Interactions Between River Floods and Human Activities on Sediment Transport in a Macrotidal Estuary

Abstract River floods and human activities would impact land‐to‐sea sediment transport, which is essential for understanding the evolution of the global sediment cycle in the Anthropocene era. This study focused on investigating how river floods and a dike constructed in 2005 along a river channel influence sediment transport from the Ou River Estuary to the East China Sea. A validated three‐dimensional sediment transport model based on the Finite Volume Community Ocean Model was utilized for this study. The presence of the dike obstructs alongshore currents and fish migrations, leading to negative effects on marine ecology. Therefore, selective dismantling and ecological restoration measures are deemed necessary. Three scenarios were considered in this study: no‐dike, dike‐constructed, and dike‐partially‐removed conditions, along with various types of river floods. The findings indicate that the monthly sediment flux to the sea decreased by 7.7% from 8.11 × 10 6 to 7.49 × 10 6 t following dike construction, while the proportion of cross‐shore sediment flux to the total flux increased from 37% to 59%. The dike consistently has a greater impact than river floods in their interactions. However, partially removing the dike reduces its influence and restores sediment transport to pre‐dike levels, the effectiveness of which is more pronounced with more frequent floods, larger volumes, and rising sea levels. This study provides valuable insights into the interplay between river floods and dikes on sediment transport, thereby enhancing our understanding of the repercussions of human interventions on sediment dynamics.