Browsing by Issue Date, starting with "2024-06-09"
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- 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.
- 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.