Slope-Area Method (US Customary) for Discharge

from "Chow, V.T., Maidment, D.R., Mays, L.W., 1988, Applied Hydrology: New York, McGraw- Hill."

Manning's n Tables Manning's n values for Channels, Closed Conduits Flowing Partially Full, and Corrugated Metal Pipes.

Manning's n Table TxDOT Manning's n Table

Estimates discharge in US customary units from

Q = (1.49/n)*A*(A/P)^(2/3)*S^(1/2)
    Q is the discharge (cubic feet per second)
    n is Manning's roughness coefficient (read from table)
    A is cross sectional flow area (square feet)
    P is wetted perimeter (feet)
    S is friction slope (often the channel slope is substituted)

Enter Value for Manning's n:      

Enter Value for Area (sq. ft.):     

Enter Value for Wetted Perimeter (ft.): 

Enter Value for Dimensionless Slope: