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.