FEMA Flood Hazard Areas
|Feature Dataset Name||STAND-ALONE|
|Originator||Metro Data Resource Center|
|Bureau||Bureau of Planning and Sustainability|
|Abstract|| The FEMA Flood Hazard Layer represents the location and attributes of flood insurance risk zones from the Flood Insurance Rate Map (FIRM) databases published by the Federal Emergency Management Agency (FEMA), and any Letters of Map Revision (LOMRs) that have been issued against those databases since their publication date. It is updated on a monthly basis. |
The FIRM Database is the digital, geospatial version of the flood hazard information shown on the published paper FIRMs. The FIRM Database depicts flood risk information and supporting data used to develop the risk data. The primary risk classifications used are the 1-percent-annual-chance flood event, the 0.2-percent-annual-chance flood event, and areas of minimal flood risk.
The floodway, 100-year floodplain/SFHA (Special Flood Hazard Area), and the 500-year floodplain are all derived from this dataset.
|Purpose||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.|
|Supplemental Information|| The NFHL dataset is a compilation of effective FIRM Databases (a collection of the digital data that are used in GIS systems for creating new Flood Insurance Rate Maps) and Letters of Map Change (Letters of Map Amendment and Letters of Map Revision only) that create a seamless GIS data layer for a State or Territory. It is updated on a monthly basis. The FIRM Databases are compiled in conjunction with the hardcopy FIRMs and the final FIS reports. The specifics of the hydrologic and hydraulic analyses performed are detailed in the FIS reports available for each jurisdiction. The results of these studies are submitted in digital format to FEMA. These data and unrevised data from effective FIRMs are compiled onto the base map used for FIRM publication and checked for accuracy and compliance with FEMA standards. As new FIRM Databases are received the individual FIRM layers are sewn into the nationwide layers of the NFHL. LOMRs for the FIRM Databases in the NFHL are cut directly into the NFHL data layers as they are being produced and finalized. |
The NFHL incorporates all FIRM Databases published by FEMA and any LOMRs that have been issued against those databases since their publication date. The NFHL consists of vector files and associated attributes produced in conjunction with the hardcopy FEMA FIRM. The published effective FIRM and FIRM Database are issued as the official designation of the SFHAs. As such they are adopted by local communities and form the basis for administration of the NFIP. For these purposes they are authoritative. Provisions exist in the regulations for public review, appeals and corrections of the flood risk information shown to better match real world conditions. As with any engineering analysis of this type, variation from the estimated flood heights and floodplain boundaries is possible. Details of FEMA's requirements for the FISs and flood mapping process that produces these data are available in the Guidelines and Standards for Flood Risk Analysis and Mapping. Attribute accuracy was tested by manual comparison of source graphics with hardcopy plots and a symbolized display on an interactive computer graphic system. Independent quality control testing of the individual FIRM Database components of the NFHL was also performed. To obtain more detailed information in areas where Base Flood Elevations (BFEs) and/or floodways have been determined, users are encouraged to consult the Flood Profiles and Floodway Data and/or Summary of Stillwater Elevations tables contained within the FIS reports that accompany the individual FIRM Database components of the NFHL. Users should be aware that BFEs shown in the S_BFE table may represent rounded whole-foot elevations. These BFEs are intended for flood insurance rating purposes only and should not be used as the sole source of flood elevation information. Accordingly, flood elevation data presented in the FIS report must be used in conjunction with the FIRM for purposes of construction and/or floodplain management. The 1-percent-annual-chance water-surface elevations shown in the S_XS table match the regulatory elevations shown in the FIS report.
The FEMA flood hazard data is now maintained by Metro and updated quarterly.
|Last Dataset Update||06/19/2019 10:55|
|Last Source Update||06/19/2019 09:57|
|Maintenance/Update Frequency||As needed|
|Extent||Regional (Oregon Counties only)|
|Horizontal Position Accuracy|| The NFHL consists of vector files and associated attributes produced in conjunction with the hardcopy FEMA FIRM. The published effective FIRM and FIRM Database are issued as the official designation of the SFHAs. As such they are adopted by local communities and form the basis for administration of the NFIP. For these purposes they are authoritative. Provisions exist in the regulations for public review, appeals and corrections of the flood risk information shown to better match real world conditions. As with any engineering analysis of this type, variation from the estimated flood heights and floodplain boundaries is possible. Details of FEMA's requirements for the FISs and flood mapping process that produces these data are available in the Guidelines and Standards for Flood Risk Analysis and Mapping. Horizontal accuracy was tested by manual comparison of source graphics with hardcopy plots and a symbolized display on an interactive computer graphic system. Independent quality control testing of the individual FIRM Database components of the NFHL was also performed. |
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.
Vertical datum is NAVD88.
|Horizontal Position Accuracy Link|
|North Bounding Coordinate||767573.669291346|
|South Bounding Coordinate||584934.780511811|
|East Bounding Coordinate||7784533.69849082|
|West Bounding Coordinate||7507450.36515748|
|Theme Keyword(s)||flood hazard, floodplain, fema, special flood hazard area, SFHA, floodway, 100-year floodplain, 500-year floodplain|
|Theme Keyword Thesaurus|
|Place Keyword Thesaurus|
|Access Constraints||Available for Public Use|
|Use Constraints|| These data are sold under the agreement that the user may use the data in its business activity and for no other purpose whatsoever. |
User shall not allow access to the data by any other person or organization, unless authorized in writing by the Metro DRC or,
if the other party is a contractor providing services to a government requiring usage of the data in order to provide contractual services.
User shall not duplicate the data except for the following:
(1) User may make one backup copy of the data, and
(2) User may translate the data into other formats and/or media.
|Source Dataset Type||File Geodatabase|
|Distribution|| Grid: State plane coordinate system 1983(91). |
Units: International feet
Datum: North American Datum of 1983/1991 (HPGN)
Liability: The information in this file was derived from digital databases on the City of Portland GIS. Care was taken in the creation of this file. The City cannot accept any responsibility for errors, omissions, or positional accuracy. There are no warranties, expressed or implied.
Format: Shapefile or File Geodatabase Feature Class - Data will be provided via City of Portland FTP Site.
Online Resource: http://portlandmaps.com/opendata
Online Instructions: City of Portland Public/Open Data is distributed via the PortlandMaps Open Data Site - http://portlandmaps.com/opendata. Data not available on the PortlandMaps Open Data site can be requested by contacting the City of Portland CGIS Group - firstname.lastname@example.org
Transfer Size: varies
SPCS Zone Identifier: 5076
| File(s) |
|BDS_Boundary||Special Flood Hazard Area (FEMA)||No|
|BDS_Layers||FEMA 500 Year Flood Zone||No|
|BDS_Layers||FEMA Special Flood Hazard Area (100 Year)||No|
|Hazard||FEMA 500 Year Flood Zone||No|
|Hazard||FEMA Special Flood Hazard Area (100 Year)||No|
|Hazard||Reduced Flood Risk due to Levee||No|
|Column Sort||Column Name||Column Alias||Column Type||Column Size||Domain Value(s)||Column Description||1||DFIRM_ID||DFIRM_ID||String||6||Study Identifier. For a single jurisdiction flood risk project, the value is composed of the two-digit State FIPS code and the four-digit FEMA 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). Within each FIRM Database, the DFIRM_ID value will be identical.||1||VERSION_ID||VERSION_ID||String||11||Version Identifier. Identifies the product version and relates the feature to standards according to how it was created.||1||FLD_AR_ID||FLD_AR_ID||String||32||Primary key for table lookup. Assigned by table creator.||1||STUDY_TYP||STUDY_TYP||String||28||Study Type. This describes the type of flood risk project performed for flood hazard identification||1||FLD_ZONE||FLD_ZONE||String||17||Flood Zone. This is a flood zone designation. These zones are used by FEMA to designate the SFHAs and for insurance rating purposes||1||ZONE_SUBTY||ZONE_SUBTY||String||72||Flood Zone Subtype. This field captures additional information about the flood zones not related to insurance rating purposes. For example, insurance rate zone Shaded X could have “PROTECTED BY LEVEE” or “0.2 PCT ANNUAL CHANCE FLOOD HAZARD CONTAINED IN STRUCTURE.” Types of floodways are also stored in this field.||1||SFHA_TF||SFHA_TF||String||1||Special Flood Hazard Area. If the area is within a SFHA this field would be true ("T").||1||STATIC_BFE||STATIC_BFE||Numeric||8||Static Base Flood Elevation. This field will be populated for areas that have been determined to have a constant Base Flood Elevation (BFE) over a flood zone. The BFE value will be shown beneath the zone label. In this situation the same BFE applies to the entire polygon. This normally occurs in lakes or coastal zones.||1||V_DATUM||V_DATUM||String||17||Vertical Datum. The vertical datum indicates the reference surface from which the flood elevations are measured. Normally this would be North American Vertical Datum of 1988 for new studies. This field is only populated if the STATIC_BFE field is populated. Acceptable values for this field are listed in the D_V_Datum table.||1||DEPTH||DEPTH||Numeric||8||Depth This is the depth for Zone AO areas. This value is shown beneath the zone label on the FIRM. This field is only populated if a depth is shown on the FIRM.||1||LEN_UNIT||LEN_UNIT||String||16||Length Units. This unit indicates the measurement system used for the BFEs and/or depths. Normally this would be feet. This field is only populated if the STATIC_BFE or DEPTH field is populated.||1||VELOCITY||VELOCITY||Numeric||8||The velocity measurement of the flood flow in the area. Normally this is applicable to alluvial fan areas (certain Zone AO areas). This value is shown beneath the zone label on the FIRM. This field is only populated when a velocity is associated with the flood zone area.||1||VEL_UNIT||VEL_UNIT||String||20||Velocity Unit. This is the unit of measurement for the velocity. This field is populated when the VELOCITY field is populated.||1||AR_REVERT||AR_REVERT||String||17||Flood Control Restoration Zones – Zone AR Classification. If this area is Zone AR in FLD_Zone field, this field would hold the zone that area would revert to if the AR zone were removed. This field is only populated if the corresponding area is Zone AR. Acceptable values for this field are listed in the D_Zone table, but should only include one of AE, AO, AH, A, and X domain values. Does not apply to data in Oregon at present.||1||AR_SUBTRV||AR_SUBTRV||String||57||Flood Control Restoration Zones – Zone AR Classification Zone Subtype. If this area is Zone AR in FLD_Zone field, this field would hold the zone subtype that area would revert to if the AR zone were removed. This field is only populated if the corresponding area is Zone AR. NOTE: The symbol ‘%’ is a reserved symbol in most software packages, so the word ‘percent’ was abbreviated to ‘PCT.’ Acceptable values for this field are listed in the D_Zone_Subtype_ table. Does not apply to Oregon.||1||BFE_REVERT||BFE_REVERT||Numeric||8||Flood Control Restoration Zones – BFE Revert. If zone is Zone AR in FLD_Zone field, this field would hold the static base flood elevation for the reverted zone. This field is populated when Zone equals AR and the reverted zone has a static BFE. Does not apply to data in Oregon at present.||1||DEP_REVERT||DEP_REVERT||Numeric||8||Flood Control Restoration Zones – Depth Revert. If zone is Zone AR in FLD_Zone field, this field would hold the flood depth for the reverted zone. This field is populated when Zone equals AR and the reverted zone has a depth assigned. Does not apply to data in Oregon at present.||1||DUAL_ZONE||DUAL_ZONE||String||1||Flood Control Restoration Zones – Dual Zone Classification. If the flood hazard areas shown on the effective FIRM shall be designated as “dual” flood insurance rate zones (i.e., Zone AR/AE, Zone AR/AH, Zone AR/AO, Zone AR/A), this field will be coded as true. It should be false for any for AR Zones that revert to Shaded X. Acceptable values for this field are listed in the D_TrueFalse table. Does not apply in Oregon.||1||SOURCE_CIT||SOURCE_CIT||String||21||Source Citation. Abbreviation used in the metadata file when describing the source information for the feature. The abbreviation must match a value in L_Source_Cit.|