The area within a flood plain subject to a 1-percent or greater chance of flooding in any given year.
The area designated as a flood hazard area on a community’s flood hazard map or as otherwise legally designated.
(International Plumbing Code® 202.0)
Mechanical Code…
The greater of the following two areas:
(1) The area within a floodplain subject to a 1 percent or greater chance of flooding in any given year.
(2) The area designated as a flood hazard area on a community’s flood hazard map, or otherwise legally designated.
(Uniform Mechanical Code® 208.0)