In Aveiro (NW coast of Portugal), a coastal monitoring programme was carried out in sequence of a shoreface nourishment intervention (over than 2 M m${}^3$) performed in 2020. In this programme, almost one year of biweekly subaerial topographies and quarterly bathymetric surveys have been collected along a 10 km coastal stretch between June 2020 and June 2021. In this study, topographic and bathymetric surveys were analysed to assess the expectation that if the shoreface nourishment is located in sufficiently shallow water depths, its landward movement will feed adjacent beaches and, consequently, increase the subaerial beach volume. Results show that the subaerial beach volume is well correlated with the 1.05 m (above MSL) isoline displacement through time. While the seaward limit of the shoreface nourishment moved landwards about 200 m, the shoreline proxy (isoline of 1.05 m) displayed a maximum seaward displacement of 60 m. The displacement of the shoreline proxy was highly variable in space, along the 10 km coastal stretch, and also in time, during storm events. During such events, both landward and seawards displacement of the shoreline proxy took place, depending on the spatial position. Moreover, while beaches close to the initial shoreface nourishment intervention displayed faster accretion patterns than those located farther away, the well-defined onshore movement of the shoreface nourishment did not result in a considerable beach volume increase. The achieved results were also compared against case studies of shoreface nourishments with similar volumes performed worldwide.

Current coastal protection strategy in Portugal defines beach and shoreface nourishment as a valid measure to mitigate coastal erosion in some erosional hot-spots, being considered as an adaptation measure under the present climate change scenario, including the impacts of sea level rise. However, scant objective data on shoreface nourishments are available to evaluate performance of this type of intervention in mitigating beach erosion and managing coast risk. We present the first monitoring results of a ≈2.4 × 10⁶ m³ shoreface nourishment on the Aveiro coast (Costa Nova—Ílhavo), the largest until now in Portugal, focusing on its morphological development, impacts on adjacent beaches due to alongshore spreading and cross-shore redistribution, and contribution to the sediment budget of the nourished sediment cell. The analyses are based on high-resolution coastal monitoring data, provided by the Portuguese COaStal MOnitoring Program (COSMO). A Multiple Monitoring Cell (MMC) approach was used to evaluate local and feeder efficiency of the nourishment, sediment budget exchanges within both the placement and wider survey domains (≈1 km² and 12 km², respectively). Results show rapid (ca. 6 months) morphological change over the placement area, with a decrease of about 40% of the initial volume. Fast onshore sediment redistribution explains part of this change, placed sand having merged with the pre-existing bar system increased the volume of the shallower nearshore. Longshore transport is reflected by increasing the robustness of the bar downdrift of the placement area and also explains the negative sediment budget (0.75 × 10⁶ m³) of the survey domain, which corresponds to losses through its southern boundary. Sediment spreading also induced accretion of the subaerial section of Costa Nova beaches in front of the placement area, reversing their long-term erosive trend. In contrast, this trend persisted at downdrift beaches. This suggests that the time lag of the subaerial beach response to this intervention increases with the distance to the placement area, and reversal of the erosive trend will only be noticeable in the following years. This study provides new insights on the time scales of beach response to high-magnitude shoreface interventions in high-energy wave-dominated sandy coasts, which will support decision making regarding similar operations designed to manage erosional hot-spots elsewhere.

The evaluation of beach hydromorphological behaviour and its classification is a complex issue. The main objective of this study was to develop new methodologies to identify coastal features/patterns. Pixel-based and object-oriented classification algorithms were used and a new approach was developed based on Principal Components Analysis and Histogram (PCAH) segmentation, to identify and analyse morphological features and hydrodynamic patterns. The PCAH method consists of three stages: preprocessing, PCA and histogram-based segmentation. Both manual and automatic approaches were addressed regarding the identification of the classes obtained from the segmentation stage. The dataset was composed from two aerial photographs and one IKONOS-2 image. The supervised classification algorithms present good results for both aerial photographs and the IKONOS-2 image. For the two aerial photographs the best results were found for the maximum likelihood classifier and for the IKONOS-2 image the best result was achieved with the parallelepiped classifier. The object-oriented classification performance for the aerial photographs and for the IKONOS-2 image also presented good results. The PCAH method led to promising results, with proportions of correctly classified pixels greater than 90% for the classes ‘Sea’, ‘Sediments+breaking zone’ and ‘Beach’.

This work aims to provide a more complete characterization of coastal erosion mitigation and climate change adaptation measures by presenting a participatory approach that integrates medium- to long-term perspectives, considering simultaneously social, environmental, economic and engineering dimensions to help decision makers implement sustainable climate change adaptation (CCA) strategies. The work lists, explains and characterizes existing climate change mitigation and adaptation measures as well as their costs and positive and negative social, environmental and economic impacts, in three distinct databases. These databases are discussed, complemented and validated in participatory moments with local stakeholders of the Ovar Municipality, Portugal, which represents the case study to support the proposed methodology. Although Ovar is a pilot case, the integrated framework for resilient CCA has a global application with respect to methodologies and concepts. The proposed approach is useful to help coastal management entities to engage in more efficient, effective and beneficial planned action to mitigate coastal erosion and adapt to future climate change effects. The open-source databases and the participatory approach facilitate decision makers and coastal communities to navigate the complexity of solutions and build consensus around collective actions for coastal areas.

This work aims to shed some light on longshore sediment transport (LST) in the highly energetic northwest coast of Portugal. Data achieved through a sand-tracer experiment are compared with data obtained from the original and the new re-evaluated longshore sediment transport formulas (USACE Waterways Experiment Station’s Coastal Engineering and Research Center, Kamphuis, and Bayram bulk formulas) to assess their performance. The field experiment with dyed sand was held at Ofir Beach during one tidal cycle under medium wave-energy conditions. Local hydrodynamic conditions and beach topography were recorded. The tracer was driven southward in response to the local swell and wind- and wave-induced currents (Hsb=0.75m, Tp=11.5s, θb=8−12°). The LST was estimated by using a linear sediment transport flux approach. The obtained value (2.3×10−3m3⋅s−1) approached the estimation provided by the original Bayram formula (2.5×10−3m3⋅s−1). The other formulas overestimated the transport, but the estimations res...