<p>Seepage studies related to earth dams are essential for such dams’ planning and building processes to ensure necessary safety and efficiency. The core layer plays a vital role in decreasing the seepage flow through the body of the earth dams and increasing the safety factor of the hydraulic structures against the piping phenomena and their failure. This study numerically analyzes seepage in zonal embankment dams. The objective is to investigate the impact of core dimensions on flow through dams to determine the optimal dimensions and materials. SEEP/W model examines seepage through the interior core of zoned earth dams, while the numerical model evaluates slope stability and failure. The study is divided into two phases: first, it looks at how different zone forms affect dam construction and geometry; second, it looks at how different core materials affect dam construction and geometry. The shapes examined were the vertical shape, the trapezoidal core, and the inverse trapezoidal shape with different b/h and B/h ratios. The core dimensions are established based on minimum seepage, exit gradient, and maximum safety factor. The findings indicated that the ideal configurations are a trapezoidal core exhibiting ratios of b/h = 0.2 and B/h = 1.3. Three types of material were used: mealy dolomite, normal clay, and sand type C. Sand type C outperformed all other types of clay in reducing leakage and exit gradients (by about 97.6%), and powder dolomite provided a good safety factor result (by about 1.72%).</p>