Preferential Flow and Hydraulic Conductivity of Forest Soils

Macroscopic analytical methods, based upon the capillary rise formula and the Hagen‐Poiseuille equation, were used to quantify the combined effects of soil‐pore size and preferential flow on the hydraulic conductivity of forest soils. A density function was derived that relates effective pore diameters of heterogeneous soil‐pore systems to measured hydraulic conductivity. Density functions derived for soils from sites with different topographic influences and disturbance effects characterized the effect of preferential flow on their hydraulic conductivity. It was shown that macroscopic methods can describe preferential flow without having to resort to microscopic examination of individual pores. If the required properties of the undisturbed parent soil (hydraulic conductivity and equivalent pore size) have been characterized, then these methods can predict the effect of disturbance on the hydraulic behavior of the soils.