Calibration of Manningʹʹs Roughness Coefficient in the Rivers

ABSTRACT: The basis of the hydraulic relations and the numerical methods of solving the equations differ from each other in different mathematical models. Hence, the current research is a comparison between the results of the hydraulic models in determining the available difference level. In this way, to simulate the Bashar river, having completed the required information, the HEC-RAS and MIKE11 models were separately calibrated and the floodʹs hydraulic analysis was performed by these models using the roughness coefficients 0.052 and 0.039, respectively. It should be noted that the difference between the results of two hydraulic models HEC-RAS and MIKE11 is because of the performance of the equations which are used in each model to perform calculations of the flow simulation. In the model HEC-RAS, the steady flow equations have been used and the model MIKE11 has employed the steady flow equations. So, our recommendation as a technical point is that the selection of the same Manningʹs roughness coefficients for different hydraulic models causes error in the flow simulation process.