Hydraulic functioning of permeable pile groins

Abstract

Beach erosion, the loss of sand from a beach due to longshore and/or cross-shore sediment transport mechanisms, is a challenging problem. In order to stabilize the beach and to slow down the rate of beach erosion, the construction of hard hydraulic structures is a traditional option. Groins are one of the oldest man-made hydraulic structures designed to intercept the longshore sediment transport and to stimulate sediment deposition within the groin compartments. However, erosion is likely to appear at the downdrift beach stretch of a groin system, due to lack of sufficient sand feeding from the updrift groined beach reaching the downdrift beach. To alleviate sand starvation at a downdrift beach of groins, groins are suggested to be gradually shorter and more permeable approaching the downdrift terminal groin. The primary advantage of permeable groins, compared to impermeable groins, is they do not entirely block longshore currents. The large openings of permeable groins allow littoral drift to flow through. The shoreline response to permeable groins is comparable to a straight line, other than a zig-zag shape response to impermeable groins. Nevertheless, even though the benefits of permeable groins seem obvious, the research on the subject of the hydrodynamics of permeable groins in coastal waters is limited.