Rainfall Intensity‐Duration‐Frequency Formulas

Abstract

A new general rainfall intensity‐duration‐frequency formula is presented, utilizing a method similar to, but more accurate than one previously developed. The previously developed formula was based on the average depth‐duration ratio of about 40 percent and the mean depth‐frequency ratio of 1.48. It is shown that this formula is only a particular form of the writer's more general formulation. The earlier formula, however, requires only the 10‐yr 1‐hr rainfall depth instead of the writer's three rainfall depths (i.e., 10‐yr 1‐hr, 10‐yr 24‐hr, and 100‐yr 1‐hr). The ratios of 1‐hr to corresponding 24‐hr depth and 100‐yr to corresponding 10‐yr depth can be computed from the required three rainfall depths in the writer's method so that geographical variation of rainfall can be evaluated in terms of both ratios.