Investigation of hydraulic flow and sediment transport in Non-prismatic compound channels

In rivers with a compound section, typically the relatively high roughness of floodplains, as compared with the main channel, grounds the speed difference in these two ( main channel and floodplains). The velocity dissimilarity also creates shear layers at the interface point of the main channel and the floodplain. The development of shear layers will also cause turbulence in the mutual plane of the main channel and the floodplain. In such conditions, the average flow speed cannot be applied to compute parameters such as shear stress, bed-load discharge, and so forth. Laboratory experiments was carried out to investigate the effects of floodplain divergence on flow hydraulic and the rate of sediment transport through roughness and different divergent angles. This research 36 tests were done at a concrete flume with compound channel cross section (9 and 27 tests with prismatic and Non-prismatic cross section respectively). By using a micro-propeller and ADV (with 200 Hz frequency) in different sections the velocity were measured. For depth ratio of 0.15 0.25 was used the micro-propeller and depth ratio 0.35 was used the ADV. The results reveal that the increase in all three factors of roughness, divergence angle, and relative depth cause dramatic changes in hydraulic of flow and sediment transport.