Direct Numerical Simulation of Hortonian Runoff Resulting from Heterogeneous Saturated Hydraulic Conductivity

Abstract

A two-dimensional rainfall-runoff model is used to systematically explore the aggregate effect of spatially heterogeneous saturated hydraulic conductivity, Ks , on Hortonian runoff generation. The fully dynamic model integrates overland flow and infiltration to allow for the “interactive infiltration” process (run-on). Rainfall events varying in time and intensity were simulated on synthetic hillslopes with random and spatially correlated Ks fields. Model grid size discretization recommendations are developed to fully capture the variation in Ks and avoid limiting the spatial interactive infiltration opportunities as found in analysis of the effects of model grid size on spatially uncorrelated hillslopes. Our results show that on highly correlated Ks fields, relative to the hillslope length, the infiltration due to interaction is less than half that of uncorrelated fields for low intensity events. Previous findings, are also substantiated and further explored, with explicit consideration of model discreti...