The effect of structures density in the banks of meandering rivers on the flow characteristics during floods

Rivers as a natural drainage of a watershed have always been of interest in draining the runoff resulting from precipitation, especially during floods. Due to the formation of most cities and villages on the banks of rivers and the construction of structures in their floodplains, during floods, the pattern of river flow always undergoes changes, so it is necessary to study the interaction of flood flows of meandering compound channel in these areas. In this research, by using Flow3D software, which is a powerful software in the field of computational fluid dynamics, the flow structure and bed shear stress in meandering compound channel under the effect of structural density of floodplain during floods have been investigated. For this purpose, six types of structural density of 0, 8, 16, 11, 25 and 44% have been used on the floodplain using non-submerged blocks with distances of 7, 14, 21, 28 and 35 cm. The results of the numerical simulation showed that with the increase of structural density in the floodplain from zero to 44%, the average velocity of the main channel, the maximum water surface elevation and the amount of flow passing through the main channel increased by 51%, 25% and 84% respectively. Also, with the increase in structural density on the floodplain, the amount of bed shear stress has increased so that the maximum bed shear stress has increased from 1.32 to 4.61 pascal (250 percent) and moves towards the center of the main channel.