Unravelling the Response of the Guadiana Ebb-Tidal Delta to Extreme Wave Events

Abstract 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.