The Barqueiro Ria, located on the north coast of the Iberian Peninsula, is one of the Galician “Rías Altas”, which includes Arealonga Beach, the longest beach in the Ria, located in the inner portion. During the 1990s strong erosion has been registered on the beach and associated dunes, while a wide intertidal spit has grown westward. This behaviour is related to the hydrodynamic and sedimentary characteristics of the Ría and Sor Estuary. Tide and wave influence are evaluated using numerical simulations for storm events. Seasonal topographic monitoring of beach and dune profiles and surface sediment samples allow to describe the variations in sedimentary volume and map sediment units. Furthermore, grain size parameters trends are used to determine the sediment transport patterns. Three different zones have been defined along beach and foredune according to their sedimentary dynamics behaviour: i) Eastern zone, with a clear erosive tendency generating the backshore and foredune destruction ii) Middle zone, with dune erosion but sediment accumulation in the intertidal zone, and iii) Western zone, where the beach presents an accumulative profile, with a well developed supratidal area and active dunes.