Beaches are spaces of paramount importance for coastal societies currently threatened by coastal erosion. Their preservation requires accurate quantification of their changes in order to understand their behavior and to propose efficient solutions. Landsat 8 and Sentinel 2 mid-resolution satellites offer free-of-charge images with great potential for coastal monitoring. From them, it is possible to automatically extract the shoreline position as a quantitative indicator of the beach morphology

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... ver large territories and with high temporal frequency. Beach changes take place at different spatial and temporal scales, typically responding to coastal storms and human interventions on the coast. The collection of large packages of satellite-derived shorelines (SDS) at the coastal sector València-Cullera (W Mediterranean) covering the period 2013-2020 makes it possible to characterize the state of its beaches and their width changes over space and time.Results reveal a widespread erosional trend, most likely caused by a shortage of sediment in the coastal system. Thus, the majority of the beaches are not capable of restoring their previous conditions after storm-driven retreats. The information provided by the SDS also shows the ineffectiveness of the nourishment actions, at least in the way they have been carried out, and the urgent need for a strategy to address the erosion problem.