How does riprap protect the upstream face of an embankment dam?

Riprap protects the upstream face of an embankment dam by acting as a protective layer of stones or concrete chunks placed on the slope.1

This layer is essential for maintaining the structural integrity of the dam by preventing erosion caused by wave action. Because embankment materials—such as earth or rockfill—can be susceptible to the movement of water, the riprap serves as a physical barrier that shields the finer soil particles from being washed away by the constant motion of the reservoir water. By mitigating this surface erosion, riprap helps ensure the side slopes remain stable and prevents the degradation of the dam's upstream face.21