Sand bypassing

Sand bypassing is the engineered transfer of sediment past a barrier such as a jetty, inlet, or harbor entrance to restore the littoral drift that the structure interrupts. Without it, sand piles up on the updrift side and the downdrift coast starves and erodes. A fixed bypassing plant pumps sand through a pipeline across the inlet, while mobile bypassing uses a dredger to lift it from the updrift fillet or a trap and place it downdrift. The design rate matches the net annual longshore transport, often tens to hundreds of thousands of cubic meters a year. The Tweed River and Nerang plants are long-running fixed examples.