Nonlinear Transformation of Storm Waves and Impacts on Nearshore Mound in Haeundae Beach, Korea

Park, W.K.; Moon, Y.H.; Chang, S.Y.; Jeong, W.M.; Chae, J.W.; Ryu, K.H.; Chang, Y.S., and Jin, J.Y., 2018. Nonlinear Transformation of Storm Waves and Impacts on Nearshore Mound in Haeundae Beach, Korea. 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. 1131–1135. Coconut Creek (Florida), ISSN 0749-0208.

Haeundae beach is the most popular beach in South Korea which has been suffered from serious erosion problem. To protect the beach erosion, various countermeasures such as beach nourishments, submerged breakwaters and nearshore mound have been conducted. However during typhoon Chaba (1618), extreme storms caused significant beach erosions. Extensive field measurements have been made to monitor the storm impacts on the beach changes. This study focuses on (i) the nonlinear transformation of the very high waves over the submerged shoals in coastal waters and nearshore mound placed parallel to the shoreline, and (ii) the consequent morphological changes. For numerical modeling, SWAN was used for offshore wave propagation and XBeach of non-hydrostatic mode for hydrodynamics and sediment transport simulations. It is found that the storm waves were significantly transformed by submerged shoals through wave breaking due to the shallow water depth and generation of super harmonics with significant amount of wave energy transferred from the primary waves, and similar process occurred around the nearshore mound. Specifically, the impacts of the nearshore mound on beach evolution were pronounced for the beach erosion control with respect to wave energy dissipation, onshore sediment transport, and sediment trap in the lee of the mound.