| Cavitation number σ | Design requirements |
| >1.80 | No cavitation protection is required |
| 0.25 - 1.80 | The flow surface can be protected by flow surface treatment (e.g. smoothing all surface roughness) |
| 0.17 - 0.25 | Modification of the design (e.g. increasing boundary curvature) |
| 0.12 - 0.17 | Protection by addition of aeration grooves or steps |
| <0.12 | Surface cannot be protected and a different configuration is required (assumption) |