FEMA Flood

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Overview

The National Flood Hazard Layer (NFHL) is a geospatial database that contains current effective flood hazard data for those communities where maps have been digitized. FEMA provides the flood hazard data to support the National Flood Insurance Program. You can use the information to better understand the level of FEMA-estimated flood risk and type of flooding in an area.

The NFHL is made from effective flood maps and Letters of Map Change (LOMC) delivered to communities. NFHL digital data covers over 90 percent of the U.S. population. New and revised data is being added continuously.

This dataset comprises the Flood Hazard Zones layer of NFHL.

Data

Attributes

depth

This is the depth for Zone AO areas

number
dfirm_id

Study Identifier. For a single-jurisdiction Flood Risk Project, the value is composed of the two-digit State Federal Information Processing Standard (FIPS) code and the fourdigit FEMA Community Identification (CID) code (e.g., 480001). For a countywide Flood Risk Project, the value is composed of the two-digit State FIPS code, the three-digit county FIPS code, and the letter 'C' (e.g., 48107C).

string
velocity

Velocity measurement of the flood flow in the area. Normally this is applicable to alluvial fan areas (certain Zone AO areas). Field is populated only when a velocity is associated with the flood zone area.

number
dual_zone

Dual zones (AR/AE) are flood zones in a current restoration area (AR) but with additional risk of flooding from other water sources not addressed by the flood protection system being restored. This means that despite the completion of a levee repair project, the area will continue to be in a high risk flood zone due to a flooding source other than the AR Zone source.

string
flood_zone

Flood Zone. This is a flood zone designation. These values are used by FEMA to designate the SFHAs and for insurance rating purposes.

string
study_type

Study type. Describes the type of Flood Risk Project performed for flood hazard idenetification.

string
version_id

Version Identifier. Identifies the FIRM product version and relates the feature to standards according to how it was created.

string
length_units

Units of measuring system referred to in static_base_flood_elevation and/or depth

string
flood_area_id

FEMA-assigned unique identifier for this flood area

string
velocity_units

Units of measurement for the velocity of the 1-pct annual chance flood

string
vertical_datum

Vertical Datum. Indicates the reference from which the flood elevations are measured. Only populated if static_base_flood_elevation is populated.

string
source_citation

Source citation

string
flood_risk_level

Summary flood risk level high, moderate, low, undetermined, or na, based on combination of flood_zone and flood_zone_subtype. Flood zones beginning with 'A' or 'V' are designated as high-risk areas (100-year flood zone). Flood zone 'B', and most 'X' zones are designated as moderate-risk areas (500-year flood zone). Flood zones 'C' and 'X (unshaded)' (i.e. with subtype 'AREA OF MINIMAL FLOOD HAZARD') indicate minimal flood risk. Areas labeled with zone D have undetermined flood risk. Flood risk level not applicable in areas with zone 'NP' (not populated) or 'OW' (open water).

string
flood_hazard_area

Indicates whether area is within a FEMA-designated Special Flood Hazard Area (SFHA).

string
flood_zone_subtype

Flood Zone Subtype. Captures additional information about the flood zones not related to insurance rating purposes.

string
static_base_flood_elevation

Static Base Flood Elevation. Populated for areas that have been determined to have a constant Base Flood Elevation (BFE) over a flood zone. This normally occurs in lakes or coastal zones.

number

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