Impacts of Reclamation on Hydrodynamic and Suspended Sediment Transport in the Bohai Sea.

Since the 1970s, extensive land reclamation has been carried out in the Bohai Sea. However, reclamation activities were prohibited in 2018. Using the MIKE3 numerical model, this study selected 1976 and 2018 as representative years before and after reclamation, respectively, and developed a highly accurate three‐dimensional hydrodynamic and sediment transport model for the Bohai Sea. The model was employed to access the effects of reclamation on tidal waves, tidal prism, residual current, tidal flux (TF), and suspended sediment flux (SSF). The results revealed that after reclamation, the amphidromic points of M2 and S2 shifted southward near Qinhuangdao, and eastward near the Yellow River estuary. The M2 amplitude in the Bohai Bay exhibited a maximum increase of 30 cm. In the Bohai Sea, the tidal prism decreased by 3.95%, suggesting a decrease in water exchange capacity. The TF in the Bohai Sea and Laizhou Bay decreased by 0.7% and 12%, respectively, while increasing by 16% in Bohai Bay and 12% in Liaodong Bay, primarily due to the variations in tidal waves. Furthermore, SSF decreased by 6% in the Bohai Sea, but increased by 125% in Bohai Bay and 114% in Laizhou Bay. The significant increase in SSF in Bohai Bay and Laizhou Bay was mainly attributed to the higher suspended sediment concentrations and the stronger residual current velocities near the Yellow River estuary. This study provides comprehensive insights into the impacts of reclamation on TF and SSF in the Bohai Sea, which could contribute to marine resource development and the planning of environmental restoration projects. Plain Language Summary: In the Bohai Sea, land reclamation has been accelerated since 1970s. Due to negative effects on aquaculture and channel, reclamation activities were prohibited in 2018. However, no research on annual tidal flux (TF) and suspend sediment flux (SSF) in the Bohai Sea has been reported. We have established high‐precision hydrodynamic and sediment transport model to analyze the impacts of reclamation on TF and SSF in the Bohai Sea. The findings revealed that reclamation led to a decrease in TF in the Bohai Sea and Laizhou Bay, while caused an increase in TF in Bohai Bay and Liaodong Bay. After reclamation, the SSF decreased in the Bohai Sea, while increased in Bohai Bay, Laizhou Bay and Liaodong Bay. After reclamation, the suspended sediment concentration and residual current velocity near the Yellow River estuary increased significantly, which was the main reason for the significant increase of SSF in Bohai Bay and Laizhou Bay. The Bohai Sea served as both the "source" of Yellow Sea muddy area and the "sink" of Yellow River which carried a large amount of sediment. The research on how reclamation affecting the TF and SSF in the Bohai Sea was essential for the sedimentation system of the East China Seas. Key Points: After reclamation, the area of Bohai Bay reduced, however, the tidal prism increased by nearly 10% due to the increase of tidal rangeAfter reclamation, tidal flux and water exchange capacity decreased in the Bohai Sea and Laizhou Bay, while increased in Bohai BayAfter reclamation, sediment flux decreased in the whole Bohai Sea and increased in three bays, particularly in Bohai Bay and Laizhou Bay [ABSTRACT FROM AUTHOR]