What is the typical range for roughness height of concrete channel

I am trying to find a reasonable roughness height range for concrete channel. The manning n should be 0.014. Can anyone suggest an equation to calculate the corresponding roughness height?

I see mostly this parameter is treated as a calibration parameter. Has anyone calibrated roughness height for concrete channel, could you share your range?



The answer depends to some extent on your grid size as you are trying to pick variability in roughness and smoothness in the the boundary layer. The value is to be expected to be in the mm scale, around 2-5 mm. There may be an equation but we can’t provide it right now.

This is not a highly sensitive parameter and only required for fine tuning. Bathymetry is the key to your model calibration.

The relation between manning’s roughness and bottom drag is shown in the following figure. For details, please look at book “Hydrodynamics and Water Quality : Modeling Rivers, Lakes, and Estuaries” by Zhen-gang Ji.