FEMA Flood Zones

Abstract

The FEMA Flood Zones data shows areas that have a 1% annual chance of a flood event (100-year flood zone) and areas that have a 0.2% annual chance of a flood event (500-year flood zone).

FEMA calls flood zone data the Flood Insurance Rate Map (FIRM) database.

DFIRM is a digital version of FEMA's new updated Flood Insurance Rate Maps (FIRM). FEMA is engaged in a multi-year process to update all FIRMs in the US.

Purpose

According to FEMA:

The FIRM is the basis for floodplain management, mitigation, and insurance activities for the National Flood Insurance Program (NFIP). Insurance applications include enforcement of the mandatory purchase requirement of the Flood Disaster Protection Act, which "... requires the purchase of flood insurance by property owners who are being assisted by Federal programs or by Federally supervised, regulated or insured agencies or institutions in the acquisition or improvement of land facilities located or to be located in identified areas having special flood hazards, " Section 2 (b) (4) of the Flood Disaster Protection Act of 1973. In addition to the identification of Special Flood Hazard Areas (SFHAs), the risk zones shown on the FIRMs are the basis for the establishment of premium rates for flood coverage offered through the NFIP. The FIRM Database presents the flood risk information depicted on the FIRM in a digital format suitable for use in electronic mapping applications. The FIRM Database serves to archive the information collected during the Flood Risk Project. (from FEMA metadata)

Time Period of Content

  • Beginning date: 2002
  • Ending date: 2016

Update Frequency

As needed for updates

Publish Date

7/2016

Originator

FEMA

Publisher

FEMA

Theme Keywords

flood zone, floodplain, hazard, Flood Insurance Rate Map, FIRM, NFIP, flooding

Place Keywords

Florida

Source Scale

1:12,000

Horizontal Accuracy

+/- 38 feet

Vertical Accuracy

According to FEMA:

The reliability of the floodplain boundary delineation is quantified by comparing the computed flood elevation to the ground elevation at the mapped floodplain boundary. The tolerance for how precisely the flood elevation and the ground elevation must match varies based on the flood risk class, which is a function of population, population density, and/or anticipated growth in floodplain areas. A horizontal accuracy of +/- 38 feet is used to determine the compliance with the vertical tolerances defined for each risk class. The range of differences between the ground elevation (defined from the topographic data used for the Flood Risk Project) and the computed flood elevation is between +/- 1.0 foot at the 95% confidence interval for areas with high population within the floodplain and/or high anticipated growth and Special Flood Hazard Areas (SFHAs) with high flood risk to +/- one-half the contour interval at the 85% confidence interval for areas with low population and densities within the floodplain and small or no anticipated growth and SFHAs with low flood risk. Independent quality control testing of the individual FIRM Database components of the NFHL was also performed. (from FEMA metadata)

Format

File Geodatabase

Format Details

Polygon

Projection

Geographic NAD83

Field Names

ColumnDescription
FLD_ZONEFlood Zone, e.g. A, AE, etc.
FLOODWAYFloodway
SFHA_TFIN or OUT of Special Flood Hazard Area (100 year flood zone)
STATIC_BFEBase Flood Elevation
V_DATUMVertical Datum
DEPTHBFE. The rounded, whole-foot elevation of the 1-percent-annual-chance flood. This is the value of the BFE that is printed next to the BFE line on the FIRM.
LEN_UNITBFE units, normally feet
VELOCITYVelocity Measurement - n/a for Florida
VEL_UNITUnit of Measurement for Velocity
AR_REVERTIf the area is Zone AR, this field would hold the zone that the area would revert to if the AR zone were removed.
BFE_REVERTIf Zone is Zone AR, this field would hold the static base flood elevation for the reverted zone.
DEP_REVERTIf Zone is Zone AR, this field would hold that flood depth for the reverted zone.
SOURCE_CITSource Citation
ACRESAcreage of flood zone polygon
COUNTYCounty
FLOODPLAINFlood plain description
RISK_LEVELInsurance risk level
DESCRIPTCode description
SOURCEDATEEffective map date

fld_zone column:

Code Description
A 100-year floodplain, no BFEs determined.
AE 100-year floodplain, with BFEs determined.
AH 100-year floodplain, with ponding, with BFEs determined.
AO 100-year floodplain, with sheet flow, with BFEs determined.
AREA NOT INCLUDED Area Not Included in any flood study.
D Possible but undetermined flood hazards.
OPEN WATER Open Water
V 100-year floodplain with wave action, no BFEs determined.
VE 100-year floodplain with wave action, with BFEs determined.
X Outside flood zone
X500 500-year flood zone
0.2 PCT ANNUAL CHANCE FLOOD HAZARD CONTAINED IN CHANNEL 500-year flood zone in channel

Note: BFE = Base Flood Elevation

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