Sapientia
Repositório Científico da UAlg
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Unravelling the response of the Guadiana ebb-tidal delta to extreme wave events
Publication . Rubio, Carlos; Garel, Erwan; Zarzuelo, Carmen; López-Ruiz, Alejandro
This study investigates the morphodynamic response of the Guadiana ebb-tidal delta to extreme wave storms using a process-based numerical model. Field data including wave climate, wind and bathymetry were integrated into the Delft3D model, calibrated and validated with hydrodynamic data collected at the lower estuary in 2013, 2015 and 2023 and bathymetric maps of the ebb delta from 2016 and 2017. The analysis focuses on the impact of Storm Emma (February-March 2018), characterised maximum wave height up to 7.1 m. Results show that Emma induced a significant shift in sediment dynamics, causing retreat and erosion of the updrift shoal complex (with a net sediment volume loss of 2.40%), sediment transfer to the downdrift complex (that gained sediment volume of 0.32%), and channel rotation.. These changes contrast with the seaward growth of the shoal under mild conditions observed during non-extreme conditions, as between 2016 and 2017. The results highlight the importance that large extreme wave events can have on the morphodynamic evolution of ebb tidal deltas.
Use of sub-pixel imagery classification to assess salt marsh plants’ adaptation
Publication . Carrasco, Rita; Astori, Alexandra; Kombiadou, Katerina
The inherent heterogeneity of coastal wetlands and the small size of halophytic plants present challenges in accurately sensing plant species, even with very high-resolution satellite imagery. This study used sub-pixel imagery classification methods on high spectral and spatial resolution imagery from Worldview-3 to predict plant species distribution in a mesotidal coastal wetland system. The predicted sub-pixel fractional abundance of plant species is discussed for three targeted wetland categories in the Ria Formosa lagoon: naturally evolving patches, patches modified by human activities, and patches affected by coastal squeeze. The Random Forest Regression algorithm was proven to be highly effective in unmixing the spectral signal of halophytic vegetation, enabling the retrieval of plant species distribution (7 plant species). To train the algorithm, field observations were used to classify satellite images. Differences in band feature importance for key species and bare soil were observed across the various sites. The comparison of species distribution between sites suggests that, in addition to biotic factors, other environmental influences likely affect ecological succession; therefore, large-scale mapping approaches based on remote sensing should be undertaken with caution. The results are important for understanding the diverse ecological behavior of marsh plants within the same system and highlight the variability in plant reflectance and the need for ground truthing when sensing plant cover from satellite data.
Coastal dynamics in the Black Sea observed from optical and SAR satellite images
Publication . Jiang, Dalin; Marino, Armando; Ionescu, Maria; Gvilava, Mamuka; Savaneli, Zura; Loureiro, Carlos; Spyrakos, Evangelos; Tyler, Andrew; Stanica, Adrian
This paper presents an overview of the approach developed to detect coastal dynamics by combining Synthetic Aperture Rader (SAR) and optical images. The method was developed with Sentinel-1 SAR and Sentinel-2 MSI images with a spatial resolution of 20 m, to detect the coastline changes in the Black Sea between 2016 and 2023. When compared with in situ measurements, the results showed that our approach provides reliable results with the rate of coastline change having a root mean square error of 1.73 m/year. In the Black Sea, around half the coastline changes are a result of natural process, and around 35% associated with coastal engineering. Natural coastline changes were mainly observed in deltaic areas, such as the Danube Delta. 91% of the artificial changes were found in the southern Black Sea coast on the Turkish coastline, and are a result of airport and harbour construction, and land reclamation activity. The results of this study can provide information on interventions that support the sustainable coastal zone management.
Sensing and actuation as a service for health data integration
Publication . Guerreiro, Joel
In the last few years, many advances in sensing usage have been developed, and their application on healthcare is substantially growing due to many factors, but the most important one is the patient's physical parameters data gathering for remote monitorization and intervention. Sensing and actuation as a service using clouds as basis may provide a platform to directly connect the patient's sensors to the health care providers and fast monitor or intervene in case of alarm, especially on elderly people. In Portugal, all patient's data is collected to a personal patient data register (health portal), that can be seen by any medical and technical health staff working on public institutions. This study aims to design a framework using sensing and actuation as a service on clouds able to provide data integration into the Portuguese National Patient Data Register and alarm triggering for fast medical intervention.
Parameterised barrier morphological evolution for future storm impact assessment
Publication . Loureiro, Carlos; Horsburgh, Nicola; Ferreira, Óscar
Coastal storm impacts are mainly determined by the interaction of extreme water levels with barrier morphology, particularly the height of the foredune. While future projections of storm hydrodynamic forcing, integrating sea level rise, tides, waves and storm surges, are readily available, predicting future barrier morphology at a decadal scale remains a challenge due to uncertainties in modeling morphodynamic processes. This study proposes a simplified model to predict future foredune morphology at decadal scale and determine storm impacts on coastal barriers, focusing on the critical role of foredune morphology. The model identifies three morphological behavior modes based on the nature of the sediment budget and associated shoreline dynamics, distinguishing between: “keep-up mode” for accreting barriers, “catch-up mode” for stable to mildly accreting barriers, and “give-up mode” for eroding barriers. Application to the Portuguese coast, specifically the eroding barrier of Torrão do Lameiro, demonstrates that even with rising sea level and higher total water levels, storm impacts remain within the same regime by 2050. This simplified model offers a practical approach for considering an evolving foredune morphology, which can support first-order assessments of future storm impacts in changing climate.