Influence of Stream Interactions on the Carrying Capacity of Two-Stage Channels

Streams of water in channels that have a compound cross section interact with each other. The most characteristic feature of such channels is the transfer of momentum and mass from the main channel to the floodplains. A laboratory experiment was conducted in a two-stage channel to investigate the impact of stream interactions on discharges. Various roughness conditions of the channel bottom and sloping banks were considered. An original idea was to eliminate stream interactions using glass walls placed in the interface between the main channel and the floodplains. This resulted in significant differences in water levels between these parts of the channel. Measured mean-time velocities were used to analyze changes of discharges in the main channel and floodplains in cases when the streams interact with each other and when these interactions are eliminated. A comparison of the measured velocity distributions for various parts of the compound channel with measurements taken when the floodplains were disconnected from the main channel showed that the mean velocity increased in the main channel and in the floodplains. The results obtained could constitute significant information for the increasingly popular two-stage channel building projects for hydraulic engineering purposes.