Long-Term Monitoring and Morphological Response to Repeated Beach Nourishments in a Critical Coastal Sector: Lido di Dante Beach, Emilia-Romagna, Italy

Among low-lying sandy coasts, where erosion represents a major challenge, artificial beach nourishment is widely used as a mitigation strategy. This study investigates the long-term morphological evolution of Lido di Dante beach in northern Emilia-Romagna, Italy, where three regional nourishment interventions (Progettoni 2, 3, and 4) were carried out between 2007 and 2025. The dataset comprises twelve topo-bathymetric surveys covering the complete monitoring sequences (PRE, POST, M1, and M2). Sediment budgets, DEMs of Difference, cross-shore profiles, and beach slopes were analysed within three sectors (I, II, and III) characterized by different coastal-defence configurations. All interventions produced marked beach widening, with local elevation increases. However, substantial sediment redistribution occurred during the subsequent monitoring phases. During POST–M1, losses relative to the supplied volumes were 12% and 82% in Sectors I and II after P2 (Sector III was not nourished), 62%, 99%, and over 100% after P3, and 3%, 45%, and 43% after P4. These results indicate a spatially heterogeneous response associated with nourishment distribution, coastal-defence configuration, and local morphodynamic conditions. The recurring post-nourishment losses demonstrate that sediment placement in this area produces substantial short-term recovery without ensuring long-term stability, thus supporting the need for repeated interventions and accurate multi-temporal topo-bathymetric monitoring.