Hydraulic Model Development using HEC-RAS and Determination of Manning Roughness Value for Shatt Al-Rumaith


Selection of appropriate Manning’s coefficient is critical to the accuracy of computed water surface profiles. Moreover , estimation of channel roughness parameter is of key importance in the study of open- channel flow particularly in hydraulic modeling .Hence, it is essential to calibrate the channel roughness coefficient for open channel whether natural or artificial . In the present study , it is attempted to calibrate the value of Mannnig’s “n” coefficient by comparing the computed water surface profiles with observed one , using HEC-RAS steady flow model for shatt al-Rumaith channel in Al- Muthanna (Iraq ) . For this calibration , the flows for the year 2014 has been considered . It is found that the value of Manning's roughness coefficient for shatt al-Rumaith shows a good agreement between the computed with observed water surface profiles , is n=0.023and n= 0.04 for main channel and floodplain respectively