Shoreline change along the Yombunjin sandy coast (DPR Korea) during Typhoon Maysak (2020): comparison of four longshore sediment transport formulae

In this study, the shoreline change along the Yombunjin sandy coast in the Kyongsong Bay of DPR Korea during the Typhoon Maysak (2020) was analyzed and compared using the four longshore sediment transport (LST) formulae incorporated into the shoreline evolution model proposed by (Coast Eng 114:1-8 2016), known as DHM. The results showed that the modified Kamphuis 2013 formula (Coast Eng 75:29-39, 2013) had the highest skill value (0.92) and the lowest standard deviation (sigma) of 1.27 m when compared to the remaining three LST formulae, i.e., the Kamphuis (1991) formula, the Kamphuis (2002) formula and the (Coast Eng 90:23-39 2014) formula. From ten years of the National Center for Environmental Prediction (NCEP) reanalysis wind data, it is realized that obliquely incident southeast waves became dominant in the Kyongsong Bay in recent years. During the typhoon, the maximum shoreline retreat was calculated to be about 10.7 m at the transect 2, while the maximum shoreline advance to be about 7.8 m at the transect 10, suggesting that the study area is experiencing locally severe shoreline retreat. It can be concluded that the shoreline change along the Yombunjin sandy coast was mainly due to the increase in the LST by obliquely incident southeast waves, and that understanding the contributions of sediment transport to shoreline changes can allow for coastal risk management strategies that are more targeted and effective in this coastal region experiencing severe shoreline retreat.