Comparison of Horton's, Smith's, and Green-Ampt's infiltration equations using flooding infiltrometer data in engineering applications

The hydrologic cycle represents the interaction of water between the earth's surface and the earth's atmosphere. Precipitation, evaporation, interception, infiltration, surface runoff, and subsurface flow make up the integral components of the hydrologic cycle (Veissman et al., 1989). The hydrologic cycle is of major interest to engineers. Many times, small, ungaged watersheds are the focus of engineering projects. The desired project outcome consists of the basin's direct runoff hydrograph because the runoff hydrograph provides a peak flow rate, time of peak flow, and a volume of direct runoff. Engineers use these values to design flood protection.

Engineers are always searching for more accurate ways to model small, ungaged watersheds. The current standard practice is to use a design storm in conjunction with the Natural Resources Conservation Service (NRCS) Curve Number (CN) Procedure to predict abstractions for a storm event to produce a direct runoff hydrograph for the basin (Veissman et al., 1989). The NRCS-CN procedure is simple to use to estimate abstractions, but simplicity does not always produce the most accurate solution.

The major research objective is to show that infiltration equations improve confidence in the results of a surface-runoff analysis for intense short-duration stormevents. The infiltration equations used for this research are the Horton (1933), Smith (1972), and Green-Ampt(1911) infiltration equations.