Design and performance of permeable groins on a low-energy natural beach

Abstract

Beach erosion, ubiquitous of sandy coasts around the world, can be exacerbated or mitigated with the use of hard engineering solutions including groins. The use of groins has been discouraged in many countries despite its capability to reduce sand losses. This study aims to design a 15 m permeable groin that allows sediment bypassing. Field experiments were conducted on a low-energy, sea-breeze dominated micro-tidal beach at the northern Yucatan peninsula during both mean and extreme wave conditions. Firstly, a short-term experiment consisted in monitoring the structure performance for 24 h during typical sea breeze conditions and the subsequent beach recovery after the structure removal. Secondly, a multi-day (60 days) experiment was conducted to investigate the performance of a single- and double-groin system during both mean and local storm conditions. Beach surveys were conducted to evaluate the beach response. Shoreline variability shows sediment accretion on the east side of the structure during sea breezes, whereas during NNW storm events, the accretion occurred on the west side. Importantly, on a scale of days, sediment bypassing occurs, and hence a net accretion was measured at both sides of the structure. During this time, a second structure was deployed 30 m apart to test the performance of a double-groin system, finding a net shoreline advance at all beach transects. Thus, low-crested short-length permeable groins are found to be a suitable emergency mitigation measure against beach erosion in micro-tidal environments causing moderate shoreline change.