Hasil untuk "Harbors and coast protective works. Coastal engineering. Lighthouses"

Elina Apine, Marta Payo Payo, Amani Becker et al.

Coastal areas are vital hubs for diverse ecosystems and socio-economic activities, but they face significant threats from climate change, biodiversity loss and pollution. These challenges require urgent, cooperative actions and interdisciplinary approaches to develop sustainable solutions. However, interdisciplinarity requires blurring traditional academic disciplinary boundaries, and this can be a challenge. Increasingly, early-career researchers (ECRs) are undertaking interdisciplinary research while facing uncertainty about their career progression. In this research paper, we explore the challenges and opportunities faced by ECRs in the United Kingdom conducting Interdisciplinary Coastal Research (IDCR). We draw on findings from internal workshops, webinar discussions and an online survey, all conducted in 2024. The main barriers to IDCR are systemic in nature and include demanding workload, short-term contracts, ineffective supervisory and limited institutional support. Generally, ECRs felt positive about the benefits of interdisciplinarity to coastal research and their career development, but some ECRs expressed feelings of impostor syndrome. Enhanced flexibility in approaches, improved communication and open-mindedness are among the proposed solutions. This research highlights the mismatch between the ambition and the day-to-day reality of ECRs working in IDCR and provides recommendations for IDCR, which can both enhance the experience of ECRs and secure better outcomes for coastal areas.

Yanjie Sun, Xiaolong Song, Haijue Xu et al.

The Yellow River Estuary (YRE) in China has transitioned to a complex multi-channel regime since 2013, making understanding terminal channel morphodynamics crucial for effective water and sediment management. The current study investigates the controls on channel evolution in both non-estuarine and estuarine reaches of YRE, differentiated by bifurcation locations, using a multi-method approach. For the non-estuarine reach, wavelet analysis was applied to satellite-derived river centerlines (2003–2022) to quantify channel migration and its relation with fluvial forcing. In the estuarine reach, the interplay between fluvial and marine processes and their influence on channel migration were assessed. The analysis was complemented by scaled physical modeling experiments. The results indicate that in the non-estuarine reach, the erodibility of the channel, primarily governed by the median grain size of the bed material, exerts a dominant control on channel migration, with higher discharge consistently enhancing mobility by providing the necessary erosive energy. The concentration of incoming suspended sediment plays a secondary role, as much of it can be transported through the reach without causing significant local morphological change. The estuarine reach exhibits three distinct morphological states: limited mouth oscillation, minor bifurcation, and major bifurcation/avulsion. River discharge is the primary driver of these changes, while marine forces exert a stabilizing influence. Crucially, both physical modeling and field data indicate that local bed material characteristics—shaped by selective sediment transport and deposition—significantly influence estuarine morphodynamics, more so than upstream sediment supply parameters alone. Effective management of the YRE requires an integrated approach considering the spatial variability of bed material and the temporal dynamics of hydraulic conditions. The current study emphasizes the importance of distinguishing between bed material properties and suspended load characteristics for predicting morphodynamic responses in sediment-rich, highly managed river systems.

Ömer Faruk Karaca, Kadri Yürekli

In studies on water resources planning and management, regular and complete hydrological data such as streamflow and sediment data are needed. Since the existing data generally do not fully reflect the entire process, the process needs to be modeled in order to make more reliable decisions. The aim of this study is to investigate the possibilities of estimating the sediment amount with the ANN technique, which can be used in many areas today, with the streamflow and sediment measured from 20 sediment gauging stations (SGS) established by State Hydraulic Works (SHW) in the Euphrates-Tigris Basin and to try to determine the most appropriate network structure. The ANN structures to be used were determined as the most commonly used Radial Basis Artificial Neural Network (RBANN), Feed Forward Back Propagation Artificial Neural Network (FFBP) and Multilayer Artificial Neural Network (MLP). The obtained results were compared with the Multiple Linear Regression (MLR) method. The highest R2 values obtained were determined as 0.9683 and 0.9969 in the RBANN model, 0.9546 and 0.9820 in the MLP model, 0.9735 and 0.9732 in the FFBG model with the CG and LM algorithms, respectively. When only the mean values of the test values according to the ANN models were examined, the highest value was again obtained as 0.8507 in the RBANN and LM algorithms. In terms of sediment estimation, the highest R2 value in the ANN analysis was found in the RBANN model LM algorithm as 0.9804 in the train phase, 0.9969 in the testing phase and 0.9970 in the cross-validation phase.

Wonder Kofi Adzigbli, Julian Bloomer, John Morrissey

The study focuses on the impact of climate change and spatial planning policies on coastal landscape dynamics. We examine the present and future coastal land use/land cover (LULC) change for southwestern Ghana under the coastal resilience (CR) scenario and coastal planning (CP) scenario. It employs an integrated approach of a review of literature and satellite imagery analysis to map coastal land use/land cover (LULC) change, from 2010 to 2020, to predict future landscape transitions under a coastal resilience approach and then contrast it with a scenario where development of the coast continues. The results show a continual decline in wetlands, from 1882.43 ha in 2010 to 1743.49 ha in 2020. Increased development would dominate the landscape under a scenario where coastal planning continues to expand, whereas cultivated, agricultural lands and vegetation are likely to increase under a coastal resilience scenario in 2035 and 2057. This study recommends that government and other stakeholders should consider coastal landscape restoration plans and programmes towards landscape sustainability for Sustainable Development Goals (SDG) 11 and 13.

Abhinav Sharma, Celso Castro-Bolinaga, Natalie Nelson et al.

Fluvial sediment pulses pose a significant threat to the overall ecological health of river systems. Nonetheless, the scarcity of monitored and published data underscores the importance of devising innovative methods for understanding and measuring how river systems react to the introduction of sediments across the fluvial domain. The objective of this study was to create a modeling framework based on reflectance–turbidity that can be applied in regions with both limited and abundant data. Various combinations of predictor variables, training algorithms including linear regression and additional machine learning methods, and input data availability scenarios were examined to comprehend the factors influencing turbidity prediction on a regional scale. The results indicated that, for Washington state, the random forest algorithm, utilizing a combination of reflectance-based predictors and sediment delivery index (SDI) as predictors, produced the most accurate outcomes (data rich: NSE = 0.54, RSR = 0.68, data scarce: NSE = 0.47, RSR = 0.73). However, when tested on three locations in Washington experiencing sediment pulses, the reflectance–based turbidity prediction model consistently underestimated the peak high and peak low turbidity levels for the Elwha River. The model also exhibited consistent inaccuracies in predicting the initial phase of sediment pulses following the Oso Landslide. Nevertheless, promising results were observed for the Toutle River, downstream to the St. Mt. Helens Volcanic eruption site. Overall, the inclusion of SDI in the model enhanced its efficiency and transferability. By enabling the reconstruction of fluvial sediment pulses in data-scarce regions following dam removals, this integrated approach contributes to advancing our understanding of how rivers respond quantitatively and predictively to these disturbances in sediment supply.

Tim Henri Josephus Hermans, Renske de Winter, Joep Storms et al.

While adapting to future sea-level rise (SLR) and its hazards and impacts is a multidisciplinary challenge, the interaction of scientists across different research fields, and with practitioners, is limited. To stimulate collaboration and develop a common research agenda, a workshop held in June 2024 gathered 22 scientists and policymakers working in the Netherlands. Participants discussed the interacting uncertainties across three different research fields: sea-level projections, hazards and impacts, and adaptation. Here, we present our view on the most important uncertainties within each field and the feasibility of managing and reducing those uncertainties. We find that enhanced collaboration is urgently needed to prioritize uncertainty reductions, manage expectations and increase the relevance of science to adaptation planning. Furthermore, we argue that in the coming decades, significant uncertainties will remain or newly arise in each research field and that rapidly accelerating SLR will remain a possibility. Therefore, we recommend investigating the extent to which early warning systems can help policymakers as a tool to make timely decisions under remaining uncertainties, in both the Netherlands and other coastal areas. Crucially, this will require viewing SLR, its hazards and impacts, and adaptation as a whole.

Anderson Targino da Silva Ferreira, Regina Célia de Oliveira, Maria Carolina Hernandez Ribeiro et al.

Microplastics (MPs) are polymeric particles, mainly fossil-based, widely found in marine ecosystems, linked to environmental and public health impacts due to their persistence and ability to carry pollutants. In São Paulo’s northern coast, geomorphological factors and anthropogenic activities intensify the deposition of these pollutants. Through multivariate techniques, this study aims to investigate the role of the morphometrical parameters as independent variables in quantifying the distribution of MPs on the region’s sandy beaches. Using beach face slope (tanβ) and orientation (Aspect) derived from remote sensing images, calibrated by in situ topographic profiles collected through GNSS positioning, and laboratory analyses, six machine learning models Random Forest, Gradient Boosting, Lasso and Ridge regression, Support Vector Regression, and Partial Least Squares regression were tested and evaluated for performance. The Gradient Boosting model demonstrated the best performance, indicating its superior capacity to capture complex relationships between predictor variables and MPs deposition, followed by Random Forest model. Morphometric analysis revealed, once again, that in this coastal section of São Paulo, beaches with Sloping profiles oriented toward the SSW are more susceptible to MPs accumulation, especially near urban centers. Ultimately, incorporating geomorphological variables into predictive models enhances understanding of MPs deposition, providing a foundation for environmental policies focused on marine pollution mitigation and coastal ecosystem conservation while also contributing to achieve SDG 14.

Tahera Attarwala, Amin Boukari, Gulnihal Ozbay

Bivalves such as oysters rely on aragonite and calcite for shell formation via the biomineralization of calcium carbonate. Ocean acidification reduces carbonate ion availability, compromising shell growth and inducing dissolution under undersaturated conditions (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>Ω</mi></mrow></semantics></math></inline-formula> < 1). This study assessed the aragonite and calcite saturation state (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>Ω</mi></mrow></semantics></math></inline-formula>) as a proxy for evaluating habitat suitability for oyster aquaculture and restoration. Temperature, salinity, pH, and total alkalinity were monitored across multiple sites and used to calculate the aragonite and calcite saturation state via the Seacarb package. Calcium hardness and dissolved oxygen were also measured to evaluate compliance with hatchery water quality standards. Results indicated temporal and spatial fluctuations in saturation states, with frequent undersaturation during cooler months. Spearman correlation analyses demonstrated significant positive relationships between temperature and salinity (<i>p</i> = 0.46), between pH and aragonite saturation state (<i>p</i> = 0.72), and between alkalinity and aragonite saturation state (<i>p</i> = 0.51). These findings highlight the importance of carbonate chemistry variability and seasonal drivers in determining the suitability of sites for oyster cultivation and restoration under changing environmental conditions.

Andi Egon, Eugene Farrell, Gregorio Iglesias et al.

This study analyses the impacts of winter storms on beach response, as well as the subsequent recovery during spring and summer, at a dissipative sandy beach in Brandon Bay, Ireland. Shoreline dynamics were assessed through the integration of field data from five survey campaigns conducted between October 2021 and November 2022 with a 1D Xbeach (version 1.23) numerical model. Cross-sectional profiles were measured at seven locations, revealing pronounced erosion during winter, followed by recovery in calmer seasons, especially in the lower beach zone. The model effectively simulated short-term storm-induced morphological changes, demonstrating that rates of shoreline retreat and profile alteration are higher in the eastern bay, where wave energy is greater. Most morphological changes occurred between the low and high astronomical tide marks, characterized by upper beach erosion and lower beach accretion. Models were subsequently employed to examine future climate scenarios, including sea level rise and increased storm intensity. The projections indicated an exponential increase in erosion rates, correlated with higher storm wave heights and frequencies. These results highlight the dynamic response of dissipative beaches to extreme events and reinforce the necessity for adaptive coastal management strategies to address the escalating risks posed by climate change.

Changjiang Ma, Yang-Guang Gu, Richard W. Jordan et al.

Freshwater lakes in China face increasing environmental pressures due to rapid urbanization and industrialization, with metal pollution emerging as a significant concern. Despite this, the ecological risk assessment of metal mixtures in lake sediment remains limited. The current study addresses this gap by utilizing the diffusive gradients in thin films (DGT) technique to investigate the distribution and ecological risk of metals and arsenic in surface sediment of Hongze Lake, China. Substantial variations in metal concentrations were found across sampling sites, with average values of manganese (Mn) (1,730.56 μg/L) and iron (Fe) (930.58 μg/L) being notably high. The ecological risk quotient (RQ) values for Mn and Fe exceeded 1 at all sites, indicating substantial ecological risks, while copper (Cu) and arsenic (As) had RQ values near or above 1 at most sites. A joint probabilistic risk assessment using the species sensitivity distribution (SSD) method revealed a 30.31% probability of concurrent toxic effects on aquatic organisms. These results highlight the pressing need for proactive measures to mitigate metal contamination risks in Hongze Lake. The current study provides critical insight into the ecological risks associated with metal pollution and underscores the importance of effective environmental management to preserve the lake's ecosystem.

James R. Tweedley, Stephen J. Beatty, Alan Cottingham et al.

Estuaries that become closed from the ocean through the formation of a sand bar are particularly susceptible to degradation and often experience poor water quality and fish kills. Sampling was conducted seasonally for two years in the deeper waters of the Vasse–Wonnerup (southwestern Australia) after a large fish mortality event to identify the fish species present and determine if richness, abundance, diversity and faunal composition differed among regions and over time. Species richness, abundance and diversity were far greater in the downstream regions than in the upstream regions, reflecting patterns in salinity. Catch rates of two marine estuarine-opportunist mugilids (<i>Mugil cephalus</i> and <i>Aldrichetta forsteri</i>) and an estuarine-resident sparid (<i>Acanthopagrus butcheri</i>), which were the species most affected by the mortality event, were relatively stable. It is suggested that before sampling commenced, mugilids had entered the estuary following an artificial sand bar breach, while the loss of 0+ (new recruits) <i>A. butcheri</i> in the mortality event and subsequent recruitment failure prevented stocks from increasing. Temporal shifts in fish composition were driven by less abundant species, which utilized the estuary more opportunistically. Increases in the occurrences and abundances of these species coincided with an open bar and salinities close to those of seawater. The data also show how the estuary responds to differing hydrodynamic phases and artificial breaches.

Nobuyuki Ono, Takatomo Miyake, Kenki Kasamo et al.

This study investigated the thermo-hydrodynamic groundwater environment of a sandy beach where a unique sand bathing method attracts many visitors. The discussed temperatures covered a wide range, from the normal to the boiling temperature of water. We, at first, examined the feasible conditions for sand bathing and found that the volumetric water content was the crucial factor. Comprehensive field observations were implemented to elucidate two physical quantities: the groundwater flow and the temperature in the sand layer. The latter one was found to be governed by the groundwater level and tidal fluctuations. The characteristics obtained were found to be consistent with the feasible conditions in the landward area. While in the offshore area, the temperature was proved to have suddenly dropped. These results strongly suggest that the underground heat source is distributed in specific spots. A numerical model to describe the groundwater flows and the heat transfer mechanism was developed based on a saturated/unsaturated seepage flow model. The computational results were found to adequately reproduce the observed spatial temperature distribution. The reproduction ability of the model was found to be limited in terms of temporal variations; it was good for the groundwater level, but not for the temperature in the sand.

William R. Laton, John H. Foster

The San Elijo Lagoon experienced a sudden shift in sedimentation type around 1000 AD, as evidenced by the ¹⁴C dating. This shift is marked by a sharp boundary between a lower layer of medium to fine sand and an upper layer of dark, silty clay that reflects the lagoon closure. The dated sediments also reveal a history of marine conditions in the lagoon basin since about 7400 ± 140 years before the present (ybp), when the sea level was −12.2 meters (m), and the shoreline was 400 m away from the current location. The sea level rose at a rate of 2.84 m per 1000 years until about 4170 ± 100 ybp. After that, the rising sea level slowed and reached the present level about 3100 years ago. However, the lagoon remained closed after about 730 to 1180 ybp, with only fine organic sediment accumulating in the basin, which coincides with a severe drought in the southwest around 1150 AD. A higher sedimentation rate is interpreted from bluff erosion as seen after 520 ± 40 ybp but without enough stream flow to force the reopening of the lagoon.

Edward A. Willsteed, Leslie New, Joseph O. Ansong et al.

Quantifying and managing the cumulative effects of human activities on coastal and marine environments is among the foremost challenges in enabling sustainable development in the twenty-first century. As the speed with which these environments are changing increases, there is greater impetus to resolve the evident problems facing governance systems responsible for managing cumulative impacts. Policymakers and regulators recognise the need to assess and manage cumulative effects, as evidenced by widespread legislation requiring cumulative effects assessment (CEA). Yet there is ample evidence that we are not turning the tide in terms of balancing good environmental health with increasing demands of already degraded coastal and marine spaces that are increasingly impacted by climate change. This paper reviews the current state of knowledge regarding scientific and practical advances in CEA, assesses whether these advances are being applied in decision-making and identifies where challenges to implementation exist. Priority research questions are formulated to accelerate the inclusion of effective CEA in marine and coastal planning and management.

Nicole Zuck, Laura Kerr, Jon Miller

Nearshore sandbars are common features along sandy coasts. However, identifying sandbars within a beach profile traditionally requires a large historical dataset or subjective input from an observer. Several existing methodologies rely on reference profiles, which is problematic for new study sites with limited data sets and for nourished beaches that have drastic fluctuations in the cross-shore. This novel technique is suitable for beaches where a reference profile does not exist, as it identifies morphological sandbar features by a quantitative automated process. The technique identifies sandbars with a minimum steepness of 2% grade and a minimum height of 0.2 m. The morphological boundaries of sandbars were previously not well-defined, especially the seaward limit of the sandbar, contributing to difficulty in comparing surveys and sandbar morphologies. This technique standardizes the definitions of the bar limits mathematically via standard MATLAB functions, thus removing subjectivity and allowing results to be replicated. Bar identification is focused on the beach profile below the mean high water line, not cross on-shore positions, making the technique appropriate for nourished shorelines as well as those with large seasonal fluctuations. The automated technique was tested on 840 profiles collected near a recently completed beach nourishment project in Long Branch, NJ, USA. Results indicate success in identifying prominent sandbars within the test data set.

Thomas A. Schlacher, Brooke Maslo, Matthieu A. de Schipper

Coasts form the universal stage on which people interact with the global ocean. Our history is inextricably intertwined with the seashore, being a rich tapestry of archaeological sites that paint a vivid picture of people hunting, foraging, fishing and scavenging at the edge of the sea. Seascapes inspire diverse art forms celebrated through the ages. The world’s sandy beaches have a flummoxing duality of anthropocentric purpose—ranging from the horrors when being theatres of war to first love under a rising moon. ‘Man’s Love of the Sea’ continues to draw people towards the shore: the narrow coastal strip contains everything from holiday cottages to mega-cities. This coastal concentration of the human population is problematic when shorelines erode and move inland, a geological process fastened by climate change. Society’s response is often a heavy investment in coastal engineering to complement and enhance the natural storm protection capacity of beaches and dunes. The coast’s immense cultural, social, and economic significance are complemented by a wealth of natural riches. In the public’s eye, these ecological values can pale somewhat compared with more imminent ecosystem services, particularly protecting human properties from storm impacts. To re-balance the picture, here we illustrate how peer-reviewed science can be translated into ‘cool beach facts’, aimed at creating a broader environmental appreciation of ocean shores. The colourful kaleidoscope of coastal values faces a veritable array of anthropogenic stressors, from coastal armouring to environmental harm caused by off-road vehicles. Whilst these threats are not necessarily unique to coastal ecosystems, rarely do the winds of global change blow stiffer than at the edge of the sea, where millions of people have created their fragile homes on shifting sands now being increasingly eroded by rising seas. Natural shorelines accommodate such changing sea levels by moving landwards, a poignant and powerful reminder that protecting the remaining natural land is primus inter pares in coastal management. There is no doubt that coastal ecosystems and coastal communities face august trials to maintain essential ecosystem services in the face of global change. Whilst bureaucracies are not always well equipped to counteract environmental harm effectively, using measures carrying a social license, many communities and individuals have encouragingly deep values connected to living coastlines. Building on these values, and harnessing the fierce protective spirits of people, are pivotal to shaping fresh models that can enhance and re-build resilience for shores that will continue to be a ‘baroque embarrassment of coastal riches’.

Mojtaba Zoljoodi

Cyclones are as one of the most dangerous meteorological phenomena of the tropical region that generate strong winds and heavy rainfall, impacting coastal regions. Behavior of tropical cyclone trajectories needs to be better understood in order to find predictable aspects of landfall potentially. This research aims to analyze the cyclone tracks statistically and then study of the associated meteorological effects of Gonu cyclone in June 2007 as an example. Using the cluster analysis (K-mean method) 5 principal clusters have been derived and spatial – temporal studies including the monthly variation of cyclone trajectories and their intensity and frequencies are performed. The 4th cluster indicated more spatial variability and expansion (4º-31ºN and 48.5º-78ºE). The second cluster showed the highest frequency with 349 events as well as the highest maximum intensity and standard deviation of 235.2km/h and 47.96km/h respectively. During 1-7 June 2007, the Gonu super cyclone traversed the Arabian Sea and reached the Iranian southern regions affecting the coastal infrastructures and communities. In this 7-day period the daily composite maps of different atmospheric levels showed that by intensifying of Gonu cyclone the axis of subtropical high pressures in the lower levels moved to the east and in the 500hp level they moved to the northward over the study region.

Hadi Amlashi

Un-trenched submarine pipelines will experience the wave and current loads during their design lifetime which potentially tend to destabilize the pipeline both horizontally and vertically. These forces are resisted by the interaction of the pipe with the surrounding soil. Due to the uncertainties involved in wave, current and soil conditions, there will be a complex interaction between wave/current, pipeline and seabed that needs to be properly accounted for. The design of submarine pipelines against excessive displacement due to hydrodynamic loads (DNV-RP-F109) is defined as a Serviceability Limit State (SLS) with the target safety levels as given in DNV-OS-F101 (2013). In this paper uncertainties associated with on-bottom stability design of submarine pipelines are investigated. Monte Carlo Simulations (MCS) are performed as the basis for probabilistic assessment of the lateral stability of the pipeline located on the seabed. Application of the method is illustrated through case studies varying several design parameters to illustrate the importance of each design parameter for exceeding a given threshold of the SLS criterion. Uncertainties in significant wave height and spectral peak period are found to be important parameters in describing the UR distribution. Type of soil has also an impact on the distribution of UR, i.e. how the passive resistance in the pipe-soil interaction model is accounted for. Therefore, the definition of characteristic values of both loads and resistance variables are important for the Utilisation Ratio (UR).

Farhad Hosseinlou, Alireza Mojtahedi, Mohammad Ali Lotfollahi Yaghin

This work introduces a structural integrity assessment strategy for Jacket structures based on the finite element model updating and a novel simplified method. Hereof, model reducing and model updating procedure is established based on a optimization technique. Since the number of measured degrees of freedom is most of the time restricted in practice, this paper represents a methodology using the cross model cross mode method (CMCM) in combination with an iterative procedure which uses limited, spatially incomplete modal information. This research is an empirical study on a laboratory model of a jacket structure with the aim of establishing Refined Simplified FE Model (RSM) to conduct damage detection. In addition to elimination of uncertainty effects in the damage detection results, RSM technique is employed because of practical considerations and also this technique provides a fast damage zone diagnosis procedure. Also, improved reduction scheme is utilized based on static reduction scheme to carry out damage detection in jacket structure.

Jalili, Shad, Biglarkhani

This article deals with response of cylindrical shell subjected to loading of Under Water Explosion (UNDEX) when water current is introduced to the surrounding environment. Cylindrical shells as one of main basic structural elements in construction of marine and submarine facilities are prone to UNDEX threat. Due to vicissitudes of conducting experiments in this field and also complicated inherent of fluid-solid interaction phenomenon, numerical models can be used as an effective tool for scrutinizing the problem. In this study, a submerged thin walled cylindrical shell and its surrounding water discretized by coupled shell Lagrangian elements and Eulerian cells respectively. Simulations are performed in AUTODYN hydrocode. For better perceiving of phenomenon, studies are done for two various explosive charge stand-off distances. Results show that introduction of flow to water, can tangibly change the symmetrical configuration of flow- less problem. Due to intricate interaction of water flow and explosion bubble, distribution of UNDEX overpressure and impulse is disturbed and this leads to un-symmetric deformation of cylindrical shell. Also amplitudes of deflection are reduced obviously by increasing flow velocity.