Effects of intertidal reclamation on tides and potential environmental risks: a numerical study for the southern Yellow Sea

Intertidal (tidal flat) reclamation along the Chinese coastline, especially which is in Jiangsu Province, has increased markedly in recent years. However, the hydrodynamic disturbance and environmental impacts of this activity are not yet fully understood. In this study, a process-based depth-averaged model is used to evaluate quantitatively the possible impacts of intertidal reclamation for the southern Yellow Sea region. The simulation results show that reclamation of both inshore and offshore intertidal areas of ~1800 km² (according to the approved governmental reclamation scheme) would result in three remarkable changes in tidal patterns: enhanced M₂ and M₄ tidal amplitudes in coastal areas, strengthened negative tidal asymmetry in the southern region of the sand ridge system, and an enhanced tidal energy flux toward offshore through the main channels in the south. These changes would result in some negative impacts. The enhancement in local tidal amplitude could increase the probability of coastal hazards, and the offshore sediment transport tendency resulting from negative tidal asymmetry in the south could lead to severe erosion. The enhanced energy flux transported offshore may also affect far-field regions. On the other hand, alternative reclamation of ~400 km² of offshore intertidal area could significantly minimize hydrodynamic disturbances to the local tidal system. Offshore reclamation with lower environment impacts may be the future for coastal development. To cope with the potential environmental risks caused by reclamation, it is recommended to strengthen environmental impact assessment and overseeing of reclamation plans, and advance international cooperation in terms of coastal management. Our findings provide a reference for coastal management in countries with substantial areas of tidal flats.