Coastal structures, such as revetments, are built to protect specific areas and facilities from the attack of extreme waves. However, unexpected environmental damage could be induced from these structures when inappropriately applied. Here, we present the results of measurements carried out using a video monitoring system, indicating the rapid collapse of a coastal revetment due to the attack of storm waves. The destruction occurred in sequence; that is, it was initiated by human activities, followed by a natural disaster. First, the beach in front of the revetment was eroded, even under moderate wave conditions, because sediments transported into this area were blocked by a rip-rap jetty. After the beach width was severely reduced due to the erosion, the revetment collapsed when storm waves attacked the area. The destruction seems accidental and inevitable because it was directly caused by the storm. However, it could have been avoided by predicting and preventing the erosion due to the jetty. This study provides insights into sequential processes that lead to the failure of coastal revetments, which could be applied for prevention of similar anthropogenic disasters.

The long-term trend of swell-like waves invading the east coast of Korea was identified by using observations and hindcast data from 1979 to 2016. We defined a swell-like wave as a wave with a height of 2 m and a peak period of 10 s on the basis of a literature review of human casualties and property damage in the region. In total, 179 swell-like wave cases were detected from 1979 to 2016, with 132 cases caused by extratropical cyclones (ETCs). The track density analysis indicated that the ETCs were mainly generated on the east coast of China, over the East/Japan Sea, and over the Kuroshio-Oyashio extension region and then moved northeast. This reflects the prevailing wind direction, which was the most significant factor in generating the swell-like waves. The number of swell-like waves has been significantly increasing since the 2000s. This increasing trend of swell-like waves is linked with the synoptic eddy activity with a correlation of 0.53. They were associated with the reversed meridional gradient of surface air temperature and the consequent negative vertical wind shear anomaly near 40° N.

Harmful algal blooms (HABs) are types of phytoplankton overgrowth that adversely affect marine ecosystems and aquaculture resources. One such HAB species, Cochlodinium polykrikoides, occurs irregularly and causes significant damage to the aquaculture industry along the coastal regions of Korea. In this study, we developed and implemented an integrated system to detect and predict HAB occurrences in real time. This system comprises four main components: (1) a real-time detection system utilizing acoustic sensing, ocean weather, water temperature, salinity, and chlorophyll, satellite images, genetic analysis, and optics; (2) a prediction model system based on current and tidal, HAB occurrence, and HAB movement and diffusion models; (3) an additional data based on HAB information of sampling data and HAB information of GPS data, and (4) an integrated information system utilizing data storage servers and a visualization platform. We applied and assessed the efficiency of this integrated system in the South Sea of Korea from 2017 to 2019. Particularly, HABs occurred significantly in 2019, and the system demonstrated the feasibility of detection and prediction under field conditions. Implementing a more advanced integrated detection and prediction system in the field is anticipated to minimize the damage caused by irregular HAB occurrences every year.

<!-- *** Custom HTML *** --> Choi, J.W.; Song, K.M., and Choi, J.Y., 2019. Accuracy improvement of particle tracking model using 2-D current measurement (HF-Radar) data. 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. 251-255. Coconut Creek (Florida), ISSN 0749-0208. The accuracy of the particle tracking model (PTM), which is widely used for predicting spilled oil diffusion and supporting search and rescue in the ocean, is significantly affected by current and wind, which necessitates the development of suitable accuracy improvement techniques to increase human safety and preserve the environment. To address this issue, we herein established a method of improving PTM accuracy by comparing high-frequency radar (HFR) current data with those of the coastal model. Particle tracking was simulated using a ∼300-m-resolution current field of the Korea Operational Oceanographic System (KOOS) coastal circulation forecasting system, a ∼3-km-resolution current field of the HFR system installed on Jeju Island, and a 4-km-resolution KOOS weather forecasting system (wind data). To compare the effects of two currents on PTM accuracy, drifters were dropped from the center of the HFR-system grid, and performance was evaluated by comparing the actual drifter moving path with that predicted by PTM. PTM accuracy was calculated by comparing the acceptable duration and accuracy (drifting object located within 1 km) with 10-day moving path data, and the application of two-dimensional current measurement data and wind data was shown to significantly increase prediction accuracy.

The parametric typhoon model is a powerful typhoon prediction and reproduction tool with advantages in accuracy, and computational speed. To simulate typhoons’ horizontal features, the longitude and latitude of the typhoon center, central pressure, radius of maximum wind speed (Rmax), and background states (such as surface air pressure and wind speed) are required. When a typhoon approaches or is predicted to affect Korea, the Korea Meteorological Agency (KMA) notifies the above-mentioned parameters, except for the Rmax and background state. The contribution of background wind and pressure is not very significant; however, Rmax is essential for calculating typhoon winds. Therefore, the optimized Rmax for the typhoons over the past five years was estimated at each time step compared with the in situ wind observation record. After that, a fifth-order polynomial fitting was performed between the estimated Rmax and the radius of strong wind (RSW; >15 m/s) provided by the KMA. Finally, the Rmax was calculated from the RSW via the empirical equation, and the horizontal fields of typhoon Hinnamnor (2211) were reproduced using a parametric model. Furthermore, the ocean storm surge height was adequately simulated in the surge model.

Choi, J.W.; Kwon, J.I.; Heo, K.Y., and Choi, J.Y., 2020. Hindcasting of search and rescue cases using the trajectory model based on KOOS (Korea Operational Oceanographic System). In: Malvárez, G. and Navas, F. (eds.), Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No. 95, pp. 900–904. Coconut Creek (Florida), ISSN 0749-0208.The most important consideration for search and rescue (SAR) is to accurately predict the trajectory of missing persons or vessels to secure a search area and the golden time for rescuing survivors. The SAR modeling system of the Korea Operational Oceanographic System (KOOS) is directly linked to the Weather Research and Forecasting model (WRF), the Modelo Hidrodinâmico (MOHID), and the Modular Ocean Model (MOM5). The SAR prediction result produced by KOOS is provided to the Korea Coast Guard, which is responsible for SAR missions in Korea. In this study, numerical model results were evaluated using actual accident case and the trajectory data of drift buoys. Prediction accuracy was explored using 1) two different horizontal resolutions (300 m and 4 km) of the MOHID and 2) two different time resolutions (MOHID: 1 h; MOM5: 1 day) at the same horizontal resolution (4 km). The analysis of drift prediction accuracy showed that prediction accuracy was relatively high for the MOHID at a resolution of 300 m, which was a higher horizontal resolution close to the coast. This provided more accurate tidal current results. The time resolution in the offshore region affected ocean currents, and prediction performance was relatively high for the MOHID at a resolution of 1 h. Based on these results, it was found that securing high-resolution data in time and space is essential for improving the performance of drift prediction in adjacent seas in the Korean Peninsula.