SCS Curve Numbers for Urban Areas1
Cover Description		Curve Numbers for Hydrologic Soil Group
Cover Type and Hydrologic Condition	Average Percent Impervious Area2	A	B	C	D
Fully Developed Urban Areas (Vegetation Established)
Open Space (Lawns, Parks, Golf Courses, Cemeteries, etc.):3
Poor condition (grass cover <50%)		68	79	86	89
Fair condition (grass cover 50% to 75%)		49	69	79	84
Good condition (grass cover >75%)		39	61	74	80
Impervious Areas:
Paved Parking Lots, Roofs, Driveways, etc.
(excluding right-of-way)		98	98	98	98
Streets and Roads:
Paved; curbs and storm sewers (excluding right-of-way)		98	98	98	98
Paved; open ditches (including right-of-way)		83	89	92	93
Gravel (including right-of-way)		76	85	89	91
Dirt (including right-of-way)		72	82	87	89
Western Desert Urban Areas:
Natural desert landscaping (pervious areas only)4		63	77	85	88
Artificial desert landscaping (impervious weed barrier desert shrub with 1- to 2-inch sand or gravel mulch and basin borders)		96	96	96	96
Urban Districts:
Commercial and business	85%	89	92	94	95
Industrial	72%	81	88	91	93
Residential Districts by Average Lot Size:
1/8 acre or less (town houses)	65%	77	85	90	92
1/4 acre	38%	61	75	83	87
1/3 acre	30%	57	72	81	86
1/2 acre	25%	54	70	80	85
1 acre	20%	51	68	79	84
2 acres	12%	46	65	77	82
Developing Urban Areas
Newly Graded Areas:
(pervious areas only, no vegetation)5		77	86	91	94
1Average runoff condition, and Ia = 0.2S. 2The average percent impervious area shown was used to develop the composite CN's. Other assumptions are as follows: impervious areas are directly connected to the drainage system, impervious areas have a CN of 98, and pervious areas are considered equivalent to open space in good hydrologic condition. CN's for other combinations of conditions may be computed using figure 2-3 or 2-4 of Technical Release 55, Urban Hydrology for Small Watersheds, USDA, June 1986. 3CN's shown are equivalent to those of pasture. Composite CN's may be computed for other combinations of open space cover type. 4Composite CN's for natural desert landscaping should be computed using figure 2-3 or 2-4 of Technical Release 55, Urban Hydrology for Small Watersheds, USDA, June 1986, based on the impervious area percentage (CN = 98) and the pervious area CN. The pervious area CN's are assumed equivalent to desert shrub in poor hydrologic condition. 5Composite CN's to use for the design of temporary measures during grading and construction should be computed using figure 2-3 or 2-4 of Technical Release 55, Urban Hydrology for Small Watersheds, USDA, June 1986, based on the degree of development (impervious area percentage) and the CN's for the newly graded pervious areas.

SCS Curve Numbers for Cultivated Agricultural Lands1
Cover Description			Curve Numbers for Hydrologic Soil Group
Cover Type	Treatment2	Hydrologic Condition3	A	B	C	D
Fallow	Bare Soil	-	77	86	91	94
	Crop residue cover (CR)	Poor	76	85	90	93
		Good	74	83	88	90
Raw Crops	Straight row (SR)	Poor	72	81	88	91
		Good	67	78	85	89
	SR+CR	Poor	71	80	87	90
		Good	64	75	82	85
	Contoured (C)	Poor	70	79	84	88
		Good	65	75	82	86
	C+CR	Poor	69	78	83	87
		Good	64	74	81	85
	Contoured & terraced (C&T)	Poor	66	74	80	82
		Good	62	71	78	81
	C&T+CR	Poor	65	73	79	81
		Good	61	70	77	80
Small Grain	SR	Poor	65	76	84	88
		Good	63	75	83	87
	SR+CR	Poor	64	75	83	86
		Good	60	72	80	84
	C	Poor	63	74	82	85
		Good	61	73	81	84
	C+CR	Poor	62	73	81	84
		Good	60	72	80	83
	C&T	Poor	61	72	79	82
		Good	59	70	78	81
	C&T+CR	Poor	60	71	78	81
		Good	58	69	77	80
Close-Seeded	SR	Poor	66	77	85	89
		Good	58	72	81	85
	C	Poor	64	75	83	85
		Good	55	69	78	83
	C&T	Poor	63	73	80	83
		Good	51	67	76	80
1Average runoff condition, and Ia = 0.2S. 2Crop residue cover applies only if residue is on at least 5% of the surface throughout the year. 3Hydraulic condition is based on combination factors that affect infiltration and runoff, including (a) density and canopy of vegetative areas, (b) amount of year-round cover, (c) amount of grass or close-seeded legumes, (d) percent of residue cover on the land surface (good >= 20%), and (e) degree of surface roughness. Poor: Factors impair infiltration and tend to increase runoff. Good: Factors encourage average and better than average infiltration and tend to decrease runoff.

SCS Curve Numbers for other Agricultural Lands1
Cover Description		Curve Numbers for Hydrologic Soil Group
Cover Type	Hydrologic Condition	A	B	C	D
Pasture, Grassland, or Range - Continuous Forage for Grazing2	Poor	68	79	86	89
	Fair	49	69	79	84
	Good	39	61	74	80
Meadow - Continuous Grass, Protected from Grazing and Generally Mowed for Hay	-	30	58	71	78
Brush - Brush-Weed-Grass mixture with Brush the Major Element3	Poor	48	67	77	83
	Fair	35	56	70	77
	Good	304	48	65	73
Woods - Grass Combination (Orchard or Tree Farm)5	Poor	57	73	82	86
	Fair	43	65	76	82
	Good	32	58	72	79
Woods6	Poor	45	66	77	83
	Fair	36	60	73	79
	Good	304	55	70	77
Farmstead - Buildings, Lanes, Driveways, and Surrounding Lots	-	59	74	82	86
1Average runoff condition, and Ia = 0.2S. 2Poor: <50% ground cover or heavily grazed with no mulch. Fair: 50% to 75% ground cover and not heavily grazed. Good: >75% ground cover and lightly or only ocassionally grazed. 3Poor: <50% ground cover. Fair: 50% to 75% ground cover. Good: >75% ground cover. 4Actual curve number is less than 30; use CN = 30 for runoff computation. 5CN's shown were computed for areas with 50% woods and 50% grass (pasture) cover. Other combinations of conditions may be computed from the CN's for woods and pasture. 6Poor: Forest litter, small tress, and brush are destroyed by heavy grazing or regular burning. Fair: Woods are grazed but not burned, and some forest litter covers the soil. Good: Woods are protected from grazing, and litter and brush adequately cover the soil.

SCS Curve Numbers for Arid and Semiarid Rangelands1
Cover Description		Curve Numbers for Hydrologic Soil Group
Cover Type	Hydrologic Condition2	A3	B	C	D
Herbaceous - Mixture of Grass, Weeds, and Low-Growing Brush, with Brush the Minor Element.	Poor	-	80	87	93
	Fair	-	71	81	89
	Good	-	62	74	85
Oak-Aspen - Mountain Brush Mixture of Oak Brush, Aspen, Mountain Mahogany, Bitter Brush, Maple, and other Brush.	Poor	-	66	74	79
	Fair	-	48	57	63
	Good	-	30	41	48
Pinyon-Juniper - Pinyon, Juniper, or both; Grass Understory.	Poor	-	75	85	89
	Fair	-	58	73	80
	Good	-	41	61	71
Sagebrush with Grass Understory.	Poor	-	67	80	85
	Fair	-	51	63	70
	Good	-	35	47	55
Desert Shrub - Major Plants include Saltbush, Greasewood. Creosotebush, Blackbrush, Bursage, Palo Verde, Mesquite, and Cactus.	Poor	63	77	85	88
	Fair	55	72	81	86
	Good	49	68	79	84
1Average runoff condition, and Ia = 0.2S. For range in humid regions, use "SCS Curve Numbers for other Agricultural Lands." 2Poor: <30% ground cover (litter, grass, and brush overstory). Fair: 30% to 70% ground cover. Good: >70% ground cover. 3Curve numbers for group A have been developed only for desert shrub.