Flood zone

Flood zones are the FIRM's risk vocabulary: the Special Flood Hazard Area zones covering the one-percent-annual-chance floodplain — including the coastal high-hazard designations where wave action adds structural standards — and the moderate- and minimal-hazard designations outside it. Zone identity determines which rules attach: insurance mandates and construction standards concentrate in the SFHA, with the strictest requirements in the wave-exposed coastal zones.

Zone letters are shorthand, not physics: they encode which flood source was studied and what the model concluded at adoption. Two practical cautions follow — zone boundaries are horizontal lines over vertical risk, and minimal-hazard designation means the map's studied sources, not all water. Elevation and loss history complete what the letter starts.