I don't pretend to know the answer to your question, other than to say that the controllers will always have a bit up their sleeve for unexpected events.
Where I live, just after the Christmas flooding there was a sudden cloudburst below the dam. Fortunately there was enough capacity in the dam's flood mitigation airpsace to allow the outflow to be briefly lowered dramatically. Which totally avoided damage downstream from the unexpected cloudburst.
Are you sure that there will be no more heavy rain today or tomorrow?
