Transient seepage analysis using numerical methods is characterized by an increase in the required number of input parameters when compared with a steady-state analysis. Among these additional parameters are those that represent unsaturated soil characteristics, and obtaining these unsaturated soil properties is generally more difficult, requires special testing apparatus, takes longer than conventional tests, and thus costs more. To obtain more reliable transient seepage results with reasonable effort, this study demonstrates which input parameters are more critical and sensitive to the modeling results. The soil water characteristic curve, volumetric water content, and saturated hydraulic conductivity are determined experimentally and varied within a reasonable range of each value in the numerical model; and the pore water pressure at a certain point in the model is compared to determine the influence of each parameter on the modeling results. Based on this analysis, the most sensitive and critical parameters are identified. These results will allow an assessment of the relative cost-benefit ratio so that the desired accuracy can be achieved at lowest cost.