Search

Nakdong river estuary is being operated with the goal of expanding the period of seawater inflow from this year to 2022 every month and creating a brackish water area within 15 km of the upstream of the river bank. In this study, the deep learning algorithm Long Short-Term Memory (LSTM) was applied to predict the salinity of the Nakdong Bridge (about 5 km upstream of the river bank) for the purpose of rapid decision making for the target brackish water zone and prevention of salt water damage. Input data were constructed to reflect the temporal and spatial characteristics of the Nakdong River estuary, such as the amount of discharge from Changnyeong and Hamanbo, and an optimal model was constructed in consideration of the hydraulic characteristics of the Nakdong River Estuary by changing the degree according to the sequence length. For prediction accuracy, statistical analysis was performed using the coefficient of determination (R-squred) and RMSE (root mean square error). When the sequence length was 12, the R-squred 0.997 and RMSE 0.122 were the highest, and the prior prediction time showed a high degree of R-squred 0.93 or more until the 12-hour interval.

Shoreline variations occurring in sea areas are caused by the combined effect of sediment transport due to the inflow and outflow of sediment caused by waves at the left and right boundaries of the sea area and the depth of movement limit. Although many studies have been conducted to understand the characteristics of sediment transport, assessment on valid sediment run-off supplied to the sea area from mountains and rivers in sea areas with river inflow and research on the sediment budget analysis considering the topographical characteristics of South Korean sea areas are insufficient. Therefore, the establishing mitigation measures considering comprehensive viewpoints is necessary to systematically respond to various natural and anthropogenic causes. Moreover, further research related to the setting and analysis of major parameters must be conducted for improving the prediction performance as well as the evaluation system for analyzing the sediment budget, which is a quantitative evaluation index for coastline management optimized for domestic waters. This study aimed to establish a comprehensive analysis system for analyzing the sediment run-off generated in domestic sea areas and develop a shoreline model (In-MPaS model) considering mixed grain sizes for advancing sediment run-off analysis. With the observation data, the parameters necessary for the numerical analysis were set, the sensitivity of the In-MPaS model according to the particle size distribution of the sediment constituting the sea area was evaluated, and the major parameters for improving the prediction performance were analyzed. Consequently, it was found that the prediction performance of the In-MPaS model improved in terms of valid sediment run-off as well as the sediments constituting the sea area (which was assumed to have mixed grain sizes rather than a single grain size(D50). In particular, considering the topographical properties that regulate sediment transport due to the island (Deokbong Mountain) at the foreside of the river mouth bar, the shoreline prediction performance was significantly improved with the application of groins, which exhibit structurally similar performance.

An integrated sediment management approach that includes the recovery of the amount of declined sediment supply is effective as a fundamental solution to coastal erosion. During planning, it is essential to analyze the transfer mechanism of the sediments generated from estuaries (the junction between a river and sea) to assess the amount and rate of sediment discharge (from the river to sea) supplied back to the coast. Although numerical models that interpret the tidal sand bar flushing process during flooding have been studied, thus far, there has been no study focusing on the formation and development processes of tidal sand bars. Therefore, this study aims to construct wave deformation, flow regime calculation, and topographic change analysis models to assess the amount of recovered sediment discharge and reproduce the tidal sand bar formation process through numerical analysis for integrated littoral drift management. The tidal sand bar formation process was simulated, and the wave energy and duration of action concepts were implemented to predict the long-term littoral movement. The river flux and wave conditions during winter when tidal sand bars dominantly develop were considered as the external force conditions required for calculation. The initial condition of the topographic data directly after the Maeupcheon tidal sand bar flushing during flooding was set as the initial topography. Consequently, the tidal sand bar formation and development due to nearshore currents dependent on the incident wave direction were reproduced. Approximately 66 h after the initial topography, a sand bar formation was observed at the Maengbang estuary.

The swash zone is an area that causes a change in the shape of a beach by generating sediment transport under the influence of intermittent waves, where wave run-up and run-down are infinitely repeated in the final stage of the shoaling process. However, the ability to predict the sediment transport is extremely poor despite the swash zone being an extremely important area in terms of offshore disaster prevention. In particular, many researchers are conducting studies on the development of various types of observation equipment and analysis techniques because the turbulent flow of active fluid dominates the sediment transport and is an extremely important parameter for the analysis of the transport mechanism. However, in flow velocity measurement, it is difficult to measure a quantitative representative flow velocity over time because the swash zone has a shallow water depth and an active turbulent flow. Expensive equipment and short-time measurement are also limitations. Therefore, the purpose of this study was to evaluate the applicability of nonintrusive space-time image velocimetry(STIV) to analyze the flow characteristics of fluid in the swash zone, such as the movement velocity and period of intermittent waves in the shoaling process. The prediction accuracy was improved by removing various noises included in the images with the introduction of artificial intelligence for immediate and accurate calculation of the representative flow velocity using images that can be obtained easily. Consequently, it was discovered that the spatial representative flow velocity occurring in the swash zone, change in the wave period according to the shoaling effect, rip current and surface velocity can be measured.

The severe coastal erosions are being accelerated along the east coast of South Korea owing to the intermittent erosions and depositions caused by the imbalance between the effective sediment volume supplied from coasts and rivers and the sediment transport rate. Consequently, many studies are being conducted to develop coastal-erosion reduction measures. To accurately determine the cause of coastal erosion, the causes of the erosion and deposition should be accurately diagnosed, and a comprehensive evaluation system for the sediment transport mechanism in the watershed and sea while considering regional characteristics is required. In particular, realizing the evaluation of the effective sediment volume that flows from the river to the sea through observations is a highly challenging task, and various research and developments are required to realize it, as it is still in the basic research stage. The purpose of this study was to systematically analyze the comprehensive sediment budget for coastal areas. First, an analytical system was developed. Then, a shoreline model was constructed by considering the size of the mixed particles. The parameters required for developing the model were determined using the observation data to improve the shoreline model. A sediment runoff model was applied to evaluate the effective sediment volume supplied from the river to the sea, and the applicability of this model was evaluated by comparing it with the sediment supply volume according to the soil and water assessment tool model. The representative wave and the input parameters of the model were set using the observation data of several years. It was found that the prediction performance of the shoreline change model improved when the effective sediment volume was considered, and the particles of the sediment on the shore were assumed to comprise multiple sizes. In particular, the prediction performance improved when the balance of the sediment budget was adjusted by applying a groin having a structurally similar performance to take into consideration the geographic features of the Deokbongsan (island) in front of the river mouth bar. The model demonstrated a good performance in reproducing long-term shoreline changes when the characteristics of the sea waves and the effective sediment volume were considered.

Kim, M.-K.; Kim, T.-W.; Yoon, J.-S., and Kim, Y.-J., 2021. Analysis of storm surge considering waves on the southeastern coast of South Korea. 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. 216–220. Coconut Creek (Florida), ISSN 0749-0208. The effects of high waves should be considered to accurately interpret storm surges occurring in coastal areas; however, the general theory is that the rise in water level due to radiation stress would have little impact on the west and south coasts of South Korea because waves tend to be considerably attenuated due to the topographic characteristics of the rias style coast. However, in a study by Mase et al. (2011), the storm surge owing to Typhoon Isewan was predicted; the results obtained indicated that the water level considerably rose due to the effects of waves even in Nagoya Bay, where high waves do not develop due to topographic characteristics. Therefore, the present study aimed to build a storm surge model for the southeastern coast (rias style) of South Korea and to examine the sensitivity of the wave to the rise in water level. By examining the typhoon, a rise in water level due to radiation stress was observed in some areas on the southeastern coast of South Korea. This result suggests the necessity of a storm surge analysis considering the effect of high waves even in areas where they do not develop due to topographic characteristics.

Kim, Y.-J.; Kim, T.-W.; Yoon, J.-S.; Hur, D.-S, and Kim, M.-K., 2021. Shoreline change prediction for integrated coastal erosion management. 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. 121–125. Coconut Creek (Florida), ISSN 0749-0208. The mechanism of sediment transport occurring in littoral zone shows complex patterns. Establishing an accurate longshore sediment budget prediction is difficult. Littoral drift flowing into and out of the coast shows sensitive responses to natural and anthropogenic changes in the surrounding area. In particular, at the coast where rivers are located, the littoral drift is significantly affected by the inflow of sediment from the upstream. However, the sediment management at the coast has been conducted by respective measures established in different areas, such as mountains in the upstream region, dams, rivers, and coasts, and thus, measures are established without an appropriate feedback between these different areas. Therefore, determining the exact causes of erosion occurring in the coastal zone is challenging. In addition, for accurate prediction of sediment budget in coastal areas, it is necessary to construct a model with mixed particle size distribution that can consider the properties of sediment inflow from the river and the sediment constituting the sea area. Thus, for integrated coastal erosion management, based on the determination of sediment transport mechanism flowing into the coastal zone, accurate estimation of sediment transport rate and sediment budget prediction according to the shoreline changes affected by waves play an important role. In this study, a series of mechanism of sediment transport flowing into the sea area through the river was analyzed, and the sediment budget according to the shoreline change occurring in the sea area was estimated. The sediment load flowing into the sea area and the representative wave acting on the sea area were calculated to construct the IN-MPS (INje-Mixture Particle Shoreline) model considering the sediment particle size distribution in mixed condition. The accuracy of the model was evaluated by comparing the results obtained from the model with those of long-term observations by calculating the exact sediment budget in the coastal zone, and when the inflow from the river and the mixed particle size distribution of sediment were considered, the accuracy in the shoreline change prediction was improved.

Kim, T.-W.; Kim, Y.-J.; Yoon J.-S., and Kim, M.-K., 2021. Changes in power generation at Sihwa Lake Tidal Power Plant with the installation of submerged breakwaters. 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. 146–150. Coconut Creek (Florida), ISSN 0749-0208. Tidal power generation uses potential energy generated by vertical movements of the sea level to run a hydro turbine to produce electricity; thus, it is suitable for areas with large differences between tidal waves. The Sihwa Lake Tidal Power Plant situated on the west coast of South Korea is located at the center of the 11.2-km-long Sihwa Seawall. It generates power by using the increased water level in the outer region during ebb, and it discharges the seawater inflow caused by power generation during flood. In this study, the EFDC (Environmental Fluid Dynamics Code model), which can reproduce the operation patterns of the Sihwa sluice gate and considers permeable structures, was applied to predict the effect of changes in seawater flow resulting from the installation of impact reduction facilities on the nearby offshore of the Sihwa Lake Tidal Power Plant. To calculate the amount of power generated using a numerical model, a year-long daily operation record of the tidal power plant in 2013 was analyzed and used as input conditions (sluice gate operation, runoff) of the numerical model. In addition, a relational expression was derived using the data—inner/outer water-level difference (ΔH), hydro turbine water flowrate (Q), and power generated (W)—and the power output was calculated using the inflow rate calculated by the numerical model.

Kim, Y.-J.; Itoh, S.; Oya, Y., and Yoon, J.-S., 2018. Study on storm surge prediction model considering typhoon characteristics for largest scale. In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 736–740. Coconut Creek (Florida), ISSN 0749-0208. The coastal area of Japan has been damaged yearly with many storm surges and flooding disasters in the past, including those associated with tropical cyclones (TCs). Also, the scale of damage is increasing rapidly due to the changing global climate and environment. As the disasters due to storm surges become unpredictable, more measures should be taken to prevent serious damage and casualties. Therefore, in this study, the aim is to mitigate the unpredictable damage by assuming storm surges of the largest scale and to propose a storm surge model that considers the characteristics of TCs. The main objectives of ...

The coastal area of Japan has been damaged yearly by storm surges and flooding disasters in the past, including those associated with typhoons. In addition, the scale of damage is increasing rapidly due to the changing global climate and environment. As disasters due to storm surges become increasingly unpredictable, more measures should be taken to prevent serious damage and casualties. The Japanese government published a hazard map manual in 2015 and obligates the creation of a hazard map based on a parametric model as a measure to reduce high-scale storm surges. Parametric model (typhoon model) accounting for the topographical influences of the surroundings is essential for calculating the wind field of a typhoon. In particular, it is necessary to calculate the wind field using a parametric model in order to simulate a virtual typhoon (the largest typhoon) and to improve the reproducibility. Therefore, in this study, the aim was to establish a hazard map by assuming storm surges of the largest scale and to propose a parametric model that considers the changing shape of typhoons due to topography. The main objectives of this study were to analyze the characteristics of typhoons due to pass through Japan, to develop a parametric model using a combination of Holland&rsquo, s and Myers&rsquo, s models that is appropriate for the largest scale of typhoon, and to analyze the parameters of Holland&rsquo, s model using grid point values (GPVs). Finally, we aimed to propose a method that considers the changing shape of typhoons due to topography. The modeling outcomes of tide levels and storm surge heights show that the reproduced results obtained by the analysis method proposed in this study are more accurate than those obtained using GPVs. In addition, the reproducibility of the proposed model was evaluated showing the high and excellent reproducibility of storm surge height according to the geographic characteristics.

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.

In recent years, debris flow disaster has occurred in multiple locations between high and low mountainous areas simultaneously with a flooding disaster in urban areas caused by heavy and torrential rainfall due to the changing global climate and environment. As a result, these disasters frequently lead to large-scale destruction of infrastructures or individual properties and cause psychological harm or human death. In order to mitigate these disasters more effectively, it is necessary to investigate what causes the damage with an integrated model of both disasters at once. The objectives of this study are to analyze the mechanism of debris flow for real basin, to determine the PMP and run-off discharge due to the DAD analysis, and to estimate the influence range of debris flow for fan area according to the scenario. To analyse the characteristics of debris flow at the real basin, the parameters such as the deposition pattern, deposit thickness, approaching velocity, occurrence of sediment volume and travel length are estimated from DAD analysis. As a results, the peak time precipitation is estimated by 135 mm/hr as torrential rainfall and maximum total amount of rainfall is estimated by 544 mm as typhoon related rainfall.

Kim, T.W.; Kim, Y.J.; Cho, W.C.; Park, B.W., and Yoon, J.S., 2019. Study on the characteristics of the hydraulic environment in the down-stream area according to the discharge of Changnyeong-haman weir. 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.151-155. Coconut Creek (Florida), ISSN 0749-0208.This study refined the reproducibility of a stream cross section of the Nakdong River using the Modified EFDC model and examined the salt water flow from the external sea to the river upstream according to the changing gate open rate of Nakdong River estuary barrage and the influent flow and tide level conditions in the Changnyenong-Haman Weir using a numerical model. Furthermore, numerical simulations were conducted and the hydraulic characteristics were examined to investigate the flushing effect according to the changing discharge of the Changnyenong-Haman Weir in the event of a salt wedge.

Yoon, I.J. and Hong, J.-W., 2019. Development of disaster prevention system based on deep neural network using deep learning with dropout. 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. 186-190. Coconut Creek (Florida), ISSN 0749-0208.Recently, unprecedented abnormal climates and disasters of the greatest intensity have increased worldwide due to various problems such as global warming. In particular, from the Great East Japan Eartquake in March 2011, Japan has suffered from the highest frequency of disasters (floods, earthquakes, etc.) and the single largest external force (tsunami) that have not been experienced before. For such disasters of the maximum frequency, the hard and soft countermeasures alone have limitations and it is critical to integrate and appropriately harmonize them with various disaster prevention systems.The purpose of this study is to develop a flood risk management information system to support natural disaster mitigation measures. The main function of the disaster prevention support system is to select the most similar one to a typhoon before landing based on past typhoon data and artificial intelligence (AI) technology and to present guidelines for prior disaster prevention activities according to various disaster factors caused by the selected typhoon (e.g., water level and river flow rate). A database was constructed for 189 typhoons that directly or indirectly affected the target area among those that occurred between 1950 and 2017, and a system was developed by applying AI technologies such as Deep Neural Network (DNN) and Dropout. The main parameters of this database are typhoon route, central pressure, moving speed, precipitation, water level, and flow rate. For the grid sizes of the model, 2° and 1° in longitude and in latitude were considered. The system search results showed the highest reliability of the model at the grid size of 1° when only typhoon route, center pressure, and moving speed were considered compared to the results of considering other parameters.

In general, many instrumentations of slope rely on theory or experience because on-site accessibility and long term instrumentation are difficult to conduct the instrumentation of slopes. Also the prediction of disaster is very difficult. Therefore experimental research was conducted about an effective method to predict collapse of slope and on-site applicability in this study. The collapse of slope was able to be predicted by applying AE sensor which we call WEAD to the failure criteria. The parameters of AE generated during the collapse of slope were secured through bending shear test. Test construction was applied to the slope with a history and a possibility of collapse. As a result, it is shown that AE parameters do not exceed the failure criterion and is found to be stable slopes. As the real symptoms of collapse did not appear, AE was found to have excellent applicability.

Free radical-mediated oxidative stress has been implicated in the pathogenesis of numerous chronic diseases. Vitamin E is known to play an important role in the free-radical quenching process. However, clinical trials with vitamin E have yielded contrasting results in the prevention of several diseases related to oxidative stress. This study was undertaken to investigate the antioxidative and humoral immunologic effects of vitamin E supplementation in three different age groups: young (mean age 32.7 +/- 5.7 y), middle-aged (mean age 47.0 +/- 5.0 y) and elderly (67.6 +/- 4.7 y) women. Volunteer subjects were given a supplement of 400 IU dl-alpha-tocopherol acetate for 6 wk. Thiobarbituric acid reacting substances (TBARS) in the plasma significantly decreased with vitamin E supplementation. In addition, the radical scavenger activities (RSA) of red blood cells significantly increased with vitamin E supplementation in all age groups. However, humoral immune response modulation was not observed following vitamin E supplementation. Even though there is no clear indication that vitamin E supplementation is necessary to improve the humoral immune functions, vitamin E supplementation may be beneficial to all adult age groups as a preventive measure for complications related to oxidative damage.

This paper designs service logic and information flow for IN service enhancement, which increase call completion rates in a wireless intelligent network environment. In order to apply this logic to mobile services, we propose the dynamic queue manager applied call queueing service feature in the service control point (SCP). In the case of wireless IN service subscribers, the home location register (HLR) handles the supplementary service registration flags to notify the queue manager of the corresponding service subscribers mobility. In addition, we present the operation of the queue manager and the dynamic queue management mechanism, which dynamically manages the queue size based on the parallel server queueing model as the wireless subscribers roam the service groups due to their mobility characteristics.

The explosive growth of the Internet combined with the widespread availability of highly mobile small hosts in the form of laptop and palmtop computers, and personal digital assistants, has created a big demand for the concept of Mobile IP. In the base Mobile IP, if the distance between the visited network and the home network of the mobile node is large, the signaling delay for these registrations may be long. Also the two main problems faced are the loss of registration packets and crashes of entities that maintain location caches. Therefore to solve this problem, the solution for performing registrations locally in the visited domain in order to reduce registration delay and to support micro mobility is proposed. In this paper, we propose that a hierarchical structure may be helpful to fast handoff in mobile environments. In company with the fast handoff, reliability is a great concern to the designers of mobile computing systems.