On the interaction between infiltration and Hortonian runoff

A model which couples the kinematic wave approximation for Hortonian overland flow and the conceptual approach developed by; Corradini er cri. (1997) [J. Hydrol., 192, 104-124] For local infiltration was used to investigate the effects of random spatial variability of saturated hydraulic conductivity, K-s, on the outflow hydrograph at hillslope scale. The model incorporates a representation of infiltration of overland flow running over pervious downstream areas ("run-on" process). Single rainfall pulses and complex storms over two soils. representative of a silty loam and a sandy loam soil, were considered. Our results suggest that for realistic values of the coefficient of variation of K-s, the nln-on process cannot be disregarded, because it produces a significant decrease of overland flow during both the rising and the recession limb of the hydrograph. Furthermore, the role of the level of spatial correlation of K-s was found to be typically minor and the run-on process concurred to this result. The possibility of simplifying the stochastic problem by a deterministic approach based on the use of a uniform lumped value of K-s was also examined and rainfall patterns adequate for this simplification were deduced in terms of scaled storm intensity and storm duration. (C) 1998 Elsevier Science B.V.