Morphological evolution of the Guadiana ebb-delta at shore times scales

• Autor(a) principal: Gutierrez, Blanca Mendiguren
• Data de Publicação: 2020
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10400.1/15279
• topic: Ebb-delta; Mixed-energy inlet; Morphological evolution; Storm events; Domínio/Área Científica::Ciências Naturais::Outras Ciências Naturais

The Guadiana estuary (southern Portugal) has undergone drastic changes in the morphology of the ebb-tidal delta and inlet channel due to anthropogenic activities: jetty construction, closure of a major dam and dredging activities. The morphologic evolution of the mixed-energy ebb-tidal delta of the Guadiana estuary and its response to the ocean climate, is examined using a series of sequential satellite images (Sentinel-2) and bathymetric maps spanning six years. To achieve these goals, the outer edge at the three main morphological features of the ebb-delta was identified, namely the updrift lateral bar, the outer shoal and the downdrift complex. The evolution of the sandy shoals was examined over both datasets through six profiles across the ebb-delta, evidencing a series of landwards and seawards migrations. The wave climate was studied independently for southeast (SE) and southwest (SW) swells. Furthermore, storm events were defined based on a significant wave height higher than 2.5 m and a duration of these events of at least 6 hours. A total of 53 storm events were identified and analysed separately according to the dominant incoming direction of the storms. Additionally, the impact of the swells and of the storm events in the behaviour of the sandbars was researched regarding their normalised wave power. This last analysis evidenced a relation with the migration of the ebb-delta shoals. Finally, it was possible to identify the normal behaviour of the ebb-delta shoals under the dominant swells (SE and SW) and the severe impact of extreme storm events (such as Emma storm). The Guadiana ebb-tidal delta morphology displays a strong seasonal pattern due to the strong reliance on the local hydrodynamic conditions, depicting a morphological cyclic recession of the shoals after storm events, which yields a progressive counter clockwise rotation over the ebb-delta.