Influence of Posidonia oceanica accumulation on beach morphodynamics: A remote sensing study

Beach morphology is influenced by climate-related changes, such as rising sea levels, shifting weather patterns, and storms, as well as human activities, making continuous monitoring essential for understanding its evolution. Within this dynamic context, some beaches develop morphological features that help attenuate the impact of high-energy events, effectively acting as natural barriers against coastal erosion and flooding. This research explores the role of Posidonia oceanica banquettes, natural seagrass accumulations, in influencing beach dynamics, shoreline stability, and dune development, processes that are common along much of the Mediterranean coast. The study developed a new methodological approach by integrating aerial ortophotos with high-temporal-resolution multispectral satellite imagery, to analyse beach evolution in the presence of Posidonia banquettes, with a focus on the impact of storm events. This approach examines shoreline, dune, and Posidonia accumulations through a combination of remote sensing techniques, enabling both medium-term through Satellite-Derived Shoreline (SDS) (∼10 years) and long-term analyses (∼70 years) using orthophotos. The results highlight the complex interactions between human activities, storm events, and natural processes, particularly the role of Posidonia accumulation in shaping beach and dune morphology. Medium-term analysis has offered detailed perspective on recent beach changes, illustrating fluctuations in Posidonia berms related to storm events and correlating shoreline positions with dune evolution. Meanwhile, long-term orthophotos analysis has provided insights into sediment transport dynamics and revealed trend patterns over extended timeframes. This integration of SDS data and aerial imagery leveraged the identification of “hotspot areas” by analysing the relationship between shoreline changes and dune toe retreat. • Shoreline monitoring using satellite and aerial images identified erosion and accretion areas. • The SDS allowed observation of shoreline fluctuations, including banquette formation. • Posidonia accumulation contributes to dune growth and erosion protection. • Kernel density maps identified dune erosion hotspots driven by shoreline interactions.