FCT1-Teses
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Percorrer FCT1-Teses por Objetivos de Desenvolvimento Sustentável (ODS) "ODS 11 — Cidades e Comunidades Sustentáveis"
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- 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.
- 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.
- Importance of forcing parameters and geological controls on coastal hazards of a sandy urban beach (Cadiz, Spain).Publication . Sacnun, Sara; Ferreira, Óscar Manuel Fernandes Cerveira; Garzón, Juan Luis; Plomaritis, TheocharisCoastal regions experience various hydrodynamic and geomorphological processes across different timescales. In geologically controlled coastal settings, inherited geological factors can significantly influence beach morphology, sometimes more so than present-day dynamics. This thesis investigates the role of geological features in shaping the dynamics of La Victoria Beach in Cádiz, Spain and how they interact with other forcing parameters focusing on erosion and overwash processes during extreme weather events. The study integrates bathymetric, wave, tidal, and topographic data to model pre- and post-storm profiles for significant storms. Using the XBeach numerical model, the thesis explores the influence of the nearshore rocky platform and the offshore reef on wave energy and sediment transport. The model simulations assess various scenarios, including the presence or absence of geological features and changes in future sea level. Results indicate that geological features, such as rocky platforms and reefs, create pronounced alongshore gradients in wave energy, leading to significant variations in beach morphodynamics. These features act as natural barriers, reducing the impact of storm waves and stabilizing beach morphology. The study also highlights the importance of wave direction, as variations can significantly alter erosion and overwash patterns. The study further demonstrates that moderate increases in sea level can exacerbate coastal hazards, amplifying erosion and overwash risks. The calibrated XBeach model proves effective in predicting beach morphological changes under different conditions, though deviations in sediment accumulation and erosion rates suggest the need for further model refinement and localized data integration. The present thesis investigates on how geological features influence coastal hazard dynamics, providing a foundation for developing adaptive coastal management strategies. By integrating geological controls, wave dynamics, and climate change projections, coastal managers can better protect urban beaches like La Victoria from increasing natural and anthropogenic threats.
- Modelling storm-induced erosion in coastal embayments in the Victoria Coast (Southern Australia) supported by citizen science dataPublication . Hemanath, Lavanya; Loureiro, Carlos; Garzon, Juan L.Storms play a crucial role in shaping coastal landscapes, driving significant morphological changes and influencing short and long-term beach stability. The significance of understanding coastal storms and their associated impacts is pivotal for coastal management. Coastal erosion responses to storm events vary significantly depending on the coastal geomorphology of the beaches. This thesis investigated the performance of the XBeach model in simulating storm erosion in selected embayed beaches on the coast of Victoria (Australia). High-resolution Citizen Science datasets were employed to calibrate and validate the models in Apollo Bay, Marengo and Port Fairy beaches. The models were extensively calibrated to simulate the erosional response to high-intensity storms, and validated with lower intensity storms. Calibrated models accurately reproduced storm induced erosion with excellent performance scores of BSS - 0.9 and RMSE - 0.2 for all the study sites. A sensitivity analysis performed by varying parameters like wetslp, dryslp, gamma, alpha and delta, revealed that the models were extremely sensitive to a combination of gamma and delta values, but showed limited variation in performance for changes in wetslp and dryslp. The models exhibited a high degree of sensitivity to the antecedent topography of the profiles considered, with the beach face slope being the major factor controlling the modelled storm erosion response, thus the selection of facua, beta, gammax, gamma2, and facsl values for each site was contingent upon the steepness of the profiles considered. This indicated that site-specific hydrodynamics and morphological conditions controlled the response of the beaches to storms. Thus, sites with similar coastal characteristics exhibited similar responses to storms, and the model parameterisations obtained for a specific site resulted in reasonale to poor performance scores when applied to other sites. The beach slope, reflecting the morphodynamic state of the beach, showed that the geological controls on embayed beaches indirectly influenced XBeach parameterization through adjustments related to the slope.
- Nature-based solutions (NbS) for coastal ecosystem resilience enhancement: towards a conceptual model for marine pollution mitigationPublication . Boe, Gardawheh Gad; Sousa, Vânia Serrão; Ndah, AnthonyCoastal ecosystems, including mangroves, salt marshes, and coral reefs, perform various vital functions such as flood mitigation, erosion prevention, habitat conservation, and carbon sequestration. However, these ecosystems are encountering unparalleled challenges primarily due to climate change and anthropogenic activities that contribute to marine pollution, jeopardizing ecosystem integrity. The deterioration and destruction of coastal habitats undermine the natural resilience of these regions. Thus, the implementation of meticulously designed Nature-based Solutions (NbS) can facilitate the restoration and rehabilitation of compromised coastal ecosystems, mitigate marine pollution, and enhance economic and societal advantages in a cost-effective and sustainable manner. Examples encompass the rehabilitation of essential habitats, including seagrass and salt marshes, to safeguard biodiversity and facilitate carbon sequestration, as well as the management of coastal habitats to conserve biodiversity and shield populations from extreme weather phenomena. This master's thesis seeks to perform a thorough evaluation of the efficacy and potential of Nature-based Solutions (NbS), including habitat restoration, green infrastructure, and ecological engineering, in mitigating pollution effects and fostering long-term environmental sustainability, while also formulating a conceptual model for their effective application. The research will enhance the understanding of coastal resilience and offer pragmatic recommendations for coastal management and planning.
- Risk assessment for beach users in the rocky coasts of the AlgarvePublication . Dimabayao, Julius John Togores; Ferreira, Óscar; Loureiro, CarlosBeach tourism is a major global industry responsible for the extensive use and occupation of beaches. On the rocky coasts of the Algarve region in southern Portugal, the influx of visitors to beaches adjacent to coastal cliffs creates a risk, as beachgoers can be exposed to mass movements from these cliffs. While the general understanding of hazards due to mass movements in coastal cliffs has been extensively studied and hazard mitigations have been implemented, these measures do not account for the exposure potential of beach users. Consequently, they do not quantify the risk level for those staying on cliff-bound beaches. This study proposes a methodology to define a coastal index and quantify the risk over time and space for beach users, based on the integration of hazard and exposure. The methodology is applied to selected cliff-bound beaches in the central Algarve, with the resulting index values visualized geospatially. The results suggest how the hazard, exposure, and coastal index values vary temporally and spatially. The hazard index is shown to vary seasonally across different hazard zones. Meanwhile, the exposure index values differ based on two methods that explore (1) temporal variation, and (2) temporal and spatial variation of beach occupancy. Both methods influence the coastal index: the first highlights seasonal changes in the risk levels, while the second provides detailed spatial risk patterns, identifying beach locations where risk levels are higher. These risk hotspots are influenced by seasonality and the proximity of the cliffs to beach concessions, where people often congregate. This study demonstrates the effectiveness of the coastal index in quantifying risk and highlights its adaptability to any cliff-bound beach, provided the necessary datasets can be obtained. The results can assist coastal managers in planning appropriate adaptation measures for risk reduction by minimizing people’s exposure.