Manning's n

Manning's 'n' of vegetated surfaces

'n' value range	Good condition turf grass	Other
0.002 - 0.010	Where the average depth of flow is at ≥ 2 times the height of the vegetation	Supple tree seedlings such as willow or cottonwood growing where the average depth of flow is at ≥ 3 times the height of the vegetation
0.010 - 0.025	Where the average depth of flow is between 1 - 2 times the height of the vegetation	Moderately dense weeds, or tree seedlings growing where the average depth of flow is from 2 -3 times the height of the vegetation
0.025 - 0.050	Where the average depth of flow is about equal to the height of the vegetation	8- to 10-year-old willow or cottonwood trees inter-grown with some weeds and brush (none of the vegetation in foliage)
0.050 - 0.100	Where the average depth of flow is < 0.5 times height of the vegetation	bushy willow trees about 1 year old inter-grown with weeds along side slopes (all vegetation in full foliage)