Contemporary Sedimentary Environment Evolution and Its Response to Human Activities in the Minjiang Subaqueous Delta and Surrounding Waters
[Objective]River deltas are sensitive areas of land-sea interaction with intense human activities,and continue to be the focus of international research.[Methods]Based on grain-size analysis of surface sediments in the Minjiang River delta and surrounding waters,this study discusses the evolution of the contemporary sedimentary envi-ronment in the area.[Results]It is shown that the dominant to-and-fro tidal current within the estuary gradually changes into a rotating seaward flow,and that the current speed decreases from the subaqueous delta to the offshore area.The sediments in the study area are mainly sand,silt and sandy silt,with mean grain-sizes of 1.57 Φ,6.7 Φ and 5.62 Φ.From the estuary to the adjacent coastal shelf area,coarse-particle content decreases and fine-particle con-tent gradually increases.In addition,grain size trend analysis indicates that the sediment delivered by the Minjiang River is transported towards the E,SE and NE when it enters the estuary.After the fine sediment passes through the subaqueous delta,it tends to be transported offshore towards the SE and NE.A multivariate statistical analysis of sed-iment composition,grain size parameters and water depth integrating the geographical location,sediment source and hydrodynamic conditions indicate that the contemporary sedimentary environment in the study area is divided into four sub-sedimentary districts.The study reveals the effect of different influences on the sedimentary environment and demonstrates its response to human activities.[Conclusions]The results of this study provide advice for estuary resource development and ecological environment protection.
subaqueous deltaMinjiang River estuarygrain-size parametersediment transport trendsedimentary environment