Observation of Rapid Seabed Erosion Near Closure Depth During a Storm Period at Hujeong Beach, South Korea

Abstract

We report extraordinary seabed erosion that occurred at a depth of ~8.3 m at Hujeong Beach, South Korea. The seabed was eroded for 0.7 m during a ~2.3‐day period under storm conditions. The maximum significant wave height was ~3.8 m, which was unexpected considering the traditional closure depth concept. Four storm events were recorded within 36 day of the experimental period, but the severe erosion only occurred during the first storm. The erosion started when the nearbed flow velocity rapidly increased to reach its maximum at 0.27 m/s, and it continued until this velocity remained at its maximum. Additional factors responsible for the unanticipated erosion process were the current and wave skewness. The erosion was facilitated when the current direction was actively changing and the magnitude of positive skewness increased during the storm period. These factors are likely to have intensified the nearbed flow turbulence and bed shear stress.

Numerical Simulation of the Locality of Erosional Damages by Storm Waves in Searching for Measures to Conserve Bonggil Beach, Korea

“…Exp. 2 was designed to measure geographic and hydrodynamic data such as waves, currents, and suspended sediment concentration using instrument frames that mounted acoustic sensors (Do et al, 2019). During the period of Exp.…”

“…The eroded shorelines are recovered in months, as a natural process, under mild wave conditions following the storms due to slow but steady onshore sediment motions caused by wave nonlinearity (Hsu and Hanes, 2004), which results in the balance of the shoreline positions without retreat or advancement in the long run. However, under specific conditions such as extraordinary storm waves, the damage on the shore could be too severe so that the recovery process may take a long time of years or even decades (Forbes et al, 2004) because the high wave power under these storms could carry the sediments to the areas where the waves and currents could not affect the sediment motion under normal wave conditions (Do et al, 2019). Sometimes, the damage could hardly be recovered when the coastal structures built to protect the shore were broken (Do et al, 2021a).…”

Collapse of a Coastal Revetment Due to the Combined Effect of Anthropogenic and Natural Disturbances

“…However, since the breakwaters of the NPP have been built, the balance has been broken and the beach has been eroded [20]. To understand the coastal processes in this area, various experiments have been performed by the East Sea Research Institute (ESRI) of the Korea Institute of Ocean Science and Technology (KIOST) using the VMS [20] and acoustic instruments [21]. The VMS was installed at the top of a 30 m high metal tower in the middle of Hujeong Beach (Figure 1).…”

Intelligent Buoy System (INBUS): Automatic Lifting Observation System for Macrotidal Coastal Waters

“…Similarly, acoustic sensors, such as the Nortek Acoustic Wave and Current Profiler (AWAC; Pedersen et al, 2007), are mounted on a bottom-fixed frame facing upward to measure waves and currents (Jeong et al, 2020). In addition to wave and current measurements, the instruments fixed to the seabed can be used to measure the near-bed properties such as the sediment concentration and seabed morphology (Do et al, 2019). Other examples of observation systems that are commonly applied in coastal waters include surface buoys that measure nearsurface properties and atmospheric data.…”