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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. [ABSTRACT FROM AUTHOR]

The subaerial delta of the Yellow River has undergone a notable reshaping process with drastic changes in erosion and accretion patterns both temporally and spatially. These morphological changes not only have significant impact on the long-term evolution of delta but also pose severe threat to the existing infrastructures adjacent to the eroding delta lobe. This paper presents a data-based study of waves, currents, sediments and subaqueous bedforms including the application of Principal Component Analysis (PCA) to the measured coastal profiles in order to understand qualitative and quantitative processes that are responsible for the observed changes. The results demonstrated that the Yellow River Delta has recently been dominated by recession process due to the reduced sediment supply from the Yellow River in the recent decades. A critical threshold of river sediment discharge was formulated and used to explain the observed morphodynamic processes. It was found that the coast of the Yellow River Delta could be broadly divided into three geomorphic zones: the area near abandoned delta, the estuarine area, and Laizhou Bay. At the nearshore zone of the abandoned delta, waves are the main agent for bed erosion and sediments suspension. The tidal current is effective in transporting suspended sediments and exerts the main control on the depths of the erosion-accretion balance zone on the coastal profiles. The area near the present estuary has seen rapid deposition with the progradation rate being governed by the relative intensity of fluvial and marine processes while the coasts in Laizhou Bay are stable and the particular characteristics of the tidal current field prevent the sediments supplied by the Yellow River from reaching this area. [ABSTRACT FROM AUTHOR]