Most soils in nature exhibit some degree of layering, while infiltration theory is largely confined to homogeneous profiles. This study was conducted to describe general infiltration features of a two‐layer system, including the often‐studied crust case as a limit. The general analytic theory for infiltration models leads to several related robust relations for homogeneous soils. The resulting analytic expressions relate infiltrability, f , to infiltrated water, I . This type of expression is uniquely general in describing the decay of f with I for either saturation or flux boundary conditions, and in describing the onset of ponding for flux boundary conditions. This study explores the applicability of this theory when the soil profile is composed of two layers. A numerical solution of Richards' equation is used as an experimental tool, applied to a general set of possible soil changes that may occur at the layer interface. The special case of layers with “absorption matched” infiltrability parameters exhibits complex behavior when the interface is encountered at large I . The behavior of the layered system exhibits the same unifying f ( I ) response to flux boundary conditions as does a homogeneous profile, which lends unexpected generality to the I ‐based analytical infiltration model.
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Roger E. Smith (1990) studied this question.