Flow structures in asymmetric compound channels with emergent vegetation on divergent floodplain

Knowledge and management of hydraulic processes including flow pattern, sediment transport, and flood level prediction in natural rivers require proper understanding of interactions between flood flow and vegetation in floodplains. This study examined the flow structures and turbulence parameters in an asymmetric non-prismatic compound channel with different vegetation densities in divergent floodplain. Due to existence of vegetation, the bed shear stresses in the middle and end of the divergence floodplain decrease 78.5% and 86%, respectively. Also, the depth-averaged velocity in vegetated floodplain diminishing by about 60% and 69%. The results revealed that the production and dissipation of Reynolds shear stresses and the formed shear layer depend on the vortex shedding frequency formed behind each single rod and is very unstable. Finally, some equations were presented to estimate friction factor based on rod Reynolds number, calculate the frequency of the vortices generated behind the elements and the local drag coefficient.

Automated summary

This study examines the influence of vegetation on flow structures and turbulence parameters in floodplains. The presence of vegetation significantly reduces bed shear stresses and depth-averaged velocity, and the production and dissipation of turbulence are closely related to the presence of vegetation.