Jin-Hee Yuk

Swell Prediction for the Korean Coast

ABSTRACT Yuk, J.-H.; Kim, K.O.; Jung, K.T., and Choi, B.H., 2016. Swell prediction for the Korean coast. The accurate prediction of abnormally high waves occurring in the East Sea during winter is important in terms of the prevention of coastal disasters along the east Korean coast. This study attempts to hindcast the abnormally high swell wave events that occurred in October 2006 and February 2008 using the unstructured grid wave model UnSWAN with high-resolution reanalysis data from the European Centre for Medium-Range Weather Forecasts as meteorological inputs. The model used in this study incorporates an additional weighting factor for the relative wave-number in dissipation source term to improve swell propagation and wave period. Wave heights and periods are well reproduced compared with the observational data. Examination of the meteorological data and model results shows that the abnormally high waves in October 2006 were induced by the overlap of a swell wave and a wind-generated wave with nearly the same heading directions; the wave generated in February 2008 was, however, induced by the swell that propagated over very long distances from the northeastern area of the East (Japan) Sea due to enhanced atmospheric low pressure. Use of the reanalysis meteorological data and a wave model equipped with a weighting factor is found to be useful in identifying the generation mechanisms as well as reasonable estimates of abnormally high wave events.

Simulation of Typhoon Bolaven using Integrally Coupled Tide-Surge-Wave Models based on locally Enhanced Fine-Mesh Unstructured Grid System

ABSTRACT Kim, K.O.; Yuk, J.-H., and Choi, B.H., 2016. Simulation of Typhoon Bolaven using integrally coupled tide-surge-wave models based on locally enhanced fine-mesh unstructured grid system. 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. 1127 - 1131. Coconut Creek (Florida), ISSN 0749-0208. The integrally coupled wave-tide-surge models based on hydrodynamic and spectral wave models with an unstructured mesh system were tested in the typhoon Bolaven, which hit the Korean Peninsula in 2012 and caused the deaths of 19 victims. The identical and homogeneous mesh allows the physics of wave-circulation interactions to be correctly resolved in both models. The unstructured mesh can be applied to a large domain allowing all energy from deep to shallow waters to be seamlessly followed. The model results were compared with the observations, and the model performance was evaluated. The results show that it is important to incorporate the wave-current interaction effect into coastal areas in the wave-tide-surge coupled model. The model should consider effects of depth-induced wave breaking, wind field, currents and sea surface elevation in the prediction of waves. The resulting modeling system can be used for hindcasting (prediction) and forecasting the wave-tide-surge coupled environments at complex coastlines, shallow water and fine sediment areas, such as around the Korean Peninsula.

Integral Tide-Surge-Wave Model of the Yellow Sea for Understanding Local Sediment Transport

ABSTRACT Choi, B.H.; Yuk, J.-H., and Kim, K.O., 2016. Integral tide-surge-wave model of the Yellow Sea for understanding local sediment transport. 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. 208–212. Coconut Creek (Florida), ISSN 0749-0208. Numerical simulations of tide and tidal current for the effect of the new port on Saemangeum area were carried out based on finely resolved meshes and integral tide-surge-wave model of the whole Yellow Sea and also for a compact model optimized for the field operation. The resulting modelling system can be used for hindcasting (prediction) the tide-surge-wave coupled environments at complex coastline, shallow water and fine-grained sediment area like areas around Korean Peninsula. We investigated and discussed the changes of tidal residual current, maximum bottom shear stress and tidal energy dissipation due to the new port for Saemangeum area where the construction of new large port is being built.

Analytical Rapid Prediction of Tsunami Run-up Heights

An approach based on the combined use of a 2D shallow water model and analytical 1D long wave run-up theory is proposed which facilitates the forecasting of tsunami run-up heights in a more rapid way, compared with the statistical or empirical run-up ratio method or resorting to complicated coastal inundation models. Its application is advantageous for long-term tsunami predictions based on the modeling of many prognostic tsunami scenarios. The modeling of the Chilean tsunami on February 27, 2010 has been performed, and the estimations of run-up heights are found to be in good agreement with available observations.

The simulation of a storm surge and wave due to Typhoon Sarah using an integrally coupled tide-surge-wave model of the Yellow and East China Seas

The Yellow and East China Seas are characterized by shallow shelf seas, seasonal monsoons and typhoons, especially the Korean Peninsula’s western coastal area, which features large tides, a complex coastline and many islands. This study implemented an integrally coupled tide-surge-wave model based on an unstructured grid to evaluate the impact of Typhoon Sarah, which occurred in September of 1959, on the Yellow and East China Seas and, specifically, the southern coast of Korea in terms of waves and storm surges. The model results projected a significant wave height of 2–7 m, a mean wave period of 4–14 sec, and positive surge heights that were 0.3–1 m along the southern coast of Korea. Additional model runs included two independent model runs for waves and tides, and one tide-surge model run was conducted to investigate the interactions in the wave, tide and storm surge processes. The coupled tide-surgewave model reasonably reproduced wave properties and storm surges, but uncoupled models, i.e. independent models, slightly overestimated waves and surges. The wave forces associated with the gradient radiation stress resulted in water being elevated into coastal regions, thereby the water elevation increased onshore and the reverse happened offshore. A possible water level change due to a storm equivalent to Typhoon Sarah in the year 2100 was estimated by considering a mean sea level rise of 70 cm and was generally in the range of 70–100 cm in the Yellow and East China Seas and approximately 68 cm along the southern coast of Korea.

Swell Propagation Caused by Typhoon Passage to the Yellow and East China Seas

ABSTRACT Kim, K.O.; Yuk, J.-H.; Jung, K.T., and Choi, B.H., 2017. Swell propagation caused by typhoon passage to the Yellow and East China Seas. 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. 144–148. Coconut Creek (Florida), ISSN 0749-0208. Typhoons generate big swells frequently propagating over the East China Sea, the wide continental shelf sea with depth shallower than 200 m. The characteristic features of swell propagation into the Yellow and East China Seas caused by typhoon Herb in 1996 has been investigated applying a ray-tracing technique and a spectral wave model (SWAN) with an unstructured-mesh grid system. This study discusses the generation and propagation of the swells into the Yellow and East China Seas using the integration of ray trajectories and model-based simulated wave. Calculated and observed wave heights and periods at Gadeokdo, Korea are found to be in reasonable agreement with each other.

Wind-Induced Water Exchange between Stratified Basins

ABSTRACT Yuk, J.-H.; Aoki, S., and Joh, M., 2016. Wind-induced water exchange between stratified basins. 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. 188–192. Coconut Creek (Florida), ISSN 0749-0208. Water exchange between Inohanako Estuary and Hamanako Bay, Japan with density stratification is investigated using the field data. The basins are connected by a narrow channel with length 200 m through which waters and nutrients are exchanged between them. The principal axis of channel between two basins is located nearly in the north-south direction, thus it is natural that the water flow between the estuary and bay is influenced more by the north-south component of wind than the east-west component of that. Although the relationship between water exchange and the east-west component of wind is relatively low compared with the north-south component, the water exchange is controlled by this. In this study, using the field data measured by ADCP and CTD in summer months of 2009, a mechanism of wind-induced water exchange was investigated and discussed. A simple theoretical approach suggested that the dynamic response of density surface in Hamanako Bay to the wind force caused the circulating flow in the channel. The change of water density was more remarkable in Hamanako Bay than in Inohanako Estuary in response to the wind direction, and the surface layer in Hamanako Bay became thinner during the westerly wind. This study shows that the water exchange associated with the east-west wind is caused by the difference of water pressures between Inoahnako Estuary and Hamanako Bay, which is induced by the fluctuation of density interface between the surface and bottom layers due to wind.

Typhoon Morakot Induced Waves and Surges with an Integrally Coupled Tide-Surge-Wave Finite Element Model

ABSTRACT Kim, K.O.; Yuk, J.-H.; Lee, H.S., and Choi, B.H., 2016. Typhoon Morakot induced wave and surges with an integrally coupled tide-surge-wave finite element model. 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. 1122 - 1226. Coconut Creek (Florida), ISSN 0749-0208. A coupled system of unstructured-mesh SWAN and ADCIRC, running on the same unstructured mesh, has been applied to simulate storm surges and waves during typhoon Morakot in August 2009. Emphasis is placed on the effect of wave-tidal current interaction on storm surges and wind waves. Two advantages of this system are that the physics of wave-circulation interactions can be satisfactorily resolved, and a large domain covering a deep ocean and shallow shelf can be dealt with seamlessly, requiring no mesh nesting. Wave refraction and directional spreading induced a wave-current effect, which was confirmed by the cross correlation between the observed significant wave periods and the wave-current angle. The results from the application of the system show that waves resulting from a typhoon can be reasonably simulated in a coastal area. The effect of coupling wave heights and wave periods is found to be approximately 5% and 10%, respectively. Spectral characteristics such as directional spreading and refraction support the influence of tidal current effects on wind waves. This coupled system is a good starting point for operational wave-tide-surge forecasting and can be easily extended to regional sites of interest without a significant increase in the computational burden. The system currently uses a set of depth-integrated equations that simplifies the vertical structure of the current, radiation stress, surface stress and bottom boundary layer.

Extreme tsunami inundation at Babi Island due to Flores earthquake induced tsunami in 1992

In this paper we investigated the phenomenon of extreme run-up at Babi Island in Indonesia caused by the 1992 Flores earthquake (Mw = 7.8) using a series of three-dimensional numerical modeling experiments. Simulations were carried out to investigate how much the presence/absence of the coast of Flores affects the generation of the extreme inundation at Babi Island through the reflection process of tsunami waves.