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ABSTRACT Kim, M.; Lim, H.S.; Do, J.-D.; Kim, S.-S.; Lee, H.J., and Shim, J.-S., 2018. Variations of nearshore currents induced by seasonal waves in Haeundae. 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. 1551–1555. Coconut Creek (Florida), ISSN 0749-0208. Haeundae, located on the southeastern coast of the Korean Peninsula, is a famous sand beach with a 1.6 km long, 70 m wide coastline. It suffers from wave-induced beach erosion in both summer and winter. For beach restoration, the Korean government has conducted beach nourishment (620,000 m3), and installed submerged breakwaters at both ends of the beach. Despite these efforts, the beach is still vulnerable to erosion caused by high waves. To understand beach erosion processes and sediment transport mechanisms, the government initiated an R&D project for the development of coastal erosion control technology since 2013. As part of the project, we have measured over three years of AWAC measurements at a water depth of 22 m and 1.8 km from the beach. Intensive measurements of wave, current, sediment transport near the surf-zone in summer and winter have been made using AWAC, VECTOR, and ADV with OBS. Analyses of nearshore currents induced by seasonal waves in the surf-zone have shown that cross-shore currents in summer are mainly induced by strong waves from the SSW or S that propagate to the beach due to wave breaking and shoaling effects on the reef near the beach. However, longshore currents in winter are induced by high waves from the E or ESE that propagate to the shoreline by diffraction at the east coastline. Eroded sand in summer returns along the beach by cross-shore and weak longshore currents induced by waves from the SSW or S. However, suspended sand in winter is moved to the west by strong longshore currents induced by waves from the E or ESE. Due to its pocket beach shape, beach erosion and sediment transport are caused by variations of nearshore currents induced by seasonal waves. [ABSTRACT FROM AUTHOR]

ABSTRACT Shim, W.J. and Kim, C.W., 2018. The necessity of coastal management in Busan Considering human and natural conditions: The case of barrier islands in Nakdong-estuary. 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.1501–1505. Coconut Creek (Florida), ISSN 0749-0208. The Busan coasts have complex natural and human conditions including dynamic coastal, river processes and human activities. These complex natural and human factors have had direct and indirect impacts on the coastal areas of Busan, so a spatially integrated approach for management is required. Especially, the barrier islands located in the Nakdong River estuary are proper examples that show the effect of the sediment budget as natural and human conditions. This research aims to identify the effects of natural and human conditions on the barrier islands. The area of the barrier islands, sediment budget from the watershed, the amount of dredging at Nakdong-Estuarine-Dam and land use coverage were compared using correlation analysis. The more sediment eroded from watershed and the less sediment was dredged at Nakdong-Estuarine-Dam, the larger area of the barrier islands. This indicates that boundary conditions such as the supply of sediment from the rivers are related to the barrier islands; thus river and watershed management are important. Regarding land use, used and barren areas are positively correlated with the barrier islands, but water, forests and agricultural lands are negatively correlated. Internal factors within Busan, such as coastal modifications and urban growth, are affecting coastal dynamics, which change the sediment budget. These results show that the barrier islands sensitively respond to boundary conditions from the river and watershed and to internal conditions such as shoreline management and development. Therefore, for the effective management of Busan's coasts, it is necessary to consider how natural and human conditions interact spatially. [ABSTRACT FROM AUTHOR]

ABSTRACT Woo, S.-B. and Yoon, B.I., 2018. Numerical simulation of fortnightly modulations of the convergence zone by residual volume transport in a macrotidal estuary. 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. 606–610. Coconut Creek (Florida), ISSN 0749-0208. This study examines the fortnightly modulation of convergence zone by residual volume transport of main channel using a numerical model in the tidally dominated Han River estuary (HRE), South Korea. The numerical model, EFDC (Environmental Fluid Dynamics Code), was simulated for 124 days, from May to August 2009, and used observed freshwater discharge for major rivers of HRE. The residual volume transport discharged into the HRE from the Yeomha channel and Seokmo channel had a ratio of 44:56 over thirty days under normal freshwater conditions. The model results show that a temporal variation of the residual volume transport (Lagrangian transport = Eulerian transport+Stokes transport) is formed near the Yeongjong Bridge with spring-neap variability, and net transport is outflowed to the west through the channel between Ganghwa and Yeongjong. Due to magnitude change of the residual volume transport by fortnightly (spring-neap) modulation, convergence zone (junction location of residual volume transport) show upward and downward spatial variation. We found that the convergence zone moves downstream during the spring period because of; 1) strong net downward barotropic flow by increased sea level difference between upstream and downstream during the spring tide; 2) decreased baroclinic flow towards the upstream of the main channel, caused by intensified tidal mixing during the spring period; and 3) increased outflow through the tidal flat channel between Ganghwa and Yeongjong during the spring period. [ABSTRACT FROM AUTHOR]

Lim, H.S.; Kim, M.; Do, J.-D.; Kim, S.-S.; Lee, H.J., and Kim, D.H., 2018. Variation of nearshore currents induced by seasonal waves in Haeundae. 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. 686–690. Coconut Creek (Florida), ISSN 0749-0208. Wave-induced currents at Anmok, located on the eastern coast of the Korean Peninsula, are one of the main causes of beach erosion related to high waves. Coastline changes induced by beach erosion and deposition are predominantly caused by sediment transport in the surf zone. This sediment transport is generated by wave-induced currents and depends on the wave height and direction. To understand beach erosion processes and the sediment transport mechanisms, field measurements of beach elevation and water depth were conducted for one month in winter 2015–2016. Using AWAC, ADP, VECTOR, and Aquadopp Profiler with OBS, intensive observations were made of waves, currents, and sediment transport in the surf zone. Wave and current variations were simultaneously analyzed at a water depth of approximately 18 m (W1) using long-term deployed AWAC data. Wave statistical analysis at station W1 shows that high waves from the NNE and NE are dominant in winter due to strong northeasterly winds from the NE. However, in summer, high waves coming from the NE and ENE are prevalent due to seasonal winds from the E and SE. By analyzing currents observed in the surf zone with waves, we found that a cross-shore current is generated by high waves, predominantly in winter, with incoming waves normal to the shoreline. Following the direction of incoming waves, longshore currents are separated into SE or NW directions depending on high waves come from the NNE or ENE, respectively. The variations of wave-induced currents caused by incoming wave height and direction accounts for the observed beach erosion and sediment transport, which in turn leads to beach cusp formation and crescentic sand bar migration during high wave periods. [ABSTRACT FROM AUTHOR]