Search

In this study, hydraulic experiments were performed for three types of cross sections depending on the presence or absence of pipeline of CTSB(Caisson-Type Submerged Breakwater), in which slit-upper-level drainage and lower-level drainage are installed to reduction the water level behind the submerged breakwaters. Additionally, based on the measured hydraulic characteristics, we compared the changes in the wave reflection, transmission and dissipation coefficient around the submerged breakwaters three cases with or without drainage with a solid caisson that has no slit-upper-level and lower-level drainage. Therefore, wave control around the submerged breakwaters is better using the Caisson-Type solid than with the slit-upper-level drainage and lower-level drainage. Moreover, reduction of water level behind the submerged breakwaters is better using the slit-upper-level drainage and lower-level drainage than Caisson-Type solid. its effect is excellent when with TTP are used.

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.

Hur, D.-S.; Lee, W.-D.; Lee, S.-Y., and Jeong, Y.-M., 2021. Experimental study on reduction of water level behind a caisson-type submerged breakwater. 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. 211–215. Coconut Creek (Florida), ISSN 0749-0208. In this study, hydraulic model experiments were performed for four types of cross sections depending on the presence or absence of drainage channel of Caisson-Type submerged breakwaters, in which slit-upper-level and lower-level drainage channels are installed to lower the water level behind the submerged breakwaters. Additionally, based on the measured water level data, compared the changes in the average water level behind the submerged breakers for cases with or without drainage channels with a Solid-Caisson that has no slit-upper-level and lower drainage channels. Hence, in submerged breakwaters with a slit-upper-level drainage channel, the rear water level was reduced by 27.1∼52.5% compared to that with Solid-Caisson, and it was reduced by 36.8∼62.2% and 67.4∼81.5%, in the case of lower-level drainage channel and the combined case, respectively. Therefore, lowering of water level behind the submerged breakwaters is better using the lower-level drainage channel than with the slit-upper-level drainage channel. Moreover, its effect is excellent when both are used. The Caisson-Type submerged breakwater proposed herein was found to be effective in reducing the rear water level and the flow in the openings, thereby securing the stability of the submerged breakwaters.

Lee, W.D.; Choi, S.; Hwang, T.; Park, J.R., and Hur, D.S., 2021. Experimental study on the correlation between wave overtopping and reflection over an absorbing revetment: Non-breaking wave Conditions. 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. 584–588. Coconut Creek (Florida), ISSN 0749-0208. This study performed a hydraulic model experiment to analyze the correlation between wave overtopping and reflection over an absorbing revetment in regular wave fields without wave breaking. Regular waves that last 1.2–2 s and 1.0–2.6 cm high were generated in a two-dimensional wave tank with a depth of 50 cm. With respect to the experimental conditions, an absorbing revetment with two layers of Tetrapods (TTPs) installed on a foundation mound of sand stone was considered. To calculate the reflection coefficient, the time waveform measured using the wave gauges was substituted into a two-point method to separate the incident and reflected waves, while the overtopping rate was directly measured in a separate overtopping tank. According to the experimental results, the water surface waveform in front of the revetment differed depending on the presence of wave overtopping. Under the overtopping condition, the water level in front of the revetment increased and then gradually decreased. Under the non-overtopping condition, the water level continuously increased and then quickly decreased. With respect to wave reflection, under the non-overtopping condition, the reflection coefficient increased as the surf similarity parameter increased. Under the overtopping condition, the distribution of the reflection coefficient was below a certain level and exhibited no clear trend. As the surf similarity parameter increased, the water level at the time of wave overtopping increased. In addition, the longer the duration of wave overtopping, the greater the overtopping rate was. According to the analysis of the correlation between wave overtopping and wave reflection within the same period, the reflection coefficient generally decreased as the overtopping rate increased. However, this phenomenon was not observed in any of the experimental results.

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.

A submerged breakwater is a coastal structure built under water with excellent landscape. The depth of the crest of the breakwater should be maintained at more than a certain level in order for the submerged breakwater to control waves properly. This means that the effect of blocking waves deceases sharply at high tide in coastal areas with large tidal differences. In this study, we proposed a Tide-Adapting Submerged Breakwater (TA-SB) to overcome this problem, and then we conducted hydraulic model experiments to evaluate the performance of the TA-SB for controlling waves. The experimental results showed that the tapered wings attached to the crest of the TA-SB helped induce forced breaking waves. In particular, they were very effective in blocking waves and attenuating wave energy at high tide. In addition, the wave control performance of the proposed TA-SB was far superior to the Tide-Adapting Low-Crested Structure (TA-LCS) of the previous study.

When underwater blasting is conducted, both shock waves and water waves have an effect on adjacent coastal areas. In this study, an empirical formula for estimating the details of water waves caused by underwater blasting was applied to a non-reflected wave generation system, and a 3D numerical wave tank (NWT) was improved to reproduce the generation and propagation of such water waves. The maximum elevations of the propagated water waves were comparatively analyzed to determine the validity and effectiveness of the NWT. Good agreement was demonstrated between the empirical and simulation results. The generation and propagation of water waves were also simulated under each underwater blasting scenario for the removal of the Todo islet at the Busan Newport International Terminal (PNIT). It was determined that the water waves generated by the underwater blasting scenario examined in this study did not have a significant impact on the PNIT. In addition, multiple-charge blasting caused higher wave heights than single-charge blasting. As the amount of firing charge increased, the wave height also increased. Finally, larger water waves were generated during the later blasting conducted at a deeper depth as compared with an earlier blasting conducted at a relatively shallow depth.

For decades, solitary waves have commonly been used to simulate tsunami conditions in numerical studies. However, the main component of a tsunami waveform acts at completely different spatial and temporal distributions than a solitary waveform. Thus, this study applied a 2-D numerical wave tank that included a non-reflected tsunami generation system based on Navier-Stokes equations (LES-WASS-2D) to directly simulate the run-up of a tsunami-like solitary wave on a slope. First, the waveform and velocity due to the virtual depth factor were applied to the numerical wave tank to generate a tsunami, which made it possible to generate the wide waveform of a tsunami, which was not reproduced with the existing solitary wave approximation theory. Then, to validate the applied numerical model, the validity and effectiveness of the numerical wave tank were verified by comparing the results with the results of a laboratory experiment on a tsunami run-up on a smooth impermeable 1:19.85 slope. Using the numerical results, the run-up characteristics due to a tsunami-like solitary wave on an impermeable slope were also discussed in relation to the volume ratio. The maximum run-up heights increased with the ratio of the tsunami waveform. Therefore, the tsunami run-up is highly likely to be underestimated compared to a real tsunami if the solitary wave of the approximation theory is applied in a tsunami simulation in a coastal region.

A low-crested structure (LCS) is an excellent feature not only because it provides shore protection but also because it is fully submerged. However, in order to properly control waves, it is necessary to maintain a certain range of crest height and width in consideration of the wave dimensions at the installation area. According to previous studies, an LCS has some wave breaking effect when the crest width is more than a fourth of the incident wavelength and the crest depth is less than a third of the incident wave height. In other words, if the crest width of the LCS is small or the crest depth is large, it cannot control the wave. Therefore, when an LCS is installed in a large sea area with a great tidal range in consideration of the landscape, waves cannot be blocked at high tide. In this study, the hydraulic performances of a typical trapezoidal LCS with a constant crest height and a low-crested structure with an adjustable crest height, which was called a tide-adapting low-crested structure (TA-LCS) in this study, were compared and evaluated under various wave conditions through hydraulic experiments. It was found that the wave transmission coefficients of the TA-LCS at high tide were lower than the values for the typical LCS based on empirical formulas. In addition, the hydraulic performances of the TA-LCS for wave reflection control were 12.9?30.4% lower than that of the typical LCS. Therefore, the TA-LCS is expected to be highly effective in controlling the energy of incoming waves during high tide even in a macro-tidal area.

Jeon, H.S.; Hur, D.S.; Park, J.R.; Yoon, J.S.; Kim, I.H., and Lee, W.D., 2018. 3-D numerical investigation on effect of flow structure and water level on vegetation distribution in an open channel. 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. 71–75. Coconut Creek (Florida), ISSN 0749-0208.The in-stream vegetation is recognized to have significant ecological and aesthetic importance in managing floods and restoring rivers. However, it also disturbs the velocity of running fluid by increasing the resistance of flow, and raises the water level because of reduced discharge area at times of flood. Therefore, it is very important to study the hydraulic characteristics of vegetation distribution, and this study carried out a numeric simulation for quantitative and qualitative analysis. The simulation applied Navier-Stokes solver based on PBM (Porous Body Model), LES (Large Eddy Simulation) and VOF (Volume of Fluid), and the estimated drag coefficients of vegetation with Reynold's number. A comparison between the measured and calculated water depth and depth-averaged velocity found that conventional and new experiments were highly consistent. A numeric water tank was also used in this study to discuss the hydraulic characteristics of vegetation by measuring the velocity and water level depending on different vegetation zones and incidental conditions. The result showed that full vegetation in an open channel reduced velocity and raised water level because of the drag of vegetation, while half vegetation on one side or at certain part of the channel substantially reduced the hike of water level. Therefore, vegetation should be distributed appropriately when applying that in river management or restoration after an accurate analysis on the hydraulic characteristics of vegetation distribution.

Hur, D.S.; Jeong, Y.M.; Lee, J.L.; Kim, I.H., and Lee, W.D., 2018. Energy generation efficiency due to wave overtopping on floating-overflow-type wave energy converter. 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. 1341–1345. Coconut Creek (Florida), ISSN 0749-0208.The current heightened interest in renewable energy motivated this investigation into the efficiency of wave power generation, which can produce electricity from the infinite energy source of ocean waves. The subject chosen was a floating-overflow-type wave energy converter (FOWEC), which is a comparatively simple type of power generation equipment among the various types of wave power equipment. Because FOWEC is a floating body, it functions not only for power generation, but also as a floating breakwater. In this study's hydraulic model experiments, FOWEC time waveforms were measured, and the reflection and transmission coefficients were computed. In addition, the outflow velocity from the FOWEC overtopping water tank was measured and compared with the theoretical value. The results confirmed that the FOWEC exhibited some degree of wave control in its role as a floating breakwater. The freeboard for the overtopping waves on the lowest FOWEC had an average wave reflection coefficient of 0.43 and an average wave transmission coefficient of 0.21. As wave overtopping increased (as the freeboard decreased and the incident wave height increased), the effective velocity ratio of the outflow from the overtopping tank increased. However, as the freeboard decreased, the effective head decreased, and therefore the energy that could be received was smaller than when the freeboard was higher. In order to maximize the generation efficiency, conditions that allow for overtopping should be implemented with a FOWEC that can maintain an optimal freeboard for appropriate wave overtopping and effective head.

Lee, W.D.; Yoo, Y.J.; Jeong, Y.M.; Jeong, Y.H., and Hur, D.S., 2018. Experimental Investigation of the Effects of Revetments on Seawater Intrusion in Coastal Aquifers. 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. 441–445. Coconut Creek (Florida), ISSN 0749-0208. Sea level rise due to global warming and the decline in groundwater levels due to the misuse of groundwater resources can decrease the seawater and groundwater pressure gradient, which can, in turn, increase seawater intrusion into coastal aquifers. Many researchers have conducted theoretical, experimental, and numerical analyses on the effects of changes in seawater and groundwater levels on coastal aquifers. In this study, modeling experiments were conducted in a sandy tank to analyze revetment and underground obstacles that influence seawater intrusion in coastal aquifers. We focused on ...

A river mouth is a physically dynamic area. In this study, we analyze the hydrodynamic characteristics of this area by performing hydraulic experiments to investigate wave-current interaction by building a river mouth model in a 3-D wave basin. Using the results of these hydraulic experiments, we analyze the hydrodynamic characteristics of the region in which wave-current coexist in the river channel and the vicinity of the river mouth. We observe that, in a river channel, the turbulence flow field develops more rapidly when both waves and current are present as opposed to a situation where no current exists. This contributes to the wave energy loss, resulting in wave attenuation. This phenomenon is more obvious when the ratio between the current velocity and wave celerity, V c / C i increases. From the wave reflection measurements, we observe that the reflection coefficient increases as V c / C i increases. This causes wave attenuation in the wave-current interaction. We observe the changes in the wave heights, bottom flow, and horizontal velocity distributions in the areas where wave-current coexist in the river mouth. In particular, the measured horizontal velocity distribution shows the influence of the flow field on the combined effects of the wave and current velocity components. We observe that there is a close relationship between the wave-current interaction and sediment transport near the river mouth.

Yeom, G.-S.; Mizutani, N.; Hur, D.-S., and Lee, W.-D., 2017. Application of a modified estimation formula for collision force of deformed drifting containers under tsunami conditions. Damage from a tsunami can be divided widely into direct damage and indirect damage by drifting bodies owing to a run-up wave. Indirect damage attributable to freight containers, which play a major role in international trade, is a concern owing to the effect on international and domestic economic activities. Recently, Japan incurred tremendous damage from a tsunami that occurred after the 2011 Great East Japan Earthquake and recorded the greatest amount of economical loss and highest wave run up (40 m in the Ryori district of Ofunato City) historically (PIANC Marcom WG53, 2010). A previous study proposed an estimation formula for a collision force of a container at drift from a run-up tsunami, which comprises the impulse and momentum of the container and the added mass. In this study, a modification of the existing ...

Hur, D.S.; Cho, W.C.; Yoon, J.S.; Kang, C., and Lee, W.D., 2017. Applicability of multiple submerged narrow-crested breakwaters for reduction of mean water level in rear side and flow control. 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. 179–183. Coconut Creek (Florida), ISSN 0749-0208. In this study, to confirm the applicability of multiple submerged narrow-crested breakwaters (SNCBs), a 3-D numerical simulation was conducted. The numerical simulation used the numerical model developed for analyzing the 3-D flow structure around the submerged breakwaters. In addition, to verify the validity and effectiveness of the numerical model, the wave height distribution and mean water level distribution around impermeable submerged breakwater (ISB) and permeable submerged breakwater (PSB) were compared with the results of the numerical model experiment. As a result, the simulate...

Lee, W.D.; Cox, D.T., and Hur, D.S., 2017. Numerical model study on the wave and current control by coastal vegetation. 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. 219–223. Coconut Creek (Florida), ISSN 0749-0208. In this study, three-dimensional numerical simulations were conducted to investigate the effect of the coastal vegetation on the wave and current controls. The model was modified to apply three-dimensional Navier-Stokes solver based on porous body model for the direct simulation of the wave energy dissipation through the vegetation. The new formula of a vegetation drag coefficient based on the wave-vegetation interaction was proposed through the hydraulic model tests and the formula was implemented to the model. The modified numerical model was tested and the results were compared with the experimental results to verify the numerical model capability. The mod...

Kim, I.H.; Kim, J.; Jeong, Y.-M.; Hur, D.S., and Shin, S., 2017. Field observation and numerical modelling on the hydrodynamics behind a submerged breakwater. 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. 304–308. Coconut Creek (Florida), ISSN 0749-0208. In 2014, a submerged breakwater installed near the erosion hot spot and the beach is being formed to salient beach behind the structure at Anmok beach, which is located on the east coast of Korea. The field monitoring has been carried out for past three years in order to investigate the change of beach morphology and shoreline before and after the breakwater construction. Wave gages were installed in the offshore location, in front of the breakwater and in the behind of the breakwater to investigate the wave height variation. A three-dimensional numerical model based on the Navier-Stokes equation with a Large Eddy Simula...

Park, J.R.; Jeon, H.S.; Jeong, Y.M., and Hur, D.S., 2017. Numerical analysis on energy dissipation of tsunami through vegetation zone. 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. 194–198. Coconut Creek (Florida), ISSN 0749-0208. We have improved a 2-D Numerical Wave Tank (NWT) based on a Porous Body Model (PBM) for the simulation of energy dissipation during the interaction with a tsunami. In order to quantitatively evaluate the energy dissipation by vegetation drag during the process, the fluid resistance with regard to the vegetation and the vegetation drag coefficient according to the Reynolds number were applied. Moreover, to confirm the validity and effectiveness of the improved NWT, the results were compared with the existing numerical experimental results of tsunami vegetation interaction. The comparison showed that the water waveforms of the tsunami around the ...

In this study, hydraulic model experiments were conducted to measure the saltwater–freshwater equilibrium interface in a coastal aquifer with underground obstructions such as an impermeable seawall. To analyse the hydraulic characteristics inside the coastal aquifer, numerical analysis was conducted using a non-hydrostatic Navier-Stokes solver based on the Porous Body Model (PBM), which can directly analyse groundwater flow. A unique saltwater–freshwater equilibrium interface that does not appear in typical coastal aquifer analyses was observed in a sandy tank experiment. In the experiment, the rise of the groundwater level behind the seawall increased the pressure gradient and groundwater flow rate, causing the saltwater–freshwater interface to move towards the sea and a freshwater region to form on the seabed in front of the seawall. The numerical analysis enabled close examination of the groundwater level distribution, groundwater flow, seawater–freshwater interface, and pore water pressure characteristics of the coastal aquifer with underground obstructions. The sandy tank experiment also provided an understanding of the hydraulic characteristics of groundwater in the coastal aquifer with a seawall, which previously could not be accurately analysed. The experimental and analytical results demonstrated that the rise of groundwater level due to underground obstructions in the coastal aquifer increased the pressure gradient and groundwater flow rate and slowed seawater intrusion. This principle can be employed to sufficiently reduce seawater intrusion of coastal aquifers.

The purpose of this study was to investigate the effect of the porosity of a submerged breakwater on wave fields, including snapshots of the wave, velocity profiles of the water over the structure, and the kinetic energy of the wave. Two-dimensional experiments were conducted for submerged trapezoidal breakwaters with impermeable and permeable layers in a two-dimensional wave tank. The flow fields obtained by the particle image velocimetry (PIV) technique are presented to understand the flow characteristics due to the waves’ interactions with the submerged impermeable and permeable breakwaters, and these characteristics showed that the vertical velocity dominant flow occurred under the crest of the wave. In addition, the kinetic energies were compared for different porosities and wave conditions. The comparisons of the wave flow fields and kinetic energy distributions showed that the different pattern of the dissipated kinetic energy was dependent on the porosity. The dissipation of kinetic energy also was observed to increase as the wave period increased. The comparisons indicated that greater amounts of energy were dissipated for longer wave periods.

This study used Navier-Stokes Solver(LES-WASS-2D) for analyzing hydrodynamic characteristics with high order in order to analyze self-burial mechanism of pipeline with spoiler under steady flow. For the validity and effectiveness of numerical model used, it was compared and analyzed with the experiment to show flow characteristics around the pipeline with and without the spoiler. And the hydraulic(flow, vortex, and pressure) and force characteristics were numerically analyzed around the pipeline according to the incident velocity, and shape and arrangement of spoiler. Primarily, if the spoiler is attached to the pipeline, the projected area is increased resulting in higher flow velocity toward the back and strong vortex caused by wake stream in the back. Secondly, the spoiler causes vertically asymmetric flow and vorticity fields and thus asymmetric pressure field. It increases the asymmetry of force on the pipe and thus develops large downward fluid force. Both of them are the causes of selfburying of the pipeline with spoiler.

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 Sac...

Kim, I.H.; Lee, W.D.; Shin, S.; Kim, J.H.; Hur, D.S., and Cho, W.C., 2016. The Study on Rip Current Generated by Submerged Breakwaters: Field Observation and Numerical Simulation. 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. 1352 - 1356. Coconut Creek (Florida), ISSN 0749-0208. Jetties and submerged breakwaters have been constructed at Gangmun beach, Korea, for the past several years in order to protect the beach and to secure the estuary channel. However, drowning accidents due to rip currents have often occurred in the gap between the jetty and the submerged breakwater. In this study, field observations and numerical simulations were performed to understand the mechanism of the rip current occurrences at Gangmun beach. The field investigation included the geomorphological change as well as the rip current occurrences. Three-dimension...

Lee, W.D., Kim, I.H., Yoon, J.S., Cho, W.C. and Hur, D.S., 2016. Analysis of beach deformation according to nourishing sand in haeundae beach, 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. 1372 - 1376. Coconut Creek (Florida), ISSN 0749-0208. This study has analyzed the beach deformation characteristics of Haeundae Beach, which is one of the most representative beaches of S.Korea, after beach nourishment through monitoring and performing a numerical simulation. This study was able to analyze the beach deformation characteristics after beach nourishment in depth (e.g. variations in coastline, beach profile and the area and volume of beach, and beach stabilization process) in line with the results of marine geophysical survey (Do et al., 2015). This study surveyed the marine morphological changes around Haeundae Beach caused by Typ...

In this study, numerical simulations were conducted in order to understand the role of wave-current interactions in wave deformation. The wave-current interaction mechanisms, wave reflection and energy loss due to currents, the effect of incident conditions on wave-current interactions, the advection-diffusion characteristics of saltwater, and the effect of density currents on wave-current interactions were discussed. In addition, the effect of saltwater&ndash, freshwater density on wave-current interactions was investigated under a hypopycnal flow field via numerical model testing. Turbulence was stronger under the influence of wave-current interactions than under the influence of waves alone, as wave-current interactions reduced wave energy, which led to decreases in wave height. This phenomenon was more prominent under shorter wave periods and higher current velocities. These results increase our understanding of hydrodynamic phenomena in estuaries in which saltwater&ndash, freshwater and wave-current pairs coexist.

This study applies 3-D N-S solver based on PBM (Porous Body Model), LED-WASS-3D ver 2.0 to directly analyze non-linear interaction of seawater-freshwater-coastal aquifer in order to simulate the seawater infiltration into coastal aquifer. This numerical simulation is the first trial in Korea, as well as unusual and new numerical analysis abroad. Firstly, to validate the applied numerical model, the validity and effectiveness was verified for the numerical model by comparing and considering it with the result of laboratory experiment for seawater-freshwater interface in coastal aquifer. And then it simulated the seawater infiltration into coastal aquifer considering the changed levels of seawater and groundwater in order to analyze the distribution characteristics of flow field and seawater-freshwater interface of coastal aquifer as the level difference between seawater and groundwater and rate of seawater level () increased. In addition, the characteristics of seawater infiltration were analyzed from the vertical salinity in the coastal aquifer by , which cannot be obtained from existing non-diffusion numerical models. Finally, it analyzed the effect of on the seawater infiltration distance in coastal aquifer, which was indexed.

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.

Lee, W.D.; Shin, S.W.; Jeong, Y.M., and Hur, D.S., 2014. Numerical studies on rip current control using scene-friendly structures at Haeundae Beach, Korea. The sporadically occurring rip currents put swimmers in risk during the season of every summer vacation. It is known that the rip current generation is affected by the characteristics of incident waves and bottom topography but the mechanism of the rip current occurrence is still not clear. In order to understand the mechanism of the rip current and to establish countermeasures, 3D numerical simulation was performed based on the realistic bathymetry of Haeundae Beach by using LES-WASS-3D. The numerical simulation results showed that the wave heights vary parallel to the shore line by inequality of bottom bathymetry (submerged shoal and rocks) and this wave height variation induces the water level difference. The model results also showed that the rip currents were generated through the region of relatively deep water and low water level that i...

Cho, W.C.; Kim, J.H.; Hur, D.S., and Kim, I.H., 2014. Rip currents generation by geomorphological change in Gyeongpo Beach, South Korea. Most beaches in Gangwon-do, South Korea have topographic characteristics that are mainly influenced by waves and seabed conditions. Gyeongpo Beach is one of the most famous beaches as a tourist attraction in the east coast of South Korea, and many people have visited and enjoyed sea-bathing in this area during the summer holiday season. However, rip currents are often source of danger for the swimmers because rip currents drag the swimmers away from the beach and put them to death by drowning. As Gyeongpo Beach has a straight shoreline, it is directly exposed to high waves that induce a significant change of bottom topography. Sandbars are usually formed in the processes of topographical changes from the swash zone to the surf zone and increase the possibility of rip current occurrence. Therefore, the monitoring of the topographic changes in this region is impor...

Kim, I.H.; Lee, H.S.; Kim, J.H.; Yoon, J.S., and Hur, D.S., 2014. Shoreline change due to construction of the artificial headland with submerged breakwaters. The littoral drift cell of Bongpyeong Beach in Gyeongsangbuk-do ranges from Jukbyeon harbor to Goljang harbor. The beach erosion has largely occurred due to the expansion construction of Jukbyeon harbor. Headlands were installed as a countermeasure, however, the effectiveness of headland was not good as expected because of complicated coastal hydraulic phenomena. Furthermore, the headlands spoil the coastal landscape. Therefore, in this study, the field investigation of the shoreline and beach profile was conducted to analyze the characteristics around Bongpyeong Beach from 2013 through 2014. The causes of the beach erosion were identified by physical oceanographic investigation and numerical analysis. As a result, the complicated flow characteristics due to the construction of headlands and submerged breakwaters appear. The results also sho...