The process-based XBeach model has numerous empirical parameters because of insufficient understanding of hydrodynamics and sediment transport on the nearshore; hence, it is necessary to calibrate parameters to apply to various study areas and wave conditions. Therefore, the calibration process of parameters is essential for the improvement of model performance. Generally, the trial-and-error method is widely used; however, this method is passive and limited to various and comprehensive parameter ranges. In this study, the Generalized Likelihood Uncertainty Estimation (GLUE) method was used to estimate the optimal range of three parameters (gamma, facua, and gamma2) using morphological field data collected in Maengbang beach during the four typhoons that struck from September to October 2019. The model performance and optimal range of empirical parameters were evaluated using Brier Skill Score (BSS) along with the baseline profiles, sensitivity, and likelihood density analysis of BSS in the GLUE tools. Accordingly, the optimal parameter combinations were derived when facua was less than 0.15 and simulated well the shifting shape, from crescentic sand bar to alongshore uniform sand bars in the surf zone of Maengbang beach after storm impact. However, the erosion and accretion patterns nearby in the surf zone and shoreline remain challenges in the XBeach model.

Even though submerged breakwater reduces incident wave energy, it redistributes the coastal area's wave-induced current, sediment transport, and morphological change. This study examines the coastal hydrodynamics and the morphological response of a wave-dominated beach with submerged breakwaters installed through field observation and quasi-3D numerical modeling. The pre-and post-storm bathymetry, water level, and offshore wave under storm forcing were collected in Bongpo Beach on the East coast of Korea and used to analyze the coastal hydrodynamic response. Four vertically equidistant layers were used in the numerical simulation, and the wave-induced current was examined using quasi-3D numerical modeling. The shore normal incident wave (east-northeast) generated strong cross-shore and longshore currents toward the hinterland of the submerged breakwater. However, the oblique incident wave (east-southeast) induced the southeastward longshore current and the sedimentation in the northeast area of the beach. The results suggested that the incident wave direction is a significant factor in determining the current and sediment transport patterns in the presence of the submerged breakwaters. Moreover, the quasi-3D numerical modeling is more appropriate for estimating the wave transformation, current, and sediment transport pattern in the coastal area with the submerged breakwater.

Kim, I.H., Lee, H.S. and Song, D.S., 2013. Time series analysis of shoreline changes in Gonghyunjin and Songjiho Beaches, South Korea using aerial photographs and remotely sensed imagery Given the speed and pervasiveness of anthropogenic landcover changes, especially in coastal areas, monitoring shoreline alterations and their impacts is critical for intelligent coastal development and beach use management. In this study, we describe a monitoring and analysis framework that uses aerial photography, remotely sensed imagery, and field surveys to detect changes in beach width and area along Gonghyunjin and Songjiho Beaches in South Korea. We used IKONOS imagery acquired in 2004; aerial photographs captured in 1991, 2005, 2009 and 2010; and field surveys conducted in 2010 and 2011. Based on comparisons of these data sources, we detected widespread erosion on both beaches starting in 2004, resulting in 12% reduction in the plane area of these beaches between 2004 and 2010. Most dramatically, we noted that beach width eroded by 28.5 m at the point 700 m south of Gonghyunjin Harbor, and similar declines occurred at several other locations. Erosion occurred at these locations because extended breakwaters in the Gonghyunjin Harbor either blocked or interrupted drift sand transport processes, causing sand to be carried away from some locations without accretion to replenish it. In addition, according to field surveys, we determined that erosion and accretion processes continued to vary seasonally in 2010 and 2011, resulting in smaller overall changes than those in the study years prior to 2010. However, we suggest that severe erosion may occur in the future at some locations if sand continues to be transported north onto Songjiho Beach without replenishment. Thus, we demonstrated that the construction of artificial structures around the harbor caused changes along the shoreline. Our monitoring framework has important applications for future observation of anthropogenically driven changes to this coastal area and serves as an applicable tool in other coastal regions worldwide.

Kim, I.H., Lee, H.S., Cho, W.C. and Song, D.S., 2013. Shoreline changes due to groin construction in Namae and Sodol Beaches, South Korea The present study beach has a long stretch of 5.27km bounded by Namae Harbor in north and Sodol Harbor in south which are located in the eastern coast of Korea. In 2007, a groin was constructed at the southern part of Namae Harbor. In order to analyze the pattern of shoreline change due to the groin construction, a beach survey has been accomplished since 2008 right after the groin construction. The temporal and spatial changes in beach topography are also investigated based on the echo sounding data. The survey data along the coastline showed that a continuous accretion occurred around the groin in the south of Namae Harbor due to the north-directed currents mainly due to diffracted waves formed after the groin construction. Thus the southern beach of study area has been eroded steadily. Also, beach widths and plane area of the beach in the south of the groin were decreased in summer and was increased in winter season. In winter, the ground-based surveying was even impossible due to the severe sand loss in the southern part of study area. Moreover, the survey results revealed that the beach volume was increased and foreshore slope became steeper in 2011 than 2010 survey. Therefore, the continuous beach monitoring along the shoreline is necessary, especially in the seriously eroding beach such as Sodol Beach. More fundamental measures for reliable prediction of potential beach change prior to complementary construction of coastal structures are also needed to maintain the value of the beach.

Song, D.S., Kim, I.H. and Lee, H.S., 2013. Preliminary study of 3D Assessment of Coastal Erosion by Data Integration between Airborne LiDAR and DGPS Field Observations The airborne Light Detection And Ranging (LiDAR) system has been allowed in monitoring various natural hazards, so highly accurate and airborne LiDAR data have been used in the field of oceanic sciences, including a digital terrain modeling and bathymetric mapping. In this study, we adopted airborne LiDAR measurements to assess coastal erosion for the first time. The airborne LiDAR data were acquired along the east coastal zone of Korea (shoreline is about 205km). The 3D topographical data and digital orthophotos, which were obtained from aerial LiDAR with a digital camera, were integrated with the beach profiles conducted by the VRS-based DGPS surveying. The integrated dataset were relocated into a developed flight simulator module, which is a Dynamic geographical information system solution with Digital AirScape (D-DAS), for the ...