Coastal dunes are important morphological features for both ecosystems and coastal hazard mitigat... more Coastal dunes are important morphological features for both ecosystems and coastal hazard mitigation. Because understanding and predicting dune erosion phenomena is very important, various numerical models have been developed to improve the accuracy. In the present study, a process-based model (XBeachX) was tested and calibrated to improve the accuracy of the simulation of dune erosion from a storm event by adjusting the coefficients in the model and comparing it with the large-scale experimental data. The breaker slope coefficient was calibrated to predict cross-shore wave transformation more accurately. To improve the prediction of the dune erosion profile, the coefficients related to skewness and asymmetry were adjusted. Moreover, the bermslope coefficient was calibrated to improve the simulation performance of the bermslope near the dune face. Model performance was assessed based on the model-data comparisons. The calibrated XBeachX successfully predicted wave transformation and...
Two-dimensional laboratory experiments were conducted by changing the random wave conditions and ... more Two-dimensional laboratory experiments were conducted by changing the random wave conditions and structure configurations to develop a formula to predict run-up level on the tetrapod armoured rubble mound structure. The incident waves in the experiments included non-breaking, breaking, and broken wave conditions at the toe of the structure. In this study, a steep front slope (1:1.5) was set up to suggest the wave run-up formula while most of the previous studies focused on the milder sloped structures. The experimental results were compared to the previous research by van de Meer and Stam (1992). The results showed that the relative run-up height (the ratio of the run-up height to the significant wave height at the toe) converged as the incident wave steepness increased. On the other hand, the relative run-up height was highly dependent of the relative wave height (the ratio of the significant wave height to the water depth at the toe) as the incident wave steepness decreased. Then,...
Abstract Water-borne disaster debris can exacerbate the damage on the built-environment through d... more Abstract Water-borne disaster debris can exacerbate the damage on the built-environment through debris impact and debris damming loads and by decreasing the functionality of infrastructure systems after these events. Therefore, an understanding of disaster debris transport is essential for disaster management. In this paper, an experimental study of tsunami-driven debris spreading over a flat testbed was conducted considering different density conditions of debris elements. Debris elements of two different materials (densities) were considered various debris groups and starting orientation. The final dislocations and local velocity of debris elements were measured optically and compared to flow velocity. Among two debris elements in a debris group, it was found that debris elements of higher density affected the mean longitudinal displacement of the less dense debris, but the less dense debris did not affect the displacement of higher density debris. Also, it was found that the initial orientations of the debris groups had no measurable impact on the final displacement. The effects of obstacles on the passage of debris and the probability of collision to obstacles were examined and the process of debris-debris and debris-obstacle interactions from debris entrainment to final dislocation was studied. It was found that the less dense debris had a higher probability of collision with the obstacles compared to the more dense debris case. However, when the debris types were mixed, the less dense debris had a lower probability of collision. Finally, the characteristics of debris dislocation and velocity fields under various density conditions as a group were also evaluated. The reflected wave and interaction among different debris play a role in the probability of collision. However, the density of each debris element was a dominant factor in determining the collision probability.
Park, H.; Cox, D.T., and Shin, S., 2019. Physical modeling of horizontal and vertical tsunami for... more Park, H.; Cox, D.T., and Shin, S., 2019. Physical modeling of horizontal and vertical tsunami forces on the elevated overland structure. 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. 51-55. Coconut Creek (Florida), ISSN 0749-0208.In this study, two-dimensional hydraulic model tests were conducted to investigate the characteristics of the force of tsunami waves on the simplified box-type elevated structure. The vertical elevation of the structure was changed to investigate the relation between the wave force and the air gap. The tsunami waves were generated by using the error function with the full-stroke of the wave paddle to maximize inundation. The horizontal and vertical wave forces and pressures on the structure by the tsunami waves were measured, and the relation between the maximum wave force, air gap and the incident wave condition was derived. Using the measured maximum horizontal wave force from the different wave conditions, the empirical formula of the non-dimensionalized horizontal wave force as a function of the surf similarity parameter was obtained. It was found that the horizontal wave force is inversely proportional to the surf similarity parameter in the case of the unelevated structure. The experimental results also showed that the ratio of the horizontal force to the vertical force is larger in the case of broken and breaking wave conditions in the case of the elevated structures.
ABSTRACT Kim, I.H.; Lee, W.D.; Shin, S.; Kim, J.H.; Hur, D.S., and Cho, W.C., 2016. The Study on ... more ABSTRACT 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-dimensional numerical simulations were carried out to find out the occurrence mechanism of the rip currents and the countermeasure for the rip current reduction. The results showed that the mean water level difference between the gap and the area behind the submerged breakwater induced the rip currents. The numerical model results also showed that the drainage channel in the submerged breakwater can reduce the rip current magnitude.
Laboratory experiments were conducted for tsunami inundation to an urban area with large building... more Laboratory experiments were conducted for tsunami inundation to an urban area with large building roughness. The waterfront portion of the city of Seaside which is located on the US Pacific Northwest coast, was replicated in 1/50 scale in the wave basin. Tsunami heights and velocities on the inundated land were measured at approximately 31 locations for one incident tsunami heights with an inundation height of approximately 10 m (prototype) near the shoreline. The inundation pattern and speed were more severe and faster in some areas due to the arrangement of the large buildings. Momentum fluxes along the roads were estimated using measure tsunami inundation heights and horizontal fluid velocities. As expected, the maximum momentum flux was near the shoreline and decreased landward. 3D LES (Large Eddy Simulation) model with two-phase flow was used to compare its simulation results with experimental results. The model results of tsunami heights qualitatively agreed with the data coll...
Volume 2: Structures, Safety and Reliability, 2009
ABSTRACT Large-scale hydraulic model tests and detail numerical model investigations were conduct... more ABSTRACT Large-scale hydraulic model tests and detail numerical model investigations were conducted on recurved wave deflecting structures to aid in the design of wave overtopping mitigation for vertical walls in shallow water. The incident wave and storm surge conditions were characteristic return period events for an offshore island on the North Slope of Alaska. During large storm events, despite depth-limited wave heights, a proposed vertical wall extension was susceptible to wave overtopping, which could potentially cause damage to equipment. Numeric calculations were conducted prior to the experimental tests and were used to establish the relative effectiveness of several recurved parapet concepts. The numerical simulations utilized the COrnell BReaking waves and Structures (COBRAS) fluid modeling program, which is a Volume-of-Fluid (VOF) model based on Reynolds Averaged Navier-Stokes equations [1] [2]. The experimental testing was conducted in the Large Wave Flume (LWF) at Oregon State University, O.H. Hinsdale Wave Research Laboratory. The experimental test directly measured the base shear force, vertical force, and overturning moment applied to the recurved parapets due to wave forcing. Wave impact pressure on the parapet and water particle velocities seaward of the wall were also measured. Results from the experimental testing include probability of exceedance curves for the base shear force, vertical force, and overturning moment for each storm condition. Qualitative comparisons between the experimental tests and the COBRAS simulations show that the numerical model provides realistic flow on and over the parapet.
INTRODUCTION Low lying coastal communities are most vulnerable to the flooding which causes from ... more INTRODUCTION Low lying coastal communities are most vulnerable to the flooding which causes from sea-level rise (SLR), and extreme coastal flooding events such as hurricanes and tsunami. Notably, the high elevation of sea-levels due to SLR and local tidal conditions could accelerate the damages on the coastal communities. Hard coastal structures such as a submerged breakwater and seawall would consider minimizing the impacts of overland flows to the urban area from the extreme coastal events, but the effectiveness of those hard structures are significantly alter depending on the various waves and sea-level conditions.
IMPORTANCE Extreme coastal events like hurricanes and tsunamis often generate and transport debri... more IMPORTANCE Extreme coastal events like hurricanes and tsunamis often generate and transport debris, resulting in severe damage to civil infrastructure and often adversely affecting communities' resilience and recovery process. In particular, water-borne debris transported over the land often decreases critical facilities' functionality and block access for initial rescue and recovery. It is also reported that the hurricane-driven coastal debris removal could account for approximately 27% of the total disaster recovery cost in the USA. A better understanding of waterdriven debris transport is essential to predict damages and losses on coastal communities and develop a mitigation plan to minimize those losses and improve the resilience against future extreme coastal events. In this paper, an experimental study of tsunami-driven debris advection over a flat testbed was conducted considering different density conditions of debris elements.
In this study, the applicability of SBEACH for predicting the local scouring depth in front of th... more In this study, the applicability of SBEACH for predicting the local scouring depth in front of the sea dike on the run up region is examined through two-dimensional laboratory experiments. It is found that the local scouring depth at the foot of sea dike under the incidence of erosion type waves can be estimated by the slightly modified SBEACH by applying a proper boundary condition at the location of the sea dike.
The coastal sand dune is an important natural coastal protection system in the nearshore region f... more The coastal sand dune is an important natural coastal protection system in the nearshore region from storm wave damage. USACE (2013) introduced coastal dune as Nature and Nature-Based Feature for coastal resilience. Therefore, accurately predicting the dune erosion and sediment transport is very important not only to protect the coastal community from the extreme wave but also to provide design guideline for restoration. However, the ability to accurately predict the coastal dune morphodynamics has not been enough improved. The main objective of this study is to investigate erosion and deposition mechanisms of dune and sand bar by obtaining the synoptic data set of movable bed experiment during the entire storm event. Using the experimental data, this study tried to verify the numerical model (XBeachX). Moreover, box cores were used to track the storm history in surf and swash zone.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/E-Itkn36rLQ
In this study, field observations were conducted to investigate the damage mechanism of the coast... more In this study, field observations were conducted to investigate the damage mechanism of the coastal structures on a sandy beach by large waves. Series of surveys on bottom bathymetry, beach profile, and beach width were performed in order to figure out the seasonal variations of shoreline and bathymetry. Field observation results in Jundonjin beach, located on the east coast of Korea, showed the seasonal change of the beach width due to alongshore sediment transport. The coastal structures, such as sea wall and rails, with the narrowed beach during the particular season were vulnerable to the large waves, which occurs more frequently on the east coast of Korea nowadays. This study found that, in Jeongdongjin beach, the northern area near the railroad was collapsed in winter and the southern area near the coastal road was collapsed in summer by high swell waves.
Coastal hazards, such as a tsunamis and storm surges, are a critical threat to coastal communitie... more Coastal hazards, such as a tsunamis and storm surges, are a critical threat to coastal communities that lead to significant loss of lives and properties. To mitigate their impact, event-driven water level changes should be properly monitored. A tide gauge is one of the conventional water level measurement sensors. Still, alternative measurement systems can be needed to compensate for the role of tide gauge for contingency (e.g., broken and absence, etc.). Global Navigation Satellite System (GNSS) is an emerging water level measurement sensor that processes multipath signals reflected by the water surface that is referred to as GNSS-Reflectometry (GNSS-R). In this study, we adopted the GNSS-R technique to monitor tsunamis and storm surges by analyzing event-driven water level changes. To detect the extreme change of water level, enhanced GNSS-R data processing methods were applied which included the utilization of multi-band GNSS signals, determination of optimal processing window, a...
Coastal dunes are important morphological features for both ecosystems and coastal hazard mitigat... more Coastal dunes are important morphological features for both ecosystems and coastal hazard mitigation. Because understanding and predicting dune erosion phenomena is very important, various numerical models have been developed to improve the accuracy. In the present study, a process-based model (XBeachX) was tested and calibrated to improve the accuracy of the simulation of dune erosion from a storm event by adjusting the coefficients in the model and comparing it with the large-scale experimental data. The breaker slope coefficient was calibrated to predict cross-shore wave transformation more accurately. To improve the prediction of the dune erosion profile, the coefficients related to skewness and asymmetry were adjusted. Moreover, the bermslope coefficient was calibrated to improve the simulation performance of the bermslope near the dune face. Model performance was assessed based on the model-data comparisons. The calibrated XBeachX successfully predicted wave transformation and...
Two-dimensional laboratory experiments were conducted by changing the random wave conditions and ... more Two-dimensional laboratory experiments were conducted by changing the random wave conditions and structure configurations to develop a formula to predict run-up level on the tetrapod armoured rubble mound structure. The incident waves in the experiments included non-breaking, breaking, and broken wave conditions at the toe of the structure. In this study, a steep front slope (1:1.5) was set up to suggest the wave run-up formula while most of the previous studies focused on the milder sloped structures. The experimental results were compared to the previous research by van de Meer and Stam (1992). The results showed that the relative run-up height (the ratio of the run-up height to the significant wave height at the toe) converged as the incident wave steepness increased. On the other hand, the relative run-up height was highly dependent of the relative wave height (the ratio of the significant wave height to the water depth at the toe) as the incident wave steepness decreased. Then,...
Abstract Water-borne disaster debris can exacerbate the damage on the built-environment through d... more Abstract Water-borne disaster debris can exacerbate the damage on the built-environment through debris impact and debris damming loads and by decreasing the functionality of infrastructure systems after these events. Therefore, an understanding of disaster debris transport is essential for disaster management. In this paper, an experimental study of tsunami-driven debris spreading over a flat testbed was conducted considering different density conditions of debris elements. Debris elements of two different materials (densities) were considered various debris groups and starting orientation. The final dislocations and local velocity of debris elements were measured optically and compared to flow velocity. Among two debris elements in a debris group, it was found that debris elements of higher density affected the mean longitudinal displacement of the less dense debris, but the less dense debris did not affect the displacement of higher density debris. Also, it was found that the initial orientations of the debris groups had no measurable impact on the final displacement. The effects of obstacles on the passage of debris and the probability of collision to obstacles were examined and the process of debris-debris and debris-obstacle interactions from debris entrainment to final dislocation was studied. It was found that the less dense debris had a higher probability of collision with the obstacles compared to the more dense debris case. However, when the debris types were mixed, the less dense debris had a lower probability of collision. Finally, the characteristics of debris dislocation and velocity fields under various density conditions as a group were also evaluated. The reflected wave and interaction among different debris play a role in the probability of collision. However, the density of each debris element was a dominant factor in determining the collision probability.
Park, H.; Cox, D.T., and Shin, S., 2019. Physical modeling of horizontal and vertical tsunami for... more Park, H.; Cox, D.T., and Shin, S., 2019. Physical modeling of horizontal and vertical tsunami forces on the elevated overland structure. 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. 51-55. Coconut Creek (Florida), ISSN 0749-0208.In this study, two-dimensional hydraulic model tests were conducted to investigate the characteristics of the force of tsunami waves on the simplified box-type elevated structure. The vertical elevation of the structure was changed to investigate the relation between the wave force and the air gap. The tsunami waves were generated by using the error function with the full-stroke of the wave paddle to maximize inundation. The horizontal and vertical wave forces and pressures on the structure by the tsunami waves were measured, and the relation between the maximum wave force, air gap and the incident wave condition was derived. Using the measured maximum horizontal wave force from the different wave conditions, the empirical formula of the non-dimensionalized horizontal wave force as a function of the surf similarity parameter was obtained. It was found that the horizontal wave force is inversely proportional to the surf similarity parameter in the case of the unelevated structure. The experimental results also showed that the ratio of the horizontal force to the vertical force is larger in the case of broken and breaking wave conditions in the case of the elevated structures.
ABSTRACT Kim, I.H.; Lee, W.D.; Shin, S.; Kim, J.H.; Hur, D.S., and Cho, W.C., 2016. The Study on ... more ABSTRACT 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-dimensional numerical simulations were carried out to find out the occurrence mechanism of the rip currents and the countermeasure for the rip current reduction. The results showed that the mean water level difference between the gap and the area behind the submerged breakwater induced the rip currents. The numerical model results also showed that the drainage channel in the submerged breakwater can reduce the rip current magnitude.
Laboratory experiments were conducted for tsunami inundation to an urban area with large building... more Laboratory experiments were conducted for tsunami inundation to an urban area with large building roughness. The waterfront portion of the city of Seaside which is located on the US Pacific Northwest coast, was replicated in 1/50 scale in the wave basin. Tsunami heights and velocities on the inundated land were measured at approximately 31 locations for one incident tsunami heights with an inundation height of approximately 10 m (prototype) near the shoreline. The inundation pattern and speed were more severe and faster in some areas due to the arrangement of the large buildings. Momentum fluxes along the roads were estimated using measure tsunami inundation heights and horizontal fluid velocities. As expected, the maximum momentum flux was near the shoreline and decreased landward. 3D LES (Large Eddy Simulation) model with two-phase flow was used to compare its simulation results with experimental results. The model results of tsunami heights qualitatively agreed with the data coll...
Volume 2: Structures, Safety and Reliability, 2009
ABSTRACT Large-scale hydraulic model tests and detail numerical model investigations were conduct... more ABSTRACT Large-scale hydraulic model tests and detail numerical model investigations were conducted on recurved wave deflecting structures to aid in the design of wave overtopping mitigation for vertical walls in shallow water. The incident wave and storm surge conditions were characteristic return period events for an offshore island on the North Slope of Alaska. During large storm events, despite depth-limited wave heights, a proposed vertical wall extension was susceptible to wave overtopping, which could potentially cause damage to equipment. Numeric calculations were conducted prior to the experimental tests and were used to establish the relative effectiveness of several recurved parapet concepts. The numerical simulations utilized the COrnell BReaking waves and Structures (COBRAS) fluid modeling program, which is a Volume-of-Fluid (VOF) model based on Reynolds Averaged Navier-Stokes equations [1] [2]. The experimental testing was conducted in the Large Wave Flume (LWF) at Oregon State University, O.H. Hinsdale Wave Research Laboratory. The experimental test directly measured the base shear force, vertical force, and overturning moment applied to the recurved parapets due to wave forcing. Wave impact pressure on the parapet and water particle velocities seaward of the wall were also measured. Results from the experimental testing include probability of exceedance curves for the base shear force, vertical force, and overturning moment for each storm condition. Qualitative comparisons between the experimental tests and the COBRAS simulations show that the numerical model provides realistic flow on and over the parapet.
INTRODUCTION Low lying coastal communities are most vulnerable to the flooding which causes from ... more INTRODUCTION Low lying coastal communities are most vulnerable to the flooding which causes from sea-level rise (SLR), and extreme coastal flooding events such as hurricanes and tsunami. Notably, the high elevation of sea-levels due to SLR and local tidal conditions could accelerate the damages on the coastal communities. Hard coastal structures such as a submerged breakwater and seawall would consider minimizing the impacts of overland flows to the urban area from the extreme coastal events, but the effectiveness of those hard structures are significantly alter depending on the various waves and sea-level conditions.
IMPORTANCE Extreme coastal events like hurricanes and tsunamis often generate and transport debri... more IMPORTANCE Extreme coastal events like hurricanes and tsunamis often generate and transport debris, resulting in severe damage to civil infrastructure and often adversely affecting communities' resilience and recovery process. In particular, water-borne debris transported over the land often decreases critical facilities' functionality and block access for initial rescue and recovery. It is also reported that the hurricane-driven coastal debris removal could account for approximately 27% of the total disaster recovery cost in the USA. A better understanding of waterdriven debris transport is essential to predict damages and losses on coastal communities and develop a mitigation plan to minimize those losses and improve the resilience against future extreme coastal events. In this paper, an experimental study of tsunami-driven debris advection over a flat testbed was conducted considering different density conditions of debris elements.
In this study, the applicability of SBEACH for predicting the local scouring depth in front of th... more In this study, the applicability of SBEACH for predicting the local scouring depth in front of the sea dike on the run up region is examined through two-dimensional laboratory experiments. It is found that the local scouring depth at the foot of sea dike under the incidence of erosion type waves can be estimated by the slightly modified SBEACH by applying a proper boundary condition at the location of the sea dike.
The coastal sand dune is an important natural coastal protection system in the nearshore region f... more The coastal sand dune is an important natural coastal protection system in the nearshore region from storm wave damage. USACE (2013) introduced coastal dune as Nature and Nature-Based Feature for coastal resilience. Therefore, accurately predicting the dune erosion and sediment transport is very important not only to protect the coastal community from the extreme wave but also to provide design guideline for restoration. However, the ability to accurately predict the coastal dune morphodynamics has not been enough improved. The main objective of this study is to investigate erosion and deposition mechanisms of dune and sand bar by obtaining the synoptic data set of movable bed experiment during the entire storm event. Using the experimental data, this study tried to verify the numerical model (XBeachX). Moreover, box cores were used to track the storm history in surf and swash zone.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/E-Itkn36rLQ
In this study, field observations were conducted to investigate the damage mechanism of the coast... more In this study, field observations were conducted to investigate the damage mechanism of the coastal structures on a sandy beach by large waves. Series of surveys on bottom bathymetry, beach profile, and beach width were performed in order to figure out the seasonal variations of shoreline and bathymetry. Field observation results in Jundonjin beach, located on the east coast of Korea, showed the seasonal change of the beach width due to alongshore sediment transport. The coastal structures, such as sea wall and rails, with the narrowed beach during the particular season were vulnerable to the large waves, which occurs more frequently on the east coast of Korea nowadays. This study found that, in Jeongdongjin beach, the northern area near the railroad was collapsed in winter and the southern area near the coastal road was collapsed in summer by high swell waves.
Coastal hazards, such as a tsunamis and storm surges, are a critical threat to coastal communitie... more Coastal hazards, such as a tsunamis and storm surges, are a critical threat to coastal communities that lead to significant loss of lives and properties. To mitigate their impact, event-driven water level changes should be properly monitored. A tide gauge is one of the conventional water level measurement sensors. Still, alternative measurement systems can be needed to compensate for the role of tide gauge for contingency (e.g., broken and absence, etc.). Global Navigation Satellite System (GNSS) is an emerging water level measurement sensor that processes multipath signals reflected by the water surface that is referred to as GNSS-Reflectometry (GNSS-R). In this study, we adopted the GNSS-R technique to monitor tsunamis and storm surges by analyzing event-driven water level changes. To detect the extreme change of water level, enhanced GNSS-R data processing methods were applied which included the utilization of multi-band GNSS signals, determination of optimal processing window, a...
Uploads