Medium-term dynamics of a middle Adriatic barred beach

Abstract. In recent years, attention has been paid to beach protection by means of soft and hard defenses. Along the Italian coast of the Adriatic Sea, sandy beaches are the most common landscape feature and around 70 % of the Marche region's coast (central Adriatic) is protected by defense structures. The longest free-from-obstacle nearshore area in the region includes the beach of Senigallia, frequently monitored in the last decades and characterized by a multiple bar system, which represents a natural beach defense. The bathymetries surveyed in 2006, 2010, 2011, 2012 and 2013 show long-term stability, confirmed by a good adaptation of an analyzed stretch of the beach to the Dean-type equilibrium profile, though a strong short- to medium-term variability of the wave climate has been observed during the monitored periods. The medium-term dynamics of the beach, which deal with the evolution of submerged bars and are of the order of years or seasons, have been related to the wave climate collected, during the analyzed temporal windows, by a wave buoy located about 40 km off Senigallia. An overall interpretation of the hydrodynamics, sediment characteristics and seabed morphology suggests that the wave climate is fundamental for the morphodynamic changes of the beach in the medium term. These medium-term time ranges during which waves mainly come from NNE/ESE are characterized by a larger/smaller steepness and by a larger/smaller relative wave height, and seem to induce seaward/shoreward bar migration as well as bar smoothing/steepening. Moving southeastward, the bar dimension increases, while the equilibrium profile shape suggests the adaptation to a decreasing sediment size in the submerged beach. This is probably due to the presence of both the harbor jetty and river mouth north of the investigated area.