Underlying parameters affecting estimation of unsaturated permeability of soils

To date numerous indirect models have been proposed to estimate unsaturated permeability function of a soil from its Soil-Water Characteristic Curve (SWCC). These models were usually developed by combining a soil-water characteristic curve best-fit equation and a relative permeability (integration method) equation. However, not all the models lead to the same results and they vary significantly from one to another. Therefore, there is a need to investigate the underlying parameters which cause the variation between different models. A comparative study was performed on some existing and new combined estimation models. It was found from the study, that the SWCC best-fit equation and the measurement range of SWCC data greatly affect the estimation of unsaturated permeability of soils as compared to relative permeability equations.