Jetty

Jetty, man-made pier designed to aid in navigation. They are constructed primarily of wood, stone, concrete, or combinations of these materials. Breakwater jetties reduce the force of waves on a harbor or shoreline, while river jetties expedite the flow of silt through a delta. Jetties at the mouths of rivers such as the Mississippi and the Columbia funnel the water through narrow channels, thus forcing the currents to carry silt further out to sea.