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- Changes in storm impacts along the Portuguese sandy coast for different climate scenariosPublication . Kazi, Maysha; Loureiro, Carlos; Ferreira, ÓscarStorms can result in extensive damage to the socioeconomic and environmental balance along the sandy coasts. Therefore, it is crucial to understand how the hydro-geomorphological response of sandy barriers will change due to future changes in storminess. This study aims to investigate future storm impacts on two contrasting sandy barriers along the Portuguese coast, Maceda and Tavira located respectively in the northwestern and southeastern coast, and evaluate how these will change in relation to the present situation. The approach is based on the application of the storm impact scale for the present and future climate change scenarios (mid- and end-century). Modelled wave, storm surge, and sea level data were combined with high-resolution topographic data and a conceptual model of barrier evolution to determine dune morphological parameters and impact regimes for future scenarios. The main findings of this work are that, extreme water levels will consistently increase throughout the twenty first century, mostly due to the contribution of sea level rise when compared to changes in storminess. From mid to the end-century, a reduction in dune crest elevations can be observed on the southernmost section of the Maceda coast and on the western to central section of the Tavira island. Compared to the current situation, by the mid- and end-century the intensity of collision and overwash regimes is expected to become severe in Maceda. For Tavira island, the most severe storm impact regimes are expected to be overwash and inundation, which will occur over almost half of the barrier island by 2100. From the mid-to-end century for all storm return periods, the mean overwash potential will increase substantially on the southernmost section of Maceda and on the west to the central section of Tavira island, while the mean inundation potential will gradually rise along with the mean overwash potential in Tavira. The influence of sea level rise and potential changes on the barrier morphological characteristics, particularly on the dune crest, are crucial factors influencing future changes to storm impacts.
- Estimating wave runup using satellite multi-spectral imageryPublication . Ilekura, Idowu Oselumhe; Almeida, Luis Pedro; Ferreira, Óscar ManuelThe wave runup is one of the most important processes responsible for coastal hazards, including overtopping or erosion. Understanding and predicting wave runup in any coastal environment is crucial for risk and vulnerability assessment studies. Nevertheless, the lack of field observations of wave runup is one of the main limitations of the predictability of this process. Past studies have used shore-based video monitoring techniques to observe wave runup in coastal areas. However, these studies were limited in time (data acquisition periods of several months or years) and space (spatial coverage of a single beach or extension of hundreds of meters or a few kilometres). In recent years, remote sensing, in particular Satellite Imagery, have improved the capability of the onboard sensor (e.g., improved spatial resolution of optical sensors) and revisit times (time between consecutive data collection in the same point on the earth’s surface), making of this technology one with the most significant potential to overcome earth sciences challenges. The present project’s general objective is to utilize multi-spectral imagery to monitor wave runup in coastal areas, representing a novel approach compared to past runup monitoring methodologies. Wetsand (boundary between the dry and wet beach) and Waterline (boundary between the water and the beach) were extracted from the satellite images as potential runup proxies. The satellite-derived runup proxies were compared to existing wave runup formulations. The error quantification was performed using statistical descriptive parameters (e.g., RMSE, correlation coefficient, and Bias). The waterline-derived runup proxies demonstrated high correlation (Bias = 0.35, R² = 0.63, RMSE = 0.65) with the existing runup formulation, whereas the Wetsand proxies exhibited lower correlation (Bias = -0.41, R² = 0.17, RMSE = 0.95). Averaging the Wetsand and Waterline proxies improved the Bias and RMSE to 0.12 and 0.611, respectively. The optimal formulation for each proxy was employed to correct the runup formulation, which was then used to compute the 𝑅2, resulting in a refined runup formulation. The corrected formulations for each proxy were utilized to predict extreme runup events. The waterline and the average Wetsand/Waterline proxies outperformed the Wetsand proxies during low wave and tide conditions. In contrast, the Wetsand proxy outperformed both alternatives in predicting extreme runup under high wave and tide conditions. Overall, the study noted the prospect of using satellites to measure and estimate runup globally.
- Assessing the impact of beach nourishment on reducing wave overtoppingPublication . Sproul, Vega Alexander; Garzón Hervás, Juan Luis; Mendes, DiogoAs zonas costeiras densamente povoadas podem estar sujeitas aos efeitos das tempestades costeiras, que promovem galgamento oceânico e consequentes inundações costeiras. As obras de defesa costeira, como esporões e defesas longitudinais aderentes, têm sido usadas para proteger contra estes perigos e salvaguardar as áreas urbanas costeiras. Nas últimas décadas, no entanto, houve uma mudança de paradigma promovendo o uso de outras soluções de engenharia, como a alimentação artificial de praias. A praia de Quarteira é um exemplo desta mudança de paradigma. Delimitada por um campo de esporões e apoiada por uma defesa longitudinal aderente, ambos construídos no início da década de 1970, a praia foi alvo de uma alimentação artificial em 1998, com outra planeada para 2024. Apesar da sua implementação, não se quantificou a eficácia da alimentação artificial na mitigação do galgamento oceânico em Quarteira. Esta dissertação pretende determinar a eficácia do projeto de alimentação artificial planeado para Quarteira na redução do galgamento oceânico com recurso a modelação numérica. Utilizando o modo não hidrostático do modelo XBeach, este estudo simula o galgamento oceânico para três cenários: antes da alimentação artificial, após a alimentação artificial e cinco anos após a alimentação artificial. Simulou-se o impacto de cinco tempestades sintéticas, com diferentes alturas significativas da agitação marítima e períodos de onda, para períodos de retorno variando entre 5 e 65 anos. Foram analisadas as relações entre a crista do revestimento, a largura da berma e os caudais médios de galgamento das ondas obtidos nas simulações do XBeach. Esta análise levou ao desenvolvimento de duas equações empíricas para estimar os caudais médios de galgamento em função das condições hidrodinâmicas (altura significativa e comprimento de onda ao largo) e da geometria da alimentação de praia (largura da berma). Este trabalho contribuiu para o desenvolvimento de uma metodologia para dimensionar e avaliar a eficácia dos projetos de alimentação artificial de praias.
- Long-distance migrations and seasonal movements of meagre (Argyrosomus regius), a large coastal predator, along the Iberian Peninsula coastPublication . Gandra, Miguel; Winkler, Alexander; Afonso, Pedro; Abecasis, DavidBackground The meagre, Argyrosomus regius, is a large coastal predatory fish inhabiting waters from the north-eastern Atlantic and Mediterranean Sea, where it is targeted by commercial and recreational fisheries. Previous genetic studies have found an unexpectedly high population differentiation not only between the Atlantic and the Mediterranean, but also along the Atlantic coast. However, the reasons underpinning this genetic barrier remained unclear. Likewise, even though the species is amongst the world’s largest marine teleosts, knowledge about its movement ecology and migratory behaviour remains notably scarce, and primarily reliant on fisheries-dependent data. Methods In this study, we used a combination of acoustic telemetry and pop-up satellite archival tags to investigate the movements of 22 adult meagre (70–143 cm total length) along the Southwestern coast of the Iberian Peninsula. Results Our results strongly suggest that the previously reported genetic differentiation is not maintained by limited adult dispersal/movement, as hypothesized. On the contrary, we documented some of the longest individual annual migrations ever recorded for a coastal teleost, up to >2000 km, with frequent back-and-forth movements between the West and Southern Iberian coasts. Moreover, their detected regional movement patterns support the existence of a marked seasonal behavioural shift, with individuals being less active and moving to deeper waters during winter, and are consistent with spawning philopatry associated to their summer reproductive movements. Finally, we identified putative aggregation areas that may harbour important feeding/overwintering grounds. Conclusions These findings shed new light on the movement and behaviour patterns of meagre that may be of particular importance for the conservation and spatial management of this species throughout its range, and open the door to further research on functional connectivity.
- Oceanographic research in the Thermaikos Gulf: a review over five decadesPublication . Androulidakis, Yannis; Makris, Christos; Kombiadou, Katerina; Krestenitis, Yannis; Stefanidou, Natassa; Antoniadou, Chryssanthi; Krasakopoulou, Evangelia; Kalatzi, Maria-Ignatia; Baltikas, Vasilis; Moustaka-Gouni, Maria; Chintiroglou, Chariton CharlesThe Thermaikos Gulf (TG) is a semi-enclosed, river-influenced, marine system situated in the eastern Mediterranean Sea, sustaining both urban coastal regions and ecologically preserved natural areas. Facing a plethora of environmental and anthropogenic pressures, the TG serves as a critical nexus where human activities intersect with marine ecosystems. The quality and health of the TG’s marine environment are tightly linked to the socioeconomic activities of the coastal communities comprising approximately 1.5 million inhabitants. The main features of the TG’s environmental dynamics and ecological status have been scrutinized by dedicated research endeavors during the last 50 years. This review synthesizes the seminal findings of these investigations, offering an evaluation of their contribution to research, their present collective impact, and their trajectory toward the future. A severe deterioration of the TG’s environmental quality was detected in the 1970s and 1980s when the treatment of urban wastewater was completely absent. A steady trend of recovery was observed after the 1990s; however, so far, the goal of a “good environmental state” mandated by national legislation and European directives has not been achieved. A clear reduction in research was detected after 2010, associated with the recession of the Greek economy, following the “golden period” for research in the TG from the mid-1990s until the late 2000s. The most important research gaps and uncertainties are discussed, while specific targeted recommendations for the improvement of monitoring and understanding of the physical, biochemical, and ecological state of the gulf are provided: (i) increase in permanent observational stations (temporally and spatially); (ii) inclusion of all major environmental parameters; (iii) monitoring of the quantity and quality of all land-originated freshwater discharges; (iv) monitoring and management of important aspects of the marine environment that have received minimal attention in the past (e.g., coastal erosion, plastic pollution); (v) development of accurate prediction tools (e.g., numerical techniques) to support first-level responders and efficient management; (vi) establishment of a supervising public entity that would support the holistic overview and management of the entire TG. These suggestions are directed at overcoming the existing uncertainties in the knowledge of the TG, safeguarding its ecological integrity and its role as a crucial link to marine biodiversity and sustainability in the Mediterranean basin.