The fldzone attribute on each parcel is FEMA's flood zone designation, taken from the National Flood Hazard Layer (NFHL) and joined to the parcel by spatial overlay. This reference documents every value that can appear in that column — one page per zone — along with the related zonesubty, staticbfe, firmid, and firmdate columns described in the Table Schema.

What a flood zone is

A flood zone is a geographic area that FEMA has classified according to its risk of flooding, as depicted on a Flood Insurance Rate Map (FIRM). Zones are the basis for floodplain-management building requirements and for the flood-insurance rating used by the National Flood Insurance Program (NFIP). The single most important distinction is whether a parcel falls inside the Special Flood Hazard Area (SFHA) — the area with a 1% or greater chance of flooding in any given year (the "100-year floodplain").

The three risk tiers

Two further values — covered on the Special values page — are not risk classes at all:

• OPEN WATER — the polygon is a body of water, not land subject to a hazard rating.
• AREA NOT INCLUDED — the area was deliberately excluded from the FIRM study.

A note on the letters

The letters follow a rough logic worth internalizing:

• A = riverine / inland 1%-annual-chance flooding (no wave action).
• V = coastal 1%-annual-chance flooding with wave action ("V" for velocity). Always more hazardous than the equivalent A zone.
• A trailing E (AE, VE) or a number (A1–A30, V1–V30) means a Base Flood Elevation has been determined. The bare letters (A, V) mean no BFE was computed.
• H and O describe how the water arrives — ponding (AH) versus sheet flow (AO).
• X (and legacy B/C) = outside the high-risk floodplain.
• D = not yet studied.

How the values map to zonesubty

fldzone gives the zone; zonesubty refines it. Common pairings you will encounter in the data:

Each zone page below covers the subtypes that apply to it.

Reference pages

High-risk — inland (A family)

• Zone A — 1% annual chance, no BFE
• Zone AE — 1% annual chance, BFE determined (and legacy A1–A30)
• Zone AH — shallow ponding, 1–3 ft
• Zone AO — shallow sheet flow on sloping terrain
• Zone AR — temporarily increased risk during levee restoration
• Zone A99 — protected by a flood-control system under construction

High-risk — coastal (V family)

• Zone V — coastal high hazard with wave action, no BFE
• Zone VE — coastal high hazard with wave action, BFE determined (and legacy V1–V30)

Moderate to low risk

• Zone X — shaded and unshaded
• Zones B and C — legacy equivalents of shaded and unshaded X

Undetermined and non-hazard values

• Zone D — undetermined risk
• Special values — OPEN WATER, AREA NOT INCLUDED, and NULL