León-Pérez, M.C.; Hernández, W.J., and Armstrong, R.A., 2019. Characterization and distribution of seagrass habitats in a Caribbean nature reserve using high-resolution satellite imagery and field sampling. Journal of Coastal Research, 35(5), 937–947. Coconut Creek (Florida), ISSN 0749-0208.

Effective management of seagrass habitats requires detailed information about seagrass condition and distribution. This paper addresses the first step of a larger study to assess long-term changes in seagrass distribution within Caja de Muertos Island Nature Reserve, Puerto Rico. A high-spatial-resolution characterization of seagrass beds in the reserve was conducted using a WorldView-2 (WV-2) image and field data set. The WV-2–derived seafloor reflectance and bathymetry data were used to conduct an object-based image analysis (OBIA). The selection of bands for this analysis was based on in situ spectral water attenuation measurements. The resulting polygons of the OBIA were classified through a supervised classification and contextual editing. Calibration and validation of the image were conducted using 164 sampling sites. Together with traditional accuracy assessment tools, a reliability map was created to provide another metric for evaluating the map accuracy. Overall accuracy was 96.59%, and the total seagrass accuracy was 100%. Seagrass beds were found mainly west and north of the island and were mostly composed of a combination of Thalassia testudinum and Syringodium filiforme. Results suggested that light availability was not a limiting factor for seagrass colonization at the study area and that strong wave energy may be an important factor in regulating seagrass distribution. This seagrass habitat map improved upon previous mapping efforts and represents the first high-spatial-resolution map for the reserve. The data and methods used proved to be effective for mapping seagrass habitats within a highly complex benthic environment.

Jones, K.R. and Traykovski, P., 2019. Interaction of superimposed megaripples and dunes in a tidally energetic environment. Journal of Coastal Research, 35(5), 948–958. Coconut Creek (Florida), ISSN 0749-0208.

The superposition of smaller bedforms on larger dunes have been observed in multiple energetic tidal environments. This study analyzes the interaction of two scales of superimposed bedforms at Wasque Shoals, an ebb delta located approximately 1 km SE of Martha's Vineyard, Massachusetts. Data from a fixed rotary sidescan sonar deployed on a submerged quadpod captured the interaction of megaripples, or bedforms with wavelengths on the order of 1 m, with the lee side of a migrating dune with a wavelength of approximately 100 m. The net convergence of megaripples on the tidally dominant lee face of the dune suggests that the megaripples serve as an intermediate step between grain-scale transport processes and the large-scale dune migration. This conceptual model is quantitatively tested given observations of seabed elevation changes and dune migration rates. With this novel data set, two scales of bedforms were resolved on subtidal timescales, facilitating new insights into the dynamics of superimposed bedforms in tidal environments.

Voulgaris, A.; Mouratidis, C., and Vossinakis, A., 2019. Simulation and analysis of natural seawater chemical reactions on the Antikythera Mechanism. Journal of Coastal Research, 35(5), 959–972. Coconut Creek (Florida), ISSN 0749-0208.

Chemical reactions with seawater changed the bronze material and the color of the Antikythera Mechanism. The deformation and the displacement of the bronze parts are clearly evident on the visual photographs, on Antikythera Mechanism Research Project (AMRP) X-ray radiographs, and computed tomography (CT) scans as a result of the under-seawater material density change and the dehydration of the Mechanism after its removal from the Aegean/Kretan Sea bottom. In present work the first steps of the copper/bronze corrosion under the sea are simulated and presented. The geometric changes and the deformations of the Mechanism parts, which have repercussions on their shape, dimension, and relative position, are analyzed. Studying the visual photographs and the AMRP X-ray CTs of the partially preserved parts, the Functional Reconstruction of Antikythera Mechanism Project team digitally reconstructed and completed some of the lost/destroyed wooden and bronze parts and calculated the dimensions of the plates and the wooden casements of the Antikythera Mechanism ancient prototype.

Gainza, J.; Garnier, R.; Nuñez, P.; Jaramillo, C.; González, E.M.; Medina, R.; Liria, P.; Epelde, I.; Uriarte, A., and Monge-Ganuzas, M., 2019. Accelerating beach recovery by plowing the intertidal bar: A field experiment along the northern Spanish coast. Journal of Coastal Research, 35(5), 973–984. Coconut Creek (Florida), ISSN 0749-0208.

Subaerial beach width plays a vital role when it comes to protecting coastal settlements and communities from storms. In many beaches the accretionary sequence is often characterized by the onshore migration of one or several intertidal bars that can eventually weld to the shore and contribute to the increase of the dry (subaerial) beach surface. An innovative experiment was carried out in summer 2015 to accelerate the onshore movement of the intertidal bar at Laida beach, Basque Country, northern Spain, by plowing it mechanically. A control zone where the bar could evolve naturally and a test zone where the plowing was performed were both defined. The aim of this study is to assess the effect of plowing on intertidal bar migration by analyzing field data collected during the experiment. Hydrodynamic data were gathered during a 3-day field campaign. Additionally, six cross-shore transects were defined, and their topographic data were taken every 15 days. Furthermore, a video imaging system allowed following and recording the planform evolution of the beach. Analyzing each profile's topographic data, it was observed that the intertidal bar in the plowed zone moved farther onshore than the intertidal bar in the control zone, suggesting that the plowing accelerated the onshore migration of the bar. Sediment transport was calculated by feeding a sediment transport formula with the hydrodynamic measurements taken, and it was concluded that the natural onshore migration of the bar is driven by onshore transport gradients related to wave asymmetry and skewness. It is suggested that the plowing caused an increase of onshore sediment transport onto the intertidal bar. However, further study that includes other field experiments, physical modeling, or both is required to identify the processes involved.

Li, C.-Y.; Weng, W.-K.; Shih, R.-S.; Yang, C.-K., and Lo, J.-S., 2019. Enhancing wave energy harvesting with a submerged crescent-shaped plate. Journal of Coastal Research, 35(5), 985–995. Coconut Creek (Florida), ISSN 0749-0208.

Wave energy converters (WECs) are devices that capture energy from waves, which is usually dictated by wave conditions. In this study, a rectangular wave farm with generic point absorber WECs was placed behind a submerged crescent-shaped plate to investigate whether the plate increases the amount of captured energy. A numerical model that describes the wave field around the plate, based on the boundary element method, was developed and validated with experimental results. When waves move past the plate, the combined effects of shoaling, refraction, and diffraction cause waves behind the plate to increase in height. Two parameters, the dimensionless energy extraction coefficient and the buoy coverage ratio, were investigated using long- and short-period waves with the aim of enhancing energy harvesting behind the submerged crescent-shaped plate. The results suggest that increasing the energy extraction coefficient and coverage ratio do not ensure increased harvesting efficiency; rather, these parameters may cause changes in the nearby wave field because of greater wave reflection and diffraction. A dimensionless energy extraction coefficient of 1.0 and a buoy coverage ratio of 0.1 were proposed as optimal parameters for all wave periods under the conditions of this study. In this rectangular wave farm, most energy was captured in the area closest to the submerged plate (30% of the total wave farm), and a lower buoy coverage ratio caused less wave reflection and diffraction in the wave field around the plate.

Zhang, Y.; Ding, Z.; Wang, Y.; Zhao, Q., and Qin, S., 2019. Determining the damage mechanisms for buoyancy materials of deep-sea manned submersibles. Journal of Coastal Research, 35(5), 996–1002. Coconut Creek (Florida), ISSN 0749-0208.

Deep-sea manned submersibles are important platforms for ocean exploration, and their structural reliability is critical to the personal safety of the crew. In particular, the buoyancy materials of deep-sea manned submersibles are vital parts because they provide the necessary buoyancy for submersible operations. This paper first describes the overall damage of the buoyancy materials used in the deep-sea manned submersible Jiaolong that accumulated over a large number of research expeditions during years of services. The causes of the damage are analyzed by computational fluid dynamics (CFD) methods. Because Jiaolong's buoyancy materials are secured to its structural frame by bolts, the external forces that act on the submersible are concentrated on these bolts. Those external forces include the wave forces that act on the submersible when it floats on the sea surface and the buoyancy material shrinkage that occurs because of changes in environmental pressure and temperature during submarine operations. Finally, several suggestions are provided for improving the design and operation of deep-sea submersibles.

Keim, R.F.; Lemon, M.G.T., and Oakman, E.C., 2019. Posthurricane salinity in an impounded coastal wetland (Bayou Sauvage, Louisiana, U.S.A.). Journal of Coastal Research, 35(5), 1003–1009. Coconut Creek (Florida), ISSN 0749-0208.

Coastal ecosystems can be structured by tropical cyclone disturbances, which interact with coastal management to reduce, magnify, or modify local effects on ecosystems. This research quantified the rate of recovery from salinification by impounded storm surge flooding by Hurricane Katrina at a natural levee ridge forest at Bayou Sauvage, Louisiana. Salinity measurements in soils and nearby pond sediments showed that elevated salinity remained 11 years after the flooding and persisted more at lower elevations. Rain events at the site created runoff of lower salinity relative to standing water, suggesting incomplete mixing and thus slow removal of salt. Recovery rates to prehurricane salinity were estimated to be at least two decades, on the basis of existing salinity, reports of salinity after the hurricane, and data from nearby long-term monitoring stations. The severity and length of storm surge effects have likely been exacerbated by the impounded conditions.

Miranda, I.M.; Toldo, E.E., Jr.; Klein, A.H.F., and Vieira da Silva, G., 2019. Shoreline evolution of lagoon sandy spits and adjacent beaches, Lagoa dos Patos, Brazil. Journal of Coastal Research, 35(5), 1010–1023. Coconut Creek (Florida), ISSN 0749-0208.

The development of lagoon sandy spits is dependent on sediment supply (mainly through longshore transport) and is often related to erosion of updrift beaches under high-angle waves. This paper provides an understanding of the short- to medium-term shoreline evolution of three symmetrical lagoon sandy spits and the related erosion of the adjacent bay beaches of Lagoa dos Patos, Brazil. To do so, two of the most widely used methods to quantify shoreline changes were applied: the transects-from-baseline method and the change polygon method. A historical analysis of the shoreline movement of approximately three decades (1984–2013), was carried out, aiming to track the source of sediments to the spits. Alternate phases of shoreline stability, deposition, and recession (less frequent) in short time intervals (years) showed correlation with the El Niño–Southern Oscillation and Southern Annular Mode indexes. Shoreline stability along beaches in the medium term (60.4% of Arambaré and 73.9% of Graxaim beaches, by the linear regression rate calculation), together with the very low average shoreline change rate of +0.7 m y^–1 found using both methods, demonstrates that the sediment supply to the spits has been significantly reduced in the past three decades. Furthermore, the large-scale subaqueous portions of the spits are under wave-induced sedimentary reworking accompanied by the up-building of sandbanks from the submerged bars, followed by its landward migration and merging to the spit's shoreline. These results suggest that the spits of Lagoa dos Patos have their growth limited once the amount of sediment supply has been significantly reduced.

Pham, D.H.B.; Hoang, T.T.; Bui, Q.-T.; Tran, N.A., and Nguyen, T.G., 2019. Application of machine learning methods for the prediction of river mouth morphological variation: A comparative analysis of the Da Dien Estuary, Vietnam. Journal of Coastal Research, 35(5), 1024–1035. Coconut Creek (Florida), ISSN 0749-0208.

Prediction of river mouth morphological variation plays a crucial role in the study of unique brackish river ecosystems and is important for economic development. However, it is still a challenge to assess river mouth morphological variation because it is influenced by multiple factors. With the increasing availability of observation data, machine learning techniques have been widely used in the geosciences. This study aims to examine different machine learning techniques (logistic regression, neural network, bootstrap aggregating, AdaBoost, LogitBoost, and random subspace) for the prediction of estuary morphological variation probability. The Da Dien estuary, located in Phu Yen Province, Vietnam, was selected as a case study. To construct the machine learning models, the throat width of the Da Dien estuary (the dependent variable) was determined using Landsat 4, 5, 7, and 8. Six independent variables (wind energy, wind direction, swell energy, swell direction, tidal prism, and river discharge) were obtained from either local hydrological stations or worldwide data portals. Through the examination of several statistical indicators, such as receiver operating characteristic, area under receiving operating characteristic, root-mean-square error, mean absolute error, and kappa, the results indicate that among the examined techniques, the Random Subspace model outperformed all others in almost every indicator, and it provided the most accurate prediction of estuary throat width variation. There are some limitations to this approach, such as the requirement of a large amount of data and difficulties in putting human-induced factors and topographical variables into the model. However, this paper presents a promising approach for providing a rapid assessment and can aid in developing a conceptual model of the system.

Stanley, J.-D., 2019. Egypt's Nile Delta in late 4000 years BP: Altered flood levels and sedimentation, with archaeological implications. Journal of Coastal Research, 35(5), 1036–1050. Coconut Creek (Florida), ISSN 0749-0208.

Compositional and textural attributes of dated fluvial and coastal to offshore deposits of the Nile delta in northern Egypt provide a means to determine whether, when, and to what extent climate change modified sedimentation of the Nile about 4000 years ago. This mid-Holocene period has been interpreted by climatologists and earth scientists as one of increased aridity, evaporation, and salinization, along with diminished rainfall and decreased Nile flood levels. Egyptologists also consider this as a time of major historic change from the end of the pharaonic Old Kingdom to the First Intermediate Period. Attention here is paid to diverse assemblages of mineralogical, geochemical, palynological, and faunal components, as well as to grain size, in numerous sediment core samples that became significantly altered within a 200- to 300-year period between 4300 and 4000 years before present (BP). This is the approximate time of the well-recognized climatic event of ca. 4200 years BP recorded in Eastern Mediterranean and Levant regions. In some core sections, such compositional changes are also identified but over a somewhat longer period that overlaps timewise with those of the shorter 200- to 300-year phase; these are attributed to the same major climatic event around 4300 to 4000 years ago. Some seemingly older dates and highly variable sediment textural types likely result from a stop-and-go downslope fluvial transport process involving repeated sequences of alternating sediment storage and subsequent erosional events that occurred during seaward flow along this extensive fluvial system. Findings summarized herein pertaining to the Nile's response to marked changes in climate and environmental conditions about 4000 years BP are needed to better decipher Egypt's evolving societal history at that time.

Griggs, G. and Patsch, K., 2019. The protection/hardening of California's coast: Times are changing. Journal of Coastal Research, 35(5), 1051–1061. Coconut Creek (Florida), ISSN 0749-0208.

Coastal hazards involve the interaction or effects of natural coastal processes on shoreline development, infrastructure, and human activities. Future sea-level rise will affect California's coastal development and infrastructure through both flooding of low-lying areas and erosion of cliffs, bluffs, and dunes. The global rate of sea-level rise is increasing and many low-lying developed shoreline areas are already experiencing flooding at extreme high tides, particularly during periods of large storm waves. The combined effects of short-term extreme wave and tide events and the global rate of sea level increase will present greater risks in the near future for coastal California. Protecting private development and public infrastructure along shorelines has become a pressing issue for many coastal communities and the state, with a limited number of management options, each with their own costs, benefits, and effects. These options include: do nothing, beach nourishment, hard armoring structures, living or green shorelines, and managed retreat or relocation. Hard armoring structures such as seawalls and revetments have been the typical historical response to coastal erosion, and in 1971, just 2.5% of California's entire 1760-km shoreline was armored. By 2018, armor totals reached 13.9% of the entire state's coastline, a 5.5-fold increase over 47 years. None of the past or present efforts to protect shoreline development and infrastructure from coastal storm damage and shoreline erosion will be effective over the long term with rising sea levels. A growing awareness of the cumulative effects of armoring the shoreline has led the California Coastal Commission to take an increasingly critical look at any new proposals for coastal armoring.

Costa, B., 2019. Multispectral acoustic backscatter: How useful is it for marine habitat mapping and management? Journal of Coastal Research, 35(5), 1062–1079. Coconut Creek (Florida), ISSN 0749-0208.

Marine managers routinely use benthic habitat maps to make decisions about the ocean, its resources, and associated human uses. Acoustic backscatter from multibeam echosounders (MBES) is often critical for developing these habitat maps. Recent advances now allow MBES to collect backscatter at multiple acoustic frequencies. This type of data may help researchers more accurately map benthic habitats and managers more confidently make decisions. However, new research is needed quantifying how much multispectral backscatter improves the habitat characterization process and identifying which management needs would benefit most from its collection. To begin answering these questions, a case study was conducted opportunistically in Bedford Basin, Canada, with MBES bathymetry and backscatter collected at 100, 200, and 400-kHz frequencies. Underwater photos and boosted regression trees were used to characterize seven dominant benthic habitats and calculate the relative importance of multispectral backscatter to the characterization process. Response curves were generated to identify key relative frequency thresholds for differentiating among habitat types. These results indicated that multispectral backscatter can enhance the discrimination of soft bottom by 17.4%, hard bottom by 5.7%, and all habitats by 9.1%. Topographic information (e.g., depth) contributed the most to the hard-bottom maps (51.8% ± 4.0), whereas multispectral backscatter contributed the most to the soft-bottom map (46.9%). The 100-kHz frequency was the most important frequency for all habitat types. These findings suggest that multispectral backscatter maybe most useful to management applications focused on soft-bottom habitats. Single-frequency (i.e. 100 kHz) backscatter may be adequate for applications focused on hard bottom, because it only improved the models by a small amount. Researchers and marine managers can start to use this information to decide a priori which backscatter frequency (or frequencies) are best suited to support their research objectives, mapping needs, and management actions.

McFall, B.C., 2019. The relationship between beach grain size and intertidal beach face slope. Journal of Coastal Research, 35(5), 1080–1086. Coconut Creek (Florida), ISSN 0749-0208.

The relationship between beach grain size and beach face slope is investigated with data from 181 sand beaches around the world. The analysis confirms previously identified trends of increasing beach face slope with increasing sediment grain size and decreasing beach exposure to wave energy. The present work extends previous studies by using a repeatable method to classify the beach exposure to wave energy and derives equations for the beach face slope based on sediment grain size and beach exposure. The derived equations match the measured beach face slope with r² correlation coefficients of 0.87, 0.88, and 0.87 for protected, moderately protected, and exposed beaches, respectively. The derived equations allow for a rapid estimate of the beach face slope based on the sediment grain size for a range of beach exposures.

Chen, Q.; Zhu, J.; Lyu, H., and Chen, S., 2019. Determining critical river discharge as a means to provide water supply security to the Changjiang River Estuary, China. Journal of Coastal Research, 35(5), 1087–1094. Coconut Creek (Florida), ISSN 0749-0208.

Shanghai is one of the six cities worldwide experiencing severe water shortage in the 21st century. To solve the water supply shortage problem, a strategic water source transfer from the Huangpu River to the Changjiang Estuary has been completed; approximately 80% of the supply of fresh water in Shanghai is taken from the water sources in the estuary, but the estuary experiences saltwater intrusion during periods of low river discharge, e.g., the dry season. The reservoirs cannot take water if the salinity is higher than 0.45 psu at the water intakes. The longest water residence time of the Chenhang Reservoir (CHR) is 7 days; thus, the CHR will experience water supply problems if the duration of saltwater intrusion is longer than 7 days. In this study, saltwater intrusion was simulated, and the critical river discharge was ascertained under different river discharge conditions using the improved Estuarine, Coastal, and Ocean Model, semi-implicit. The saltwater spillover from the North Branch arrived in the middle reaches of the South Branch during the subsequent moderate tide and neap tide, threatening the water intake of the CHR. During a period of spring–neap tides, the longest periods for which the CHR could not take water from the Changjiang Estuary were 5.0, 6.5, and 8.2 days under river discharge conditions of 11,500, 10,000, and 9000 m³/s, respectively. The saltwater intrusion increased when the river discharge declined, and the availability of useable freshwater resources in the estuary became severe. By finely adjusting the river discharge in the model, the authors found that the critical river discharge was 9500 m³/s. If the amount of river discharge reaches 9500 m³/s, the Shanghai government can ask the Changjiang Water Resources Committee to discharge more water from the Three Gorges Reservoir to restrain the saltwater intrusion and ensure water security in the megalopolis of Shanghai.

Sanderson, D.R.; Gravens, M.B., and Permenter, R.L., 2019. Methodology for identifying a subset of representative storm surge hydrographs from a coastal storm modeling database. Journal of Coastal Research, 35(5), 1095–1105. Coconut Creek (Florida), ISSN 0749-0208.

Freely accessible databases that contain the results of large coastal storm modeling efforts are available online. Some of these databases explore coastal risks broadly (e.g., overall vulnerability to sea-level rise and storm surge), whereas other databases contain more specific modeling results (e.g., time series of storm surge hydrographs and associated significant wave heights). In the case of the latter, these databases can be composed of both synthetically defined, probabilistic storms as well as historically based storms. Some coastal storm modeling efforts have resulted in upwards of 1000+ simulated storm events. In the context of numerical models that use as input storm surge and significant wave height time series (e.g., those that rely on precomputed relational databases), use of a full probabilistic storm suite can prove to be infeasible. A methodology for identifying a subset of representative storm events from a probabilistic database is outlined in this paper. By utilizing storm surge and significant wave height time series resulting from high-fidelity numerical modeling of the U.S. Army Corps of Engineers North Atlantic Coast Comprehensive Study, a representative storm suite was developed for Crisfield, Maryland. The results of using a representative storm suite and a full storm suite were compared by simulating 75 iterations (life cycles) of a 216-year period using the Monte Carlo life cycle model G2CRM. By performing a nonparametric extreme value analysis, the stage-frequency curves resulting from the representative and the full storm suites compared favorably.

Zheng, X.; Ma, Q.; Shao, S.; Hu, Z., and Gui, Q., 2019. An improved 2D + t incompressible smoothed particle hydrodynamics approach for high-speed vessel waves. Journal of Coastal Research, 35(5), 1106–1119. Coconut Creek (Florida), ISSN 0749-0208.

The wave-generated resistance force is substantial for high-speed vessels. A thorough understanding of the wave pattern as well as its drag effect is important for improving vessel performance and optimal design. Owing to the existence of highly nonlinear waves and large deformations of the free surface, the mesh-free smoothed particle hydrodynamics (SPH) approach would provide a useful solution technique for such a practical problem. Based on the pioneering study on the combination of weakly compressible SPH with the two-dimensional (2D) + t (time) theory, the present paper carries out a further investigation on the complex wave patterns generated by a high-speed vessel, through coupling the 2D + t theory with an improved incompressible SPH (ISPH) solver. For the solid vessel boundary, a new treatment method of calculating the velocity and acceleration of the regenerated particles near the curved hull is proposed. In addition, a high accuracy numerical scheme based on the simplified finite difference interpolation (SFDI) approach is used to solve the pressure Poisson equation in the ISPH framework. The robustness of the proposed 2D + t ISPH model is demonstrated through the benchmark tests of water entry and practical applications to the self-designed laboratory experiment.

Zheng, S.; Sha, J., Wang, A., 2019. An improved storage-space selection model and algorithm for outbound shipping containers: Considering the synchronous operation of multiple gantry cranes in port terminals worldwide. Journal of Coastal Research, 35(5), 1120–1130. Coconut Creek (Florida), ISSN 0749-0208.

Enhancing operation efficiency and strengthening core competence of storage yard are vital to exist and succeed for container ports worldwide. Aiming at improving container terminals' operational efficiency, this paper researches selecting locations for outbound containers and optimizing the relocation paths during retrieval operations. The outbound containers' storage-space selection problems (OCSSSP) can be concerned with emptying all the containers stacked in one block where every outbound container is given a fixed extractive sequence with the fewest number of relocations. The OCSSSP is a Non-Deterministic Polynomial Hard Problem. To increase the practical guiding significance of research conclusion, this paper further improves the model from synchronous operations of gantry cranes. The research content extends from one single piece of equipment to multiple pieces of equipment and conducts an in-depth study on the operation of a single piece of equipment, the independent operation of multiple pieces of equipment, and the collaborative operation of multiple pieces of equipment. Numerical experiment results show that the effect of the collaborative operation between different gantry cranes is best, and the container relocation number is least. Therefore, delimiting the joint operation areas between different gantry cranes makes the operation efficiency higher and the resources more reasonably utilized. This paper is consistent with the frontier to logistics development and satisfies the needs of developing technology and solving management problems in coastal container ports worldwide; therefore, this research has meritorious theoretical perceptiveness and considerable economic practicability.