, and the current as a homogeneous velocity field with an exponential vertical distribution. A Coulomb model is implemented to model the horizontal friction between nodes and the seabed. Cylindrical buoys with three translational degrees-of-freedom are modelled by extending the simplified hydrodynamic model in use for line’s internal nodes with additional properties like cylinder height, diameter and mass. Clump weights are modelled in a similar way. For validation purposes, the results of the present software are compared with the commercially available lumped-mass based mooring dynamic software, OrcaFlex. Full article
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Open AccessArticle
Accumulation of Pore Pressure in a Soft Clay Seabed around a Suction Anchor Subjected to Cyclic Loads
J. Mar. Sci. Eng. 2019, 7(9), 308; https://doi.org/10.3390/jmse7090308 - 05 Sep 2019
Viewed by 268
Abstract
A suction anchor is an appealing anchoring solution for floating production. However, the possible effects of residual pore pressure can be rarely found any report so far in term of the research and design. In this study, the residual pore pressure distribution characteristics [...] Read more.
A suction anchor is an appealing anchoring solution for floating production. However, the possible effects of residual pore pressure can be rarely found any report so far in term of the research and design. In this study, the residual pore pressure distribution characteristics around the suction anchor subjected to vertical cyclic loads are investigated in a soft clay seabed, and a three-dimensional damage-dependent bounding surface model is also proposed. This model adopts the combined isotropic-kinematic hardening rule to achieve isotropic hardening and kinematic hardening of the boundary surface. The proposed model is validated against triaxial tests on anisotropically consolidated saturated clays and normally consolidated saturated clays. The analytical results show that the excess pore water pressure accumulates primarily on the outside of the suction anchor, whereas negative pore water pressure mainly on the inside. The maximum values of both sides appear in the lower part of the seabed. According to the distribution characteristics of the residual pore pressure, a perforated anchor is proposed to reduce the accumulation of excess pore water pressure. A comparative study generally shows that the perforated anchor can effectively reduce the accumulation of excess pore water pressure. Full article
(This article belongs to the Special Issue New Advances in Marine Engineering Geology)
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Open AccessArticle
Critical Processes of Trace Metals Mobility in Transitional Waters: Implications from the Remote, Antinioti Lagoon, Corfu Island, Greece
J. Mar. Sci. Eng. 2019, 7(9), 307; https://doi.org/10.3390/jmse7090307 - 04 Sep 2019
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Abstract
The Antinioti Lagoon is a karstified, rather pristine, and shallow coastal lagoon located in the northern part of Corfu Island in NW Greece. The present study examines the levels of metals (Al, Fe, Mn, Cd, Cu, Pb, and Zn) in the dissolved and [...] Read more.
The Antinioti Lagoon is a karstified, rather pristine, and shallow coastal lagoon located in the northern part of Corfu Island in NW Greece. The present study examines the levels of metals (Al, Fe, Mn, Cd, Cu, Pb, and Zn) in the dissolved and particulate phase, as well as in surface and core sediments, and identifies the critical processes that define their behavior. The major transport pathway of dissolved Mn, Cd, and Pb, and particulate Mn, Cd, and Zn into the lagoon is through freshwater springs, whereas surface runoff dominates the transport of particulate Al, Fe, and Cu. Interestingly, large particles (>8 μm) contain higher amounts of Al, Fe and Mn than the finer ones (<8 μm), due to flocculation of oxyhydroxides that, eventually, scavenge other metals, as well. Cadmium and Zn bound to the large particles were found to be less prone to desorption than the smaller ones and were effectively captured within the lagoon. In the sediments, diagenetic processes are responsible for post-depositional changes in the forms of metals (particularly Fe, Mn and Cd). Enrichment factors (EFs) based on local background showed that sediments are enriched in restricted areas in Cd and Pb by maximum factors 4.8 and 10, respectively. These metals were predominantly found in potentially labile forms. Thus, any interventions introducing changes in the physico-chemical conditions may result in the release of metals, with negative implications on the lagoon’s ecological quality. Full article
(This article belongs to the Special Issue Marine Sediments: Processes, Transport and Environmental Aspects)
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Open AccessArticle
Rapid Recruitment of Symbiotic Algae into Developing Scleractinian Coral Tissues
J. Mar. Sci. Eng. 2019, 7(9), 306; https://doi.org/10.3390/jmse7090306 - 04 Sep 2019
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Abstract
While the early acquisition of Symbiodiniaceae algae into coral host tissues has been extensively studied, the dynamics of the migration of algal cells into rapidly expanding coral tissues still lacks a systematic study. This work examined two Red Sea branching coral species, Pocillopora [...] Read more.
While the early acquisition of Symbiodiniaceae algae into coral host tissues has been extensively studied, the dynamics of the migration of algal cells into rapidly expanding coral tissues still lacks a systematic study. This work examined two Red Sea branching coral species, Pocillopora damicornis and Stylophora pistillata, as they were growing and expanding their tissue laterally on glass slides (January–June, 2014; 450 assays; five colonies/species). We measured lateral tissue expansion rates and intratissue dinoflagellate migration rates. Tissue growth rates significantly differed between the two species (with Stylophora faster than Pocillopora), but not between genotypes within a species. Using a “flow-through coral chamber” under the microscope, the migration of dinoflagellates towards the peripheral edges of the expanding coral tissue was quantified. On a five-day timescale, the density of the endosymbiotic dinoflagellate cells, presenting within a 90 µm region of expanding coral tissue (outer edge), increased by a factor of 23.6 for Pocillopora (from 1.2 × 104 cells cm−2 to 2.4 × 105 cells cm−2) and by a factor of 6.8 for Stylophora (from 3.6 × 104 cells cm−2 to 2.4 × 105 cells cm−2). The infection rates were fast (5.2 × 104 and 4.1 × 104 algal cells day-1 cm−2, respectively), further providing evidence of an as yet unknown pathway of algal movement within coral host tissues. Full article
(This article belongs to the Section Marine Biology)
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Open AccessFeature PaperArticle
The Influence of Free Long Wave Generation on the Shoaling of Forced Infragravity Waves
J. Mar. Sci. Eng. 2019, 7(9), 305; https://doi.org/10.3390/jmse7090305 - 04 Sep 2019
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Abstract
Different conceptual models for forced infragravity (long) waves exist in the literature, which suggest different models for the behavior of shoaling forced waves and the possible radiation of free long waves in that process. These are discussed in terms of existing literature. A [...] Read more.
Different conceptual models for forced infragravity (long) waves exist in the literature, which suggest different models for the behavior of shoaling forced waves and the possible radiation of free long waves in that process. These are discussed in terms of existing literature. A simple numerical model is built to evaluate the wave shape in space and time during shoaling of forced waves with concurrent radiation of free long waves to ensure mass continuity. The same qualitative results were found when performing simulations with the COULWAVE model using the radiation stress term in the momentum equation to force the generation and propagation of bound waves. Both model results indicate a strong frequency dependence in the shoaling rate and on the lag of the total long wave with respect to the forcing, consistent with observations in the literature and more complex evolution models. In this approach, a lag of the long wave is only observed in the time domain, not in the space domain. In addition the COULWAVE is used to investigate dissipation rates of incident free and forced long waves inside the surf zone. The results also show a strong frequency dependence, as previously suggested in the literature, which can contribute to the total rate of decay of the incident forced wave after short wave breaking. Full article
(This article belongs to the Special Issue Dynamics of the Coastal Zone)
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Open AccessArticle
Experimental Study on the Distribution of Wave-Induced Excess Pore Pressure in a Sandy Seabed around a Mat Foundation
J. Mar. Sci. Eng. 2019, 7(9), 304; https://doi.org/10.3390/jmse7090304 - 03 Sep 2019
Viewed by 279
Abstract
Mat foundations are widely used in jack-up offshore platforms to support and transfer loads. Regarding mat foundations working on the seabed, the excess wave-induced pore pressure is critical to seabed stability, which may finally cause structural failure. Therefore, it is important to investigate [...] Read more.
Mat foundations are widely used in jack-up offshore platforms to support and transfer loads. Regarding mat foundations working on the seabed, the excess wave-induced pore pressure is critical to seabed stability, which may finally cause structural failure. Therefore, it is important to investigate the distribution of the excess pore pressure in the seabed around the mat foundation. In this study, experiments were performed to study the excess pore pressure distribution around a mat foundation in scale considering the true load state by recording wave profiles and pore pressures inside a sandy seabed. To guarantee the reliability of experiments, a numerical study was conducted and compared with the experimental results. Experimental results indicate that with the existence of the mat foundation, the excess pore pressure is higher at the region, the range of which is the width of the model mat (Wm) before the structure. The maximum pore pressure appears at 0.55 Wm in front of the center of the mat foundation. In addition, the current significantly increases the range of high pore pressure area and the amplitude of the excess pore pressure. As the mat orientation changes, the position of the maximum pore pressure changes from the front to the edge of the mat. Full article
(This article belongs to the Section Ocean Engineering)
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Open AccessFeature PaperArticle
Long-Term Analysis of the Black Sea Weather Windows
J. Mar. Sci. Eng. 2019, 7(9), 303; https://doi.org/10.3390/jmse7090303 - 03 Sep 2019
Viewed by 273
Abstract
A particular aspect of the maritime operations involves available weather intervals, especially in the context of the emerging renewable energy projects. The Black Sea basin is considered for assessment in this work, by analyzing a total of 30-years (1987–2016) of high-resolution wind and [...] Read more.
A particular aspect of the maritime operations involves available weather intervals, especially in the context of the emerging renewable energy projects. The Black Sea basin is considered for assessment in this work, by analyzing a total of 30-years (1987–2016) of high-resolution wind and wave data. Furthermore, using as reference, the operations thresholds of some installation vessels, some relevant case studies have been identified. The evaluation was made over the entire sea basin, but also for some specific sites located close to the major harbors. In general, the significant wave heights with values above 2.5 m present a maximum restriction of 6%, while for the western sector, a percentage value of 40% is associated to a significant wave height of 1 m. There are situations in which the persistence of a restriction reaches a maximum time interval of 96-h; this being the case of the sites Constanta, Sulina, Istanbul or Burgas. From a long-term perspective, it seems that there is a tendency of the waves to increase close to the Romanian, Bulgarian, and Turkish coastal environments—while an opposite trend is expected for the sites located on the eastern side. Full article
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Open AccessEditorial
Advances and Current Challenges in Marine Biotoxins Monitoring
J. Mar. Sci. Eng. 2019, 7(9), 302; https://doi.org/10.3390/jmse7090302 - 02 Sep 2019
Viewed by 272
Abstract
Shellfish are filter-feeding organisms that may accumulate high levels of naturally-occurring toxins, produced by harmful algal blooms, and act as marine toxin vectors to whomever consumes them [...] Full article
(This article belongs to the Special Issue Advances and Current Challenges in Marine Biotoxins Monitoring)
Open AccessArticle
Linear Analysis of the Static and Dynamic Responses of the Underwater Axially Moving Cables to Bucket Loads
J. Mar. Sci. Eng. 2019, 7(9), 301; https://doi.org/10.3390/jmse7090301 - 02 Sep 2019
Viewed by 260
Abstract
In this study, the mechanics of an axially moving cable that is used to acquire mineral resources from the seafloor are theoretically and numerically investigated by focusing on the extent to which a load of buckets affects the cable deflection. In particular, we [...] Read more.
In this study, the mechanics of an axially moving cable that is used to acquire mineral resources from the seafloor are theoretically and numerically investigated by focusing on the extent to which a load of buckets affects the cable deflection. In particular, we construct the theoretical model of a cable, and its solutions are numerically determined using the mode expansion method. The results of the simulations performed using a varying number of buckets show that the cable deflects in response to the passage of each bucket. As the total number of buckets increases, the load of buckets acts as a continuous load. An increase in the total number of buckets naturally leads to an increase in the total load on the cable, resulting in the deviation of the paths of the buckets from a path under the zero-load state. These properties should be considered while designing cables. Full article
(This article belongs to the Section Ocean Engineering)
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Open AccessArticle
Research into the Automatic Berthing of Underactuated Unmanned Ships under Wind Loads Based on Experiment and Numerical Analysis
J. Mar. Sci. Eng. 2019, 7(9), 300; https://doi.org/10.3390/jmse7090300 - 01 Sep 2019
Viewed by 278
Abstract
With the continuous improvement of unmanned ship automation requirements, research into the automatic berthing of underactuated unmanned ships has important theoretical significance and practical value. In order to determine the trajectory of unmanned ships, the line of sight (LOS) algorithm was applied due [...] Read more.
With the continuous improvement of unmanned ship automation requirements, research into the automatic berthing of underactuated unmanned ships has important theoretical significance and practical value. In order to determine the trajectory of unmanned ships, the line of sight (LOS) algorithm was applied due to the characteristics of underactuated unmanned ships without side thrusters. In order to resist wind disturbance, the active disturbance rejection control (ADRC) method was applied to keep the ship moving on its intended trajectory. Then, to carry out the simulation analysis before the tank experiment, a remote-control simulation system based on a user datagram protocol (UDP) communication was built, and the ability of the ADRC controller to make the ship perform completely automatic berthing in both wind and no wind conditions was verified in simulations. Combined with the simulation results, a tank experiment was accomplished at the Japanese National Research Institute of Fishery Engineering. The experimental results also showed that the ADRC controller has good robustness, that the problems of insufficient autonomous route determination and the disturbance rejection ability in the process of the automatic berthing of underactuated unmanned ships are solved, and the safety of ship navigation is improved, which lays a theoretical and experimental foundation for the further development of unmanned ship control. Full article
(This article belongs to the Special Issue Advances in Oceanic and Mechatronic Systems Engineering)
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Open AccessArticle
Dynamics Simulation for Process Risk Evolution on the Bunker Operation of an LNG-fueled Vessel with Catastrophe Mathematical Models
J. Mar. Sci. Eng. 2019, 7(9), 299; https://doi.org/10.3390/jmse7090299 - 31 Aug 2019
Viewed by 397
Abstract
Liquefied nature gas (LNG) is a green energy. LNG-fueled vessels are extremely complex engineering systems. In view of the inherent hazardous properties of LNG fuel, LNG fueling is not only an important part, but it is also full of high risks in the [...] Read more.
Liquefied nature gas (LNG) is a green energy. LNG-fueled vessels are extremely complex engineering systems. In view of the inherent hazardous properties of LNG fuel, LNG fueling is not only an important part, but it is also full of high risks in the operation of LNG-fueled vessels (LNGFVs). Therefore, it is necessary to study the risk factors, and the intrinsic relationship among them between the LNG and the vessel, and to simulate the system dynamics in the process of LNGFV operation. During the process of fueling of LNGFV, at every moment the vessel interacts with the energy and information of the surrounding environment. First, the impact of the three interactions of the fueling operation process, ship factors, and environmental factors were analyzed on the risk of fueling operation, and a complete node system was proposed as to the complex system dynamics mode. Second, by analyzing the boundary conditions of the system, the relationship of factors was established via the tools of system dynamics (SD). Based on the catastrophe theory (CA), the dynamics model for the fueling of LNG is set up to study the system’s risk mutation phenomenon. Third, combined with the simulation results of the case analysis, the risk evolution mode of the LNGFV during the fueling process was obtained, and constructive opinions were put forward for improving the safe fueling of the LNGFV. Application examples show that formal description of risk emergence and transition is a prerequisite for the quantitative analysis of the risk evolution mode. In order to prevent accidents, the coupling synchronization of risk emergence should be weakened, and meanwhile risk control should be implemented. Full article
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Open AccessArticle
Dynamic Analysis of an Array of Connected Floating Breakwaters
J. Mar. Sci. Eng. 2019, 7(9), 298; https://doi.org/10.3390/jmse7090298 - 30 Aug 2019
Viewed by 331
Abstract
In this paper, a model for dynamic analysis of array of floating breakwaters is developed and tested. Special attention is given to modeling connections between neighboring elements of the array. A linear three-dimensional floating multi-body formulation is used as a foundation for the [...] Read more.
In this paper, a model for dynamic analysis of array of floating breakwaters is developed and tested. Special attention is given to modeling connections between neighboring elements of the array. A linear three-dimensional floating multi-body formulation is used as a foundation for the presented model. An additional stiffness matrix is derived which introduces the influence of the connections onto motion of the array. The stiffness matrix is used to couple motions in vertical and horizontal planes i.e., the connections are modeled in three-dimensions. The equation of motion is solved in the frequency domain. The newly developed model is tested on an array of three connected breakwaters. The motion and the performance of the breakwater array are investigated under different significant heights and directions of the incoming waves. Full article
(This article belongs to the Special Issue Dynamics of Offshore Structures)
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Open AccessArticle
Validating UAS-Based Photogrammetry with Traditional Topographic Methods for Surveying Dune Ecosystems in the Spanish Mediterranean Coast
J. Mar. Sci. Eng. 2019, 7(9), 297; https://doi.org/10.3390/jmse7090297 - 30 Aug 2019
Viewed by 371
Abstract
In the past few years, unmanned aerial systems (UAS) have achieved great popularity for civil uses. One of the present main uses of these devices is low-cost aerial photogrammetry, being especially useful in coastal environments. In this work, a high-resolution 3D model of [...] Read more.
In the past few years, unmanned aerial systems (UAS) have achieved great popularity for civil uses. One of the present main uses of these devices is low-cost aerial photogrammetry, being especially useful in coastal environments. In this work, a high-resolution 3D model of a beach section in Guardamar del Segura (Spain) has been produced by employing a low maximum takeoff mass (MTOM) UAS, in combination with the use of structure-from-motion (SfM) techniques. An unprecedented extensive global navigation satellite system (GNSS) survey was simultaneously carried out to statistically validate the model by employing 1238 control points for that purpose. The results show good accuracy, obtaining a vertical root mean square error (RMSE) mean value of 0.121 m and a high point density, close to 30 pt/m2, with similar or even higher quality than most coastal surveys performed with classical techniques. UAS technology permits the acquisition of topographic data with low time-consuming surveys at a high temporal frequency. Coastal managers can implement this methodology into their workflow to study the evolution of complex, highly anthropized dune-beach systems such as the one presented in this study, obtaining more accurate surveys at lower costs. Full article
(This article belongs to the Special Issue Application of Remote Sensing Methods to Monitor Coastal Zones)
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