# Video Monitoring of Shoreline Positions in Hujeong Beach, Korea
## 1 Introduction  
Coastal erosion is a serious problem that may cause economic and environmental damage to the coastal communities. For proper protection of coastal environments, a systematic management of the coastal zones must be implemented by the government together with local communities. Such management strategies should be built based on scientific information, which provides proper tools to understand the status of the coasts, and accurate monitoring of the on-going coastal processes, which is required to produce long-term data.  
Since the first technique using remotely sensed video images was introduced to measure the morphology and scale of sand bars [1], video monitoring techniques have been widely applied todetect shoreline positions [2; 3] as a tool for coastal zone management [4]. For example, 40 video monitoring systems have been employed in the beaches along the coasts of South Korea to calculate the seasonal and annual variation of beach areas, and these data have been used to develop coastal management plans.  
Along with their applications for coastal management, video systems have also been used for scientific applications to measure nearshore hydrodynamic processes such as longshore currents [5] and wave parameters [6; 7]. In addition, they have been applied successfully in engineering practices such as evaluating the performance of beach non-instrument [8]. Video systems are also advantageous to monitor short-term beach processes. During extreme storm events, the shoreline could be rapidly changed in a few days, and the erosion and recovery process could be analyzed using video cameras [9]. One of the greatest benefits of video monitoring over point monitoring is its wider spatial coverage achieved by processing obliquely captured image data [10]. Specifically, it provides significant advantages in monitoring complex shorelines where nearshore processes do not occur homogeneously, and thus, the shoreline change pattern becomes irregular due to the existence of rocky seabeds or nearshore sandbars.  
In this study, we analyze the shoreline variations in Hujeong Beach, South Korea, where a video monitoring system has been operating since December 2016. Hujeong Beach is characterized by active development of nearshore sandbars and as a result, its shoreline has a complex pattern with significant variations over time. In addition, there are parts of the seabed that are covered by rocks, although most parts are covered by sand, which makes the shoreline pattern more complicated. The goal of this study is, therefore, to examine the shoreline variations in Hujeong Beach that have been specifically affected by the existence of nearshore sandbars and underwater rocks in relation to the wave conditions. Although the video monitoring system itself is similar to those employed in previous studies, we believe the results of the present work are valuable as the shoreline variation data shows characteristic patterns according to the combined effects of bedforms and waves. Therefore, we used the wave data that were continuously measured during the two years of the experimental period at approximately 1 km offshore from the coast, which increased the reliability of the data in correlation with the shorelines. In addition, the shoreline positions estimated by the video cameras may contain errors when averaging the images to remove noise; thus, validation of the video data is required. For validation, we additionally employed a ship-mounted mobile light detecting and ranging (LiDAR) instrument to measure the beach topography outside the water.