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- Global spillovers between sustainable and traditional ETFS: crisis dynamics and policy implicationsPublication . Gabriel, Vítor Manuel de Sousa; Lozano, María Belén; Matias, Fernanda; Neves, Maria Elisabete; Rebelo, SandraThis paper examines the interconnections between segments of exchange-traded funds (ETFs), bridging the traditional financial perspective with the sustainability-driven approach based on the Sustainable Development Goals (SDGs) outlined in Agenda 2030. The analysis is endogenous, focusing on the shocks that emerge within the system composed of these segments. Utilizing daily data from six sustainable segments, each corresponding to different SDGs, alongside one traditional segment, spanning a sample period of approximately 14 years, the study reveals notable spillover effects. Specifically, the periods associated with the pandemic and the war in Ukraine were marked by a significant surge in information transmission across the segments. Furthermore, the findings indicate that sustainable segments exhibit a strong interdependence with their traditional counterparts, a dynamic that facilitates contagion risk and limits the effectiveness of portfolio diversification strategies.
- Assessment of wave overtopping at Praia da Vitória, Terceira, Azores, with SWASH modelPublication . Baddavidana, Dinush Shayaman Priyankera; Pinheiro, Liliana; Garzon, Juan L.; Zózimo, Ana CatarinaThe primary objective of this dissertation is to enhance the accuracy of overtopping predictions using the SWASH (Simulating WAves till SHore) model, for inclusion in the Early Warning System (EWS), HIDRALERTA, currently operational in Praia da Vitória. While existing tools within HIDRALERTA offer valuable insights, they have limitations in accurately representing waves and overtopping details. To address these limitations, this research tested the capabilities of the SWASH model by simulating past storm events and typical wave conditions across the two-dimensional model of the entire port and bay areas with complex coastal structures and bathymetry. Outcomes of the simulations were compared to predictions from the NN_OVERTOPPING2 neural network and observed images from extreme events. In the SWASH model, coastal structures were modelled as impermeable layers, with bottom roughness incorporated to enhance energy dissipation from roughness and seepage. An unstructured triangular mesh was used for the computational domain. Manning’s coefficient for the outer slope of the south breakwater, with tetrapod armour units, was calibrated using a physical model test conducted in February 2025 at the National Laboratory of Civil Engineering (LNEC). The model was replicated in SWASH at prototype scale, using two test cases that resulted in overtopping for calibration. The results demonstrate that the SWASH model effectively simulates wave propagation and overtopping in harbour and bay areas, especially over complex coastal structures. Its accuracy in estimating wave propagation and overtopping is sensitive to wave energy interactions with the bottom and slopes, influenced by the Manning coefficient. While unstructured meshes enable large-domain simulations, the quality of the mesh affects both prediction accuracy and computational time. The model is stable when using implicit time integration but unstable with explicit methods. Despite some simulation instability, most simulations reached the maximum allowed simulation time on the National Distributed Computing Infrastructure (INCD) cluster. The model’s accuracy is heavily dependent on bathymetric data, with results generally aligning with NN_OVERTOPPING2 predictions and observed images from extreme events, although underpredictions can occur. Parallel processing is currently limited to structured grids in SWASH and, there is potential for efficiency improvements with unstructured meshes. Future studies should compare SWASH results with field data to fully assess its performance.
- Vegetation and platform geometry effects on wake attenuation in wetlandsPublication . Uddin, A S M Shanawaz; Carrasco , A. Rita; Fernández, María E. MazaWetlands play a vital role in coastal protection by dissipating wave energy, reducing flooding risks, stabilizing shorelines, and offering sustainable alternative to engineered defenses. Despite extensive research on wind wave attenuation by salt marsh vegetation, further studies are needed to quantify wetlands ability to mitigate the impact of wind and boat generated waves, and enhance their use as a Nature-based Solution towards sustainable coastal protection strategies. The aim of this study was to investigate the role of wetlands vegetation and morphology in dissipating wave energy in the Ria Formosa lagoon, southern Portugal. This was accomplished through a comprehensive analysis of how vegetation characteristics and profile morphology influence wave attenuation, utilizing field measurements and numerical modelling. Specifically, after understanding physical mechanisms and validate the SWAN model, this model was employed to assess the effects of different boat wake intensities, vegetation densities, and platform geometries on wave energy reduction. The results obtained demonstrate that wetland platforms with gentle slopes and around 100 meters length seemed to be the most effective on reducing wave energy, but they only contribute to 10% of the overall wave attenuation, with the remaining attenuation being promoted by the vegetation. Densely vegetated profile achieved 68% wave energy reduction compared to sparse or non-vegetated ones. Zostera noltei provided greater attenuation than Spartina maritima at only higher wave heights. Nevertheless, the occurrence of mixed-species vegetation proved to be more effective than just having single vegetation, for the same geometry. Wave attenuation increased with both wave height and vegetation density, up to a saturation point at around 4800 stems/m2 for Zostera noltei and 1400 stems/m2 for Spartina maritima. These findings suggest that optimizing both biological and platform characteristics is essential for maximizing coastal protection. The research highlights the need for comprehensive field measurements, with diverse ecological settings, tidal dynamics, varied geometries and salt marsh species to more effectively capture complex interactions between waves and wetland ecosystems. The outcomes provide practical recommendations for designing and managing resilient wetlands to support sustainable and adaptive coastal defense strategies.
- Compound flooding on an estuarine environment: case study of tagus estuaryPublication . Romero, Fabian Yesid Soler; Almeida, Luis Pedro; Hervas, Juan L. GarzonThe combined occurrence of coastal, fluvial and/or pluvial flood drivers can lead to compound flood events, which can trigger devastating social, economic, and ecological impacts, particularly in low-lying zones, including estuarine environments. A great number of these areas, which are home to significant populations worldwide, are increasingly at risk, as the intensity, phasing and frequency of such drivers are projected to change. These flood-induced impacts arise from the potential increase in inundation magnitude due to the non-linear interactions between various flood drivers, where their combined effects can exceed the simple sum of their individual contributions. Understanding their joint impacts and accurately estimating compound flood magnitudes is therefore essential for effective coastal management and disaster risk reduction. In this study, a numerical modeling framework was applied to analyze the interaction between different flood drivers (storm surge, peak river discharge, extreme rainfall and astronomical tides) in the Tagus Estuary. The first phase involved a coupled hydrodynamic model (MOHID), implemented to simulate tidal, wave, and current circulation within the estuary using oceanic and riverine boundary conditions. Based on these results, a flood model (SFINCS) was applied to simulate flooding processes along the northern and southern margins of the estuary under various scenarios. The flood model was validated using a storm event that occurred in the study area in December 2022. Subsequently, joint probability and extreme value analysis for 100-year return period values were estimated for the flood drivers and used to define multiple modeling scenarios along with different Sea Level Rise projections. These scenarios were designed to examine the flood driver’s interaction, focusing on the flood magnitudes in the context of compound flooding. This study demonstrated that compound events resulting from the interaction of pluvial/fluvial and coastal drivers can increase flood extent and depth by three to four times compared to events driven solely by coastal forces, such as a storm surge coinciding with spring tides in the estuary. Furthermore, the analysis revealed that rainfall is the primary cause of flooding in the Tagus Estuary.