| Description | ‘n’ |
|---|---|
| Metal pipe spun concrete lining | 0.007 |
| Wrought iron | 0.008 |
| Smooth pre-cast well jointed concrete | 0.009 |
| Uncoated cast iron; well-aligned glazed vitrified clay | 0.01 |
| Spun concrete | 0.011 |
| Monolithic concrete; rough pre-cast concrete; butt-jointed drain tile; slimed sewers | 0.013 |
| Pre-cast pipes with mortar squeeze at joints; well pointed brickwork | 0.015 |
| Old brickwork; foul sewers with grease, lime encrusted or sludge | 0.019 |
| Corrugated pipe D = 0.4 m | 0.014 + 0.02 (D in metres) |
| Corrugated pipe D > 0.4 m | 0.020 + 0.002 (D in metres) |
| Description | Manning ‘n’ |
|---|---|
| Concrete lined, screeded and smoothed | 0.014 |
| Gunite concrete, not smoothed with sandy deposits | 0.018 |
| Irrigation canal in hard-packed smooth sand | 0.020 |
| Canal excavated in silty clay | 0.024 |
| Channel with cobble stone bottom | 0.028 |
| Natural channel with fairly regular cross-section | 0.035 |
| Natural channel, irregular section, grass slopes | 0.040 |
| Dredged channel, irregular side slopes, grass and weeds | 0.050 |
| Irregular channel with dense growth, little foliage | 0.080 |
| Irregular channel with dense growth, with much foliage and vegetation | 0.110 |