West Virginia GIS Technical Center, 20111101, Statewide 100-year Floodplain Polygons for West Virginia.Online Links:
This is a Vector data set. It contains the following vector data types (SDTS terminology):
Planar coordinates are encoded using coordinate pair
Abscissae (x-coordinates) are specified to the nearest 0.001024
Ordinates (y-coordinates) are specified to the nearest 0.001024
Planar coordinates are specified in meters
The horizontal datum used is North American Datum of 1983.
The ellipsoid used is Geodetic Reference System 80.
The semi-major axis of the ellipsoid used is 6378137.000000.
The flattening of the ellipsoid used is 1/298.257222.
West Virginia GIS Technical Center
(304) 293-9463 (voice)
ehopkins@wvu.edu
This data set was developed primarily for use in the West Virginia GIS Technical Center's web-based Flood Tool, which enables users to estimate flood risk and the "in" or "out" status of specific properties or structures relative to areas (Flood Zones) of 1% annual chance flooding.
Data sources used in this process:
Data sources used in this process:
Data sources used in this process:
Data sources used in this process:
Federal Emergency Management Agency (FEMA), 2008, Effective Countywide DFIRMs for West Virginia: Federal Emergency Management Agency, Washington, DC, USA.Online Links:
Federal Emergency Management Agency (FEMA), 1988, Digital Q3 Flood Data: Federal Emergency Management Agency (FEMA), Washington, DC, USA.Online Links:
FEMA Cooperating Technical Part, Flood mapping contractors, Unpublished Material, Draft DFIRM Data.Online Links:
The DFIRM Database consists of countywide vector files and associated attributes produced in conjunction with the hard copy FEMA FIRM. The published effective FIRM and DFIRM maps 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 Flood Insurance Studies (FISs) and flood mapping process that produces these data are available in the Guidelines and Specifications for Flood Hazard Mapping Partners. 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 FEMA's DFIRM databases 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 Effective DFIRM databases. Users should be aware that BFEs shown in the S_BFE table 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 theDFIRM database S_XS table match the regulatory elevations shown in the FIS report. This data set does not include cross section (XS) or BFE information.
Horizontal accuracy of Effective DFIRM data 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 FEMA's DFIRM database was also performed.
Data contained in the DFIRM Database files reflect the content of the source materials. Features may have been eliminated or generalized on the source graphic, due to scale and legibility constraints. With new mapping, FEMA plans to maintain full detail in the spatial data it produces. However, older information is often transferred from existing maps where some generalization has taken place. Flood risk data are developed for communities participating in the National Flood Insurance Program (NFIP) for use in insurance rating and for floodplain management. Flood hazard areas are determined using statistical analyses of records of river flow, storm tides, and rainfall; information obtained through consultation with the communities; floodplain topographic surveys; and hydrological and hydraulic analysis. Both detailed and approximate analyses are employed. Generally, detailed analyses are used to generate flood risk data only for developed or developing areas of communities. For areas where little or no development is expected to occur, FEMA uses approximate analyses to generate flood risk data. Typically, only drainage areas that are greater than one square mile are studied.
The floodplains depicted in this data have been compared to the NFHL, Effective DFIRM, Preliminary DFIRM or Q3 source material to check for alignment errors or omissions. Effective DFIRMs, including the NFHL, which is compiled from Effective DFIRM data, have been subjected, during production and after delivery, to more thorough analysis and checking for spatial agreement of features.
Are there legal restrictions on access or use of the data?
- Access_Constraints: None
- Use_Constraints:
- This data is derived from effective, preliminary and draft FEMA flood data, but is not intended to replace official FEMA publications. Acknowledgement of FEMA and the West Virginia GIS Technical Center will be appreciated in presentations or publications that make use of this data.
(304) 293-9463 (voice)
ehopkins@wvu.edu
No warranty expressed or implied is made by the West Virginia GIS Technical Center regarding the utility of the data on any other system nor shall the act of distribution constitute any such warranty.
| Data format: | ESRI Shapefile (version 1) |
|---|---|
| Network links: |
<http://wvgis.wvu.edu/data/dataset.php?action=search&ID=373> |
(304) 293-9463 (voice)
ehopkins@wvu.edu