Long, J.H.; Hanebuth, T.J.J.; Alexander, C.R., and Wehmiller, J.F., 2021. Depositional environments and stratigraphy of Quaternary paleochannel systems offshore of the Georgia Bight, southeastern U.S.A. Journal of Coastal Research, 37(5), 883–905. Coconut Creek (Florida), ISSN 0749-0208.

Paleochannels are common subsurface geological features beneath inner continental shelves and coastal plains and are important archives of ancient depositional environments. This study, focusing on a 450-km portion of the inner continental shelf of the SE United States, adds to understanding of the timing of paleochannel development, the paleoenvironments in which they formed, and the mechanisms that drove their formation. Integrated analysis of 1089 km of high-resolution seismic reflection data and 12 sediment cores reveals that (1) most paleochannels documented here formed in backbarrier environments (estuarine or lagoonal) and were subsequently filled during transgression or following avulsion, preserving mud-rich, tidally influenced deposits; (2) the preservation of nonmarine deposits is rare; (3) paleochannels are either solitary or amalgamated, forming paleochannel complexes within which they are arranged in multistory (vertically stacked) or multilateral (horizontally offset) configurations, a product of local hydrodynamic conditions, antecedent geology, glacioeustatic cycles, and regional isostatic adjustments; and (4) a general southerly increase in the overall degree of channelization is observed across the Georgia Bight, a function of long-term accommodation, interaction with underlying stratigraphy, and dominant coastal processes. The composition and spatiotemporal distribution of paleochannel systems has implications for understanding the long-term evolution and preservation of complex coastal systems and informing regional Quaternary sea-level reconstructions.

Finkl, C.W. and Makowski, C., 2021. Alongshore classification and morphometric analysis of developed coastal belts: An example from Uruguay, South America. Journal of Coastal Research, 37(5), 906–922. Coconut Creek (Florida), ISSN 0749-0208.

Approximately half of the 666-km long Uruguayan coastal belt length is characterized by continuums of developed urban centers that are associated with ports and harbors, residential, recreational, military, shore protection, and/or commercial facilities that occur in association with agricultural pursuits. Modification of the Biophysical Cross-shore Classification System (BCCS) to include such features of anthropogenic change along with naturally occurring coastalscapes permits classification of developed and undeveloped coastal belts based on interpretation of satellite imagery. Characterization of alongshore domains was based on conjoining archetypes into catenary sequences that typify coastal belts both alongshore and cross-shore. Based on interpretation of satellite imagery acquired from Google Earth Pro, Uruguayan coastal belts were divided into six separate departments (Rocha, Maldonado, Canelones, Montevideo, San Jose, Colonia) and characterized by the alongshore widths of archetypes that extended from offshore to several kilometers inland. Compilation of coastal belt catenas showed that promontories and headlands, which comprise resistant igneous and metamorphic rocks, function as anchor points along the shore and are widely interspersed by sedimentary (littoral) domains that contain mainland and barrier beaches that are backed by beach-dune couplets, wetlands, lagoonal flats, and developed upland archetypes. Typical alongshore super domains, which were concised from cross-shore archetypical consequences, include the following predominant types of sequences: Barrier-Beach-Dune, Beach-Dune-Lagoon, Beach-Dune-Wetland, Beach-Dune-Upland, Beach-Cliff-Upland, Beach-Wetland-Flat-Lagoon, and Rock-Cliff-Upland. Certain archetypes, such as rock and developed, were prevalent throughout the coastal belt codifications with their representative symbolizations appearing in the variable code sequences of domains and super domains. Morphometric analysis tables were also compiled with alongshore lengths of domains and super domains, as well as percentages of individual department and Uruguayan coastal belts. This examination of the Uruguayan coast showed for the first time that the BCCS can characterize anthropogenically developed units with naturally occurring biophysical features. Interpreted cross-shore transects, alongshore domains, and all-encompassing super domains allow for a comprehensive classification and morphometric analysis of offshore, inshore, and onshore components along Uruguay's natural and developed coastal belts.

Harris, M.E. and Ellis, J.T., 2021. Comparing tropical cyclone and king tide impacts on a South Carolina coastal dune system. Journal of Coastal Research, 37(5), 923–932. Coconut Creek (Florida), ISSN 0749-0208.

Coastal populations face an ever-growing threat as natural hazards increase in frequency and magnitude. In South Carolina, king tides (abnormally high tides) responsible for coastal flooding have increased by 126% between 2014 and 2019. King tides present an evolving threat as sea levels rise, yet the implications for coastal dune response have not been investigated. This study compares the geomorphic impacts from king tides to two tropical cyclones on a South Carolina barrier island during four time periods (TPs): Hurricanes Florence (TP1) and Michael (TP2) and two subsequent periods (TP3 and TP4) with king tides but devoid of tropical cyclone activity. Florence resulted in the greatest average change to the dunes, with normalized volumes (nv) equivalent to –11.6 m³/d. During Michael, the average change rate was nv = –1.5 m³/d. Dune changes during TP3 and TP4 averaged nv = –1.7 m³/d and nv = –2.3 m³/d, respectively. The reduction rate during nonstorm conditions is indicative of the erosive potential of king tides. The erosive potential should be further investigated in conjunction with king tide magnitude and frequency. Smaller, more pervasive coastal hazards, such as king tides, should be more strongly considered, in addition to larger singular events, such as tropical cyclones, when investigating the geomorphic change of coastal dune systems.

Francis, H. and Traykovski, P., 2021. Development of a highly portable unmanned surface vehicle for surf zone bathymetric surveying. Journal of Coastal Research, 37(5), 933–945. Coconut Creek (Florida), ISSN 0749-0208.

This study reviews the design and subsequent effectiveness of a prototype autonomous survey vehicle built to collect data specifically in the surf zone. The breaking wave transitional zone between ocean and land is an important location to survey due to its impact on human infrastructure and vulnerability to the effects of climate change. However, this environment is notoriously difficult to survey due to its shallow depth and the turbulence of waves and currents. Three distinctive design choices were made at the beginning of the project with the goal of operating in the surf zone: First, the surface vehicle is light (15 kg) and fast (up to 7 m/s), both characteristics intended to enable one person to deploy it quickly and easily into the surf zone. Second, an electric motor that is connected to a jet drive eliminates a combustion engine's air intake, which can be contaminated with seawater and sand. The jet drive also removes any danger of spinning propellers and allows the vessel to run in very shallow water. Finally, the vessel has a foam bulb hatch cover that is watertight and allows the vessel to right itself if capsized by a wave. The outcome of this development effort is an unmanned vessel that has the maneuverability and power sufficient for surf zone operations and is self-righting. It runs off the waypoint based Ardupilot Mavlink program, which allows rapid transitions from autonomous modes to remote controlled modes and has a runtime of approximately 1.5 hours. The vessel has initially been used with a single beam echosounder and precision GPS to create highly detailed shallow water bathymetric maps. This study demonstrates this technique as a highly efficient method of creating bathymetric maps in coastal environments.

Wu, B.; Huang, W.; Deng, Z.; Zhang, Z.; Xu, J., and Chen, H., 2021. Stability analysis of metro shield construction in sandy soil strata under tidal forces in coastal areas. Journal of Coastal Research, 37(5), 946–952. Coconut Creek (Florida), ISSN 0749-0208.

The tidal effect on coastal areas is one of the main factors affecting groundwater. The groundwater including the unconfined aquifer layer and confined underground water layer is the main hazard source in the construction of a shield tunnel in the sandy soil area of a subway. It is necessary to study the influence of shield tunneling on land subsidence when the tides affect the underground diving position in the coastal area. In this article, the surface deformation of a simulated shield tunnel at different water levels and different tunneling lengths in sandy soil environment is measured through a model test, and the relationship between land subsidence, tunnel deformation, and water level change is analyzed. The results show that the change in groundwater level caused by tide will directly affect the floating or subsidence of the shield tunnel. Finite element simulation analysis during the process is carried out, and the influence of rising underground water level on the structure of the shield tunnel in terms of displacement and deformation is studied in detail, revealing the influence law of rising underground water level on the shield tunnel structure. The numerical results are well validated with the experimental results. Therefore, the influence of tide should be considered in the construction of an inshore shield tunnel, and the construction time window should be selected reasonably according to the tidal law.

Potter, L., 2021. Remote sensing of wetland area loss and gain in the western Barataria Basin (Louisiana, U.S.A.) since Hurricane Katrina. Journal of Coastal Research, 37(5), 953–963. Coconut Creek (Florida), ISSN 0749-0208.

The goal of this study was to analyze the recent record of Landsat satellite imagery to better understand spatial patterns and infer processes of change in marshland vegetation cover in coastal Louisiana wetlands. The study area covered subbasins of the western Barataria Basin near the Bayou Lafourche in southeastern Louisiana. Bayou Lafourche's estuaries have seen some of the highest rates of wetland conversion to open water of any coastal zone in the United States. The Landsat Normalized Difference Water Index (NDWI) was used in this study to map changes in land/water fractions at a 30-m pixel resolution between October 2005 (post-Katrina) and October 2018. Validation boat surveys were conducted in July 2020 to visually verify the presence or absence of (>1 m) emergent vegetation growing on marshlands across several subbasins, with photographs collected at more than 150 target locations along the route. Based on NDWI change, a total of 42.3 km² was estimated to fall into the category of wetland loss since 2005. The leading subbasins for these recent wetland-to-water conversions made up most of the southwestern portion of the study area just north of Port Fourchon. The consistently low distance detected between the majority of wetland loss cells and locations of historical oil and gas wells implies that effects of well drilling and extraction have had a continuing negative impact on marshland degradation in the basin. Conversely, a total of 34 km² was estimated to fall into the category of recent wetland gain, with much of the new vegetation growth verified to have been restored within several shoreline protection and dredging projects. It was concluded that the positive contributions made by such shoreline enhancement and marshland nourishment projects in Lafourche Parish to offset wetland losses over the past 15 years should not be underestimated.

Lan, J.; K.C., D.; Hu, L., and Gao, Y., 2021. An experimental study of the dynamic shear modulus and damping ratio of calcareous sand in the South China Sea. Journal of Coastal Research, 37(5), 964–972. Coconut Creek (Florida), ISSN 0749-0208.

The marine deposits in the South China Sea are characterized by an abundance of calcareous sand. The dynamic characteristics and properties of this sand are important for potential engineering seismic analysis and infrastructure development in this oil- and gas-rich region. The present study aims to investigate the dynamic shear modulus and damping ratio of typical calcareous sand in the South China Sea. A series of dynamic triaxial tests under the strain control condition of cyclic loading were conducted, with a specific focus on the effects of relative density and confining pressure. The normalized dynamic shear modulus increases with the increase in confining pressure, and the shear modulus–shear strain relationship can be adequately described with the well-known Hardin-Drnevich model. However, the influence of confining pressure tends to decline in the sand samples of high initial relative density. Overall, the variations in the damping ratio as affected by confining pressure or relative density are not very significant. The experimental results were assessed and found to be reasonably consistent with some of the previously reported results in the literature.

Stotts, S.; Callahan, J., and Gulledge, O., 2021. Impact of channel dredging and straightening in an Atlantic white cedar (Chamaecyparis thyoides L. (B.S.P.)) freshwater tidal wetland. Journal of Coastal Research, 37(5), 973–986. Coconut Creek (Florida), ISSN 0749-0208.

Once prominent up the eastern coast of the United States, freshwater wetlands with Atlantic white cedar (AWC; Chamaecyparis thyoides L. (B.S.P.)) are now vanishing due to saltwater intrusion and anthropogenic landscape alterations. This study utilizes a historic, anthropogenic disturbance to provide insight into the AWC response to salinization. A major straightening and dredging project in the 1920s, including 16 oxbow cuts, allowed brackish water to move upstream in the St. Jones River in Dover, Delaware, leading to the die-off of an AWC swamp. The sampled AWC experienced climate change, storms, hydrologic alterations, and sea-level rise. Annual ring width and suppression event chronologies were developed from dead AWC and were compared to groupings of climate variables in the predisturbance (1895–1920) and postdisturbance (1928–1958) periods. Results of the dendrochronological analysis indicate that the AWC in this study died at an average age of 49.3 years, earlier than typically expected for such species. After the straightening and dredging, the AWC experienced changes in growth response to temperature while suppression events became positively correlated with elevated temperature (p = 0.024) and high precipitation (p = 0.019). The system also showed signs of becoming more sensitive to storm events in the postdisturbance period.

Isla F.I. and Espinosa M., 2021. The gravels of the Rio De La Plata: The Holocene beaches of Bella Vista, Uruguay. Journal of Coastal Research, 37(5), 987–992. Coconut Creek (Florida), ISSN 0749-0208.

The Río de la Plata has a ría-type estuary, with a coastal plain dominated by fine to very-fine sands to the south and a tectonic coast to the north dominated by fine to coarse sand. Although the headlands of the river were dominated by fluvial processes related to the deltaic lobes of the Parana River, the Paraná Guazú, and Paraná de las Palmas, the outer estuary is subject to wave action that increased significantly during storms from the SE. Wave statistics confirmed a littoral drift responsible for the spits at the outlets of affluent rivers deflected to the west (Solís Grande, Solís Chico). At the northern Uruguayan coast the interval between Bella Vista and Las Flores is composed of gravel that is described here. Bella Vista beach has two berms; the upper berm is partially covered by eolian sands. Las Flores beach consists of a single berm where gravels segregate upward and sand moves toward the river coastline. The storm berm of Bella Vista includes finer gravels (3–6 cm) whereas the gravels from the tidal berms (both beaches) are coarser, from 6 to 15 cm. According to the Zingg diagram, oblate and tabular gravels abraded by the wave action dominate. Considering old photographs, these gravel berms are stable and relicts from the highstand of the Middle Holocene. They were, therefore, derived by waves from submerged deposits originally derived from the Complex Sierra de las Animas.

Swanson, R.L.; Giglio, K.W., and Chi, L., 2021. Restoring a degraded, sentinel New England salt marsh to mid-20th century conditions (Flax Pond, New York, U.S.A.). Journal of Coastal Research, 37(5), 993–1011. Coconut Creek (Florida), ISSN 0749-0208.

Flax Pond, located between Crane Neck and Old Field Point on the north shore of Long Island, is designated as a Significant Coastal Fish and Wildlife Habitat by the U.S. Fish and Wildlife Service and as a Scenic Recreational Reserve by the New York State Department of Environmental Conservation. The pond's tidal prism has been reduced about 18% over the past half-century as its inlet has shoaled and its tidal range diminished 33%, 0.6 m, all in low water. Reduced flushing has led to loss of wetlands, reduced water quality, increased pond salinity, and nighttime summertime hypoxia with concomitant reduction in pH. Historic charts, topographic surveys, and vertical aerial photographs were used to study the evolution of the pond's inlet from Long Island Sound (LIS). Tide, tidal current, and water quality observations were made and/or historical measurements were acquired at these locations: the pond's inlet, a proposed seawater intake for the Flax Pond Marine Laboratory, and the U.S. Geological Survey (USGS) water quality station some 650 m into the pond. The flux of water through the inlet from LIS and the change in bed slope through the pond inlet were measured. USGS data within the pond were used to determine when hypoxic conditions are likely to occur: an increase in bottom-water salinity of 2.1 in 9 years and in the elevation of low water of 18 mm y^–1 from 2008–14. The environmental benefits of reconfiguring the inlet to increase the tidal prism to that of the 1970s were explored. This would reduce the existing flushing time by more than 50%. The design of the cross-sectional shape for the inlet is based on this tidal prism and a compatible depth entering LIS; it should stabilize the inlet opening and improve much needed pond flushing.

Spyrou, D. and Karambas, T., 2021. Experimental and numerical simulation of cross-shore morphological processes in a nourished beach. Journal of Coastal Research, 37(5), 1012–1024. Coconut Creek (Florida), ISSN 0749-0208.

This paper presents the results of an experimental and numerical research carried out to reproduce the cross-shore evolution of nourished sandy beaches. An extensive two-dimensional laboratory investigation was performed to study the cross-shore profile evolution after the application of a beach nourishment method. A 1:20 scale physical model was carried out in the Laboratory of the Department of Hydraulics and Environmental Engineering, Aristotle University of Thessaloniki. The analysis considered only cross-shore sediment transport. Long-shore sediment transport is considered negligible. Consequently, the obtained results are related to the short-term response of the cross-shore profile. Ten different wave combinations were generated in an attempt to reproduce erosive conditions. Experimental results are given in terms of wave parameters, bed slope, and berm height of the nourished beach. An advanced nonlinear wave model was developed to simulate cross-shore morphodynamical processes. The comparison between the experimental and numerical beach profile indicated good agreement. Also, comparisons between Dean's analytical method and the experimental results were made.

Clark, G.S.; Busch, M.H., and Crawford, K.M., 2021. Effect of salt, nutrients, and native microbe additions on common dune restoration grasses. Journal of Coastal Research, 37(5), 1025–1034. Coconut Creek (Florida), ISSN 0749-0208.

Sand dunes are a valuable resource that shelters coastal communities and wildlife. Unfortunately, their survival is threatened by commercial development and erosion accelerated by climate change. Restoring sand dunes is challenging because of the difficulty in establishing vegetation in such a hostile environment. Restoration practitioners have responded by choosing stress-tolerant native species, adding nutrients, or incorporating native microbial communities into transplanted soils, but little is known about how these practices interact. In other systems, native microbes sometimes increase plant performance and salt tolerance. Nutrient additions promote growth but may inhibit development of beneficial fungi and disproportionately benefit some plant species at the expense of community diversity. To explore these interactions, two grasses commonly used in dune restorations—Panicum amarum and Uniola paniculata—were grown in a greenhouse and exposed to soil with and without native microbiota and to a range of nutrient and salinity treatments. Native microbial additions had little impact on live, aboveground biomass or the salt tolerance of the nursery-grown plants. Nutrient additions did not inhibit beneficial fungi. In fact, the density of extraradical hyphae in the soil increased by an average of 31% across all plants subject to a balanced, slow-release fertilizer. The two grasses responded differently to the salinity and nutrient treatments. Under a 2.5% salinity treatment, average live aboveground biomass for P. amarum fell 52%, compared with a 5.5% increase for U. paniculata. None of the nutrient additions affected U. paniculata; however, a combination of nitrogen and phosphorus increased P. amarum live, aboveground biomass by 356%. The strong response of P. amarum to fertilization offers a path to rapid growth of dune vegetation, but it may foster that species' dominance, which could lower the plant community's aggregate resistance to salinity.

Xie, Y.; Li, P.; Xu, S.; Chen, J., and Feng, H., 2021. Failure probability and security risk analysis of gravity-wharf structures in port engineering. Journal of Coastal Research, 37(5), 1035–1041. Coconut Creek (Florida), ISSN 0749-0208.

To assess the security risk of the gravity-wharf overall structure, the failure probability of the overall structure of the gravity wharf is analyzed based on the Rosenblueth method combined with the structural reliability theory. By constructing the serial system of a gravity wharf, a simplified failure model of the overall structure of a gravity wharf is established to obtain the failure probability of the whole wharf structural system. Thus, the security risk assessment of the gravity-wharf structure is realized. The calculation and analysis of the failure risk of a gravity caisson wharf indicates that the reliability index of the gravity-wharf structure at design low water level is much lower than that at design high water level. And at the design low water level, the overall structure has the largest failure probability. The reliability index of antisliding stability of a gravity caisson wharf at design low water level is about 20.6% lower than that at design high water level. And the reliability index of anti-overturning stability at design low water level is about 11.9% lower than that at design high water level. Meanwhile, the failure probability of anti-overturning of the caisson wharf structure is higher than that of antisliding at the same water level. The analysis method in this paper needn't consider the distribution characteristics of each parametric variable, the calculation efficiency of which is high. The analysis conclusions can provide reference for the failure probability and security risk assessment of the gravity-wharf overall structure.

Yu, H.; Sun, H., and Chen, M., 2021. The evolution of industrial structure for marine economic growth in China: An empirical study on the effects of rationalization and optimization. Journal of Coastal Research, 37(5), 1042–1052. Coconut Creek (Florida), ISSN 0749-0208.

Against the background of China's new normal economy, the adjustment of the marine industrial structure is still a key issue, but current research on the relationship between the marine industrial structure and marine economic growth has not reached a consistent conclusion. This paper measures the structure of the marine industry with two indicators of the rationalization and optimization of the industrial structure and constructs a fixed effects model to explore the effects of the marine industrial structure on marine economic growth and the mechanism using panel data of China's coastal provinces, cities, and districts from 1997 to 2016. The results show the following. (1) In the study period, the rationalization of the marine industrial structure promoted marine economic growth, whereas the optimization of the marine industrial structure restrained marine economic growth. (2) The mediation test shows that the rationalization of the marine industrial structure promotes the growth of the marine economy by improving the labor productivity of the marine industry, whereas the optimization of the marine industrial structure restrains the growth of the marine economy by curbing the productivity of the marine service industry. (3) After adding the moderator of government intervention into the model, it is found that the higher the degree of government intervention is, the more significant the promoting effect of the rationalization of the marine industrial structure on marine economic growth, and the negative effect of the optimization of the marine industrial structure on marine economic growth is significantly reduced.

Zhu, Y.; Zhang, J., and Tang, Q., 2021. An innovative method for the spatial sampling analysis of sea surface temperature in the Pacific-Indian Oceans. Journal of Coastal Research, 37(5), 1053–1062. Coconut Creek (Florida), ISSN 0749-0208.

In this study, a pragmatic approach is presented for evaluating the spatial representativeness of the point-scale drifting buoy sea-surface temperature (SST) over the joined area of Asia and the Pacific-Indian Ocean with that help of the high-resolution satellite-derived SST at multipixel scales. The relative spatial sampling error (RSSE) and coefficient of sill (CS) are selected to investigate consistency between the drifting buoy SST and pixel mean value of satellite-derived SST and representativeness of drifting buoy SST at pixel scales of 25 km, 50 km, and 100 km, respectively. The results show that at the 25-km scale, the consistency between the drifting buoy SST and the satellite-derived SST is high, and the spatial heterogeneity within the pixel scale is not obvious, i.e. only two measurements with RSSE are larger than the critical value of all 43,748 measurements. But with the increase in the scale, the number of the drifting buoy SST, which is inconsistent with the satellite-derived SST, is obviously increased (the number of the inconsistent point measurement at the scale of 50 km increased to 42, and at the scale of 100 km it is 59), and the spatial heterogeneity is enhanced. This spatial variation along the direction of latitude change is more obvious. Combining spatial consistency and spatial heterogeneity, no point-scale measurements of the worst spatial representativeness occur at the 25-km pixel scale, in which RSSE and CS are above the critical value. Although drifting buoy SST keeps a high consistency with satellite-derived SST, there are measurements of obvious local variation within pixel scales, and this variation is more obvious along the direction of latitude change. The spatial representativeness of the drifting buoy SST is unstable. This method is helpful to remove the poor-quality reference points during the validation of satellite-derived products, taking point-scale measurements as reference.

Yin, X.; Lu, Q.; Lu, Y.; Zou, J., and Wan, L., 2021. Hydrodynamic optimization of foreship hull-form using contrastive optimization algorithms. Journal of Coastal Research, 37(5), 1063–1078. Coconut Creek (Florida), ISSN 0749-0208.

In this study, a hydrodynamic optimization design of the foreship hull-form for the Series 60 ship is presented in terms of minimum wave-making resistance by using contrastive optimization algorithms. The partially parametric approach was developed to modify the original foreship hull-form. The wave-making resistance as an objective function was obtained by the Rankine source panel method with nonlinear free-surface boundary conditions in which the numerical computation results were validated against available experimental data and found to be in good agreement with the test. Different optimal design methods were proposed based on the minimum wave-making resistance: the nonlinear programming method (NLP), the nondominated sorting genetic algorithm (NSGA-II), and particle swarm optimization (PSO). Through the implementation and integration of the hull-form deformation module, the hydrodynamic module, and the optimization module the hydrodynamic optimization framework can be established subsequently. This module realizes the full automation of ship-shape optimization design and searches for the most efficient target through intelligent optimization algorithm. The hydrodynamic optimization applications for the Series 60 ship indicate that the wave-making resistance is reduced distinctly at various Froude numbers by the contrastive optimization algorithms and each optimized foreship hull-form is smoothing. The present study demonstrates an effective and robust integrated approach for the hydrodynamic optimization of ship design.