The runoff coefficient is a term used to describe the fraction of total rainfall that is a part of the total runoff volume for a certain area of land. It can also be used to describe the ratio of the depth of the runoff to the depth of rainfall.
The runoff coefficient is a mathematical number that is used to describe the amount of rainfall in a certain area of land. Runoff of water occurs during heavy rainfall. Different land masses have different runoff abilities. This gives them different runoff coefficients. Factors that may alter the runoff coefficients include soil types, vegetation and the slope of the land.