Pickens, B.A.; Taylor, J.C.; Finkbeiner, M.; Hansen, D., and Turner, L., 2021. Modeling sand shoals on the U.S. Atlantic shelf: Moving beyond a site-by-site approach. Journal of Coastal Research, 37(2), 227–237. Coconut Creek (Florida), ISSN 0749-0208.

The demand for offshore marine sands has escalated worldwide as sediments are needed for increasingly frequent beach renourishment and barrier island restoration. Sand shoals are often used as a source for dredging material because of the high volume of sand per unit area. Yet, investigations of shoals are typically conducted on a site-by-site basis, and a broader understanding of shoal availability is needed for strategic decision-making, including the mitigation of ocean use conflicts. Here, the primary objective was to model shoal distribution across the U.S. Atlantic shelf, including the Gulf of Mexico. Publicly available bathymetry data were obtained at a relatively coarse 90-m resolution. Variables of depth, standard deviation of depth, slope, bathymetric position index, and distance to shoreline were used as predictors to identify shoals. Unsupervised classifications of the seafloor were conducted to distinguish shoals and swales. Classification accuracy was assessed with validation databases of identified sand resources and named shoals compared to random locations; a visual assessment was also conducted. Shoals were further characterized by their origin. The classifications showed shoals and swales differed from the seafloor. Shoals were more shallow, had higher slope, a higher standard deviation of depth, were closer to the shoreline, and had a more positive bathymetric position index. Shoals were classified on 4.7% of the U.S. Atlantic shelf, and validation showed a percent agreement of 65–93%. Classified shoals visually coincided with the shape and extent of known sand resources. Shoals were characterized as cape-associated, bedform, isolated shelf, or uncharacterized. For the continental shelf, multivariate predictors represented the heterogeneous sloping substrates and the flat, high relief crests of sand shoals. The ability to classify shoals with 90-m resolution bathymetry data in the U.S. Atlantic reveals the methodology may be applicable to identify sand shoals elsewhere in the world with currently available data.

Finkl, C.W. and Makowski, C., 2021. Alongshore classification and morphometric analysis of coastal belts: The state of Oregon, USA. Journal of Coastal Research, 37(2), 238–271. Coconut Creek (Florida), ISSN 0749-0208.

Classification of the state of Oregon coastal belt (western United States) was based on the interpretation of satellite imagery using the Biophysical Cross-shore Classification System (BCCS). This seven-county, 480-km stretch was subdivided based on coastal archetypes that formed distinct bio-geomorphological and ecological sequences on both alongshore and cross-shore axes. Shore-parallel and shore-perpendicular units were concomitantly determined by cognitive inspection of satellite images, in which cross-shore archetypical sequences were observed in the first instance to have alongshore spread that could be secondarily codified in terms of alongshore catenas. Because shore-normal transects encompass marine, coastal, and terrestrial environments that have a shore-parallel width, it was possible to extrapolate cross-shore classificatory units into alongshore stretches called domains. Characterization of alongshore domains was based on conjoining archetypes into catenary sequences that typify coastal belts both alongshore and cross-shore from adjacent offshore areas to several kilometers inland. Compilation of coastal belt catenas showed that promontories and headlands, which are composed of resistant igneous and metamorphic rocks, function as anchor points along the shore and are interspersed by sedimentary (littoral) coastal belts that contain mainland and barrier beaches backed by dune, wetland, flat (estuaries), or upland archetypes. A consizement of several alongshore domain catenary sequences within a particular coastal segment thus formed an overarching super domain. Typical alongshore super domains consisted of the following sequences: Barrier-Beach-Dune (Ba-Be-Du), Barrier-Beach-Dune-Wetland (Ba-Be-Du-W), Beach-Dune-Upland (Be-Du-U), Beach-Dune-Wetland (Be-Du-W), Beach-Cliff-Upland (Be-Cl-U), Beach-Wetland-Flat (Be-W-F), and Rock-Cliff-Upland (R-Cl-U). Morphometric analysis of each county allowed the determination of specific characteristics for each super domain (e.g., alongshore length, percentage of the county coastal belt, and percentage of the Oregon coastal belt). Furthermore, archetype morphometrics were calculated to show which cross-shore archetypical features were most prevalent along the state's coastal belt. This examination of the Oregon coast showed that the alongshore classification of coastal belts on a regional scale, which is based on cross-shore biophysical interpretations, offers the opportunity to characterize offshore, inshore, and onshore eco-geomorphological features through the use of super domains and morphometric analysis. This approach to coastal classification thus serves as a blueprint for the comprehensive characterization of coastal belts worldwide.

Houston, J.R., 2021. Sea-level acceleration: Analysis of the world's high-quality tide gauges. Journal of Coastal Research, 37(2), 272–279. Coconut Creek (Florida), ISSN 0749-0208.

Coastal sea-level acceleration is analyzed using all of the world's high-quality tide gauge recordings with lengths of at least 75 years that extend through 2017–19. Earlier studies have demonstrated that tide gauge recordings of at least 75 years in length are required to reduce the effects of multidecadal variations on acceleration. There are 149 tide gauge records that meet the criteria. Mean and median sea-level accelerations based on these gauges were 0.0128 ± 0.0064 mm/y² and 0.0126 ± 0.0080 mm/y², respectively, both at the statistically significant 95% confidence level. The mean acceleration is larger than that of earlier studies that analyzed fewer gauges or considered record lengths shorter than 75 years.

Hanlon, L.M., 2021. First recorded account of arbuscular mycorrhizal fungi in sand dunes in south eastern Australia: Biogeography and species richness. Journal of Coastal Research, 37(2), 280–290. Coconut Creek (Florida), ISSN 0749-0208.

Coastal arbuscular mycorrhizal fungi on incipient foredunes survive in extreme and environmentally stressful ecosystems that are regularly eroded and replaced. These dunes encounter strong, salt-laden winds, sea-water overwash, and low nutrients and are subject to storms of greater magnitude than established foredunes, often being scarped. The species richness of coastal arbuscular mycorrhizal fungi was examined in sand dunes, as well as in the roots of mixed vegetation and grasses growing in the dunes, to elucidate differences in species between the incipient foredune and established foredune gradients and to address the paucity of information on the biogeography of coastal arbuscular mycorrhizal fungi. Seventy-three operational taxonomic units were identified through DNA analyses and classified into 16 arbuscular mycorrhizal species, of which Glomus spp. was dominant in both dune niches. Three species were specific to the established foredune ecosystem, and four discrete species were found in the incipient foredune ecosystem, demonstrating a robustness to disturbance. Additionally, one discrete species of arbuscular mycorrhizal fungus was found in the two incipient foredune grasses. All nucleotide sequences have been accepted and assigned accession numbers by GenBank. The identification of microbial biota in coastal sites is of vital importance in allowing more informed decisions to be made on the restoration and conservation of coastal sand dunes or ecosystem remediation. It is postulated that these results are the first to report the biogeography and species richness of arbuscular mycorrhizal fungi on the southern coast of Australia.

Burns, C.J.; Alexander, C.R., and Alber, M., 2021. Assessing long-term trends in lateral salt-marsh shoreline change along a U.S. East Coast latitudinal gradient. Journal of Coastal Research, 37(2), 291–301. Coconut Creek (Florida), ISSN 0749-0208.

Marshes are valuable intertidal habitats that respond to changes in their environment, and their perimeters can rapidly advance or retreat over time. This study used the analyzing moving boundaries using R (AMBUR) tool kit to measure approximately 70 years of edge change at salt marshes within three Long-Term Ecological Research sites along the U.S. East Coast: Georgia Coastal Ecosystems (GCE), Virginia Coast Reserve (VCR), and Plum Island Ecosystems (PIE). At each site, changes were assessed at the open-fetch marsh outer perimeter as well as throughout interior channels of varying sizes. At the open-fetch marsh outer perimeter, both the PIE and VCR study marshes exhibited significant net retreat, with the fastest rates in areas exposed to high fetch where wave action is strong, whereas the GCE marsh exhibited significant net advance. Changes in the sinuous interior channels were smaller, with channels often retreating on one edge but were balanced by advance on the opposite bank. When advance and retreat in the interior channels were considered along with the outer perimeter, the GCE and VCR study marshes exhibited dynamic stability in which overall marsh edge showed no significant net change, and the overall rate of marsh retreat at PIE, although still significant with respect to the uncertainty of the analysis, was considerably reduced. This study demonstrates the importance of assessing shoreline changes throughout the marsh, as rates of retreat and advance at the open-fetch marsh perimeter may differ greatly from those in the interior, and not be indicative of the overall change in marsh edge.

Eulie, D.O.; Leonard, L., and Polk, M., 2021. Sediment deposition and availability in riparian wetlands. Journal of Coastal Research, 37(2), 302–315. Coconut Creek (Florida), ISSN 0749-0208.

Coastal flooding and sea-level rise have the potential to negatively influence the ability of coastal wetlands to accumulate sediment, threatening the persistence of coastal wetlands. This study examines sediment availability, deposition rates, and elevation change in two types of tidally-dependent riparian wetlands to understand their ability to persist in the wake of rising sea level. Tidal marshes and riparian swamp habitats in blackwater and brownwater river systems were studied over a 32-month period between 2004 to 2007. Wetlands along the brownwater river system exhibited significantly greater and more variable deposition rates than those located along the blackwater river system (p < 0.05). The brownwater marsh lost –1.7 cm of elevation and the blackwater marsh lost –1.1 cm of elevation, while the brownwater swamp site had an increase of 7.0 cm and the blackwater swamp site exhibited an increase in elevation of 0.7 cm. Within the Cape Fear River Estuary, a combination of sediment availability, organic content, and wetland type (tidal brackish marshes, riparian freshwater swamp forests) are what most strongly influenced patterns of deposition but are strongly temporally and spatially influenced. Marshes in the Cape Fear River are losing elevation, while riparian swamps are, at the time of this study, maintaining their current elevation. Coastal tidal wetlands are under increasing pressure from climate change, sea-level rise, and urban development resulting in vertical drowning. Tidal marshes in the Cape Fear River are not able to maintain elevation, and riparian swamp forests may also be unable to as the magnitude of these pressures increase.

Balle, G.R.A.; Ahouansou, D.M.M.; Sintondji, L.C.O., and Agbossou, E.K., 2021. Analyses of short- and long-term shoreline trends of the southwest Benin coast. Journal of Coastal Research, 37(2), 316–325. Coconut Creek (Florida), ISSN 0749-0208.

Coastal zones are the economic heart of coastal countries and are therefore densely populated. In recent times, coastal zones are found to be globally eroding at variable spatiotemporal scales, leading to loss of business activities, ecosystems, economic lands, and infrastructures. Similar to elsewhere in the world, in West Africa and particularly the Benin Republic, the problem of the eroding shoreline is on the increase. Currently, the Grand-Popo section (the western part of the Benin coast) is experiencing serious shoreline change, which is causing the destruction of physical infrastructure and ecosystems. This study aims to determine the shoreline change trends in the study area over approximately a 10-year period from 1988 to 2018. To attend this objective, the SPOT and Sentinel-2 remotely sensed data of 10-m resolution were used, and the shoreline feature was extracted using the high-water line as an indicator. The shoreline feature dynamics were analysed using the Digital Shoreline Analysis System extension in ArcGIS, where the shoreline change statistics were computed and analysed. The results indicate that from 1988 to 2001, a high net shoreline accretion occurred, representing 80.39% of the entire study area at an average rate of 3.46 m/y. From 2001 to 2012, the Grand-Popo shoreline was affected by erosion representing approximately 85.17% of the study area at an average erosion rate of –4.54 m/y. Net shoreline accretion corresponding to 76.08% of the entire study coast at an average rate of 7.98 m/y also occurred between 2001 and 2012. Considering the entire study period (1988 to 2018), 68.51% of the shoreline accreted at an average rate of 0.79 m/y whereas 31.49% of the entire coast eroded at an average rate of –0.75 m/y. Major erosion was observed near the mouth of the Bouche du Roy estuary.

Castagno, K.A.; Donnelly, J.P., and Woodruff, J.D., 2021. Grain-size analysis of hurricane-induced event beds in a New England salt marsh, Massachusetts, USA. Journal of Coastal Research, 37(2), 326–335. Coconut Creek (Florida), ISSN 0749-0208.

Tropical cyclones pose a growing threat to coastal infrastructure and livelihood. Because instrumental and historic records are too short to help us understand interactions between tropical cyclones and climate on a longer scale, proxy records are the only means for reconstructing millennia of tropical cyclone impacts. This study determines grain-size trends in storm-induced overwash deposits along a transect of sediment cores from a salt marsh in Mattapoisett, Massachusetts, to characterize sorting trends and compare deposits associated with individual storms. The overwash deposits preserved within the high-marsh peat provide a record spanning the last two millennia. Building on a 2010 study, a different approach was used to accurately determine the grain-size distribution of overwash deposits from cores in a transect running perpendicular to the adjacent sandy/gravely barrier. Although maximum grain-size values are expected to decrease as distance from the barrier increases, not all event deposits that were studied follow this trend within uncertainty. Analysis of the storm event beds reveal a significant difference in settling trends between historic and prehistoric deposits, with historic deposits largely displaying landward-fining trends and prehistoric deposits largely displaying landward-coarsening trends. This suggests changes in the hydrodynamic or that geomorphic regime may have altered the way in which storm beds were deposited at this site. This new in-depth, transect-based approach has utility for improving the accuracy of future storm reconstructions, particularly for events for which no historic record exists.

Wei, C. and Theuerkauf, S.J., 2021. A novel multitemporal approach for satellite-derived bathymetry for coastal waters of Palau. Journal of Coastal Research, 37(2), 336–348. Coconut Creek (Florida), ISSN 0749-0208.

Shallow water bathymetry is important for understanding biogeophysical and socioeconomic processes in coastal areas. In recent years, satellite-derived bathymetry (SDB) methods have been increasingly used to provide high-resolution bathymetry estimation in different regions using single remote sensing images. To tackle the common issues of single-image SDB, such as data gaps due to cloud coverage and false bathymetry due to water turbidity, this study applied a novel multitemporal workflow for SDB estimation in Palau, a Pacific Island nation. This workflow implements the typical empirical SDB steps to calculate relative water depth (i.e. log ratio of the blue and green band) of 20 Landsat 8 images that were composited and subsequently related to in situ depth measurements to estimate true depth. Before composition, a histogram equalization approach was employed to normalize the images and identify clear water areas of each image pair by applying a 1% difference threshold. To achieve better performance, different methodological options at three key steps were evaluated, including temporal composition (mean vs. median), point data extraction (direct vs. bilinear interpolation), and regression (linear vs. piecewise vs. polynomial). Among 12 models, the polynomial model built upon bilinearly interpolated mean composition data performed the best, accurately estimating water depth up to the extinction depth of 13.7 m (45 ft), with a root mean square error of 1.76 m (5.77 ft). This multitemporal approach, with proper methodological choices according to local circumstances, could be applied to other regions to derive gap-free and accurate bathymetry estimations.

Liu, S.; Gao, M.; Hou, G., and Jia, C., 2021. Groundwater characteristics and mixing processes during the development of a modern estuarine delta (Luanhe River Delta, China). Journal of Coastal Research, 37(2), 349–363. Coconut Creek (Florida), ISSN 0749-0208.

The Luanhe River Delta (LRD) is divided into two parts, the ancient LRD and the modern LRD (MLRD), and has formed since 7000 calibrated years before present (cal yr BP). The MLRD developed from 2500 cal yr BP. Influenced by paleoclimatic changes and human activity, its groundwater environment is complex. In this study, groundwater monitoring methods, hydrochemistry, and isotopes are used to determine the groundwater characteristics and mixing processes during MLRD development. The groundwater dynamics show seasonal variations. The groundwater salinity distribution features vertical zones and is the same as the stratal distribution. The saline groundwater formation involves evaporation, condensation, hydrolysis, dissolution of evaporated salts, and mixing of groundwater with different qualities and hydrochemical compositions. Brackish water and saline water are the result of mixing between fresh and highly saline waters in deep groundwater based on the hydraulic conditions and the dispersion effect. The formation of the MLRD, which can be described as natural reclamation, provides good groundwater flow and mixing channels. Based on hydrochemical data, the mixing model, and the hydrochemical facies evolution diagram, salinity in shallow groundwater is influenced by seawater intrusion and saline water intrusion. The concentrations of sodium and chloride can indicate the intrusion degree. Precipitation and other freshwater inputs provide the main recharge sources that lead to freshening of the shallow groundwater. Close to the sea, the water exchange between groundwater and seawater is intense, which can lead to similar hydrochemical characteristics of groundwater and local seawater. Saline water intrusion in deep groundwater is more serious than that in shallow groundwater because there is no other freshwater recharge to deep groundwater.

Carvalho, A.M.; Lima Jr., S.B.; Maia, L.P.; Claudino-Sales, V.; Gastão, F.G.C.; Eduardo, L.M.; Pinheiro, L.S., and Silva, M.V.C., 2021. Understanding polydirectional aeolian cross-strata architecture in a coastal unidirectional wind regime. Journal of Coastal Research, 37(2), 364–379. Coconut Creek (Florida), ISSN 0749-0208.

Crescentic dune fields along the NE coast of Brazil were analyzed to justify processes associated with the wide range of cross-strata dip directions in aeolian deposits found in a unidirectional wind regime. Multiple spatial and temporal field-based methodologies were employed, including trenching, ground penetrating radar (GPR), and photogrammetry. Wind dynamics, coastline morphology, bounding surface developing processes, and dune migration patterns were also considered. Analysis revealed a relationship between small- and large-scale morphologies of the crescentic dune field. The interactions of crescentic dune crests, in association with the superposition of multiple superposed dunes, explain the majority of cross strata and dip directions found in dune trenches and GPR sections. This study provides convincing evidence that microscale structures observed within trenches and GPR sections are compatible with the macroscale slipface position observed within the dune field. Small-scale changes in wind direction, caused by the dune crest morphologies themselves, explain much of the supposedly unexpected strata dip directions that arc through from 90° to 180°. The presence of near-surface water tables supports the formation and preservation of aeolian cross-strata sequences.

Yue, B.; Liu, S.; Yan, Z.; Liao, J., and Gao, M., 2021. Geomorphological difference and genesis of typical sandy coasts in the northern and southern Shandong Peninsula. Journal of Coastal Research, 37(2), 380–388. Coconut Creek (Florida), ISSN 0749-0208.

Two landform monitoring sections of sandy coasts in the southern and northern Shandong Peninsula are chosen as the research objects. Empirical orthogonal functions were used to extract the spatial characteristics function and time characteristics function of the first four modes from the monitoring data in summer and winter from December 2012 to December 2015. Characteristics of spatial changing and beach flat variation of the two sandy coasts were analyzed. Differences in geomorphic features and sedimentary characteristics between the southern and northern coasts have been compared. The difference and impact factors of the dynamic environment in the northern and southern Shandong Peninsula were discussed in this paper. The results show that the first characteristic function is the main model of showing beach section change. On the southern coast, the beach section presents a gradually enhancing trend characteristic from a beach berm to a broken belt. The northern coast shows the main fluctuation characteristic from the high tidal zone to an upper limit of the upper bound, which is related to waves and tides. Moreover, the second and third characteristic functions are controlled by seasonal periodic changes in stormy waves. The fourth characteristic function is speculated to be related to accidental factors.

Waldron, M.C.B.; Carter, G.A., and Biber, P.D., 2021. Using aerial imagery to determine the effects of sea-level rise on fluvial marshes at the mouth of the Pascagoula River (Mississippi, USA). Journal of Coastal Research, 37(2), 389–407. Coconut Creek (Florida), ISSN 0749-0208.

Coastal marshes provide valuable ecosystem services yet are increasingly vulnerable to sea level rise (SLR).To facilitate a better understanding of how fluvial marshes along the Gulf of Mexico coast are responding to regional SLR of around 3.7 mm per year, this study used aerial imagery to map land cover at the mouth of the Pascagoula River at 20-year intervals, beginning in 1955 and ending in 2014. High-resolution land cover maps were created for each image date based on a maximum likelihood classification scheme using spectral and textural image features. This marsh ecosystem, at the mouth of the largest free-flowing river by volume in the contiguous United States, should be more resilient to sea level rise than other Gulf Coast marshes, with little restriction to sediment supply and relatively low subsidence rates measured nearby. However, the results of this study show that marsh area declined by 1073 ha (17.5%) and rates of marsh conversion to open water increased over the studied time period. Although modeling studies indicate that coastal marshes worldwide may persist under accelerated SLR, these observations suggest that marsh extent in the sediment-rich Pascagoula River Estuary will continue to decline, signifying vulnerability among other marsh ecosystems along the northern Gulf of Mexico coast.

Lucia, G.; Polyak, V.J.; Ginés, J.; Fornós, J.J.; Ginés, A.; Asmerom, Y., and Onac, B.P., 2021. Chronology of middle Pleistocene coastal karst evolution and relative sea-level changes in Mallorca. Journal of Coastal Research, 37(2), 408–420. Coconut Creek (Florida), ISSN 0749-0208.

Sea-level change affects the geomorphic evolution of littoral regions in multiple ways. In carbonate coastal regions, sea-level oscillations control the type and occurrence of karst processes such as mixing corrosion, speleothem deposition, and collapse. A variety of cave deposits exist above, below, and at sea level. Among these, the vadose speleothems can provide indirect constraints on maximum sea-level boundaries, record changes from vadose to phreatic phases as littoral groundwaters flood the caves due to sea-level rise, and document different coastal speleogenetic stages. Here, new U-series ages for speleothems from three sites along the eastern coast of Mallorca (Cala Falcó, Dimoni, and Sa Ferradura) are presented and used to discuss the effects of relative sea-level oscillations upon coastal karst evolution between ∼1500 and ∼440 kyr before present. The paleo-speleothem record provides new timeframes for periods of vadose conditions allowing to place some relative sea-level constraints in the western Mediterranean, particularly for the Marine Isotope Stages 16 to 12. Periodic sea-level oscillations following glacial/interglacial cycles caused morphological changes within the paleo-caves. The sequences of collapsed karst features and vadose speleothems, coupled with geomorphological evidence and previous published sea-level records, support an interpretation for the occurrence of breakdown events during cold intervals following MIS 11, 9, and 7 sea-level high stands. Further collapses and dismantling of caves happened after MIS 5 high sea stands and throughout the Holocene.

Thakare, L.M. and Shitole, T.A., 2021. Vulnerability assessment of the Ratnagiri coast (Maharashtra, west coast of India). Journal of Coastal Research, 37(2), 421–432. Coconut Creek (Florida), ISSN 0749-0208.

The Ratnagiri coast, situated in Maharashtra state, West Coast of India, is potentially vulnerable to the erosional hazards, frequent rehabilitation of land, and accelerated sea-level rise. In recent years, the evidence shows erosional threats and gradual submergence along the creeks and lowlands of Ratnagiri. To deliberate the vulnerability of these hazards, vulnerability ranking was assigned using a coastal vulnerability index (CVI) using six geophysical parameters. The datasets were obtained from the satellite data of Landsat series from the years 1973, 2015, and 2019 to derive geomorphology of the coast and coastal landforms. Shoreline change along Kelshi, Kachave-Undi-Waravde region, and Mirya bay and beach have been evaluated using the Digital Shoreline Analysis System by demarcating the baseline and shorelines from the series of Landsat data. Data obtained is re-improvised with Google data for updating the recent change in the study area. Elevation data is extracted from Advanced Spaceborne Thermal Emission and Reflection Radiometer data of 30 m spatial resolution, the susceptibility of coastal inundation was derived using General Bathymetric Chart of the Oceans data, and this has indicated northerly submergence of the coast, prone to become vulnerable. The tidal variations along two major gauging stations were extracted from Windows Unix program for Tides 32 software for Rajapur and Mormugao stations. The CVI results in the categorization of areas with a high-risk vulnerability along the beaches, creeks, and estuaries of Kelshi, Jaigad, Rajapur, and Kajali, while low-risk areas like cliffs and shoals are geologically confronted. The findings from the CVI suggest the need for identifying and mapping such vulnerable areas and is an initial step to emphasize coastal regions for climate change adaptations.

Hossain, M.S.; Muslim, A.M.; Pour, A.B.; Mohamad, M.N.; Alam, S.M.R.; Nadzri, M.I., and Khalil, I., 2021. Mapping different types of shorelines from coarse-resolution imagery: Fuzzy classification method can deliver greater accuracy. Journal of Coastal Research, 37(2), 433–441. Coconut Creek (Florida), ISSN 0749-0208.

Coastal zones are among the most structurally complex ecosystems, though their complex shorelines are threatened because of both natural and anthropocentric influences. There are a smaller number of studies that dealt with developing remote-sensing techniques for detecting and mapping different shoreline types (ST) using coarse-resolution imagery. This study examined fuzzy c-means (FCM), wavelet interpolation, and fuzzy maximum likelihood to map shorelines over Seberang Takir (Malaysia) for different STs. These three fuzzy classification methods were applied to simulated IKONOS (with 16- and 32-m spatial resolutions) image covering the four STs. The positional accuracy of shorelines was assessed in terms of root mean square error (RMSE). The visual inspection and RMSE values showed that variations in accuracies were evident, predominantly due to differences in STs; fuzzy algorithm improved the accuracy. FCM can predict shoreline positions with greater accuracy than the other two methods.

Qu, K.; Sun, W.Y.; Ren, X.Y.; Kraatz, S., and Jiang, C.B., 2021. Numerical investigation on the hydrodynamic characteristics of coastal bridge decks under the impact of extreme waves. Journal of Coastal Research, 37(2), 442–455. Coconut Creek (Florida), ISSN 0749-0208.

Extreme waves, such as freak waves or rogue waves, occur unexpectedly in the ocean and have extremely large wave heights. Extreme waves often are attributed to the process of wave focusing. Coastal structures such as bridges are highly susceptible to extreme waves and have caused substantial damage to coastal infrastructure in the past. Although impacts of various types of waves on coastal bridges have been studied in the past, hydrodynamic loads on bridge deck under the impact of extreme waves have not yet been investigated. This work adds to the existing body of work by systematically carrying out numerical investigations on the hydrodynamic characteristics of coastal bridge decks under the impact of extreme waves generated by wave focusing. Simulations were carried out by creating a numerical wave tank (NWT) using the open-source flow solver REEF3D, which numerically solves the governing equations of the incompressible two-phase flow on a staggered mesh and captures the interface between air and water using a high-resolution level-set method. The NWT was validated for the case of focused waves and wave impact loads on a two-dimensional (2D) rectangular cylinder in a straight channel and compared to experimental measurements. The NWT was then used to study the hydrodynamic loads of a coastal bridge deck by considering the effects of four prominent factors, i.e. submersion depth, wave height, wave period, and water depth. The findings made in this paper enhance the understanding of the damage mechanisms of coastal bridges under the impact of extreme waves.