Changes in the Behavioral Characteristics of the Gangmun and Anmok Beaches following the Construction of Artificial Reefs

Abstract

Kim, J.; Kim, I.; Nam, J.; Song D., and Lee, H., 2019. Changes in the behavioral characteristics of the Gangmun and Anmok beaches following the construction of artificial reefs. 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. 26-30. Coconut Creek (Florida), ISSN 0749-0208.On the East coast of South Korea, there is only a small significant difference between low and high tides, meaning that seasonal wave directions appear clearly in recorded data. During summer, southeasterly waves dominate, and northward longshore drift occurs. In addition, the southward transport of littoral sediment occurs under the northeasterly waves that are dominant during winter. However, recent changes in the coastal environment, due to the development of coastal flooding prevention facilities, harbor development projects, and unusual weather conditions, have shown a tendency to increase the erosion of coastal areas. In other words, there is a repeating cycle of positive feedback, in which structures introduced to prevent a certain kind of coastal erosion cause different kinds of coastal erosion. In this study, we used field survey data to analyze the behavioral characteristics of the Gangmun and Anmok beaches for a period of seven years. The results show that the Gangmun and the Anmok beaches are very vulnerable to the effects of artificial constructs. Coastal erosion on Gangmun beach occurred through northward sediment transportation, caused by a dike that was built to avoid the closure of the mouth of Gyungpo stream. After an artificial reef and the groin were constructed to solve this erosion problem, the coastline stabilized. In the case of the Anmok beach, an imbalance in the sand budget supplied from the Namdae stream was brought about by the expansion of the Gangneung harbor, leading to significant beach erosion. After artificial reefs were installed on both beaches to prevent erosion, the area of each beach was increased and each beach's status was stabilized, as a salient beach.