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Value of "n" 0.016-0.017 0.020 0.0225 0.025 0.030 0.035 0.040-0.050 0.060-0.075 0.100 0.125 0.150-0.200 Table 4.01.* Coefficient of roughness, average channels Channel Condition Smoothest natural earth channels, free from growth, with straight alignment. Smooth natural earth channels. free from growth, little curvature. Average, well-constructed, moderate-sized earth channels in good condition. Small earth channels in good condition, or large earth channels with some growth on banks or scat- tered cobbles in bed. Earth channels with considerable growth. Natural streams with good alignment, fairly constant sec- tion. Large floodway channels, well maintained. Earth channels considerably covered with small growth. Cleared but not continuously mai ntained floodways. Mountain streams in clean loose cobbles. Rivers with variable section and some vegetation growing in banks. Earth channels with thick aquatic growths. Rivers with fairly straight alignment and cross section. badly obstructed by small trees, very 1 ittle underbrush or aquatic growth. Rivers with irregular alignment and cross section. moderately obstructed by small trees and underbrush. Rivers with fairly regular alignment and cross sec- tion. heavily obstructed by small trees and underbrush. Rivers with irregular alignment and cross section, covered with growth of virgin timber and occasional dense patches of bushes and small trees, some logs and dead fallen trees. Rivers with very irregular alignment and cross sec- tion, many roots. trees. bushes, large logs and other drift on bottom, trees continually falling into chan- nel due to bank caving. * From EM 1110-2-1409 (Reference 20) 4.08