Manning Equation Calculator
The Modified Manning Equation is used to calculate flow velocities and
volume (in cubic feet per second or cfs). This information is vitally important
when selecting a grate type and size for a given project.
- D = Depth of flow in feet
- Q = Channel flow in cfs (calculated)
- Z = Reciprocal of transverse slope (1/ST)
- S = Longitudinal slope
- N = Roughness coefficient at constant 0.016 (value for concrete and asphalt)
Enter the Longitudinal and Transverse Slopes. Enter one of the remaining variables and then press calculate:
- Depth of Flow (D)
- Total flow in cfs (Q)
- Spread of flow in feet
To Calculate flow capture of specific Neenah Grates, select a catalog number and grate style from the K Chart drop-down.
- Select the catalog number for the appropriate "K" chart and from the chart "Determine the "K" value based on the Longitudinal and Transverse slopes entered in Step 1.
- Derive the Grate Coefficient by plotting the Transverse Slope (ST)
and Longitudinal Slope factors onto the K Chart.
- Enter the "K" value in the space provided.
- Press Calculate.