Laserfiche WebLink
ING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL <br /> TABLE 4.3.7B VALUES OF THE ROUGHNESS COEFFICIENT$ one <br /> Type of Channel Manning's Type of Channel Manning's <br /> and Description ®n and Description 'n• <br /> (Normal) (Normal) <br /> A. Constructed Channels 6. Sluggish reaches, weedy 0.070 <br /> a. Earth, straight and uniform deep pods <br /> 1. Clean, recendiy completed 0.018 7. Very weedy reaches, deep O.t00 <br /> 2. Gravel, uniform section, 0.025 pods, or floodways with <br /> dean heavy stand of timber and <br /> 3. With short grass,few 0.027 underbrush <br /> wows b. Mountain streams, no vegetation <br /> b. Earth, winding and sluggish 0.025 in channel, banks usually steep, <br /> 1. No vegetation 0.025 trees and brush along banks <br /> 2. Grass, some weeds 0.030 submerged at high stages <br /> 3. Dense weeds or aquatic 1. Bottom: gravel, cobbles, and 0.040 <br /> plants In deep channels 0.035 few boulders <br /> 4. Earth bottom and rubble 2. Bottom: cobbles with large 0.050 <br /> sides 0.030 boulders <br /> 5. Stony bottom and weedy B-2 Flood plains <br /> banks 0.035 a. Pasture, no brush <br /> 6. Cobble bottom and dean 1. Short grass 0.030 <br /> sides 0.040 2. High grass 0.035 <br /> c. Rock lined b. Cultivated areas <br /> 1. Smooth and uniform 0.035 1. No crop 0.030 <br /> 2. Jagged and irregular 0.040 2. Mature raw crops 0.035 <br /> d. Channels not maintained, 3. Mature field craps 0.040 <br /> weeds and brush uncut c. Brush <br /> 1. Dense weeds, high as flow 1. Scattered brush. heavy 0.050 <br /> depth 0.080 w s <br /> 2. Clean bottom, brush on 2. Light brush and trees 0.060 <br /> sides 0.050 3. Medium to dense brush 0.070 <br /> 3. Same, highest stage of 4. Heavy, dense brush 0.100 <br /> flow 0.070 d. Trees <br /> 4. Dense brush, high stage 1. Dense willows, straight 0.150 <br /> B. Natural Streams 0.100 2. Cleared land with tree 0.040 <br /> B-1 Minor streams (top width at stumps, no sprouts <br /> flood stage < 100 ft.) 3. Same as above, but with 0.060 <br /> a. Streams on plain heavy growth of sprouts <br /> 1. Clean, straight, full stage 4. Heavy stand of timber, a few 0.100 <br /> no rifts or deep pods 0.030 down trees, little <br /> 2. Same as above, but more undergrowth, flood stage <br /> stones and weeds 0.035 below branches <br /> 3. Clean, winding, some 5. Same as above, but with 0.120 <br /> pods and shoals 0.040 good stage reaching <br /> 4. Same as above, but some branches <br /> weeds 0.040 <br /> 5. Same as 4, but more <br /> stones 0.050 <br /> "Note,these 'n'values are 'normal'values for use in analysis of channels. For conservative design for <br /> ;hannel capacity the 'maximum'values listed in other references should be considered. For channel bank <br /> stability the minimum values should be considered. <br /> 43.7-7 1/90 <br />