groin
Longshore drift can erode the sediment from a beach. To keep this from happening, people may build a series of groins. A groin Figure below is wall of rocks or concrete. The structure juts out into the ocean perpendicular to the shore. A groin stops the longshore movement of sand. Sand collects on the up-current side of the groin. Sand on opposite of side of the groin erodes. This reduces beach erosion.