Numerous empirical equations have been proposed to estimate the soil-water characteristic curve (SWCC). Based on the Fredlund and Xing model, a new estimation method is proposed to consider the effect of initial porosity on the SWCC. The test data from the literature are used for fitting and verifying the proposed model. From the verification results in Table 1, it can be seen that the proposed method provides significantly better estimation of SWCC for the granular soils with different initial porosities. In addition, the uncertainty of measurement data is analyzed and applied in estimating the relative permeability function (kr). Figure 1 shows that the proposed method can better predict the kr values with smaller uncertainty than the Fredlund and Xing equation.