This study presents a comprehensive sensitivity analysis of key hydraulic and geometric parameters influencing seepage through zoned earth dams, which is crucial for safe and effective hydraulic structure design. Using the Seep/w numerical model, more than 50 zoned earth dam
models were developed representing various hydraulic and geometric parameters. The sensitivity index (SI) approach is used to assess the input variables effect on different seepage outputs. The results revealed that the core permeability coefficient is the most influential factor, with
reductions of up to 99% observed in both seepage discharge and flow velocity. The downstream transition zone also plays a significant role, particularly on the pressure head, which showed an increase of approximately 70% under varying transition zone properties. Among the geometric parameters, core thickness and side slope are critical in controlling seepage, with increases in core
thickness and side slope resulting in up to 66% and 85% reductions in seepage discharge, respectively. These findings highlight the necessity of jointly considering hydraulic and geometric parameters for accurate seepage prediction and effective design of zoned earth dams.