Long-Term Shoreline Evolution and Anthropogenic Impact: Evidence from 76 Years of Coastal Change in Mazagón, Spain

Abstract The Mazagón coast (Huelva, southwestern Spain) illustrates the strong imprint of anthropogenic interventions on shoreline dynamics. This study evaluates its evolution between 1946 and 2022 by digitizing historical shorelines from aerial photographs and quantifying changes through three complementary indicators: Net Shoreline Movement (NSM), End Point Rate (EPR), and Linear Regression Rate (LRR). Statistical analyses (ANOVA and Tukey’s test) were performed to assess differences between pre- and post-construction phases of the Juan Carlos I breakwater. The results indicate a prevailing erosive trend, with mean retreat rates of − 1.4 m/yr and localized shoreline losses exceeding 100 m. Prior to the breakwater, variability was moderate, but after its construction, the shoreline displayed marked spatial asymmetries: the northern sector continued to recede, while the southern sector exhibited stability and even localized accretion, with NSM values surpassing + 80 m in some transects. These patterns reflect the disruption of littoral drift and sediment compartmentalization induced by the harbor structures. The findings highlight how rigid engineering solutions redistribute, rather than resolve erosion problems and demonstrate the dual influence of storm events and human interventions on shoreline trajectories. From a management perspective, this case study emphasizes the need for integrated and adaptive strategies, including process-based and nature-based approaches, to address erosion in sediment-limited coasts. Graphical Abstract The graphical abstract illustrates the long-term shoreline evolution of the Mazagón coast (SW Spain) over a 76-year period (1946–2022), highlighting the impact of the Juan Carlos I breakwater on coastal dynamics. The data component is represented through the geographical location of the study area and the spatial extent of the analyzed coastline. The analyses are based on GIS techniques and the Digital Shoreline Analysis System (DSAS), using key indicators such as Net Shoreline Movement (NSM), End Point Rate (EPR), and Linear Regression Rate (LRR). The model is structured around a comparison between pre- and post-breakwater conditions, allowing the identification of temporal changes in shoreline behavior. The results reveal a dominant erosive trend, particularly in the northern sector, contrasted with relative stability or localized accretion in the southern sector, demonstrating a clear spatial asymmetry. The conclusion emphasizes that the breakwater disrupts littoral drift processes, leading to sediment redistribution rather than erosion mitigation, and highlights the need for adaptive coastal management strategies.