// multi-utility computation suite · offline · instant · precise
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sci.SCS-CN-runoff-depth Calculator
Calculates runoff depth Q from rainfall depth P using the USDA-NRCS SCS curve number method: Q = (P−Ia)²/(P−Ia+S), where Ia = 0.2S. CN = 75 (moderate imperviousness) and P = 50 mm gives Q = 11.3 mm — CN ranges from 35 (forests on A soils) to 98 (impervious surfaces).
Inputs
P Mm
Reference formula or conversion factor shown for context.
Cn
Count of items or occurrences.
Ia Factor
A multiplier applied in the calculation.
Results
direct runoff Q (mm)
Sample size or count used in the calculation.
potential max retention S (mm)
Sample size or count used in the calculation.
initial abstraction Ia (mm)
Sample size or count used in the calculation.
actual infiltration F (mm)
The proportional relationship between two quantities.