Beach nourishment on low-energy coasts: Purpose and persistence (Puck Lagoon, Poland)

Low-energy coasts, though ecologically significant and highly sensitive to anthropogenic pressures, remain understudied with respect to artificial beach nourishment. This study examines the purpose, geomorphological effects, and persistence of beach nourishment interventions at two sites along the Puck Lagoon (Southern Baltic, Poland) – a semi-enclosed, sheltered low-energy coastal system of high ecological value exposed to intense tourism pressure. Using UAV-based morphological surveys, archival remote sensing data, and sediment analyses, we assessed beach changes over the two decades preceding nourishment and monitored post-nourishment evolution for two years. Results indicate an absence of erosion hazards; nourishment was therefore driven primarily by socio-economic and recreational interests rather than coastal protection needs. The natural beaches were narrow and heterogeneous, composed of cobbles, wrack, driftwood, and vegetation within a Natura 2000 site. Nourishment replaced these with relatively homogeneous fine-to medium-grained sand, even finer than the natural deposits. Initial morphodynamics in Rewa corrected design shortcomings by eroding the lower beach and infilling the nearshore. Over two years of monitoring, no significant shoreline retreat or volumetric losses were detected. In both sites, morphodynamics remained weak, merely reflecting pre-nourishment patterns. Our findings demonstrate that, on extremely low-energy coasts, nourishment effects can persist for several years without recurrent interventions. We propose a decision-making framework integrating geomorphological, ecological, and socio-economic criteria to guide sustainable nourishment planning in similar environments. These results have management implications for Integrated Coastal Zone Management in sheltered lagoonal systems worldwide, highlighting the necessity of rigorous need assessment, long-term monitoring, and ecosystem service valuation.