An experiment study of erosion characteristics of sediment bed at the yellow river delta

The modern Yellow River Delta is formed by fine-grained sediments through fast transportation and accumulation. Its coast is characterized by partially consolidated bed structure, high water content and weak erosion resistance. Despite recent advances in numerical morphodynamic modeling techniques, the current ability to predict long-term coastal changes at the Yellow River Delta is hampered by the lack of reliable data on the erosion resistance of the sediments deep in the bed. This paper describes a laboratory-based erosion study using a 30 m sediment core collected from the tidal flat on the northern coast of the Yellow River Delta in April 2004. The influence of various sediment properties such as bed stratification, grain composition, wet bulk density and water content on the measured erosion resistance has been analyzed in detail. The results reveal that there exist a definite negative relationship between the critical erosion shear stress and water content or median diameter, and also a clear positive relationship between the critical erosion shear stress and clay content. For the sediments of the same type, there was a positive relationship between the critical erosion shear stress and wet bulk density. It was also found that the erosion resistance changes considerably through depth with the lowest being near the surface and the highest at a depth of 9.1-13.5 m. The relationship between erosion rate and shear stress for erosion was shown to be dependent in a complex way on the grain distribution, sedimentation structure, wet bulk density and water content of the sediments. A number of distinct erosion behavior have been identified and although in most cases the erosion rate (ε) can be related linearly to the net bed shear stress (τ -τ_c), further study is needed to establish the erosion-stress relationship for the case where the erosion seems to show undulating behavior.