Rapid change of erosion-deposition evolution in the Minjiang estuary, Southeast China

Extreme weather events and anthropogenic activity have severely impacted the Minjiang estuary (MJE) with evolution patterns in recent decades. Determining the estuarine alluvial evolution pattern is crucial for the sustainable development of densely populated coastal areas. Using chart data, this paper analyzed how the MJE's flushing and siltation changed over time (1950–2019). The findings indicate that, in the past 70 years, the MJE has evolved through seven stages of flushing and siltation under the condition of decreasing incoming sediment: “significant siltation - siltation - minor siltation - significant erosion - significant siltation - minor siltation - significant erosion”. Despite decreased incoming material, the estuary underwent substantial siltation from 1998 to 2005. Extreme meteorological conditions were the cause of this anomaly. The “severe flushing” phenomenon occurred in the study area from 2011 to 2019, and the comparison of pre-dam and post-dam at the estuary revealed that extreme weather can only adjust in stages and cannot change the overall state of the estuary flushing due to the reduction of incoming sediment in the basin. According to the EOF (Empirical Orthogonal/Eigen Function) study of four sections of the estuary, it is most impacted by incoming sediment from the watershed, followed by severe weather conditions. Our research is crucial for comprehending how human behavior and harsh weather might affect the development of MJE, and it offers sound advice for the long-term management of MJE.