Comparative analysis of two infiltration models for application in a physically based overland flow model

In the prediction of overland flow, infiltration is an essential component, which should be modeled accurately to achieve optimum runoff rates. Many mathematical models that simulate the details of runoff and erosion process in hillslopes, where the rill-interrill configuration significantly affects overland flow, employ Horton’s model for infiltration due to its simplicity. However, Horton’s model does not handle adequately antecedent moisture condition (AMC) of soil. In this study, the Green-Ampt infiltration model is incorporated into a physically based overland flow model, which was originally coupled with Horton’s equation in an effort to improve the overland flow model’s prediction ability. In so doing, the model used the Horton and Green-Ampt model as an infiltration component separately and simulated flow to directly compare which infiltration equation performs better with the overland flow model. Calibration using laboratory data produced good results for both Horton with NSE = 0.88 and r² = 0.92 and Green-Ampt with NSE = 0.90 and r² = 0.95 while in validation, the Horton-coupled model produced lower NSE = 0.64 and r² = 0.84 than the Green-Ampt which produced NSE = 0.85 and r² = 0.85. The results suggest that the Green-Ampt equation can improve the performance of the overland flow model with its ability to account more accurately the AMC and flow processes in the soil.