Search

Cabral, A.P. and Noernberg, M.A., 2024. Morphological characteristics of an open shelf ridge at Rio Grande do Norte continental shelf, NE Brazil. Journal of Coastal Research, 40(6), 1166–1181. Charlotte (North Carolina), ISSN 0749-0208. This paper describes for the first time the occurrence of an open shelf ridge (OSR) in the South Atlantic Ocean, evidencing morphological differences with respect to occurrences in other regions. The unique configuration of this OSR derives from the characteristics of the shallow continental shelf frontal to the Calcanhar Cape, Rio Grande do Norte State, Brazil, where it is located. It is a shallow, narrow, stepped shelf with an escarpment corresponding to a drowned shoreline around the 35 m isobath. There are extensive siliciclastic and carbonate sand deposits, sand ribbons, subaqueous dune fields, coral reefs, and calcareous algae patches. The high transparency of the water allows the use of multitemporal optical satellite images from remote sensors in the bathymetric modeling and morphodynamic description, in conjunction with echo sounder surveys, in situ sampling, and modeling. The metocean conditions of the region were determined from current and wind data obtained in situ, as well as data from the Hybrid Coordinate Ocean Model (HYCOM) and Regional Ocean Modeling System (ROMS) numerical models. Combining these data allowed the identification, characterization, and analysis of the metocean patterns over the OSR. Superimposed onto the OSR, there is a field of asymmetric subaqueous dunes transverse to the ridge axis with wavelengths between 150 m and 2 km and heights between 2.5 m and 9 m, with a tendency for sediment transport offshore northwestward of the OSR crest. The synergistic effect of the dominant NE winds and the North Brazil Current with tidal currents drives the main metocean forcings. The hydrodynamic pattern for the main sedimentary deposit areas is described, and the effect of the OSR on general subaqueous dune field configuration is presented. [ABSTRACT FROM AUTHOR]

The southeastern United States Coastal Plain ecosystem contains baldcypress (Taxodium distichum) swamps and grass‐dominated marshes. These ecosystems also occurred on the exposed continental shelf during lower sea levels but are rarely preserved due to the mechanically erosive nature of transgression and regression. Two presently marine sites on the northeastern Gulf of Mexico's continental shelf contain well‐preserved woody terrestrial sediments that were the subject of previous studies. This study continues the investigation using geochemical (δ13C, δ15N, δ34S) and palynological characteristics of these formerly terrestrial sediments to determine if swamps and/or marshes existed at the time of deposition. The first site is located ∼20 km southeast of Horn Island, Mississippi (MS) and the core has terrestrial sediments radiocarbon dated to 11,066–10,228 (2σ) calibrated years BP (early Holocene). The second site is the "Alabama Underwater Forest" located ∼13 km south of Gulf Shores, Alabama (AL) and the cores have terrestrial sediments optically stimulated luminescence dated to 63 ka (±10 ka, 2σ) to 72 ka (±16 ka, 2σ) (late Pleistocene). Geochemical results for the MS sediments indicate a swamp‐to‐freshwater marsh transitional series, whereas the AL sediments indicate a swamp‐to‐saltwater marsh transitional series, both supported by palynological results. Further exploration of the geochemical results using linear discriminant analysis, trained with published geochemical data, supports the swamp and marsh interpretations. We conclude that the near‐pristine preservation of these woody deposits is not solely due to physical mechanisms, such as rapid burial, but is also coupled with anoxia‐ and euxinia‐driven biogeochemical reactions promoting wood and woody debris preservation in swamp and marsh environments. Plain Language Summary: Scientists have studied unique sites offshore of Alabama and Mississippi that contain soils, peat, wood, and tree stumps. Scientists have determined that the trees from the Alabama site are between 42,000 and 72,000 years old and were alive during the last ice age when sea levels were much lower than today. The Mississippi site contains woody peat sediments about 11,000 years old and occurred when sea levels were rapidly rising globally. These types of formally land‐based sediments are eroded as the sea level rises at the end of the glacial periods. Furthermore, wood and plant matter decay after the plant dies and become part of the soil. We investigated the chemistry of the preserved soils to understand the conditions that lead to their preservation. Chemical and pollen analyses found that these deposits are past swamp and marsh ecosystems that occurred on land similar to those occurring along the United States Gulf Coast today. Swamps and marshes have still waters with little oxygen that stop decay leading to the preservation of the wood and tree stumps. Swamps occur in depressions where water can collect and over time they fill with sediments. These preserved swamp deposits are time capsules from the past. Key Points: Multiple paleo‐terrestrial deposits containing wood and peat are preserved offshore in the northeastern Gulf of MexicoGeochemical and microfossil analyses find that these deposits are past swamp and marsh ecosystemsSwamps and marshes that are anoxic and/or euxinic promote the biogeochemical preservation of woody and organic matter [ABSTRACT FROM AUTHOR]

Numerical modeling of wave transformation, hydrodynamics, and morphodynamics in coastal regions holds paramount significance for combating coastal erosion by evaluating and optimizing various coastal protection structures. This study aims to present an integration of numerical models to accurately simulate the coastal processes with the presence of coastal and harbor structures. Specifically, integrated modeling employs an advanced mild slope model as the main driver, which is capable of describing all the wave transformation phenomena, including wave reflection. This model provides radiation stresses as inputs to a hydrodynamic model based on Reynolds-averaged Navier–Stokes equations to simulate nearshore currents. Ultimately, these models feed an additional model that can simulate longshore sediment transport and bed level changes. The models are validated against experimental measurements, including energy dissipation due to bottom friction and wave breaking; combined refraction, diffraction, and breaking over a submerged shoal; wave transformation and wave-generated currents over submerged breakwaters; and wave, currents, and sediment transport fields over a varying bathymetry. The models exhibit satisfactory performance in simulating all considered cases, establishing them as efficient and reliable integrated tools for engineering applications in real coastal areas. Moreover, leveraging the validated models, a numerical investigation is undertaken to assess the effects of wave reflection on a seawall on coastal processes for two ideal beach configurations—one with a steeper slope of 1:10 and another with a milder slope of 1:50. The numerical investigation reveals that the presence of reflected waves, particularly in milder bed slopes, significantly influences sediment transport, emphasizing the importance of employing a wave model that takes into account wave reflection as the primary driver for integrated modeling of coastal processes. [ABSTRACT FROM AUTHOR]

Relevance. Annually, the coastal areas of the Mekong Delta receive approximately 50% of the total sediment load from the Mekong River, primarily during the southwest monsoon. During the northeast monsoon, this coastal sediment undergoes reworking and is transported southwestward along the coastal areas of the Mekong delta. Aim. Analyzing the grain-size distribution of sea-bed surface sediment helps improve our understanding of sediment redistribution along the coastal areas of the Mekong Delta. Methods. In order to illustrate changes in sea-bed surface sediment grain size between the two monsoons, we focused on the median grain size, a widely used parameter for sediment transport calculation, and created spatial maps of median grain size along the coastal areas of the Mekong Delta. The analysis was based on sediment samples collected along the coastal areas of the Mekong Delta during field excursions in the southwest and northeast seasons. Results. The results reveal that median grain size during northeast (mainly ranging from 0.005 to 0.01 mm) are larger than those during southwest (primarily ranging from 0.01 to 0.05 mm). These changes in median grain size and spatial distributions are most prominent along the east coast, specifically from Soc Trang to Bac Lieu. In contrast, median grain size along the west side does not exhibit significant differences between the southwest and northeast monsoons. These observations imply a more significant sediment transport along the east coastal areas of the Mekong Delta during the northeast monsoon and provide evidence for the transportation of sediment from the east coast to the west coast during the monsoons.

Numerical modeling of wave transformation, hydrodynamics, and morphodynamics in coastal regions holds paramount significance for combating coastal erosion by evaluating and optimizing various coastal protection structures. This study aims to present an integration of numerical models to accurately simulate the coastal processes with the presence of coastal and harbor structures. Specifically, integrated modeling employs an advanced mild slope model as the main driver, which is capable of describing all the wave transformation phenomena, including wave reflection. This model provides radiation stresses as inputs to a hydrodynamic model based on Reynolds-averaged Navier–Stokes equations to simulate nearshore currents. Ultimately, these models feed an additional model that can simulate longshore sediment transport and bed level changes. The models are validated against experimental measurements, including energy dissipation due to bottom friction and wave breaking; combined refraction, diffraction, and breaking over a submerged shoal; wave transformation and wave-generated currents over submerged breakwaters; and wave, currents, and sediment transport fields over a varying bathymetry. The models exhibit satisfactory performance in simulating all considered cases, establishing them as efficient and reliable integrated tools for engineering applications in real coastal areas. Moreover, leveraging the validated models, a numerical investigation is undertaken to assess the effects of wave reflection on a seawall on coastal processes for two ideal beach configurations—one with a steeper slope of 1:10 and another with a milder slope of 1:50. The numerical investigation reveals that the presence of reflected waves, particularly in milder bed slopes, significantly influences sediment transport, emphasizing the importance of employing a wave model that takes into account wave reflection as the primary driver for integrated modeling of coastal processes.

AlMashan, N.; Al-Attar, I., and Neelamani, S., 2024. Assessment of annual sedimentation into Failaka Marina (Kuwait) and possible solutions for reduction of siltation. Journal of Coastal Research, 40(3), 527–553. Charlotte (North Carolina), ISSN 0749-0208. Sedimentation is critical for ports, harbors, and marinas, requiring accurate assessment. Failaka Marina in Kuwait is experiencing a severe noncohesive sedimentation problem. The samples collected at the seven locations along the beach showed that the beach has a uniform grain-size diameter, meaning it is poorly graded sand. The sampling at the tip of the southern breakwater showed that the shoaling is mainly sand. The suspended-sediment concentration varies from 0.025 kg m–3 to 1.2 kg m–3, whereas the mean concentration at the marina entrance is 0.85 kg m–3. The time series of the suspended solids over a year in the seawater surrounding Failaka Island shows a range of 8 to 48,069 ppm. Such a considerable variation in suspended load is due to the massive amounts of dredging and spoil disposal at Boubyan Island and Basra Port (Iraq) when a high sediment load moves around Failaka Island with a concentration of more than 40,000 mg L–1. Annual sedimentation is about 2.35 m y–1, which is responsible for blocking the main entrance for navigation. Kuwait's Ministry of Communication allocates $4 to $6 million annually for dredging and disposal activities. This study evaluates the six marina entrance modification scenarios to determine the best scenario that achieves a measurable reduction in sedimentation rate in the Marina. Six marina breakwater modifications were studied, and annual sedimentation rates were numerically computed. The study use Coupled MIKE 21/3 to simulate hydrodynamic conditions for cohesive sediment transport in a problem area. Field data from 2015 calibrated and validated the model. The primary sediment-moving force is SE wind and sea-swell waves. Littoral drift along Failaka Island's southern coastline and high suspended-sediment concentration result in littoral drift and settling. The best scenario showed a 28% sedimentation reduction and a 26% reduction in maintenance dredging costs from the six studied scenarios. [ABSTRACT FROM AUTHOR]

Coastal erosion is a pervasive global phenomenon, exemplified by the Hel Peninsula situated in the Gulf of Gdańsk, the southern Baltic Sea. The geological constitution of the Hel Peninsula, characterized by sandy and loosely consolidated material, predisposes its coastal zones to continual morphological changes. The peninsula's limited width and elevation exacerbate shoreline erosion, particularly during periods of heightened storm activity. This study scrutinizes the effectiveness of coastal nourishment interventions, with a specific focus on segments influenced by the Władysławowo port and the Kuźnica vicinity, over several years. This specific section of the coast serves as a significant case study due to its role as a transit zone for sand transport along the whole peninsula. Protective measures, including shore nourishments and coastal groynes, aim to mitigate erosion impacts. Utilizing Airborne Laser Scanning (ALS) data spanning from 2008 to 2022, erosion dynamics were analyzed. The analysis reveals significant erosion patterns coinciding with the frequency and volume of nourishment material deposition, particularly evident in heavily nourished areas proximate to Władysławowo and Kuźnica. Despite persistent monitoring endeavors, persistent erosive trends pose imminent threats to Kuźnica's infrastructure, necessitating further research into the efficacy of implemented coastal protection measures. [ABSTRACT FROM AUTHOR]

The integration of machine learning (ML) techniques in coastal engineering marks a paradigm shift in how coastal processes are modeled and understood. While traditional empirical and numerical models have been stalwarts in simulating coastal phenomena, the burgeoning complexity and computational demands have paved the way for data-driven approaches to take center stage. This review underscores the increasing preference for ML methods in coastal engineering, particularly in predictive tasks like wave pattern prediction, water level fluctuation, and morphology change. Although the scope of this review is not exhaustive, it aims to spotlight recent advancements and the capacity of ML techniques to harness vast datasets for more efficient and cost-effective simulations of coastal dynamics. However, challenges persist, including issues related to data availability and quality, algorithm selection, and model generalization. This entails addressing fundamental questions about data quantity and quality, determining optimal methodologies for specific problems, and refining techniques for model training and validation. The reviewed literature paints a promising picture of a future where ML not only complements but significantly enhances our ability to predict and manage the intricate dynamics of coastal environments. [ABSTRACT FROM AUTHOR]

Global concern on extreme events is increasing the need for real timemonitoring of the wave fields in coastal areas. High Frequency (HF) radars, a remote sensing technology widely applied to measure near real time surface coastal currents with demonstrated accuracy, can also play a major role in the operational monitoring of waves height, period and direction. However, the ability of HF radar to measure waves can be jeopardized by specific ocean-meteorological and environmental conditions. Thus, a case-to-case analysis and parameterization is necessary to ensure the best data in each study area. In the southeastern (SE) Bay of Biscay, the EuskOOS HF radar network, composed by two compact HF radar stations provides hourly surface waves data in near real time. In this work, we analyze the effects of wind and noise levels on the radar skills for wave measurement, compared with existing in-situ data obtained by an offshore buoy. Then, the HF radar wave measurements for 2022 are analyzed with special focus on the most energetic observed wave events. The analysis performed versus in-situ data shows that both stations present reliable and accurate data for waves over 1.5 m, in agreement to what can be expected for a 4.46 MHz radar. The highest correlations are observed for waves > 4 m significant wave height, which demonstrates the capabilities for monitoring highly energetic events. Interference and noise detected on very precise time slots significantly reduced the availability and reliability of the measurements. Also, local winds blowing from land direction were found to affect the agreement between radar and in-situ measurements. Recommendations extracted from the analysis are provided, with the aim that they can be extended to other HF networks for more accurate wave monitoring. [ABSTRACT FROM AUTHOR]

Andrade, H.A.A.; Rodrigues, F.C.G.; Fletcher, C.H.; Casey, G., and Giannini, P.C.F., 2024. Winter sedimentology and morphology of the Maçambaba beach–foredune system, SE Brazil. Journal of Coastal Research, 40(2), 338–352. Charlotte (North Carolina), ISSN 0749-0208. The Maçambaba Holocene coastal barrier and dune system in Rio de Janeiro state, Brazil, is located immediately west of an abrupt orientation change from SW-NE to W-E on the SE Brazilian coastline. The eolian deposits are formed by winds from the SW, associated with polar air masses advancing in austral winter, and winds from the NE, associated with summer monsoon and upwelling intensification. The active beach–foredune system consists of intermediate reflective beaches and ramp incipient foredunes in the western (km 0–km 14) and central (km 15–km 35) sectors of the barrier and intermediate to dissipative beaches with more common ridge incipient foredunes in the eastern sector (km 36–km 48). This pattern from W to E indicates a change in the beach–foredune system from a more erosional regime with lower sand supply in the west to a more depositional setting in the east. Measured at the swash line, winter mean grain size fines and granulometric sorting increases from W to E, evidence of a net longshore drift in this direction. The increase in eolian sand supply toward the east favors sand reworking by SW (onshore) winds in the winter; consequently, coastal dunes are well developed in this sector. Overwash processes frequently develop where eolian deflation favors marine inundation during winter swell events. After their formation, washover fans are typically reworked by reverse winds from the NE (offshore) in austral summer. Throughout the entire barrier system, seasonal shifts in both swell orientation and wind direction are dominant climatic factors determining the development of washover fans, blowouts, and parabolic dunes with opposing migration directions. Investigating the effect of this climatic seasonality on the beach–foredune system is critical to understanding coastal response to storm events and climatic variations on longer timescales. A barreira costeira holocênica de Maçambaba localiza-se no estado do Rio de Janeiro, Sudeste do Brasil, imediatamente a oeste de uma mudança abrupta de orientação na costa, de sudoeste-nordeste para oeste-leste. Os depósitos eólicos são formados pelos ventos de sudoeste, associados às massas de ar polar que avançam no inverno austral, e pelos ventos de nordeste, associados à monção de verão e à intensificação da ressurgência. Nos setores central e oeste da barreira, o sistema praia-duna ativo consiste em praias intermediárias refletivas e dunas frontais incipientes em rampa. No setor leste, ele é composto por praias intermediárias dissipativas e dunas frontais incipientes em cordão. A passagem de dunas frontais em rampa, na parte oeste da barreira, para dunas frontais dominantemente em cordão, na parte leste, indicam que o aporte de areia eólica é maior a leste que a oeste. Nas amostras coletadas no espraiamento, a seleção granulométrica melhora e o tamanho médio de grão diminui de oeste para leste, o que é sugestivo de transporte longitudinal de sedimentos nesse rumo. O crescimento do aporte sedimentar para leste aumenta o retrabalhamento eólico pelos ventos de sudoeste (onshore) no inverno, e consequentemente as dunas costeiras são melhor desenvolvidas no setor leste, incluindo a formação de rupturas de deflação (blowouts). Neste setor, processos de sobrelavagem costeira frequentemente se desenvolvem onde a deflação eólica favorece a inundação marinha durante eventos de swell no inverno. Após sua formação, os leques de sobrelavagem são geralmente retrabalhados pelos ventos reversos de nordeste (offshore) no verão austral. Na barreira como todo, mudanças sazonais na orientação do swell e na direção do vento são fatores climáticos dominantes que determinam o desenvolvimento e deposição de leques de sobrelavagem, blowouts e dunas parabólicas com direções de migração opostas. Investigar o efeito dessa sazonalidade climática no sistema praia-duna ativo é fundamental para entender a resposta costeira a eventos de tempestade e variações climáticas em escalas de tempo mais longas. [ABSTRACT FROM AUTHOR]

Despite considerable differences in local conditions, the average air flow parameters at coastal stations had similar seasonal and interannual patterns. The decreasing trends in average wind speeds were not reliable due to inhomogeneity in the long-term series. Being less sensitive to inhomogeneities, both the zonal and meridional components and the average air flow estimates increased in 1966â2021. The changes in flow direction and in other wind characteristics were better described as quasi-cyclic rather than using a linear trend. In the Sõrve coastal case study, the wind velocity components were separated into opposite subsets, which were one-sidedly analysed by ignoring the other direction. Both westerly and easterly sub-components increased by 0.5 m/s in 2004â2021. Regarding wind-driven coastal processes along the peninsula, the changes in the westerly component, but not in the easterly component, are important on the western coast, and vice versa for the eastern coast. Assuming the potential impacts of winds via waves and currents, the influence of long-term changes in sea ice conditions were considered. Although the forcing load was more than twice as high on the western coast, the relative effect of the âice maskâ was smaller, as ice conditions were milder there. Along the eastern coast of the Sõrve Peninsula, the prevalence of SW-directed forcing can be expected, because the westerly forcing is shaded there by land. The SW-directed flow has strengthened over the study period because of an increase in the easterly and northerly wind speed subset and a decrease in the ice cover on the Gulf of Riga.

A field assessment was carried out in May 2023 in a natural protected area in South Italy to investigate the real-time behavior and fate of common marine litter items at different depths at the nearshore and foreshore under low energetic conditions. The field data were also compared with theoretical values calculated using theoretical formulations considering the Stokes drift current, wind-induced current, and current at breaking position. The wind approached from N to W, with values ranging from 2.4 to 3.8 m/s. The propagated significant wave height ranged from 14 to 21 cm, with an associated period of 3 s. Items with a positive buoyancy recorded different velocities. Very protruding (above water surface) items were greatly affected by windage and recorded velocities from 0.23 to 0.33 m/s; higher than the theoretical values that do not take into account windage. Theoretical values correctly predicted the velocity of other less-protruding items but slightly underestimated the velocity of neutral buoyancy items, evidencing in both cases the low relevance of the Stokes drift current. Items with a negative buoyancy moved (or not) in the bottom with different velocities. Different behaviors were observed at the breaking point, where items surfed (or not) spilling breaking waves, and at the foreshore, where items moved along the plunge step or in a "zig–zag" movement due to a swash–backwash process. [ABSTRACT FROM AUTHOR]

Sandy beaches have different shoreline change rates (i.e., erosion/accretion rates). An erosive process on beaches poses risks for human-occupied areas. One example is Matinhos Beach (state of Paraná - Brazil), which has an average annual erosion rate of around 1.5 m yr-1 This study applied a methodology that combines in situ measurements and numerical modeling to simulate the physical processes in the coastal area of Matinhos during the 2018 Austral winter. Monthly DGPS surveys were carried out in the study area from June to September. The MOHID modeling system was applied to simulate hydrodynamics and sediment transport, considering waves and tidal forcing validated with in situ data. The WAVEWATCH III and SWAN models were applied in a nesting approach to simulate the waves at Matinhos Beach. The GFS was used to assess the wind conditions. The study period showed a dynamic evolution of accretion and erosion between monthly measurements with no clear pattern in most profiles. Significant sand accumulation was observed near the headland. Morphological changes were minor due to the predominance of low energy without significant storm events. The measured morphological changes are in line with the residual littoral drift obtained from the modeling results for the period. The residual current velocities were towards the southwest, with magnitudes ranging from 0.15 m s-1 to 0.2 m s-1. A slight variation in the angle of wave incidence (10°) may change the direction (southwest or northeast) and intensity of the littoral drift. The applied methodology can reduce uncertainty and support effective coastal management. However, the seasonal scales of wave climate cannot be disregarded, nor can the need for coastal oceanographic data. [ABSTRACT FROM AUTHOR]

Coastal nutrient loading has been linked to a decline in the capacity of seagrass ecosystems to sequester carbon (‘blue carbon’); however, the mechanisms are unclear. Here we investigated how nutrient loading can affect the contribution that seagrass plant material makes to blue carbon stocks by investigating plant quality-decomposition dynamics. Specifically, we used a combination of laboratory and field experiments to account for various changes in biogeochemical cycling from seagrass meadows, ranging from changes in leaf quality to CO2 fluxes. It was found that nutrient loading increased the ‘labile’ content of seagrass (i.e. increased levels of leaf nitrogen, phosphorus and soluble organic carbon (amino acid and soluble sugar content), and at the same time decreased levels of ‘recalcitrant’ carbon (i.e. materials that are harder for microbes to break down, such hemicellulose, cellulose and lignin contents). Nutrient-enriched leaves decomposed ∼ 18 % faster than non-enriched leaves (i.e. greater biomass loss from nutrient-affected seagrass), resulting in ∼ 80 % more CO2 emissions from nutrient-enriched seagrass. We also found that seagrass that naturally contained high levels of labile carbon at the start of the experiment were affected to a greater degree (i.e. higher CO2 emissions) by nutrients addition than seagrass that had high proportions of recalcitrant carbon to begin with. Overall, these findings suggest that nutrient loading can weaken the capacity of seagrass ecosystems to act as blue carbon sinks through its effect on seagrass leaf decomposability.

The acceleration of coastal processes is manifested in the form of coastal erosion, average sea level rise, drastic changes in coastlines, and more turbulent ocean waters. In this study, the coasts of Kerala and Tamil Nadu, India, were selected to identify the effects of increasing coastal processes. Therefore, it is necessary to identify and map vulnerable areas by taking into account the key parameters, such as topographical and socio-economic factors, to relate to coastal processes. The fuzzy Analytical Hierarchy Process (AHP) method was employed to identify the most vulnerable zones. The key findings revealed that about 14% and 2% of the coast of Tamil Nadu and Kerala, respectively, are classified under the physically highly vulnerable category. Similarly, ~17% and ~30% of coastal Tamil Nadu and Kerala, respectively, are highly socially vulnerable. The overall vulnerability assessment showed that 7–8% of both coastal areas were highly vulnerable. We concluded that the Thiruvallur, Chennai, Kanchipuram, Cuddalore, and Nagapattinam coasts on the east coast and the Malappuram, Thrissur, Ernakulam, Alappuzha, and Kollam coasts on the west coast were very highly vulnerable to coastal processes. Identifying vulnerable zones helps to better understand the impacts of rapid coastal processes and, with this prior estimation, the policymakers can take necessary actions to mitigate the irreversible impacts of coastal processes. [ABSTRACT FROM AUTHOR]

The integration of machine learning (ML) techniques in coastal engineering marks a paradigm shift in how coastal processes are modeled and understood. While traditional empirical and numerical models have been stalwarts in simulating coastal phenomena, the burgeoning complexity and computational demands have paved the way for data-driven approaches to take center stage. This review underscores the increasing preference for ML methods in coastal engineering, particularly in predictive tasks like wave pattern prediction, water level fluctuation, and morphology change. Although the scope of this review is not exhaustive, it aims to spotlight recent advancements and the capacity of ML techniques to harness vast datasets for more efficient and cost-effective simulations of coastal dynamics. However, challenges persist, including issues related to data availability and quality, algorithm selection, and model generalization. This entails addressing fundamental questions about data quantity and quality, determining optimal methodologies for specific problems, and refining techniques for model training and validation. The reviewed literature paints a promising picture of a future where ML not only complements but significantly enhances our ability to predict and manage the intricate dynamics of coastal environments.

This paper reports the water temperature structure and associated coastal processes in the NE part of the Black Sea. In situ temperature was measured in the water area of the Utrish Nature Reserve. The thermistor chain was moored in 2020 and included 6–10 temperature sensors with an accuracy of ±0.025 °C and time step of one minute. The seasonal variations in the water temperature, upwelling events, internal waves and diurnal cycle were analyzed. The maximum value of SST (28.6 °C) was registered in the subsurface layer in August 2021; the minimum (7.7 °C) was registered in March 2022. Estimates of the diurnal temperature cycle were obtained according to spectral analysis. Summer months show the diurnal cycle more than 60% of the time, and the cold period shows it less than 10% of the time. Internal waves appeared in thermocline with periods from 5 min to 20 h. The strongest Ekman upwelling was registered in September 2021. The water temperature dropped from 26 °C to 16 °C in 10 h. Additionally, quality assessments of two hydrodynamic models were made. The models showed a good correlation (0.9) with water temperature measurements, but RMSE could reach 1–1.8 °C for subsurface layers. Temperature variability and its characteristics are an important basis for future coastal ecosystem studies in the Utrish. [ABSTRACT FROM AUTHOR]

Coastal pelagic ecosystems are highly variable in space and time, with environmental conditions and the distribution of biomass being driven by complex processes operating at multiple scales. The emergent properties of these processes and their interactive effects result in complex and dynamic environmental mosaics referred to as “seascapes”. Mechanisms that link large-scale oceanographic processes and ecological variability in coastal environments remain poorly understood, despite their importance for predicting how ecosystems will respond to climate change. Here we assessed seascape variability along the path of the rapidly intensifying East Australian Current (EAC) Southern Extension in southeast Australia, a hotspot of ocean warming and ecosystem tropicalisation. Using satellite and in situ measures of temperature, salinity and current velocity coupled with contemporaneous measurements of pelagic biomass distribution from nine boat-based active acoustic surveys in five consecutive years, we investigated relationships between the physical environment and the distribution of pelagic biomass (zooplankton and fish) at multiple timescales. Survey periods were characterised by high variability in oceanographic conditions, with variation in coastal conditions influenced by meso-to-large scale processes occurring offshore, including the position and strength of eddies. Intra-annual variability was often of a similar or greater magnitude to inter-annual variability, suggesting highly dynamic conditions with important variation occurring at scales of days to weeks. Two seascape categories were identified being characterised by (A) warmer, less saline water and (B) cooler, more saline water, with the former indicating greater influence of the EAC on coastal processes. Warmer waters were also associated with fewer, deeper and less dense biological aggregations. As the EAC continues to warm and penetrate further south, it is likely that this will have substantial effects on biological activity in coastal pelagic ecosystems, including a potential reduction in the accessibility of prey aggregations to surface-feeding predators and to fisheries. These results highlight the import role of offshore oceanographic processes in driving coastal seascape variability and biological activity in a region undergoing rapid oceanic warming and ecological change.

Soomere, T.; Eelsalu, M.; Viigand, K., and Giudici, A., 2024. Linking changes in the directional distribution of moderate and strong winds with changes in wave properties in the eastern Baltic proper. In: Phillips, M.R.; Al-Naemi, S., and Duarte, C.M. (eds.), Coastlines under Global Change: Proceedings from the International Coastal Symposium (ICS) 2024 (Doha, Qatar). Journal of Coastal Research, Special Issue No. 113, pp. 190-194. Charlotte (North Carolina), ISSN 0749-0208. We explore the links between changes in the directional structure of moderate (>5 m/s to 10 m/s) and strong (>10 m/s) winds and similar changes in wave properties in the eastern Baltic proper. We apply modeled nearshore wave properties from 1990 to 2022 and wind measurements at selected sites. Long-term changes in the average wind speed are not coherent on the eastern shore of the sea. The predominant wave energy approach direction varies along this shore. The directional distribution of wave energy flux reflects a similar two-peak distribution of moderate and strong winds, with a persistent maximum for WSW/W/WNW winds and a secondary peak for NW or NNW winds. The magnitudes of these peaks vary by 50% in different decades. These variations do not match the similar changes to the average wind speed. [ABSTRACT FROM AUTHOR]

Eelsalu, M.; Viigand, K.; Soomere, T., and Parnell, K.E., 2024. Systematic analysis of alongshore sediment transport patterns under varying sea level conditions for evaluating stability of coastal areas in the microtidal Baltic Sea. In: Phillips, M.R.; Al-Naemi, S., and Duarte, C.M. (eds.), Coastlines under Global Change: Proceedings from the International Coastal Symposium (ICS) 2024 (Doha, Qatar). Journal of Coastal Research, Special Issue No. 113, pp. 53-57. Charlotte (North Carolina), ISSN 0749-0208. We systematically analyze wave-driven alongshore sediment transport magnitude and directional patterns in the eastern Baltic Sea under varying sea level conditions. Time series of wave properties are replicated using a nested SWAN model with a spatial resolution of 1–3 nautical miles, forced with ERA5 winds at 1 h resolution for the years 1993 to 2021. Wave-driven potential alongshore sediment transport is evaluated using the Coastal Engineering Research Centre approach and linked to the modeled sea level data. We show that 30–40% of the annual sediment transport occurs when the sea level exceeds the 90th percentile. In most of the study area the prevailing wave direction during such sea levels is the same for all situations. The study area contains three structurally different segments in terms of balance and direction of wave-driven sediment transport that host either unidirectional transport, balance of transport created by wave systems from different directions, and segments stabilized by the impact of bi-directional wave systems that are synchronized with sea level. [ABSTRACT FROM AUTHOR]

Abstract Mouth bars are the fundamental architectural elements of proximal deltaic successions. Understanding their internal architecture and complex interaction with coastal processes (fluvial, tide and wave‐dominated) is paramount to the interpretation of ancient deltaic successions. This is particularly challenging in low‐accommodation systems, because they are commonly characterized by thin, condensed and top‐truncated sections. This study analyses the exhumed Cenomanian Mesa Rica Sandstone (Dakota Group, Western Interior Seaway, USA), a fluvio‐deltaic system covering a ca 450 km depositional dip‐parallel profile. The study targets the proximal deltaic expression of the system, using 22 sedimentary logs (total of 390 m) spatially correlated within a ca 25 km2 study area at the rim of the Tucumcari Basin. Analysis of facies distributions, depositional architecture and spatial extent of stratigraphic surfaces reveals a 6–10 m thick, sharp‐based and sand‐prone deltaic package, comprising several laterally extensive (>1.4 km width) mouth bars. Composite erosional surfaces infilled with multi‐storey fluvial and marine‐influenced channel deposits (12–20 m thick, 100–250 m wide) scour locally into the deltaic package. Based on differences in sedimentary structures, bed thicknesses, occurrence of interflood beds and bioturbation indexes, four different sub‐environments within single mouth bars were distinguished. These range from mouth‐bar axis, off‐axis, fringe to distal‐fringe deposits, which reflect waning depositional energy with increasing distance from the distributary channel mouth. The interpreted mouth‐bar components also show internal variability in dominant process regime, with overall river dominance but local preservation of tide influence in the fringe and distal fringe components. Mouth‐bar deposits amalgamate to form an extensive sand‐rich sheet body throughout the study area, in which interflood mudstone to very‐fine grained sandstone beds are nearly absent. These features reflect successive coalescence of mouth bars in a low accommodation/supply (A/S) setting. These conditions promoted recurrent channel avulsion/bifurcation and thus the potential reworking of previously deposited mouth‐bar fringe and distal‐fringe sediments, where time and background processes are better recorded. Results of this study evidence internal process‐regime variability within mouth‐bar components. They also caution against the possible loss of preservation of subordinate coastal processes (e.g. tidal indicators), and consequent underestimation of the true mixed influence in low‐accommodation deltaic settings.

This paper reports the water temperature structure and associated coastal processes in the NE part of the Black Sea. In situ temperature was measured in the water area of the Utrish Nature Reserve. The thermistor chain was moored in 2020 and included 6–10 temperature sensors with an accuracy of ±0.025 °C and time step of one minute. The seasonal variations in the water temperature, upwelling events, internal waves and diurnal cycle were analyzed. The maximum value of SST (28.6 °C) was registered in the subsurface layer in August 2021; the minimum (7.7 °C) was registered in March 2022. Estimates of the diurnal temperature cycle were obtained according to spectral analysis. Summer months show the diurnal cycle more than 60% of the time, and the cold period shows it less than 10% of the time. Internal waves appeared in thermocline with periods from 5 min to 20 h. The strongest Ekman upwelling was registered in September 2021. The water temperature dropped from 26 °C to 16 °C in 10 h. Additionally, quality assessments of two hydrodynamic models were made. The models showed a good correlation (0.9) with water temperature measurements, but RMSE could reach 1–1.8 °C for subsurface layers. Temperature variability and its characteristics are an important basis for future coastal ecosystem studies in the Utrish.

The Southern California Bight (SCB), an eastern boundary upwelling system, is impacted by global warming, acidification, and oxygen loss and receives anthropogenic nutrients from a coastal population of 20 million people. We describe the configuration, forcing, and validation of a realistic, submesoscale‐resolving ocean model as a tool to investigate coastal eutrophication. This modeling system represents an important achievement because it strikes a balance of capturing the forcing by U.S. Pacific Coast‐wide phenomena, while representing the bathymetric features and submesoscale circulation that affect the transport of nutrients from natural and human sources. Moreover, the model allows simulations at time scales that approach the interannual frequencies of ocean variability. The model simulation is evaluated against a broad suite of observational data throughout the SCB, showing realistic depiction of the mean state and its variability with satellite and in situ measurements of state variables and biogeochemical rates. The simulation reproduces the main structure of the seasonal upwelling front, the mean current patterns, the dispersion of wastewater plumes, as well as their seasonal variability. Furthermore, it reproduces the mean distributions of key biogeochemical and ecosystem properties and their variability. Biogeochemical rates reproduced by the model, such as primary production and nitrification, are also consistent with measured rates. This validation exercise demonstrates the utility of using fine‐scale resolution modeling and local observations to identify, investigate, and communicate uncertainty to stakeholders to support management decisions on local anthropogenic nutrient discharges to coastal zones. Plain Language Summary: We applied and validated an ocean numerical model to investigate the effects of land‐based and atmospheric nutrient loading on coastal eutrophication and its effects on carbon, nitrogen, and oxygen cycles of the Southern California Bight, an upwelling‐dominated marine embayment on the U.S. West Coast. The model is capable of high‐resolution, multiyear hindcast simulations, which enable investigations to disentangle natural variability, climate change, and local human pressures that accelerate land‐based and atmospheric nutrient loads. The model performance assessment illustrates that it faithfully reproduces monitored ocean properties related to algal blooms, oxygen, and water acidity, among others, that can be traced to land‐based and atmospheric inputs of nutrients and carbon from human activities. The model performance assessment helps to constrain uncertainties in predictions to support ongoing conversations on approaches to reduce the effects of climate change, including considerations of management of local nutrient and carbon inputs. Key Points: The model reproduces gradients of physical and biogeochemical properties in the SCB, including seasonal, interannual, and ENSO variabilityResolving submesoscale currents increases the vertical flux of nutrients and allows realistic reproduction of wastewater plume circulationWastewater and riverine inputs are consistent with intensified nutrients, productivity, export, and remineralization nearshore [ABSTRACT FROM AUTHOR]

Coastal ecosystems are increasingly threatened by anthropogenic stressors such as harmful algal blooms and hypoxia through the combined effects of eutrophication and warming. As a major terrestrial nitrogen source to the ocean, rivers play a key role in shaping coastal nitrogen budgets and biogeochemical cycling. Combining an enhanced‐resolution, global ocean biogeochemical model with temporally changing river inputs, we estimate that elevated river nitrogen loads alone resulted in a 5.8% increase (16.6 Tg) in the global coastal nitrogen inventory from 1961 to 2010, accompanied by increases in coastal net primary productivity (+4.6%) and benthic detrital flux (+7.3%). The ecosystems most sensitive to added nitrogen were those with long residence times and strong nitrogen limitation. While even enhanced‐resolution global models remain limited in their capacity to resolve shelf‐scale responses, these basic factors provide two relevant axes for frameworks assessing the comparative coastal ecosystem susceptibility to enhanced nitrogen loads, and the effectiveness of mitigation strategies. Plain Language Summary: Over the past century, human activities have resulted in substantial global changes that threaten the stability and functionality of coastal habitats. One of these impacts was through nutrient pollution of river runoffs, which have triggered harmful algal blooms and caused low‐oxygen conditions in many coastal regions. However, it is challenging for models to simulate coastal impacts of increasing river nutrient loads, especially on a global scale and over a long period of time. Here we take advantage of some recent modeling advances to provide a global perspective on coastal ecosystem responses to increasing river nitrogen loads over the half‐century between 1961 and 2010. Overall, we show that the global coastal ocean accumulated more nitrogen over time as river nitrogen loads increased. This caused the primary production of the global coastal system (i.e., the conversion of inorganic to organic materials through photosynthesis) to increase as well. However, we found that the sensitivity of each coastal ecosystem to comparable changes in nitrogen loads varied considerably. This variability was to a large extent related to two factors: the rate of exchange between coastal waters and the adjacent ocean waters, and whether nutrients are limited for phytoplankton to conduct photosynthesis in that system. Key Points: Coastal ecosystem responses to long‐term changes in river nitrogen (N) loads are simulated using a global ocean biogeochemical modelIncreasing river N loads are linked to elevated N inventory, primary production, and benthic detrital flux in the global coastal oceanResidence time and N limitation state are important factors driving comparative coastal ecosystem susceptibility to enhanced N loads [ABSTRACT FROM AUTHOR]

Abstract Seasonal variations in the transports of total alkalinity (TAlk) and dissolved inorganic carbon (DIC) from the Lower Changjiang (Yangtze) River/Estuary to the East China Sea were investigated based on a series of field surveys in 2015–2017, including monthly samplings at Datong Station and seasonal mapping cruises in the Changjiang Estuary and the adjacent northwestern East China Sea. In comparison with historical data sets, the Changjiang TAlk flux varied around a nearly stable average over the past 55 years. This is much different from some American rivers, where TAlk export fluxes increased for a century long. To assess effects of riverine carbonate inputs on coastal carbonate chemistry, we compared several cases showing freshwater‐dilution‐induced decline in coastal aragonite saturation state (Ωarag), including rainwater dilution and riverine water dilution. Without riverine carbonate inputs, the effect of a unit of salinity decrease (due to rainwater dilution) on Ωarag was expected to be counteracted by a DIC removal of 10 μmol/kg relative to the baseline value along relevant conservative mixing line, when coastal Ωarag was close to a critical value of 1.5. Considering terrestrial carbonate inputs from Changjiang, however, the freshwater‐dilution‐induced coastal Ωarag suppression decreased by 12%. Our data also showed that more than 10% of wet‐season DIC flux discharged from the Changjiang Estuary was sequestered by biological activities in nearshore areas, while the TAlk flux was rarely affected. This biological alteration effectively transformed the terrestrial carbonate system from a feature of DIC:TAlk >1.0 to the usual seawater feature of DIC:TAlk

The existing theory for shore‐transverse rhythmic sand bars relies on morphodynamic instabilities involving the wave‐driven longshore current and rip currents. Intriguingly, transverse finger bars are common on coasts with sediment excess, something not related to those currents. Here we show that, if the actual beach profile is above the equilibrium profile, cross‐shore transport can induce an instability triggered by onshore transport together with wave refraction by the emerging bars. We use a numerical model that filters out the dynamics associated to longshore and rip currents but includes a simplified version of cross‐shore transport and is able to reproduce the formation of shore‐transverse bars. The alongshore spacing scales with the wavelength of the incident waves and the cross‐shore extent is approximately equal to the distance from shore to the depth of closure. The modeled bars compare qualitatively well with observations at El Trabucador back‐barrier beach (Ebro delta, Western Mediterranean Sea). Plain Language Summary: Beaches sometimes exhibit sand ridges (bars) nearly perpendicular to shore that tend to be quite regularly spaced alongshore. Their spacing and cross‐shore extent range from tens to thousands of meters. Intriguingly, these bars develop preferably at beaches with an abundant supply of sand such as delta barrier beaches, barrier islands and estuaries. Here we provide a possible explanation. Due to the sand excess, the bed in these beaches is very flat, the tendency for the sand to move downslope is very weak and the waves push the sand onshore. On the other hand, waves refract, that is, their crest tip on deeper water propagates faster than the tip on shallower water. As a result, they turn toward shallower areas and, thus, the onshore movement of the sand is deflected toward incipient shoals and accumulates there. This causes more intense wave refraction, which in turn brings more sand to the shallows, and so on. In this way, bars can form out of small random irregularities in bed level. Key Points: Cross‐shore sediment transport in the nearshore can be unstable in the alongshore directionThe morphodynamic instability can develop only for beach profiles above the equilibrium profileThis instability could explain transverse finger bar formation at beaches with sediment excess [ABSTRACT FROM AUTHOR]

Periods of very shallow water (water depth in the order of 10 cm) occur daily on tidal flats because of the propagation of tides over very gently sloping beds, leading to distinct morphodynamical phenomena. To improve the understanding of the characteristics of velocity and suspended sediment concentration (SSC) surges and their contribution to sediment transport and local bed changes during periods of very shallow water, measurements of near-bed flow, and SSC were carried out at two cross-shore locations on an intertidal flat along the Jiangsu coast, China. Furthermore, the role of surges in local resuspension and morphological change was explored. Results indicate that flow and SSC surges occurred at both stations during very shallow water periods. On the lower intertidal flat, flood surges were erosive, while weaker surges on the middle intertidal flat were not. Surges on lower intertidal flats resulted in local resuspension and strong turbidity, contributing up to 25% of the onshore-suspended sediment flux during flood tides, even though they last only 10% of the flood duration. When surges travel across the flats, conditions change from erosional to depositional. Velocity surges on the middle intertidal flat were too weak to resuspend bed sediment, and the associated SSC surges were produced by advection.

DaSilva, M.; Miot da Silva, G.; Hesp, P.A.; Bruce, D.; Keane, R., and Moore, C., 2021. Assessing shoreline change using historical aerial and RapidEye satellite imagery (Cape Jaffa, South Australia). Journal of Coastal Research, 37(3), 468–483. Coconut Creek (Florida), ISSN 0749-0208. The coastal zone is a dynamic area which can experience substantial natural change in short time periods, but changes are also associated with human modifications to the coastline. This case study is focused around assessing shoreline change associated with the Cape Jaffa Marina and canal estate in South Australia. The research comprises a GIS based analysis of shoreline change utilising aerial imagery from 1975 to 2005, which provides information of the morphological coastal trends prior to construction in 2008 of the marina/canal estate. In addition, imagery collected by the RapidEye satellite constellation was used to assess shoreline changes in the decade since construction, 2009 to 2019. The shoreline change statistics over the past few decades were calculated using the Digital Shoreline Analysis System extension of ESRI's ArcGIS. The image analysis workflow is based on the objective extraction of shoreline proxies from individual image statistics in a semi-automated process and is used to identify the waterline and edge of vegetation shoreline proxies in a time series analysis. The results provide a case study of a historically progradational sandy coastline experiencing substantial amounts of alongshore sediment transport, the corresponding obstruction from coastal infrastructure, and the resulting morphological changes to the Cape Jaffa shoreline. Shoreline change trends were altered from a predominantly accretional shoreline before the construction of the marina to one oscillating between extremes of erosion and accretion. The results showed significant accretion occurring updrift (Net Shore Movement (NSM) of 106 m) and significant erosion downdrift (NSM of –80 m) of the marina's training walls and entrance. The information derived from Earth observation satellites, such as RapidEye, can provide valuable insights into trend analysis due to their relatively high spatial (5 metre) and temporal resolution (5.5-day revisit). [ABSTRACT FROM AUTHOR]

Coastal environment is affected by diverse human and natural activities, more than any other natural environment. The main aim of this study is to examine shoreline dynamics of the sandy beach of Mazatlán, a medium-sized tropical coastal city in north-west Mexico. This paper specifically investigates the shoreline change as impacted by natural and anthropogenic interferences on the Mazatlán coastline. The mean high water (MHW) shoreline positions were extracted from Landsat Images (2012–2016) and a 2016 GPS field survey data. Digital Shoreline Analysis System (DSAS) was then used to investigate the dynamics of the extracted shoreline movements and the relative changes. Results showed that 96% of the coastline is undergoing yearly small-scale erosion at two distinct rates. The first at −1.9 ± 0.9 m year−1 and the other at −1.4 ± 0.2 m year−1, which are noted at Cerritos and other sections of the coastline, respectively. Changes in the coastal behaviour, here, are attributed widely to suspected sea level rise; increasing tidal range in the region; and the lack of or inadequate accommodation space for sediment movement occasioned by landed assets alongshore. These factors are not only encouraging erosion but also causing the depreciation of landward assets.

Abstract The freshwater content of the Arctic Ocean and its bordering seas has recently increased. Observing freshening events is an important step toward identifying the drivers and understanding the effects of freshening on ocean circulation and marine ecosystems. Here we present a 13 year (2003–2015) record of temperature and salinity in Young Sound‐Tyrolerfjord (74°N) in Northeast Greenland. Our observations show that strong freshening occurred from August 2005 to August 2007 (−0.92 psu or −0.46 psu yr−1) and from August 2009 to August 2013 (−0.66 psu or −0.17 psu yr−1). Furthermore, temperature‐salinity analysis from 2004 to 2014 shows that freshening of the coastal water (~range at sill depth: 33.3 psu in 2005 to 31.4 psu in 2007) prevented renewal of the fjord's bottom water. These data provide critical observations of interannual freshening rates in a remote fjord in Greenland and in the adjacent coastal waters and show that coastal freshening impacts the fjord hydrography, which may impact the ecosystem dynamics in the long term.

Featured Application: Geochemical analysis can provide valuable information about the local and regional patterns of sediment transport, distribution, provenance, and coasts' conditions. Sandy coasts are one of the most dynamic spheres; continuously changing due to natural processes (severe weather and rising water levels) and human activities (coastal protection or port construction). Coastal geodynamic processes lead to beach sediment erosion or accumulation. The coast's dynamic tendencies determine the changes in the volume of beach sediments; grain size; mineralogical; and geochemical composition of sediments. In addition to lithological and mineralogical analysis of sediments, geochemical analysis can provide valuable information about the local and regional patterns of sediment transport, distribution, provenance, and coasts' conditions. The study aims to assess trace metals' temporal and spatial distribution determined in the sandy beach sediments along the south-eastern Baltic Sea coast (Lithuania) during 2011–2018. The Lithuanian seacoast is divided into two parts: mainland and spit coast. Our results revealed that the dominant group of elements on the mainland includes Ca–Mg–Mn–Ti and on the Curonian Spit Fe–Pb–As–Co–Cr–Ni–Al, which remain unchanged during the years. The analysis included additional parameters such as beach volume, grain size and sorting, and heavy mineral concentration on the beach. The spatial analysis of trace elements indicated that the trace metal content depends on the coastal processes, but it differs in the mainland and spit sea coast. We identified a higher concentration of trace metals in the erosion-dominated areas in all analysed years on the mainland coast. On the spit coast, the trace metal concentration increased in areas associated with relict coarse sand and where the loading of sediments was active on the beach due to the northward along-shore transport. [ABSTRACT FROM AUTHOR]

Mouth bars are the fundamental architectural elements of proximal deltaic successions. Understanding their internal architecture and complex interaction with coastal processes (fluvial, tide and wave‐dominated) is paramount to the interpretation of ancient deltaic successions. This is particularly challenging in low‐accommodation systems, because they are commonly characterized by thin, condensed and top‐truncated sections. This study analyses the exhumed Cenomanian Mesa Rica Sandstone (Dakota Group, Western Interior Seaway, USA), a fluvio‐deltaic system covering a ca 450 km depositional dip‐parallel profile. The study targets the proximal deltaic expression of the system, using 22 sedimentary logs (total of 390 m) spatially correlated within a ca 25 km2 study area at the rim of the Tucumcari Basin. Analysis of facies distributions, depositional architecture and spatial extent of stratigraphic surfaces reveals a 6–10 m thick, sharp‐based and sand‐prone deltaic package, comprising several laterally extensive (>1.4 km width) mouth bars. Composite erosional surfaces infilled with multi‐storey fluvial and marine‐influenced channel deposits (12–20 m thick, 100–250 m wide) scour locally into the deltaic package. Based on differences in sedimentary structures, bed thicknesses, occurrence of interflood beds and bioturbation indexes, four different sub‐environments within single mouth bars were distinguished. These range from mouth‐bar axis, off‐axis, fringe to distal‐fringe deposits, which reflect waning depositional energy with increasing distance from the distributary channel mouth. The interpreted mouth‐bar components also show internal variability in dominant process regime, with overall river dominance but local preservation of tide influence in the fringe and distal fringe components. Mouth‐bar deposits amalgamate to form an extensive sand‐rich sheet body throughout the study area, in which interflood mudstone to very‐fine grained sandstone beds are nearly absent. These features reflect successive coalescence of mouth bars in a low accommodation/supply (A/S) setting. These conditions promoted recurrent channel avulsion/bifurcation and thus the potential reworking of previously deposited mouth‐bar fringe and distal‐fringe sediments, where time and background processes are better recorded. Results of this study evidence internal process‐regime variability within mouth‐bar components. They also caution against the possible loss of preservation of subordinate coastal processes (e.g. tidal indicators), and consequent underestimation of the true mixed influence in low‐accommodation deltaic settings. [ABSTRACT FROM AUTHOR]

Analysis of ground movement rates along the coastline and upper sections of the Ventnor landslide complex was carried out utilizing Persistent Scatterer Interferometric Synthetic Aperture Radar methods using Sentinel-1 SAR data from 2015 to 2019 (four years). Results were compared with rainfall data, historical ground investigation records and monitoring surveys carried out at Ventnor to relate observations to geology, geomorphology and rainfall. Decomposition of InSAR viewing geometries to vertical and horizontal aligned well with previous ground-based studies. Subsidence of −9.8 mm a−1 at the Lowtherville Graben and heave of +8.5 mm a−1 along the coastline south of Ventnor Park were observed. Decomposition to east-west geometry results showed an eastward displacement of approximately 12.4 mm a−1 along the coastline south of Ventnor Park, and a westward displacement of −3.7 mm a−1 throughout built up sections of Ventnor town, indicating the landslide was displacing more in an eastern direction than vertically. The cause of this movement was investigated by using publicly available intrusive boreholes paired with Persistent Scatterer Interferometry, and a new ground model spanning east-west parallel to the coastline was presented. No evidence of significant ground movement was observed along heavily protected sections of the coastline, suggesting coastal defences comprised of concrete aprons and rip rap appear to be an effective coastal management/landslide stabilisation tool when compared to rip rap alone. The mechanism of this increased stability is likely due to the combination of toe weighting and reduced toe erosion. A lag of approximately 13–20 days was observed between high rainfall events and subsequent peaks in ground displacement, which was shorter than a 29 day lag observed in a previous study. Similar observations of prolonged rainfall resulting in prolonged displacements were also observed. The study demonstrates the capabilities of the PSI methodology in identifying the same ground movements that conventional methods provide. By providing detailed analysis of ground deformation of the Ventnor landslide, we demonstrate small ground movements, validated with existing ground movement surveys. Similar methodology can be applied to coastal landslides in urban environments worldwide, providing a relatively cheap and rapid resource for coastal landslide monitoring.

We sought to resolve the extent, variability, and magnitude of productivity enrichment around a high tropical island consistent with the phenomenon of an Island Mass Effect (IME). Key biogeochemical constituents and physical oceanographic parameters were measured offshore over the upper 500 m from July 27 to August 7, 2014 around the Society Island of Mo’orea in French Polynesia in association with the nearshore measurements of the Mo’orea Coral Reef Long Term Ecological Research program. High-resolution synoptic sampling in a rectangular grid around the island revealed vertical and horizontal patterns in hydrographic conditions, inorganic nutrients, rates of productivity, and concentrations of organic matter that are characteristic of oligotrophic gyre ecosystems. Within the upper euphotic zone (0–75 m), levels of net primary productivity (NPP), chlorophyll a (Chl), heterotrophic bacterioplankton productivity (BP), and particulate organic carbon (POC) exhibited concurrent enhancement at stations located within 5–15 km of shore, relative to stations farther offshore. These observations of enhanced productivity near an island are consistent with an IME. Particulate organic matter nitrogen isotopes (POM-δ15N) were significantly lower near the island than at stations farther offshore, further emphasizing spatial differences in water column biogeochemistry consistent with an IME. Vertical profiles suggest thermocline shoaling and mixing associated with the pycnocline impinging on the island’s submerged flanks and coral reef slope may have contributed to the decreasing depth and increasing intensity of chlorophyll-a concentration in the DCM at nearshore stations relative to farther offshore. Shipboard measurements of an anticyclonic flow within the upper 75 m of the water column in the vicinity of Mo’orea suggest that retention of inorganic nutrients and organic matter near Mo’orea may also have contributed to the patterns in NPP, Chl, BP, POC, and POM-δ15N, providing a potential mechanistic understanding of the processes driving an IME.

As communities grapple with rising seas and more frequent flooding events, they need improved projections of future rising and flooding over multiple time horizons, to assist in a multitude of planning efforts. There are currently a few different tools available that communities can use to plan, including the Sea Level Report Card and products generated by a United States. Federal interagency task force on sea level rise. These tools are a start, but it is recognized that they are not necessarily enough at present to provide communities with the type of information needed to support decisions that range from seasonal to decadal in nature, generally over relatively small geographic regions. The largest need seems to come from integrated models and tools. Agencies need to work with communities to develop tools that integrate several aspects (rainfall, tides, etc.) that affect their coastal flooding problems. They also need a formalized relationship with end users that allows agency products to be responsive to the various needs of managers and decision makers. Existing boundary organizations can be leveraged to meet this need. Focusing on addressing these needs will allow agencies to create robust solutions to flood risks, leading to truly resilient communities.

Sand beach nourishment (BN) is one of the commonest “soft solutions” for shore protection and restoration. Yet it may have ecological consequences. Can this practice enhance the introduction and dispersal of non-indigenous species (NIS)? There has been little research on the impacts of nourishment on NIS, especially in the southeastern Mediterranean, a region considered most affected by invading biota. However, so far only one study referred to the possible interaction between BN and the success of invading species. It reports increasing numbers and densities of the aggressive, omnivorous Indo-Pacific moon crab, Matuta victor (Fabricius, 1781) in Haifa Bay (northern Israel) between 2011 and 2017. This research suggests a possible role of anthropogenic disturbance in the outbreak of M. victor and blames the Israel Ministry of Environmental Protection for authorizing a (rather small scale) BN in Haifa Bay in 2011 as an alleged cause for this outbreak. Circumstantial indirect evidence is not sufficient to establish the role of nourishment in promoting the establishment and dispersal of NIS. There are plenty of examples of successful settlement and rapid and large-scale distribution of NIS (including another member of the genus Matuta), especially in the eastern Mediterranean, without any BN in the region. Furthermore, the location where the M. victor specimens were sampled was exposed to more prevailing and frequent anthropogenic marine stressors than BN, such as eutrophication, pollution, fishing activities and particularly port construction. To firmly establish an assumed role of nourishment in the invasion of NIS, assessments must be based on solid and orderly planned scientific research to be designed well before the beginning of any BN. It is suggested that direct communication between environmental regulators and scientists is crucial for improving both scientific research and environmental management policies.

Seasonal variations in the transports of total alkalinity (TAlk) and dissolved inorganic carbon (DIC) from the Lower Changjiang (Yangtze) River/Estuary to the East China Sea were investigated based on a series of field surveys in 2015–2017, including monthly samplings at Datong Station and seasonal mapping cruises in the Changjiang Estuary and the adjacent northwestern East China Sea. In comparison with historical data sets, the Changjiang TAlk flux varied around a nearly stable average over the past 55 years. This is much different from some American rivers, where TAlk export fluxes increased for a century long. To assess effects of riverine carbonate inputs on coastal carbonate chemistry, we compared several cases showing freshwater‐dilution‐induced decline in coastal aragonite saturation state (Ωarag), including rainwater dilution and riverine water dilution. Without riverine carbonate inputs, the effect of a unit of salinity decrease (due to rainwater dilution) on Ωarag was expected to be counteracted by a DIC removal of 10 μmol/kg relative to the baseline value along relevant conservative mixing line, when coastal Ωarag was close to a critical value of 1.5. Considering terrestrial carbonate inputs from Changjiang, however, the freshwater‐dilution‐induced coastal Ωarag suppression decreased by 12%. Our data also showed that more than 10% of wet‐season DIC flux discharged from the Changjiang Estuary was sequestered by biological activities in nearshore areas, while the TAlk flux was rarely affected. This biological alteration effectively transformed the terrestrial carbonate system from a feature of DIC:TAlk >1.0 to the usual seawater feature of DIC:TAlk <0.9. Plain Language Summary: Changjiang (Yangtze River) serves as the second largest carbonate contributor to the ocean among the world large rivers. We examined riverine/estuarine transport fluxes of total alkalinity (TAlk) and dissolved inorganic carbon (DIC) in the continuum from the Lower Changjiang to its estuary and to the adjacent northwestern East China Sea. In comparison with historical data, the Changjiang TAlk flux varied around a nearly stable average over the past 55 years, which was much different from the American case of century‐long TAlk increase in some rivers. We also assessed effects of riverine carbonate inputs on the coastal carbonate chemistry. Results suggest that terrestrial carbonate inputs decreased the freshwater‐dilution‐induced carbonate mineral suppression in coastal zones. Based on field data, we estimated that more than 10% of wet‐season DIC flux discharged from the Changjiang Estuary was sequestered by biological activities in nearshore areas, while the TAlk flux was rarely affected. We explained how biological drawdown of riverine DIC transformed the terrestrial feature of DIC:TAlk ratio higher than 1.0 to the usual seawater feature of DIC:TAlk ratio less than 0.9, supporting Alfred C. Redfield's argument on "the influence of organisms on the composition of seawater" in the 1960s or earlier. Key Points: Changjiang (Yangtze River) export flux of total alkalinity varied around a nearly stable average over the past 55 yearsTerrestrial carbonate input from Changjiang decreased the freshwater‐dilution‐induced coastal aragonite saturation state suppression by 12%More than 10% of wet‐season DIC flux discharged from Changjiang was sequestered in coastal zones, while the TAlk flux was rarely affected [ABSTRACT FROM AUTHOR]

In this work, a novel approach based on artificial intelligence (AI) to assess the efficiency of wave energy converter (WEC) farms in coastal protection isdeveloped. We consider as a case study a beach subjected to severe erosion: Playa Granada (S Spain). More specifically, we analyse the changes in the dry beach area (quantified through the Pelnard-Considère equation) with and without wave farm protection by means of an Artificial Neural Network (ANN) model. The model is selected after a thorough comparative study involving forty ANN architectures, with one and two hidden layers, and two training algorithms (Levenberg-Marquadt and Bayesian regression). The best results are obtained with a [5-10-1] architecture trained with the Bayesian regression algorithm. Once validated, this ANN model is applied to optimize the design and position of the wave farm. The results confirm that ANN models are a useful design tool for hybrid wave farms. • Development of artificial neural network (ANN) model to design wave farms. • Dual function of wave farms: carbon-free energy production and coastal protection. • ANN with Bayesian algorithm and a [5-10-1] architecture successfully validated. • ANN model applied to find the optimum wave farm design for an eroding beach. [ABSTRACT FROM AUTHOR]

The aim of the present work is to identify the expected nearshore and offshore impact of a marine energy farm that would be implemented in the coastal environment of Portugal. Several layouts of Wave Dragon devices were considered, the distance between each system being gradually adjusted. By processing 27–years of combined wave data coming from the European Space Agency and ERA5, the most relevant conditions have been identified. The centre of each farm layout was set to approximately 3.5 km from the coast, where a more significant attenuation of wave heights in the middle of the target area was noticed, which can go up to 16% in the case of extreme events. From the analysis of the longshore currents, it was noticed that even an arrow farm layout defined by five systems may have a significant impact, by changing the peak or by smoothing the currents profile. Wave energy is an emerging renewable sector that can also contribute tocoastal protection and, therefore, the Portuguese coast represents a suitable candidate for this type of project.

The abundance of fecal-indicating bacteria in water bodies are said to be influenced by environmental conditions. The effect of environmental parameters on the changing microbial population plays an important role in coastal water quality assessment. It's crucial to comprehend these patterns in order to support management initiatives for pollution control. There are studies on faecal bacteria contamination of surface water and how environmental conditions affect it, however majority of them are based on large river basins and temperate regions of developed countries. In this paper, we study the different physicochemical and physical factors of the five recreational beaches in Mumbai, India and examine how these environmental factors affect the levels of faecal indicating bacteria, namely, coliforms in the region. A relatively high number of coliform was identified from the water and sediment samples of Marve Beach (>1600 MP N/100 ml or g), followed by Erangal Beach and Danapani Beach (∼150–350 MP N/100 ml or g), exceeding the normal standard limits of <100 MP N/100 ml set by the Central Pollution Control Board (CPCB) of India. Of the physiochemical parameters examined, BOD showed to have a strong positive correlation with the coliform bacteria. The nutrients and heavy metal concentrations did not show any major effect on the microbial population. The MIKE CMAP predicted tide, MIKE3 Flow Model FM simulated coastal current, ERA5 hourly wind, as well as SWAN model simulated nearshore wave together considerably exhibit alliance of microbial behavior in the beaches with ambient physical processes. This study reveals that Mumbai's coastal water contain significant concentrations of faecal bacteria, which, if not monitored regularly could have future consequences on the recreational activities of the region, thereby on public health. This assessment might help in simulation of water quality prediction, and for optimizing the coastal zone management and development across recreational beaches. [Display omitted] • Current, wind pattern and location are important in the faecal pollution studies. • High fecal indicating bacteria was seen in Marve Beach (>1600 MP N/100 ml or g). • BOD had a strong positive correlation with the coliform bacteria. • Nutrients and heavy metal concentration did not show effect on the study. [ABSTRACT FROM AUTHOR]