Water Hydraulics - Wastewater Operators - page 85

Table 2.4 Manning roughness CoeffiCienT, n

Type of Conduit n Type of Conduit n

Pipe Cast iron (uncoated) 0.013-0.015

Cast iron (coated) 0.012-0.014 Wrought iron (black) 0.012-0.015

Wrought iron (galvanized) 0.015-0.017 Corrugated 0.021-0.026

Steel (riveted and spiral) 0.015-0.017 Cement surface 0.010-0.013

Wood stave 0.012-0.013 Vitriied 0.013-0.015

Concrete 0.012-0.017 Metal (corrugated) 0.023-0.025

Clay, drainage tile 0.012-0.014 Wood (unplaned) 0.011-0.015

Lined channels Concrete 0.014-0.016

Metal (smooth semicircular) 0.011-0.015 Grass up to 0.020

Wood (planed) 0.010-0.015 Earth (dredged) 0.025-0.033

Cement (lined) 0.010-0.013 Earth (stony) 0.025-0.040

Cement rubble 0.017-0.030 Rock (jagged and irregular) 0.035-0.045

Unlined channels
Earth (straight and uniform) 0.017-0.025

Earth (winding) 0.023-0.030

Rock (smooth and uniform) 0.025-0.035