# Wind-Wave-Current Coupled Modeling of the Effect of Artificial Island on the Coastal Environment
## 2 Materials and Methods  
### Study Area  
The study area was the waters around an artificial island--in, Qionghai City, Hainan Island. The artificial island is the only artificially reclaimed island in Boao Town, Qionghai City, Hainan Province, about 6.8 km north of the mouth of the Wanquan River (Figure 1a). The study area is a tropical monsoon climate, with an average annual temperature of about 25.0 \({}^{\circ}\)C and an average annual precipitation of 2103.0 mm. According to the wind data from Qionghai-Wanning Meteorological Station, from 1981 to 2010, the average annual wind speed in Qionghai was 2.2 m/s, and the prevailing wind direction was mainly southerly in summer and northerly in winter. Spring and autumn represent the transition seasons between the two wind directions (Figure 1b). The tides were irregular semi-diurnal tides. The normal wave direction throughout the year was southeast, which was the main wave direction. At the same time, the coast will be affected by the Taiwan wave and the near sea wave; the sub-normal wave direction was SSE; the strong wave direction was ESE, SE, and SSE; and the SE and SSE wave directions account for 68% of the total frequency (Figure 1c).  
The construction of an artificial island began in 2011, with a circumference of 4040 m and an area of 4.61 \(\times\) 10\({}^{5}\) m\({}^{2}\). However, due to environmental problems along the shoreline, construction was stopped, and the shoreline restoration project was launched in 2021. The whole artificial island section presents the phenomenon of siltation in the middle channel and erosion on the north and south sides of the channel. Since the construction of the artificial island in 2011, the phenomenon of erosion and siltation was significantly intensified. The maximum annual average erosion and siltation distance were about 55.6 m/a and 10.2 m/a, respectively, which increased by about 22 times and 5 times compared to before construction. The monitoring data of the bank profile in 2020 showed that erosion and sedimentation occurred in both normal seasonal weather and typhoon weather, and the variation in erosion and sedimentation in the north and south coast sections increased by 2 times and 6 times, respectively, after the passage of typhoons. The reclamation of the artificial island changed the regional hydrodynamics, which were superimposed with the influence of extreme weather such as typhoons. Waves scour the loose shoals of the north and south coasts, which intensified erosion and increased the concentration of coastal suspended sediment. This sediment accumulated in the wave shadow area with weak hydrodynamics on the west side of the artificial island to form  
Figure 1: (**a**) Study area. (**b**) Rose chart of annual mean wind power in the study area. (**c**) Annual mean wave rose map of sea area around the study area.  
an intermediate silting salient [18]. In addition, the hydrodynamic environment around the artificial island was also affected by the inflow of inland rivers in Wanquan River and Tannen Town, and the hydrodynamic process is very complicated. Therefore, it is necessary to establish a local 3D mathematical model of the artificial island and the Wanquan River.