Adaptation of Horton and SCS Infiltration Equations to Complex Storms

Two equations commonly used for estimating and modeling infiltration from pervious land surfaces are those developed by Horton and the U.S. Soil Conservation Service (SCS). The main shortcoming of the Horton equation is the strong dependence of the infiltration rate on the starting time of the rain, which becomes particularly critical when a rainfall event starts at a low intensity. The SCS equation, which was originally developed for runoff and later converted to compute infiltration losses, suffers from the complete lack of a time relationship. The problems associated with these shortcomings are discussed in this paper. The Horton equation is modified to make the infiltration rate a function of cumulative antecedent infiltration. A linear filter, in conjunction with two of the Horton parameters, is suggested to delay the SCS infiltration increments. In addition, a concept proposed by Bauer to incorporate deep percolation into infiltration equations is adopted to provide for the recovery of infiltration capacity between consecutive storm bursts.