In order to fundamentally reduce the overtopping and failure rate of small earth-rockfill dams, a scaled-down model was established based on a small earth-rockfill dam project with an actual height of 15 m. The downstream slope protection was constructed using turf, cemented soil, and dry-laid stone masonry. The influence of different scour-resistant slope protection materials on the overtopping and failure process of the earth-rockfill dam was analyzed. The evolution law of breach shapes was studied, and in combination with the flow velocity and flow rate changes at the breach section, the effectiveness of different scour-resistant material-based downstream slope protection in resisting erosion damage was deeply explored. The experimental results show that under stable inflow conditions, the use of materials with high scour resistance, such as cemented soil and dry-laid stone masonry, in downstream slope protection significantly reduces the erosive force of overtopping water. This substantially extends the duration of overtopping and failure by 2-3 times. The maximum flow velocity at the breach is reduced by approximately 3%, while the maximum cross-sectional discharge decreases by a range of 10%-12%. In contrast, turf-based slope protection offers only modest delay in erosion damage, extending the breach duration by approximately one fold.