Mannings n Roughness Coefficients - Closed Conduits
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- Abraham Toribio II
The following Manning’s n Roughness Coefficient table is from the United States Department of Transportation – Federal Highway Administration: Hydraulic Engineering website:
Table B.3. Manning's n Values for Closed Conduits. | ||
|---|---|---|
Description | Manning's n Range | |
Concrete pipe | 0.011–0.013 | |
Corrugated metal pipe or pipe-arch: | ||
Corrugated Metal Pipes and Boxes, Annular or Helical Pipe (Manning's n varies with barrel size) | 68 by 13 mm (2-2/3 x 1/2 in.) corrugations | 0.022-0.027 |
150 by 25 mm (6 x 1 in.) corrugations | 0.022–0.025 | |
125 by 25 mm (5 x 1in.) corrugations | 0.025–0.026 | |
75 by 25 mm (3 x 1 in) corrugations | 0.027–0.028 | |
150 by 50 mm (6 x 2 in.) structural plate corrugations | 0.033–0.035 | |
230 by 64 mm (9 x 2-1/2 in.) structural plate corrugations | 0.033–0.037 | |
Corrugated Metal Pipes Helical Corrugations, Full Circular Flow | 68 by 13 mm (2-2/3 x 1/2 in.) corrugations | 0.012–0.024 |
Spiral Rib Metal Pipe | Smooth walls | 0.012–0.013 |
Vitrified clay pipe | 0.012–0.014 | |
Cast-iron pipe, uncoated | 0.013 | |
Steel pipe | 0.009–0.013 | |
Brick | 0.014–0.017 | |
Monolithic concrete: | 1. Wood forms, rough | 0.015–0.017 |
2. Wood forms, smooth | 0.012–0.014 | |
3. Steel forms | 0.012–0.013 | |
Cemented rubble masonry walls: | 1. Concrete floor and top | 0.017–0.022 |
2. Natural floor | 0.019–0.025 | |
Laminated treated wood | 0.015–0.017 | |
Vitrified clay liner plates | 0.015 | |