Critical rainfall duration for overland flow from an infiltrating plane surface

Abstract

Design flows from infiltrating micro-catchments are investigated using a kinematic model of overland flow and a physics-based representation of the infiltration process. Critical storm duration is shown to be governed by two relationships, one equivalent to the traditional approach of setting concentration time equal to rainfall duration and the other yielding a potentially critical duration independent of plane length. In case of two competing results, the valid one is recognized as giving the shorter of the two durations calculated. Derivation of the governing equations has been carried out preserving as much generality as possible. In addition to the equations mentioned, a “rainfall window” describing all overland flow producing storms in accordance with a given intensity-duration-frequency (IDF) relationship is identified and mathematical expressions for its evaluation are given. Practical application is demonstrated by a number of sample computations. © 1997 Elsevier Science B.V.