An improved method of sediment grain size trend analysis in the Xiaoqinghe Estuary, southwestern Laizhou Bay, China

Although deltas evolve with a regular cycle of growth and abandonment over centuries, knowledge of these cycles and their effects is important given the fact that humans tend to locate near these areas. This study examines sediment transport patterns in the Xiaoqinghe Estuary in southwestern Laizhou Bay, China, in order to identify the factors controlling the sedimentary environment in the estuary. Sediment samples collected from the bed of Laizhou Bay in 2007 were analyzed using the Gao-Collins 2-D grain size pattern analysis method and two polymodal distribution functions. The study identified three grain size subgroups (<4, 6-16, and 27-115 mu m) and mapped the distribution of the relative percentage of the three components and the mean size distribution within each component. The sediment transport trends for the three components were derived by a mathematical partitioning process. Generally, the finest grains move from the local river mouths seaward in the north and south directions, with a large anomaly suggesting input into the study area from the more distant Huanghe River in the north. In addition, fine-grained sediment is transported by marine hydrodynamic forces from the shallow sea areas toward the coast. The medium-sized grains move toward the river mouths, settling over oyster beds and sandbars that create high-turbulence zones, while the fine silt grains move seaward in northerly and southerly directions. The coarser grains tend to flow toward the coast, brought in by seaward migration, with some coarse material moving off the river mouths.