Evaluation of Longshore Drift on the East Coast of Maengbang Beach (Gangwon, Korea) through Wave and Depth Changes

Abstract

Kim, G.-S.; Ryu, H.-S., and Kim, S.-H., 2021. Evaluation of longshore drift on the east coast of Maengbang Beach (Gangwon, Korea) through wave and depth changes. 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. 499–503. Coconut Creek (Florida), ISSN 0749-0208. Numerical simulation of the sediment by the Delft3d model was conducted to examine the changes in the longshore drift transport caused by long-term wave changes at Maengbang Beach. Representative waves were identified with input reduction tools using NOAA NCEP wave data of about 40 years (i.e., January 1979 to May 2019). To verify the adequacy of the model, simulated wave and depth changes were compared with corresponding observed data for about 23-month period (from March 2017). Error analysis showed a bias of 0.05 and root mean square error of 0.23, indicating that the model results were satisfactory. Further, the observed and the simulated values of change in depth were similar. To examine the effects of long-term changes in wave characteristics, the NOAA wave data were classified into representative wave grades, and the annual trends of the representative waves were analyzed. After assessing the weight of each wave class considering the projected wave environment for year 2100, the amounts of sedimentation, deposition, and longshore drift transport were assessed for the same period. Sedimentation pattern would not change significantly compared to the current state, and the amount of the local longshore drift will likely decrease. While a local increase in the Longshore drift transport may occur, the overall drift and the amount of sediment movement are likely to remain at current levels. Regarding the coastal longshore drift under climate change, the study considered the average sea level rise as per scenarios RCP 2.6, RCP 6.0, and RCP 8.5 (IPCC, 2013). The net amount of sediment movement and its variability are projected to increase with the rise in sea level for most areas. Regarding the amount of sediment movement, local movement at the center of the coast will likely decrease compared to the present state, and, consequently, waves would have a greater impact on the edge due to sea level rise.