Among the various causes of coastal erosion, the installation of offshore breakwaters is considered the main cause that influences the most serious changes in shorelines. However, without a proper means for predicting such terrain changes, countries and regions continue to suffer from the aftermath of development projects on coastal land. It has been confirmed that the parabolic bay shape equation (PBSE) can accurately predict shoreline changes under the wave climate diffracted as a result of such development projects. This study developed a shoreline change model that has enhanced the previous shoreline change models by applying PBSE to shoreline changes into bay-shaped features. As an analytical comparison with the second term of the GENESIS model, which is an existing and well-known shoreline change model, a similar beach erosion width was obtained for a small beach slope. However, as the beach slope became larger, the result became smaller than that of the GENESIS model. The validity of the model was verified by applying it to satellite images that demonstrated the occurrence of shoreline changes caused by breakwaters for seaports on the eastern coast of Korea; Wonpyeong beach, Yeongrang beach, and Wolcheon beach. As a result, each studied site converged on the static equilibrium planform within several years. Simultaneously, the model enabled the coastal management of the arrangement of seaports to evaluate how the construction of structures causes serious shoreline changes by creating changes to wavefields.

Coastal erosion, a worldwide social issue, has garnered substantial attention. Numerous methods have been implemented to control coastal erosion problems; however, the presence of rigid structures limits erosion mitigation, thereby causing various challenges. For instance, in the case of submerged breakwaters, local scour in front of the structure and scour caused by the flow occurring in open inlets affect the subsidence and stability of the structure and can also cause structural failure. To solve these problems, this paper proposes a hybrid method of using a submerged breakwater with an artificial coral reef installation; further, this study evaluates the attenuation of waves and mitigation of sediment transportation through large-scale 3D hydraulic experiments. We found that the hybrid method with an artificial coral reef installed in the open inlet shows excellent wave control and plays a clearly beneficial role in the advancement of the shoreline. The artificial coral reef method reduced the return flow generated by the drag force at the breakwater shoulder and open inlet. In addition, scour at the breakwater shoulder was inhibited by collecting the sand escaping offshore. Simultaneously, scour at the open inlet was also mitigated. The application of the hybrid method compensated for the problems caused by local scour and erosion in the submerged breakwater, thereby leading to the improvement of its function. Therefore, the hybrid method proposed in this paper was determined to be applicable not only for submerged breakwaters, but also for various structures for controlling coastal erosion.

Kim, T.; Kwon, Y.; Hong, S.; Kim, J.; Kwon, S., and Lee, J., 2021. Wave attenuation analysis for artificial coral reefs using a physical modelling approach. In: Lee, J.L.; Suh, K.-S.; Lee, B.; Shin, S., and Lee, J. (eds.), Crisis and Integrated Management for Coastal and Marine Safety. Journal of Coastal Research, Special Issue No. 114, pp. 529–533. Coconut Creek (Florida), ISSN 0749-0208. Due to global warming and coastal development, the damages in coastal such as sea level rise and changes in coastline caused by scour and erosion are increasing, Various types of breakwaters are applied to prevent the coastal erosion, however, the problem such as scour around the structure is exacerbated, therefore a fundamental solution is needed. In this study, two-dimensional laboratory experiments were conducted in the wave flume to investigate the wave transmission phenomena of artificial coral reef. Experiments are conducted by analyzing wave transmission dependents on ratio of stem length to water depth(ls/h), wave height and wave period. Wave attenuation appeared to be most dependent on stem length to water depth(ls/h) and structure width. As incident wave height increased and the wave period decreased, the wave attenuation also increased, however, it was insignificant compared to the influence of the inundation rate. Wave attenuation increases dependents on incident wave height and period, however showed insignificant effect compared to submergence rate. In addition wave attenuation rate also affects wave energy reduction in order of ls/h > H0/h > h/L0. Based on results, we analyzed correlation between KC and CD of artificial coral reef to suggest the equation on empirical relationship. As a result, it is judged that estimating wave transmission rate and drag coefficient of artificial coral reef dependents on sectional specification can be utilized properly in working design and application.

Lee, W.D.; Kang, C.; Hong, S.; Lee, T.K., and Lee, J., 2021. Effect of wave load on decompression of underwater workers: CFD-VPM simulation. In: Lee, J.L.; Suh, K.-S.; Lee, B.; Shin, S., and Lee, J. (eds.), Crisis and Integrated Management for Coastal and Marine Safety. Journal of Coastal Research, Special Issue No. 114, pp. 614–618. Coconut Creek (Florida), ISSN 0749-0208. Hydrodynamic pressure from cyclic wave action causes water pressure increases and vibration, and these pressure changes can have a significant impact on underwater workers in high-pressure environments. This study investigated the impact of wave loading on decompression procedures for underwater workers using a coupled CFD-VPM. Computational Fluid Dynamics (CFD) were used to simulate wave propagation, and the Varying Permeability Model (VPM) was used to simulate the dive profile. Results of the wave propagation simulation showed that wave height and nonlinearity increased due to shoaling when approaching a beach, and the period was shortened. The maximum dynamic pressure head exceeded 1 m at depths less than 45 m and reached 10.3 m at a depth of 3 m. Simulations of the dive profile revealed that decompression time increased by 11 m and 9 s (28.36 %) under extraordinary wave conditions when underwater work was performed for 2 hours at a depth of 20 m. Furthermore, decompression time increased by 12 min and 40 s (10 %) at a working depth of 30 m. For safe underwater work operations under extraordinary wave conditions, decompression procedures should account for the pressure rise and vibration caused by wave action.

Lee, J.; Kim, D.H.; Lee, S., and Lee, J.L., 2016. Lagrangian Observation of Rip Currents at Haeundae Beach Using an Optimal Buoy Type GPS Drifter. In: Vila-Concejo, A.; Bruce, E.; Kennedy, D.M., and McCarroll, R.J. (eds.), Proceedings of the 14th International Coastal Symposium (Sydney, Australia). Journal of Coastal Research, Special Issue, No. 75, pp. 1177 - 1181. Coconut Creek (Florida), ISSN 0749-0208. In this study, we designed a new buoy type GPS drifter that is capable of measuring the rip current pattern in the surface layer particularly at Haeundae Beach, Korea. Our field test performance in August 2012 was successful using this new GPS drifter. Our GPS-tracked surf zone drifter can not only be easily affected by physical forces below the surface on the equipment's movement, but also unaffected by breaking waters. In this study, the design for a small, low-cost buoy type GPS drifter for collecting accurate Lagrangian data in the coastal zone is described.

Kim, H.M.; Kang, D.Y.; Kim, T., and Lee, J., 2017. Analysis of the awareness change of public CPR training in metropolitan Seoul from 2011 to 2015. 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. 30–34. Coconut Creek (Florida), ISSN 0749-0208. Cardiopulmonary Resuscitation (CPR) is the first response for a drowning victim. The quick action of lifeguards and facility operators is crucial to elevate the survival rate. However, there are plenty of beaches and waterfronts without lifeguards; therefore, bystander CPR is equally as important. To increase bystander CPR, public education is essential. This study analyzes the changing perceptions of CPR training and the change in people's confidence in executing CPR after a public CPR education program in metropolitan Seoul from 2011 to 2015. The participants were public school students, teachers, social workers, and public staff who reside in metropolitan Seoul. Between 2011 and 2015, 205,949 people participated in a public CPR training program organized by Lifesaving Society Korea. After each 2–4 hour-long training, course operators collected a questionnaire. Researchers separated the collected results into two categories-program type and training format- and from there further separated the results. In the program type (hours) category, researchers used the following delineations: (1) 2-hour long adult CPR and AED (Automated External Defibrillator); (2) 3-hour adult, pediatric, and infant CPR and airway obstruction; (3) 3-hour adult CPR, AED, and airway obstruction; and (4) 4-hour adult, pediatric, and infant CPR, AED, and airway obstruction. The training format category was further broken up as follows: (1) alternating explanations of skills with practice and (2) full lecture followed by practice. Compared to 2011, which is regarded as the beginning of the public CPR training movement an increasing number of participants responded that they have participated in CPR training before and that they had confidence in their ability to execute CPR. Most participants preferred a small class size class-no more than 20 participants- some participants described the benefits of using simple words rather than medical terminology. There is no significant difference in satisfaction with different instructors. Periodic recertification and public CPR awareness programs contribute positively to CPR execution confidence and willingness to perform CPR in everyday life. Therefore, this study concludes that public CPR programs should be expanded to more schools, work places, and public facilities. In addition, public CPR training programs need to better explain first aid. Using this study's results, training policies-such as recertification period, training format, and hours- can be modified to improve the programs' effectiveness.