Table of Runoff Curve Numbers (SCS, 1986)

Description of Land Use

Hydrologic Soil Group

A

B

C

D

Paved parking lots, roofs, driveways

98

98

98

98

Streets and Roads:

     Paved with curbs and storm sewers

98

98

98

98

     Gravel

76

85

89

91

     Dirt

72

82

87

89

Cultivated (Agricultural Crop) Land*:

     Without conservation treatment (no terraces)

72

81

88

91

     With conservation treatment (terraces, contours)

62

71

78

81

Pasture or Range Land:

     Poor (<50% ground cover or heavily grazed)

68

79

86

89

     Good (50-75% ground cover; not heavily grazed)

39

61

74

80

Meadow (grass, no grazing, mowed for hay)

30

58

71

78

Brush (good, >75% ground cover)

30

48

65

73

Woods and Forests:

     Poor (small trees/brush destroyed by over-grazing or burning)

45

66

77

83

     Fair (grazing but not burned; some brush)

36

60

73

79

     Good (no grazing; brush covers ground)

30

55

70

77

Open Spaces (lawns, parks, golf courses, cemeteries, etc.):

     Fair (grass covers 50-75% of area)

49

69

79

84

     Good (grass covers >75% of area)

39

61

74

80

Commercial and Business Districts (85% impervious)

89

92

94

95

Industrial Districts (72% impervious)

81

88

91

93

Residential Areas:

     1/8 Acre lots, about 65% impervious

77

85

90

92

     1/4 Acre lots, about 38% impervious

61

75

83

87

     1/2 Acre lots, about 25% impervious

54

70

80

85

     1 Acre lots, about 20% impervious

51

68

79

84