Shoreline evolution related to coastal development of a managed beach in Alghero, Sardinia, Italy

This work investigates the shoreline changes affecting the beaches between the resort towns of Alghero and Fertilia, on the northwest coast of Sardinia, Italy, following recent planned expansion and dredging of the main harbours. A thirty-year historical shoreline time-series and sediment grain-size changes along the beach are analysed, in order to obtain recent evidence of erosional/accretional trends. Shoreline position change rates are quantified and discussed in relation to the history of coastal development and to Posidonia oceanica seagrass litter management. This study shows that, as a whole, the sediment budget of the beach is maintained, and the total area of shoreline accretion is slightly larger than the area of retreat. However over 60% of the total 4 670 m of shoreline is retreating, mainly in the most valuable sectors of the littoral for stakeholders. The shoreline in the areas closest to the two harbour breakwaters, which were extended during the 1980s, is advancing at a rate of up to 2.8 m yr−1. Areas closer to the seawall of Punta del Paru are retreating, at a rate of up to 1 m yr−1, and the nearby dune fields are eroding. The natural dunes at Maria Pia beach are acting as a source of sand to the littoral. The use of beach-cast seagrass materials for coastal protection is widely recognised in Sardinia. This study highlights that the choice of locations for seagrass debris dumping is extremely important, particularly in a closed, largely urbanised, sedimentary system.