SCS Curve Number

The SCS curve number is a function of the soil’s permeability, land use and antecedent soil water conditions. Typical curve numbers for moisture condition II are listed in tables 2:1-1, 2:1-2 and 2:1-3 for various land covers and soil types (SCS Engineering Division, 1986). These values are appropriate for a 5% slope.

Table 2:1-1: Runoff curve numbers for cultivated agricultural lands (from SCS Engineering Division, 1986)

* Crop residue cover applies only if residue is on at least 5% of the surface throughout the year.

[2] Poor: < 50% ground cover or heavily grazed with no mulch;

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[1] Poor: < 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 occasionally grazed

[2] Poor: < 50% ground cover; Fair: 50 to 75% ground cover; Good: > 75% ground cover

[3] Poor: Forest litter, small trees, 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.

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[1] Poor: < 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 occasionally grazed

[2] Poor: < 50% ground cover; Fair: 50 to 75% ground cover; Good: > 75% ground cover

[3] Poor: Forest litter, small trees, 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.

[2] Poor: < 50% ground cover or heavily grazed with no mulch;

[3] Fair: 50 to 75% ground cover and not heavily grazed;

[4] Good: > 75% ground cover and lightly or only occasionally grazed