Transmission Characteristics of Low Crested Breakwaters (LCB) with an Emphasis on Korean Marine Environments

The transmission coefficient of Low Crested Breakwaters (LCB), the primary structural type among many countermeasures against beach erosion, is the crucial design factor that dictates the extent of beach protection by LCB. The models of d'Angremond, van der Meer, and de Jong (1996) and van der Meer and Daemen (1994) for the transmission coefficient have been popular since the most comprehensive hydraulic model test was used in its development. However, it is worthy of note that humongous tetrapod has been preferred as the construction material of LCB to quarry stone due to less adverse environmental impact and workability, and the porosity of LCB built with tetrapod is more significant than LCB built with the quarry stone. As a result, LCB deployed in Korea was designed to rise near the free surface to obtain target energy dissipation to mitigate beach erosion in rough seas. Based on these facts, it can be easily perceived that these construction environments differ from the one underlying d'Angremond, van der Meer, and de Jong (1996), van der Meer and Daemen (1994) model. In this rationale, this study examined the transmission characteristics of LCB at Bong-Po beach using the situ wave data collected from 2019.8.6.To 2019.8.21. In doing so, 3-D numerical simulation was also carried out to make up the wave observation system's limitations, which often malfunctioned in the rough seas. It was shown that transmission coefficients by d'Angremond, van der Meer, and de Jong (1996), van der Meer and Daemen (1994) are significantly different from the one based on the situ wave data. Several factors are involved in making this difference, and among these, the Korean construction environment mentioned above noticeably stands out. Based on this rationale, a modified transmission coefficient model optimized for the Korean construction environment was also developed, which showed a remarkable agreement with the measured data.