The following table presents suggested Curves Numbers for use with SCS hydrology. For additional information, see Urban Hydrology for Small Watersheds, Technical Release 55, United States Department of Agriculture, June 1986


Land Use

Percent Impervious

Hydrologic Soil Group

A

B

C

D

Urban Areas






Parking lots, roofs, driveways and streets

100

98

98

98

98

Commercial development

85

89

92

94

95

Industrial development

72

81

88

91

93

Residential development






1/8 acre lots or less

65

77

85

90

92

1/4 acre lots

38

61

75

83

87

1/3 acre lots

30

57

72

81

86

1/2 acre lots

25

57

70

80

85

1 acre lots

20

51

68

79

84

Pervious Areas






Lawns, parks, golf course, cemeteries

-

39

61

74

80

Pasture for grazing (not mowed)

-

39

61

74

80

Meadows (mowed for hay)

-

30

58

71

78

Brushy areas

-

30

48

65

73

Woods

-

30

55

70

77