Grain size characteristics of surface sediment and its response to the dynamic sedimentary environment in Qiantang Estuary,China

The composition and grain size characteristics of sediment in estuarine and coastal environments provide important information on the material source, hydrodynamic environment, environmental events, etc. However, few studies have focused on the sediment characteristics of the entire Qiantang Estuary, particularly, on the correlation between hydrodynamics and sediment properties. Through systematic sampling of the surface sediment in a large area of the Qiantang Estuary, the spatial distribution characteristics of the surface sediment of the Qiantang Estuary, such as the grain size composition and particle size parameters, in different sections of the estuary area are analyzed. By comparing the particle size data of different estuaries, the similarities and differences of the particle size parameters of the Qiantang Estuary and other estuaries are compared and analyzed. According to the differences in the sediment composition, the distribution status of the particle size frequency curves and the morphological characteristics of the probability curves in the entire study area, the Qiantang Estuary is divided into 7 dynamic depositional areas: Fuchunjiang Hydropower Station–Fuyang, Fuyang–Qibao, Qibao–Cao'e River, Cao'e River–Zhapu, North Shore of Hangzhou Bay, middle part of Hangzhou Bay, and South Shore of Hangzhou Bay, which are different from the previous estuary segmentation system. The study area is divided into 13 dynamic depositional sub-regions using the Pejrup M triangle diagram. Combining the calculation results of the mathematical model and the Pejrup M triangle diagram, the relation between the dynamic deposition environment and the bottom shear stress is discussed. It is found that the spatial distribution of the bottom shear stress in the study area is in good agreement with the zoning of the dynamic sedimentary environment.