Runoff curve number

Description

Surface runoff is the water flow that occurs when the soil is infiltrated to full capacity and excess water from rain. The runoff curve number (also called a curve number or simply CN) is an empirical parameter used in hydrology for predicting direct runoff or infiltration from rainfall excess. CN has a range from 30 to 100. Lower numbers indicate low runoff potential while larger numbers are for increasing runoff potential. The lower the curve number, the more permeable the soil is.

Related formulas

Variables

CNRunoff curve number (dimensionless)
SThe potential maximum soil moisture retention after runoff begins ( the potential maximum soil moisture retention after runoff begins (dimensionless in this equation) (dimensionless)