You can lower the full supply level to create airspace or a flood mitigation zone. This would trade off the available water supply in exchange for dam safety protection.

However, almost all dams in an extreme event are filled multiple times over by the inflow, thus making any lowering of the storage prior to the event futile.

But it is a valid point and in some dams can be useful.

How you mean construction methods? Dams generally are not supposed to overtop and the spillway prevents this. But if the rainfall is more intense the spillway may not be large enough, resulting in overtopping (which fails the dam).

Unfortunately it’s more extreme events and lesser annual rainfall. So bad news bears for humanity in general.