Theory 29/Water Resources Engineering
Spillway Safety Is a Flood Ratio
The claim
Dam safety is set by the ratio of spillway capacity to probable maximum flood, not by the return period used in design.
01Mechanism
Overtopping is the failure mode that matters; whether it occurs depends on capacity relative to the extreme event, not on the frequency of ordinary floods.
02Predictions
- P1Overtopping risk should track the ratio.
- P2Design return period alone should mispredict.
03Refutation
Risk tracking design return period would remove the ratio.