I-D-F e, b, d Equation

I-D-F curves can be fit to equations. The most common form of these equations is:


I	=	rainfall intensity (in/hr.)
T	=	rainfall duration (min.)
e, b, d	=	rainfall equation coefficients

This equation represents the mathematical relationship between the rainfall intensity and the rainfall duration for a storm of a given frequency and a given geographical location. The rainfall equation coefficients vary with storm data frequency and storm data location.

To use rainfall equations properly requires that they yield results that are consistent with the historical rainfall data for the design locale. If the preceding equation does not provide such consistency, then it is not appropriate for your design.