# Video Monitoring of Shoreline Positions in Hujeong Beach, Korea
## 6 Conclusions  
The shoreline evolution pattern of a sandy beach was investigated using a video monitoring system and wave measurements in Hujeong Beach, Korea. The beach is suspected to be vulnerable to erosion because the input source of sediments has been blocked by construction of a breakwater at the northern end, while the beach continues to lose sand at the opposite end. The beach is also characterized by crescentic sandbars that actively develop in the northern part of the nearshore region. In the other side of the beach, the seabed is covered by numerous underwater rocks. In addition, a rocky island is located at the southern end of the beach. These sandbars and rocky structures played significant roles in shaping the beach shorelines in concert with the incoming waves. During the two-year period of the observation, the overall area of the beach decreased \(\sim\)10%. However, there were times when the beach area rapidly increased, which made the time variation pattern of beach evolution highly complicated. The erosion or accretion of the shoreline generally agreed with the expected situation based on the wave conditions. However, the response of the beach to a short-term storm event such as Typhoon Kong Rey was not clearly recorded. The video monitoring data was difficult to measure owing to the harsh weather during the storm. The results showed that the beach area increased when the waves obliquely approached the shore, whereas it decreased when the waves approached in a normal direction to the shore, even though the wave energy was not clearly differentiated between them. In addition, the accretion of the shoreline did not occur uniformly along the beach. Instead, there were locations where the shoreline significantly protruded toward the sea. These areas corresponded to the locations where the horns of sandbars developed, which showed an example of out-of-phase coupling between the sandbars and the shoreline. As an evidence, the waves were observed to break at the same locations as the horns, which indicates that the wave energy in the lee areas of the horns was reduced to produce a longshore sediment transport gradient, resulting in shoreline accretion. Along with the sandbars, underwater rocks developed in the southern part of the beach. These rocks played a similar role to that of the sandbars, breaking the waves to produce a sheltering area in the lee. When the waves approached the shore in a normal direction, the longshore drift of sediment became weaker and offshore sediment transport occurred uniformly along the coast, which made the shoreline to become flatter. The results of this study indicate that the incoming wave directions are important in shaping the sandy shorelines, and this must be considered when designing beach facilities and coastal structures for various purposes. In addition, the seabed topography and the distribution of bedforms should be carefully investigated as they may also affect the shoreline evolution pattern. In this study, the examples of in-phase coupling between the sandbars and the shoreline have not been observed, which is expected to occur under different wave conditions and will be investigated in future studies. The contributions of each author are as follows: conceptualization, Y.S.C., J.-D.D., W.M.J. and J.-Y.J. ; methodology, J.-D.D. and C.H.K. ; formal analysis, J.-D.D. and Y.S.C. ; investigation, J.-D.D. and Y.S.C. ; resources, J.-D.D., W.M.J., C.H.K. and J.-Y.J. ; data curation, J.-D.D. ; writing--original draft preparation, J.-D.D. and  
Figure 13: Satellite image captured from Google Earth near L1–L3 measured on 13 February 2019. The image shows that the waves are breaking at the locations where the sandbar horns developed, and the shoreline was advanced at the corresponding locations. Y.S.C. ; writing--review and editing, J.-D.D. and J.-Y.J. ; visualization, J.-D.D. and Y.S.C. ; project administration, Y.S.C. and J.-Y.J. ; funding acquisition, Y.S.C. and J.-Y.J.