<p>In this study, experiments were conducted on physical models to simulate heavy rainfall in reservoirs. The primary aim was to clarify how the inclination of the embankment foundation terrain affects seepage behavior within the embankment during water storage and rainfall infiltration. Seepage behavior was measured under three conditions: water-level rise only, rainfall only and a combination of both. Embankments with inclined foundations exhibited water seepage times one-third shorter than those without inclination, particularly at the downstream toe. Conversely, the seepage lines were 30&#xa0;mm lower than those in embankments without inclination. This indicates that seepage flow converging toward the inclined foundation terminal intensified outflows toward the exterior, which potentially increases failure susceptibility. For inclined embankments, the hydraulic gradient at the downstream toe during failure was approximately 0.4. The findings demonstrate that conventional design guidelines are insufficient for evaluating reservoir stability, making a three-dimensional assessment that considers rainfall infiltration and foundation inclination essential.</p>