The influence of river point bars on flood hydraulic using geometric model

Abstract

Points bar formation has an important role to changing the hydraulic behavior during floods. In this study, topographic maps at 1:1000 scale for 40 km. given reach of river channel were used in HEC-GeoRAS and HEC-RAS softwares to simulate the geometric features and hydraulic behavior. The hydraulic behavior of Haraz river located in northern Iran, with 25 years of flood data was simulated in two scenarios of present channel conditions and without any point bar. Therefore, the effects of point bars were assessed on flood flow depth and zone, flow velocity and also water shear stress. The results indicated that the formation of point bars causes the flow resistance, its direction to the banks, accelerates erosion and increases the depth of flood. Also, point bars have increased the flood zone by reducing the flow capacity in a cross section of the river channel. Additionally, the increase in flow depth, flood zone, and water shear stress on the channel buffers were estimated 33.33, 95.57, and 66.67%, respectively. These changes are depending on the dimensions of point bars and the rate of flow reduction in a cross section of the channel given reach.