Research On The Influence Of Sea-crossing Bridge And Island On Suspended Sediment Concentration Based On HY-1C

This study mainly used the remote sensing data of Chinese new marine satellite HY-1C CZI during October to December 2019 to study the distribution of suspended sediment in the Hangzhou Bay and Pearl River Estuary,combined with satellite images and in-situ data to establish inversion algorithm of suspended particulate matter(SPM)in high turbidity water and low turbidity water.And explore the influence of Hangzhou Bay Bridge,islands,and Hong Kong-Zhuhai-Macao Bridge on the distribution of SPM.Based on the remote sensing algorithm,the HY-1C satellite remote sensing data is used to explore the distribution of suspended sediment in Hangzhou Bay and Pearl River Estuary.It is found that the concentration of suspended sediment in Hangzhou Bay is between 100mg/L and 1600 mg/L,which is a high SPM in the estuary area.The general root mean square error(RMSE)is 29.67 mg/L,and the SPM in Hangzhou Bay is high during the flood and ebb tide.Then extracted the suspended sediment data of the upper and lower of the Hangzhou Bay Bridge for comparison.It is found that the SPM at the downstream of the bridge is higher than that at the upstream of the bridge during the flood and ebb tide,and the difference is 200-400 mg/L.The concentration of suspended sediment around the island is slightly higher than that in the surrounding waters,and the concentration of suspended sediment in the downstream of the island is higher.The vortex street phenomenon downstream of the island can be found through the concentration distribution of suspended sediment around the island.Generally,the length of the vortex street downstream of the island is in the range of1000-8000 m.Factors affecting the formation of vortex streets include Reynolds number,ocean current speed and the shape of obstacles,etc.The islands induce vortex streets to cause regular changes in the concentration of suspended sediment.The study on the concentration of suspended sediment in the Pearl River Estuary found that the concentration of suspended sediment in this area is between 20 mg/L and 120 mg/L,which is lower than that of Hangzhou Bay,and the water is relatively clear.The change in the concentration of suspended sediment in the upstream of the Hong Kong-Zhuhai-Macao Bridge is the same as that in the downstream.However,the concentration of suspended sediment in the upstream of the bridge is lower than that in the downstream,and the concentration difference is between 10 mg/L and 20 mg/L.The SPM in the estuary area is not only affected by tidal currents,topography,and wind,but also by other factors,such as sea-crossing bridges and islands.The sea-crossing bridge interacts with islands and ocean currents,thereby affecting the distribution of SPM.The significance of this research aims at the development model,which is applicable to invert the SPM in the coastal waters by HY-1C CZI data,such as high suspended sediment concentration(Hangzhou Bay)and low suspended sediment concentration(Pearl River Estuary).It reveals the factors affecting the distribution of SPM in the coastal waters,more measures can be provided on the environmental protection of the coastal waters and the management of coastal engineering.