Runoff Curve Number

Written by Jerry Ratzlaff on . Posted in Geotechnical Engineering

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

 $$\large{ CN = \frac{ 1000 }{ S \;+\; 10 } }$$

Where:

$$\large{ CN }$$ = runoff curve number

$$\large{ S }$$ = the potential maximum soil moisture retention after runoff begins