fldzone = 'AH'

Risk tier: High — inside the Special Flood Hazard Area (SFHA).

Zone AH is a 1%-annual-chance floodplain characterized by shallow flooding, usually ponding, with average depths typically between 1 and 3 feet. It occurs where water collects in flat or depressed areas rather than flowing across the land. Because it is a detailed-study zone, Base Flood Elevations are determined.

How the flooding occurs

Where AO describes water flowing down a slope as a sheet, AH describes water pooling. Think of a low-lying basin, a closed depression, or the backwater behind an obstruction where runoff accumulates to a predictable elevation.

Base Flood Elevation

• AH publishes a BFE — a water-surface elevation, not a depth.
• Where a uniform elevation applies, it appears in staticbfe (feet, NAVD 88).

Building and insurance implications

• Flood insurance is federally required for mortgaged structures.
• New and substantially improved buildings must have the lowest floor elevated to or above the BFE.
• Adequate drainage paths around structures are commonly required so ponded water is not trapped against the building.

zonesubty values

Zone AH polygons typically carry no subtype.

In the data

SELECT lrid, parceladdr, staticbfe
FROM   lr_parcel_us
WHERE  fldzone = 'AH';

See also: Zone AO (shallow sheet flow), Zone AE (standard detailed-study floodplain).