i’m not an engineer, so maybe others with experience can comment, but isn’t it unusual there’s only 1 main spillway? other dams around here have several so that even if 1 failed, they could cut it and still keep releasing. isn’t engineering for safety about redundancy?
It depends on the purpose of the dam, if it is hydro electric or water reservoir only. Other factors are storm flow/snow pack modeling when originally designed. Snow pack melt is trickier because it may come off all at once if temperatures rise too fast or over a longer period of time if temperatures rise more slowly.
The emergency spillway should have been designed at an elevation and width that would have prevented the extreme stresses on the dam structure which would lead to catastrophic failure.