EFFECTS OF SEDIMENT GRADATION ON THE GEOMETRY OF RIVER DELTAS
摘要
A series of laboratory experiments were conducted to evaluate the influence of the size-distribution of sediments on the formation and geometry of alluvial deltas. In the previous studies by the first author,only coarse sediments, which move under bed-load conditions, were used as the testing material. In this study, mixing fine grain materials into the experimental sediments created certain suspended load.Results of the new experiments show significant differences in the geometry of deltas as a consequence of incorporating the suspended load. Dimensionless plots for different geometrical parameters show that the geometry of the deltas, normalized by several selected characteristic lengths, is still independent of the size-distributions of sediments. The plane geometry of the deltas can still be described by a Gaussian function as in the previous studies. In addition, transverse and longitudinal profiles can also be fitted by the hyperbolic and linear functions, respectively. Based on this analysis, however, the distribution coefficients of the functions mentioned above vary with the grain size distributions, which will be a sound indicator of the quantitative classification for alluvial deltas.