How does a ski-jump spillway reduce erosion below a high dam?

A ski-jump spillway reduces erosion below a high dam by deflecting the jet of spilling water away from the base of the structure.12

By discharging the water from a level above the dam's foundation, the spillway ensures that the high-velocity flow lands well clear of the immediate downstream area. This design prevents the intense, concentrated erosion of the riverbed that typically occurs at the toe of a dam when water is allowed to flow directly down the structure's face. By shifting the impact zone farther downstream, the energy of the water is dissipated in a location where it is less likely to compromise the structural integrity of the dam's foundation.12