Development and Geometric Similarity of Alluvial Deltas

Movable bed experiments from a flume into a basin were conducted to study the development of alluvial deltas. The experimental setup was aimed at the bed-load mode. Results showed that the development of the delta can be divided into three stages. In the first stage, the delta progressed mainly in its length, and a successfully derived equation described the shape of the delta in this stage. In the second stage, the delta developed mainly in its width. The length, width, front thickness, and central thickness of the delta were used to scale the geometric similarity. The plane geometry of deltas can be described using Gaussian functions. Transverse and longitudinal profiles fit the hyperbolic and linear function, respectively. The length, width, and thickness of the delta deposition at the end of the second stage have their own maximum values, R_c, B_m, and Z_f, respectively, for each case. The total volume V of sediment deposition could be simply related to these maximum values by V = αR_cB_mZ_f + β with shape parameters α and β around 0.178 and 174. The third stage was characterized by the interactions between the delta development and stream-channel variations. The ratios of the delta slope to the channel slope were closely related to the occurrence condition of the stream channel. Finally, the temporal variations of stream channels were investigated qualitatively.