Jung Lyul Lee

Introduction to Automated System in HAECUM (HAEundae Current Model)

ABSTRACT Lee, J.; Yoo, C., and Lee, J.L., 2014. Introduction to automated system in HAECUM (HAEundae Current Model. Wave-induced currents must be predicted for the sake of public safety, and coastal flows and waves are produced at each time step and each grid point by means of a systematic interface of the hydrodynamic and wave models. The flow velocity is influenced by the tides, wave-induced currents, and free surface flow from the waves, and a forecasting system has been written into a software package called the Haeundae Current Model (HAECUM) in order to provide a user-friendly simulation tool for end-users. The HAECUM system has been written in a modular manner with two sub-models: a wave model that uses radiation stress and a current model. The flow velocity and the water level resulting from the tide-induced combined flow are determined by solving depth-integrated equations of mass and motion, and the forcing terms in this model include the surface pressure, surface shear stress due to wind, bottom friction, Coriolis effects, and tide potential. The radiation stresses are used as feedback for the the circulation model to calculate the wave-induced current.

Vertical Structure of Rip Current Observed at Haeundae Beach

ABSTRACT Kim, I.; Lee, J.L.; Hwang, J.S.; Lee, S., and Lee, J., 2014. Vertical structure of rip current observed at Haeundae Beach. On 4 and 7 August, 2012, more than 200–300 people were swept away by the fast moving seaward current at Haeundae Beach, which is located on the southeastern corner of the Korean Peninsula, and they then had to be rescued Beach patrons were carried away 50 to 100 meters away from the shore by rip currents, to an area where swimming is restricted due to safety reasons. Rip currents are narrow currents that begin close to the shoreline and strongly flow seaward through the surf zone and beyond. Although rip currents can cause tragic accidents and are of considerable interest to scientists and to the general public, our current understanding of the spatial and temporal behavior of rip currents is limited. As a result, the Korean Meteorological Administration installed monitoring equipment that can assess weather conditions and issue rip current warnings on Haeundae beach starting from 2010. Rip current kinematics and beach morphodynamics were measured for 50 days at Haeunadae beach using several instruments, including velocity and pressure sensors, such as an Aquadopp profiler for shallow water, and the morphology consisted of a low-tide terrace with incised quasi-periodic rip channels, which are representative of transverse bars. The spatial distribution of the sediment is reflected in the background rip current flow field with mean velocity magnitudes within the rip channel that increase offshore both with a decrease in the tidal elevations and with an increase in the sea-swell energy. The vertical velocity profile on the bar indicated that the flow was predominantly shoreward. The Aquadopp profiler is a high-resolution current profiler that operates at sub-cm scales and collects data at up to 8 Hz. The instrument is generally used in boundary layer studies at the bottom 1–2 meters of the ocean and in low energy environments. In addition, the HR profiler excels at providing flow details that are not attainable with any other instrument. In this study, the data from the Aquadopp profiles was used to investigate the detailed vertical structure of dangerous rip currents at Haeundae beach, and we were able to quantitatively understand the mechanism of a rip current.

Quantitative Risk Assessment for Beach Drowning Management

ABSTRACT Yang, B.; Lee, J.; Hwang, J.S.; Kweon, H.M., and Lee, J.L., 2014. Quantitative risk assessment for beach drowning management. The beach is recognized as the most important resource because it provides the best recreational amenity to tourists. However, the beach safety aspect is getting more relevant, because the drowning risks all over the world are much too high and do not decrease enough. Especially, drowning is a major public health problem with substantial personal, societal, and economic costs, each year many people drown at the beach and many more are seriously injured. In Korea, most of the beach safety services belong to personnel rescue services. In contrast, Australia and the United Kingdom have developed several practical integrated beach risk management programs and safety systems. In this study, we have carried out field survey for beach safety on 4 popular beaches along the Korean coast, and conducted a beach risk audit and prepared a report. In addition, we developed a quantitative risk assessing method with reference to the Australian method. In this method, three parameters that were related to emergency rescue factor, risk avoidance factor and safety preparedness factor, are included in the risk assessment for management purpose. The purpose of coastal drowning risk assessment is to make decisions, based on the outcomes of risk analysis, about which risks need treatment priorities. From these results, we will implement preferred treatment options or an action plan for managing the beach safety in order to minimize the risk of injury by drowning.

Managing Effect of Hot Spot Shoreline Behind a Power Buoy Energy Farm

ABSTRACT LEE, J. L., LEE, J. Y. and KIM, I. H., 2011. Managing Effect of Hot Spot Shoreline Behind a Power Buoy Energy Farm. In: Micallef, A. (ed.), MCRR3-2010 Conference Proceedings, Journal of Coastal Research, Special Issue, No. 61, pp. 309–316. Grosseto, Tuscany, Italy, ISSN 0749-0208. A powerbuoy energy farm is taken into account to generate and deliver green energy to a small town located in Kangwon coast, Korea. The wave heights are reduced on the lee side of a power buoy energy farm. Therefore, ocean energy devices can also protect the coastline from erosion without changing the physical scenes dramatically. Many coastal communities have suffered from the coastal erosion problem. One of the traditional ways to improve the condition has been to build breakwaters, which reflect waves to adjacent areas. The erosion of the unprotected coastlines then gets worse because the energy has to be released in action here and there. Our numerical study involves two modules: 1) wave dynamics analyzed by a plane-wave approximation, and 2) concurrent wave-induced currents. The numerical approaches of the wave-structure interaction have concerned several authors with the direct inclusion of evanescent modes, which require significant CPU time and computational storage. Recently, Lee and Lee (2001) and Lee and Lee (2003) proposed a simple plane wave, wide-spacing approximation method to add scattering terms to the traditional mild-slope equation without inclusion of evanescent modes. Evanescent modes are only considered in analyzing the scattering characteristics for a single buoy.

Monitoring and Analysis of Bacterial Communities during a Summer Season on Gyeongpo Beach

ABSTRACT Lee, J.L.; Kim, I.H.; Yeon, Y.J., and Lee, J., 2017. Monitoring and analysis of bacterial communities during a summer season on Gyeongpo 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. 249–253. Coconut Creek (Florida), ISSN 0749-0208. A number of tourists visit beaches in the summer to enjoy sea bathing. However, numerous accidents occur on the eastern coast because of the topographical characteristics of the beach, and most accidents are caused by rip currents. Additionally, in the summer, as many tourists prefer beaches near swash zones, exposure to non-point pollutant sources can occur, significantly harming the health of visitors. Enterococci have shown the strongest correlation to gastrointestinal symptoms in a study examining the relationship between swimming-associated gastrointestinal illness and microorganisms. The U.S. Environmental Protection Agency found a direct relationship between the density of E. coli and enterococci in surface waters and increased swimmer-associated gastroenteritis. These reports suggest that E. coli and enterococci can be used as bacterial indicators compared to total coliform. Therefore, in this study, the safety of beach seawater was evaluated using E. coli and enterococci as bacterial indicators. Enterococcus and E. coli were isolated during the summer holiday season from the Gyeongpo Beach located on the eastern coast of Korea. The results indicated that the source of pollution near a swash zone, where people are crowded, was larger than that at the dry beach and near swimming zone.

Calculation of Rip Current Warning Index by a Vector Rose Diagram

ABSTRACT Kim, D.H.; Park, K.C.; Kim, I.; Lee, J.L., and Lee, J., 2017. Calculation of rip current warning index by a vector rose diagram. 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. 109–113. Coconut Creek (Florida), ISSN 0749-0208. Rip currents, which are sea tides that can carry swimmers into deep water beyond the breaking points, pose an immense security risk to beachgoers around the world. In Korea, rip current forecasting is divided into four warning levels: notice, watch, warning, and danger. However, the numerical results are represented by current vectors, and an additional process is necessary for converting these vectors into a predictive model. The primary goal of this study is to present a method that illustrates how to convert numerically simulated vectors into a rose diagram and how to divide this diagram into four warning levels for rip currents. The proposed method was validated by analyzing the correlation between warning indexes calculated from the present approach and those obtained from the NERiPs. The study was conducted at Haeundae Beach located in Busan, Korea. Different from the NERiPs, which is simply used to forecast the warning levels by the incident-wave conditions, this wave-induced currents model considers morphological effects.

Cause Analysis of Erosion-Induced Resort Washout on Cua Dai Beach, Vietnam

ABSTRACT Hung, N.T.; Vinh, B.T.; Nam, S.Y., and Lee, J.L., 2017. Cause analysis of erosion-induced resort washout on Cua Dai Beach, Vietnam. 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. 214–218. Coconut Creek (Florida), ISSN 0749-0208. On an eroding beach, high waves can completely wash out beaches, swimming pools, and resorts. Cua Dai shore, which is located immediately north of Thu Bon river mouth in central Vietnam, has eroded on the order of hundreds of meters in beach width. The present study estimated the erosion rate of sediment volume into the estuary through the Thu Bon river mouth by using recent satellite images, and utilized a shoreline change model to reproduce the erosion of shoreline near the river mouth. Results are in good agreement with observed data. The numerical model is modified by including the equilibrium angles that were obtained from a static shoreline equation of parabolic shape. Through the sediment conservation rule, the main cause of shore retreat is found to be sediment loss in the Thu Bon river estuary with the reduction in river sediment. The possible causes for this type of sediment loss are mining in the estuary and reduction of river flow action against waves in the river mouth with the reduced sediment supply. Proper management of Cua Dai beach requires the development of a monitoring system to fully understand beach dynamics and to mitigate the further resort washout owing to background erosion.

Lagrangian Observation of Rip Currents at Haeundae Beach Using an Optimal Buoy Type GPS Drifter

ABSTRACT 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 equipments 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.

The Application of a Rip Current Warning Decision-Process System, Haeundae Beach, South Korea

ABSTRACT Lee, J.; Cho, W.C., and Lee, J.L., 2016. The Application of a Rip Current Warning Decision-Process System, Haeundae Beach, South Korea. 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. 1167 - 1171. Coconut Creek (Florida), ISSN 0749-0208. Rip currents have the potential to pull swimmers into deep water, beyond offshore sand bars, posing a significant danger to beach goers worldwide. At Haeundae Beach in Busan, a south eastern region of South Korea, many rip current events have recently occurred, resulting in a number of people requiring rescue from these fast moving, seaward currents in 2014. The main objective of this study was to provide a warning decision-process for the occurrence of rip currents, to aid in the protection of human life in the areas where these rip currents occur. The rip current warning decision-process system developed in this work consists of both the NERiPS-H (Nearshore Rip current Prediction System for Haeundae Beach) and HAECUM (HAEundae Current Model) systems. By combining the predictive index model (NERiPS-H) and the numerical model for rip current forecasting (HAECUM), rip currents were forecasted using wave and wind data, along with forecasting information. Using this system, it possible to provide a 72-hour rip current forecast, which was made available on the KMA website. Four warning levels were chosen for forecasting of rip current occurrences by the KMA.

Hydraulic and Environmental Stability Analysis in the Estuary of Gahwa River and Sacheon Bay by the Change of Discharge of Namgang Dam in South Korea

ABSTRACT Kim, T.W., Lee, W.D., Hur, D.S., Lee, J.L and Yoon, J.S., 2016. Hydraulic and Environmental Stability Analysis in the Estuary of Gahwa River and Sacheon Bay by the Change of Discharge of Namgang Dam in South Korea. 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. 213–217. Coconut Creek (Florida), ISSN 0749-0208. Namgang dam is located in the southern part of South Korea. Flow discharged from Namgang dam for a flood control runs Kahwa river and finally reaches Sacheon bay. In a rainy or typhoon period, the discharged flow can inundate and affect the hydraulic stability and safety of estuarine areas of Kahwa river, Sacheon river, Jungseonpo river, and Jukcheon river. In this study, we performed a 3-dimensional hydraulic experiment and numerical analysis to analyze the level of water rise in the estuarine areas and environmental effect to Sacheon bay by the change of discharge of Namgang dam. A hydraulic model, based on bathymetric and aerial LIDAR survey data, was made in the scale of 1/50. The experimental and numerical results were compared with the observational results. From the experimental and numerical results, it reveals that as the amount of discharge from Namgang dam increases, water levels in the estuarine areas of Jungseonpo river and Sacheon river and the industrial area around Sacheon bay significantly increases by the effect of backwater. In addition, analyzing the measured salinity concentration, we also find out that the range of diffusion of discharged water into Sacheon bay and it takes about 20 days to recover the original salinity concentration.