I am in Delaware rather than Florida. A quick search indicates it is a minimum of 12 inches above the base flood elevation statewide. However, certain types of facilities is more and specific flood hazard management communities can require more. You should check with your local building code official.
I understand that if you area in a flood zone it is 12".
What got me wondering is that I design a pond with the 100 yr storm.
Is that now the flood zone and I need to be 12 inches above it?
Yes, you should be at least 1 foot above your 100-year pond elevation. In some circumstances you should be higher than that. It depends on the outfall and surrounding topography.