Extreme human-induced pocket beach growth on a rocky coast

A large human-induced sediment supply (~ 400 Mt) took place on the Atacama Desert rocky coast (~ 26° S) as a result of the dumping of copper mine tailings between 1938 and 1990. We show that the input of this large sediment load has affected the natural sediment dynamics in this coastal area. The coastal system counterbalanced this abrupt increase in sediment supply with rapid accretion while the dumping was active. A different accretion pattern is observed in each of the two bays that received tailings. In one of them, the tailings input occurred in its center, resulting in a radial-to-rectilinear pattern that caused the growth of an existing pocket beach. In the other bay, where the alongshore transport is hindered by a small central rocky headland, the sediment input occurred on a lateral headland, resulting in a lateral-to-bypassed pattern that triggered the formation of two artificial beaches. Once the dumping of tailings ceased, the artificial beaches have been in a period of strong erosion, although the most recently formed beach still experiences northward accretion. This work contributes to assessing the impact of large human-induced sediment supplies on rocky coasts, providing valuable data for investigating current and future coastal changes according to both natural forces and human activities and their consequences.