Runoff Curve Number

Runoff curve number, abbreviated as CN, a dimensionless number, is the water flow that occurs when the soil is infiltrated to full capacity and excess water or rain.

 

Runoff Curve Number Formula
\(\large{ CN = \frac{ 1000 }{ S \;+\; 10 }  }\)
Symbol	English	Metric
\(\large{ CN }\) = runoff curve number	\(\large{dimensionless}\)
\(\large{ S } \) = the potential maximum soil moisture retention after runoff begins	\(\large{lbf}\)	\(\large{N}\)