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Artificial Coral Reefs (ACRs) have been introduced to help solve coastal erosion problems, but their feasibility has not been assessed with field data. This study conducted a feasibility analysis of ACRs on their erosion mitigation effects by performing a case study of Cheonjin-Bongpo beach, South Korea. A numerical-physical combined analysis was carried out using a SWAN model simulation and physical model test with a scale of 1/25 based on field observations of Cheonjin-Bongpo beach. Both Dean’s parameter and the surf-scaling parameter were applied to comparative analysis between the absence and presence conditions of the ACR. The results for this combined method indicate that ACR attenuates the wave height significantly (59~71%). Furthermore, ACR helps decrease the mass flux (~50%), undertow (~80%), and maximum wave set up (~61%). The decreases in Dean’s parameter (~66%) and the surf-scaling parameter suggest that the wave properties changed from the dissipative type to the reflective type even under high wave conditions. Consequently, an ACR can enhance shoreline stability.

Shin, S.; Nam, J.; Son, S.; Kim, I.H., and Jung, T.-H., 2017. Field observation and numerical modelling of rip currents within a pocket beach. In: Lee, J.L.; Griffiths, T.; Lotan, A.; Suh, K.-S., and Lee, J. (eds.), The 2nd International Water Safety Symposium. Journal of Coastal Research, Special Issue No. 79, pp. 229–233. Coconut Creek (Florida), ISSN 0749-0208. Understanding the occurrence mechanism of rip currents are very important in terms of the sediment transport and the water safety issues. In order to investigate the rip current occurrence mechanism, field observations were carried out at Chunjin beach and a numerical model was employed to simulate rip currents by using the field observation data. The collected data set includes the beach topography, bottom bathymetries, shoreline, sand sample, and incident waves for each season. The field observation data showed the spatiotemporal variations of shoreline and sand bars. The results also showed that the rip currents were generated near t...

Kim, I.H.; Kim, J.H.; Nam, J.M.; Chang, S.Y.; Cho, W.C.; Do, K.D.; Kim, Y.J.; Song, D.S., and Lee, H.S., 2020. Changes in sand budget for littoral cell after coastal improvement project. In: Malvarez, G. and Navas, F. (eds.), Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No. 95, pp. 242–246. Coconut Creek (Florida), ISSN 0749-0208.The Munam2 harbor was constructed in 1989 and the direction of Munam river mouth was changed from the Gyoam beach to the Backdo beach in order to prevent sediment deposit within the harbor inside. In order to reduce erosion damage at the Gyoam beach, the CIP started in March 2014, and three submerged breakwaters were constructed in September 2016, as well as the beach nourishment. Therefore, the characteristics of shoreline change and bathymetric change were analyzed due to wave transmission after the implementation of submerged breakwaters in littoral drift cell. The beach monitoring was performed twice annually from 2014 to 2018, that the surveying items were shoreline change, beach profile and bathymetric change, including two times wave field observation during the monitoring period. As a result, the wave transmission rate between the W-2 and W-3 shows that the function of submerged breakwater is working effectively only when a significant wave, height over 1.3 m, occurs. However, it was analyzed that there was no wave energy reduction effect as a submerged breakwater when the significant wave height is below 0.3 m. After the submerged breakwaters were constructed to solve the erosion problem, the stable coastal line was formed on the Gyoam beach.

Kim, I.H.; Kim, J.H.; Nam, J.M.; Lee, H.S., and Song, D.S., 2019. Monitoring of coastal geomorphological changes in Wolchun Beach after LNG base construction. In: Lee, J.L.; Yoon, J.-S.; Cho, W.C.; Muin, M., and Lee, J. (eds.), The 3rd International Water Safety Symposium. Journal of Coastal Research, Special Issue No. 91, pp. 366-370. Coconut Creek (Florida), ISSN 0749-0208.Constructions of industrial facilities nearby coastal region often break a natural equilibrium between sediment budget and littoral current condition. The Wolchun beach, which is facing East Sea of South Korea, had a longshore stretch of 1.9 km before the LNG storing base was constructed. In this study, we analyzed the change patterns of the Wolchun beach topography caused by the installation of artificial structures, as well as coastal geomorphological changes. The control points in the study area were divided into 8 sections, each spaced 50 m pitch apart, for the trend analysis of the beach profiles. Also, the sea zone with 1.35 km2 area was divided into 6 sections with 300 m × 750 m per section, for the monitoring of water depth variation. The surveying results show that the area of the northern side of the Wolchun beach near the LNG storage base was continuously increased due to the accumulation of sediment after the construction of LNG base. On the contrary, the continuous erosion occurred on the south side of Wolchun beach, and it was observed that the water depth near the surf zone is deepened. Also, the bathymetric change of the test area was occurred actively, and the significantly unstable change of water depth in the region of about -10 m ∼ -15 m was confirmed to be generated by the breakwater with the disrupting of operable wave condition. It is found that the natural equilibrium has been collapsed along the unexpectedly formed shielding zone after the construction of the LNG base and the breakwater on the outside of the base.

Kim, J.; Kim, I.; Nam, J.; Song D., and Lee, H., 2019. Changes in the behavioral characteristics of the Gangmun and Anmok beaches following the construction of artificial reefs. In: Lee, J.L.; Yoon, J.-S.; Cho, W.C.; Muin, M., and Lee, J. (eds.), The 3rd International Water Safety Symposium. Journal of Coastal Research, Special Issue No. 91, pp. 26-30. Coconut Creek (Florida), ISSN 0749-0208.On the East coast of South Korea, there is only a small significant difference between low and high tides, meaning that seasonal wave directions appear clearly in recorded data. During summer, southeasterly waves dominate, and northward longshore drift occurs. In addition, the southward transport of littoral sediment occurs under the northeasterly waves that are dominant during winter. However, recent changes in the coastal environment, due to the development of coastal flooding prevention facilities, harbor development projects, and unusual weather conditions, have shown a tendency to increase the erosion of coastal areas. In other words, there is a repeating cycle of positive feedback, in which structures introduced to prevent a certain kind of coastal erosion cause different kinds of coastal erosion. In this study, we used field survey data to analyze the behavioral characteristics of the Gangmun and Anmok beaches for a period of seven years. The results show that the Gangmun and the Anmok beaches are very vulnerable to the effects of artificial constructs. Coastal erosion on Gangmun beach occurred through northward sediment transportation, caused by a dike that was built to avoid the closure of the mouth of Gyungpo stream. After an artificial reef and the groin were constructed to solve this erosion problem, the coastline stabilized. In the case of the Anmok beach, an imbalance in the sand budget supplied from the Namdae stream was brought about by the expansion of the Gangneung harbor, leading to significant beach erosion. After artificial reefs were installed on both beaches to prevent erosion, the area of each beach was increased and each beach's status was stabilized, as a salient beach.