Fingered preferential flow in unsaturated homogeneous coarse sands

The occurrence of fingered preferential flow depends on both flow and porous media characteristics. The boundary condition of unsaturated infiltration has been investigated to assess whether it produces unstable wetting in homogeneous coarse sands. Laboratory tracer experiments were conducted in two coarse sand materials; for each sand material two initial conditions of air dry and field capacity were considered. Results indicate that the commonly occurring process of nonponding rainfall can provoke fingered preferential flow in homogeneous sandy soils. This phenomenon is very predominant in dry as compared to wet initial conditions. Models of water flow and solute transport in uniform coarse soils should incorporate the effects of such fingered flow phenomenon.