Impacts of tail channel alterations on hydrodynamic and environmental conditions in Yellow River Estuary.

The geomorphological evolution of the Yellow River Estuary is dominated by sediment discharge and transport. Severe sediment deposition extends the tail channels, increasing the risk of river breach. Therefore, selecting an appropriate channel to maximize sediment transport offshore is critical while ensuring ecological safety. Since sediment and pollutant movement are controlled by hydrodynamics related to coastline changes, this study addresses the insufficiently understood water exchange capacity and its effect on sediment transport and water quality under the past, current, and future scenarios. This study examines hydrodynamics and environmental impacts associated with tail channel alterations using coupled numerical models, including hydrodynamic, sediment, water quality, and water age models. Through these models, water ages under different tail channel usage scenarios were examined. Additionally, the influences of shoreline evolution on hydrodynamics, sediment transport, and primary production were quantitatively assessed, with potential sequences for tail channel usage analyzed. Results show that these factors significantly alter nearshore hydrodynamics and sediment dispersion. The east branch of Qing 8 Cha demonstrated superior water exchange and offshore sediment dispersion capacity, indicated by a limited sediment-laden area and low primary production. While the south and north branches of the Qingshuigou Channel show similar sediment dispersion with no significant improvement to primary production, prioritizing the south branch followed by the north branch is the optimal sequence for enhancing hydrodynamic conditions, albeit at the expense of northern estuary ecology. These findings reveal the hydrodynamic properties of the Qingshuigou Channel outlets and provide insights for management strategies in the Yellow River Estuary.