A. | CLOSED CONDUITS FLOWING PARTLY FULL | | | |
| A-1. | Metal | | | |
| | a. | Brass, smooth | 0.009 | 0.010 | 0.013 |
| | b. | Steel | | | |
| | | 1. | Lockbar and welded | 0.010 | 0.012 | 0.014 |
| | | 2. | Riveted and spiral | 0.013 | 0.016 | 0.017 |
| | c. | Cast iron | | | |
| | | 1. | Coated | 0.010 | 0.013 | 0.014 |
| | | 2. | Uncoated | 0.011 | 0.014 | 0.016 |
| | d. | Wrought iron | | | |
| | | 1. | Black | 0.012 | 0.014 | 0.015 |
| | | 2. | Galvanized | 0.013 | 0.016 | 0.017 |
| | e. | Corrugated metal | | | |
| | | 1. | Subdrain | 0.017 | 0.019 | 0.021 |
| | | 2. | Storm drain | 0.021 | 0.024 | 0.030 |
| A-2. | Nonmetal | | | |
| | a. | Lucite | 0.008 | 0.009 | 0.010 |
| | b. | Glass | 0.009 | 0.010 | 0.013 |
| | c. | Cement | | | |
| | | 1. | Neat, surface | 0.010 | 0.011 | 0.013 |
| | | 2. | Mortar | 0.011 | 0.013 | 0.015 |
| | d. | Concrete | | | |
| | | 1. | Culvert, straight and free of debris | 0.010 | 0.011 | 0.013 |
| | | 2. | Culvert with bends, connections, and some debris | 0.011 | 0.013 | 0.014 |
| | | 3. | Finished | 0.011 | 0.012 | 0.014 |
| | | 4. | Sewer with manholes, inlet, etc., straight | 0.013 | 0.015 | 0.017 |
| | | 5. | Unfinished, steel form | 0.012 | 0.013 | 0.014 |
| | | 6. | Unfinished, smooth wood form | 0.012 | 0.014 | 0.016 |
| | | 7. | Unfinished, rough wood form | 0.015 | 0.017 | 0.020 |
| | e. | Wood | | | |
| | | 1. | Stave | 0.010 | 0.012 | 0.014 |
| | | 2. | Laminated, treated | 0.015 | 0.017 | 0.020 |
| | f. | Clay | | | |
| | | 1. | Common drainage tile | 0.011 | 0.013 | 0.017 |
| | | 2. | Vitrified sewer | 0.011 | 0.014 | 0.017 |
| | | 3. | Vitrified sewer with manholes, inlet, etc. | 0.013 | 0.015 | 0.017 |
| | | 4. | Vitrified subdrain with open joint | 0.014 | 0.016 | 0.018 |
| | g. | Brickwork | | | |
| | | 1. | Glazed | 0.011 | 0.013 | 0.015 |
| | | 2. | Lined with cement mortar | 0.012 | 0.015 | 0.017 |
| | h. | Sanitary sewers coated with sewage slimes, with bends and connections | 0.012 | 0.013 | 0.016 |
| | i. | Paved invert, sewer, smooth bottom | 0.016 | 0.019 | 0.020 |
| | j. | Rubble masonry, cemented | 0.018 | 0.025 | 0.030 |
B. | LINED OR BUILT-UP CHANNELS | | | |
| B-1. | Metal | | | |
| | a. | Smooth steel surface | | | |
| | | 1. | Unpainted | 0.011 | 0.012 | 0.014 |
| | | 2. | Painted | 0.012 | 0.013 | 0.017 |
| | b. | Corrugated | 0.021 | 0.025 | 0.030 |
| B-2 | Nonmetal | | | |
| | a. | Cement | | | |
| | | 1. | Neat, surface | 0.010 | 0.011 | 0.013 |
| | | 2. | Mortar | 0.011 | 0.013 | 0.015 |
| | b. | Wood | | | |
| | | 1. | Planed, untreated | 0.010 | 0.012 | 0.014 |
| | | 2. | Planed, creosoted | 0.011 | 0.012 | 0.015 |
| | | 3. | Unplanned | 0.011 | 0.013 | 0.015 |
| | | 4. | Plank with battens | 0.012 | 0.015 | 0.018 |
| | | 5. | Lined with roofing paper | 0.010 | 0.014 | 0.017 |
| | c. | Concrete | | | |
| | | 1. | Trowel finish | 0.011 | 0.013 | 0.015 |
| | | 2. | Float finish | 0.013 | 0.015 | 0.016 |
| | | 3. | Finished, with gravel on bottom | 0.015 | 0.017 | 0.020 |
| | | 4. | Unfinished | 0.014 | 0.017 | 0.020 |
| | | 5. | Gunite, good section | 0.016 | 0.019 | 0.023 |
| | | 6. | Gunite, wavy section | 0.018 | 0.022 | 0.025 |
| | | 7. | On good excavated rock | | 0.017 | 0.020 |
| | | 8. | On irregular excavated rock | | 0.022 | 0.027 |
| | d. | Concrete bottom float finished with sides of | | | |
| | | 1. | Dressed stone in mortar | 0.015 | 0.017 | 0.020 |
| | | 2. | Random stone in mortar | 0.017 | 0.020 | 0.024 |
| | | 3. | Cement rubble masonry, plastered | 0.016 | 0.020 | 0.024 |
| | | 4. | Cement rubble masonry | 0.020 | 0.025 | 0.030 |
| | | 5. | Dry rubble or riprap | 0.020 | 0.030 | 0.035 |
| | e. | Gravel bottom with sides of | | | |
| | | 1. | Formed concrete | 0.017 | 0.020 | 0.025 |
| | | 2. | Random stone in mortar | 0.020 | 0.023 | 0.026 |
| | | 3. | Dry rubble or riprap | 0.023 | 0.033 | 0.036 |
| | f. | Brick | | | |
| | | 1. | Glazed | 0.011 | 0.013 | 0.015 |
| | | 2. | In cement mortar | 0.012 | 0.015 | 0.018 |
| | g. | Masonry | | | |
| | | 1. | Cemented rubble | 0.017 | 0.025 | 0.030 |
| | | 2. | Dry rubble | 0.023 | 0.032 | 0.035 |
| | h. | Dressed ashlar | 0.013 | 0.015 | 0.017 |
| | i. | Asphalt | | | |
| | | 1. | Smooth | 0.013 | 0.013 | |
| | | 2. | Rough | 0.016 | 0.016 | |
| | j. | Vegetal lining | 0.030 | — | 0.500 |
C. | EXACAVATED OR DREDGED | | | |
| | a. | Earth, straight and uniform | | | |
| | | 1. | Clean, recently completed | 0.016 | 0.018 | 0.020 |
| | | 2. | Clean, after weathering | 0.018 | 0.022 | 0.025 |
| | | 3. | Gravel, uniform section, clean | 0.022 | 0.025 | 0.030 |
| | | 4. | With short grass, few weeds | 0.022 | 0.027 | 0.033 |
| | b. | Earth, winding and sluggish | | | |
| | | 1. | No vegetation | 0.023 | 0.025 | 0.030 |
| | | 2. | Grass, some weeds | 0.025 | 0.030 | 0.033 |
| | | 3. | Dense weeds or aquatic plants in deep channels | 0.030 | 0.035 | 0.040 |
| | | 4. | Earth bottom and rubble sides | 0.028 | 0.030 | 0.035 |
| | | 5. | Stony bottom and weedy banks | 0.025 | 0.035 | 0.040 |
| | | 6. | Cobble bottom and clean sides | 0.030 | 0.040 | 0.050 |
| | c. | Dragline-excavated or dredged | | | |
| | | 1. | No vegetation | 0.025 | 0.028 | 0.033 |
| | | 2. | Light brush on banks | 0.035 | 0.050 | 0.060 |
| | d. | Rock cuts | | | |
| | | 1. | Smooth and uniform | 0.025 | 0.035 | 0.040 |
| | | 2. | Jagged and irregular | 0.035 | 0.040 | 0.050 |
| | e. | Channels not maintained, weeds and brush uncut | | | |
| | | 1. | Dense weeds, high as flow depth | 0.050 | 0.080 | 0.120 |
| | | 2. | Clean bottom, brush on sides | 0.040 | 0.050 | 0.080 |
| | | 3. | Same, highest stage of flow | 0.045 | 0.070 | 0.110 |
| | | 4. | Dense brush, high stage | 0.080 | 0.100 | 0.140 |
D. | NATURAL STREAMS | | | |
| D-1. | Minor streams (top width at flood stage 100 ft) | | | |
| | a. | Streams on plain | | | |
| | | 1. | Clean, straight, full stage, no rift or deep pools | 0.025 | 0.030 | 0.033 |
| | | 2. | Same as above, but more stones and weeds | 0.030 | 0.035 | 0.040 |
| | | 3. | Clean, winding, some pools and shoals | 0.033 | 0.040 | 0.045 |
| | | 4. | Same as above, but some weeds and stones | 0.035 | 0.045 | 0.050 |
| | | 5. | Same as above, lower stages, more ineffective slopes and sections | 0.040 | 0.048 | 0.055 |
| | | 6. | Same as 4, but more stones | 0.045 | 0.050 | 0.060 |
| | | 7. | Sluggish reaches, weedy, deep pools | 0.050 | 0.070 | 0.080 |
| | | 8. | Very weedy reaches, deep pools, or floodways with heavy stand of timber and underbrush | 0.075 | 0.100 | 0.150 |
| | b. | Mountain streams, no vegetation in channel, banks usually steep, trees and brush along banks submerged at high stages | | | |
| | | 1. | Bottom: gravels, cobbles, and few boulders | 0.030 | 0.040 | 0.050 |
| | | 2. | Bottom: cobbles with large boulders | 0.040 | 0.050 | 0.070 |
| D-2. | Floodplains | | | |
| | a. | Pasture, no brush | | | |
| | | 1. | Short grass | 0.025 | 0.030 | 0.035 |
| | | 2. | High grass | 0.030 | 0.035 | 0.050 |
| | b. | Cultivated areas | | | |
| | | 1. | No crop | 0.020 | 0.030 | 0.040 |
| | | 2. | Mature row crops | 0.025 | 0.035 | 0.045 |
| | | 3. | Mature field crops | 0.030 | 0.040 | 0.050 |
| | c. | Brush | | | |
| | | 1. | Scattered brush, heavy weeds | 0.035 | 0.050 | 0.070 |
| | | 2. | Light brush and trees in winter | 0.035 | 0.050 | 0.060 |
| | | 3. | Light brush and trees, in summer | 0.040 | 0.060 | 0.080 |
| | | 4. | Medium to dense brush, in winter | 0.045 | 0.070 | 0.110 |
| | | 5. | Medium to dense brush, in summer | 0.070 | 0.100 | 0.160 |
| | d. | Trees | | | |
| | | 1. | Dense willows, summer, straight | 0.110 | 0.150 | 0.200 |
| | | 2. | Cleared land with tree stumps, no sprouts | 0.030 | 0.040 | 0.050 |
| | | 3. | Same as above, but with heavy growth of sprouts | 0.050 | 0.060 | 0.080 |
| | | 4. | Heavy stand of timber, a few down trees, little undergrowth, flood stage below branches | 0.080 | 0.100 | 0.120 |
| | | 5. | Same as above, but with flood stage reaching branches | 0.100 | 0.120 | 0.160 |
| D-3. | Major streams (top width at flood stage 100 ft). The n value is less than that for minor streams of similar description, because banks offer less effective resistance. | | | |
| | a. | Regular section with no boulders or brush | 0.025 | — | 0.060 |
| | b. | Irregular and rough section | 0.035 | — | 0.100 |