Abstract
Fast water infiltration during heavy rainfall events is an important issue for hillslope hydrology and slope stability. Most hillslopes are strongly heterogeneous and contain macropores and soil pipes, so that infiltrating water can bypass the soil matrix and reach rapidly deeper regions. Water infiltration into macroporous soils is usually simulated with dual-permeability models based on Richards equation (RDPM) which only describes water flow. In this article, we present a two-phase dual-permeability model (TPDPM) for simulating water and air flow in macroporous soils. Water and air flow are simulated in both domains and mass transfer for water and air between the domains is included with first-order transfer terms. The main objectives of this article are to discuss the differences between TPDPM and RDPM and to test the application of the TPDPM on the slope scale. First, the differences between RDPM and TPDPM were studied using a one-dimensional layered soil. For the chosen high infiltration rate, we observed significant differences in the macropore domain and small differences in the matrix depending on the transfer parameter. Second, we applied the model to simulate fast water infiltration and flow through an alpine hillslope, where the water flow mainly occurs in the macropore domain and the matrix domain is bypassed because it is low permeability. A good agreement of simulated and measured travel times of Wienhöfer et al. (Hydrol Earth Syst Sci 13(7):1145--1161, 2009) was obtained. Finally, we recommend using TPDPM for high infiltration in layered macroporous soils.
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