Spatial and temporal variations in grain size of surface sediments in the littoral area of yellow river delta

The impacts of human activities on the sediment load of the Yellow River and the long-term evolution of the delta have been extensively investigated, but less is known of the variation in sediment grain size in the littoral zone. In this study, the data of surface sediment samples collected from the littoral area of the Yellow River Delta in 2000 and 2007 are used to investigate the spatial distribution and transport pathway of the sediment, as well as the grain size response to the drastic decrease in riverine sediment discharge. By applying the geostatistics analysis method to grain size parameters in determining the characteristic distance in the sediment trend analysis method, an effective way to understand the movement and gradation of surface sediments around the delta has been proposed. The results show that as a whole the sediment in the inshore erosion area is coarser than that in the offshore accretion area. The grain size trends obtained reveal two converging zones of sediment movement. We find a coarsening trend in sediment from 2000 to 2007. Possible mechanisms for this trend are discussed.