EFFECTS OF SEDIMENT GRADATION ON THE GEOMETRY OF RIVER DELTAS

l INTRODUCTlONIn this study, formation of alluvial deltas was treated as a river-dominated type of topograPhy process,caused simply by sediment deposition from a channel into a wide basin. The influences of waves, tides,and density differences related to coastal effects were excluded. There have been numerous experimentalstUdies on river delta problems. For examPle, Shieh et al. (1988, 1997) used coarse sediment asexperimental material and revealed the development and the geometric simil…

EFFECTS OF SEDIMENT GRADATION ON THE GEOMETRY OF RIVER DELTAS

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 analysi s, 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.