Development and geometric similarity of alluvial deltas

Movable bed experiments from a flume into a basin were conducted to study t he development of alluvial deltas. The experimental setup was aimed at the bed-load mode. Results showed that the development of the delta can be divi ded into three stages. In the first stage, the delta progressed mainly in i ts length, and a successfully derived equation described the shape of the d elta in this stage. In the second stage, the delta developed mainly in its width. The length, width, front thickness, and central thickness of the del ta were used to scale the geometric similarity. The plane geometry of delta s can be described using Gaussian functions. Transverse and longitudinal pr ofiles fit the hyperbolic and linear function, respectively. The length, wi dth, and thickness of the delta deposition at the end of the second stage h ave their own maximum values, R-c, B-m, and Z(f), respectively, for each ca se. The total volume V of sediment deposition could be simply related to th ese maximum values by V = alphaR(c)B(m)Z(f) + beta with shape parameters al pha and beta 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 varia tions of stream channels were investigated qualitatively.