Preferential flow velocity mapping of alluvial soil using temporal electrical resistivity imaging

Riparian soils are susceptible to the formation of macropores, which provide opportunities for preferential flow in comparison to the surrounding soil matrix. Temporal electrical resistivity imaging (TERI) can locate spatial heterogeneities in soil wetting patterns caused by preferential flow through macropores. Quantifying macropore flow properties is important to optimize the design of riparian buffers. In a field evaluation of a riparian area with naturally occurring macropores, the TERI technique is able to detect the wetted zone around a macropore similar to a high hydraulic conductivity zone in a heterogeneous soil matrix. An experiment was established in a coarse soil in North Carolina to evaluate if TERI datasets could quantify the hydraulic properties of both the soil matrix and the preferential macropore pathways. Results show TERI is a viable method for calculating the vertical fluid velocity along orthogonal profiles in this coarse-grained field site. The datasets allowed the distribution and hydraulic properties of the preferential flow pathways to be quantified over a two-dimensional plane that is comparable with traditional soil datasets.