DIGITAL FLOOD INSURANCE RATE MAP DATABASE, GLOUCESTER COUNTY, VIRGINIA (ALL JURISDICTIONS)

Resource lineage description

source

source description  Source Contribution: Spatial and attribute information for Base Flood Elevations (BFEs), Cross Sections, Hydraulic Profile Baselines, Hydraulic Structures and Special Flood Hazard AreasSource Type Online

source citation

Title Flood Insurance Rate Map, Gloucester County, VA and Incorporated Areas

publication  Date   2010-09-17

presentationForm  mapDigital

cited responsible party - originator

organisation Name  Federal Emergency Management Agency

source

source description  Source Contribution: Spatial and attribute information for USGS 7.5-MINUTE QUADRANGLE GRID/INDEX (S_Quad_Index). Additionally, these map boundaries were divided to create the S_FIRM_Pan feature class. Different scales were selected based on FEMA guidelines and specifications.Source Type Online

representative resolution scale:

Scale denominator: 24000

source citation

Title NATIONAL USGS 7.5-MINUTE QUAD INDEX

publication  Date  

presentationForm  mapDigital

cited responsible party - originator

organisation Name  USGS

source

source description  Source Contribution: Spatial and attribute information for permanent benchmarks which meet FEMA specificationsSource Type Online

representative resolution scale:

Scale denominator: 24000

source citation

Title Geodetic Bench Mark Positions and Descriptions

publication  Date   2005-01-01

presentationForm  mapDigital

other Citation Details  The National Geodetic Survey (NGS) serves as the nation's depository for geodetic data in the National Spatial Reference System. These geodetic data include bench marks and other control points that provide the base of reference for latitude, longitude, height, scale, orientation, and gravity measurements used throughout the United States.

cited responsible party - publisher

organisation Name  National Geodetic Survey

Contact information

Address

, Silver Spring, MD

cited responsible party - originator

organisation Name  National Geodetic Survey

source

source description  Source Contribution: Spatial and attribute information for political lines and areas. The Gloucester County political boundary shapefiles were referenced to neighboring counties' political boundaries.Source Type Online

source citation

Title Cartographic Boundary Files

publication  Date   2006-01-01

presentationForm  mapDigital

cited responsible party - originator

organisation Name  US Department of Commerce, Bureau of the Census, Geography Division

source

source description  Source Contribution: Spatial and attribute information for hydrography linesSource Type CD-ROM

source citation

Title Gloucester Hydrography

publication  Date   2008-01-01

cited responsible party - originator

organisation Name  Gloucester County Department of Information Technology and Geographic Information Systems

source

source description  Source Contribution: The Gloucester road shapefile was referenced to provide accurate road and street name data for the annotation shown on the newly effective FIRM maps.Source Type CD-ROM

source citation

Title Gloucester Roads

publication  Date   2008-01-01

cited responsible party - originator

organisation Name  Gloucester County Department of Information Technology and Geographic Information Systems

source

source description  Source Contribution: Location of Coastal Barrier Resources System AreasSource Type Paper

representative resolution scale:

Scale denominator: 24000

source citation

Title John H. Chafee Coastal Barrier Resources System maps

publication  Date   1990-01-01

presentationForm  mapDigital

other Citation Details  The Coastal Barrier Resources Act (P.L. 97-348) of 1982 established the John H. Chafee Coastal Barrier Resources System (CBRS) which is comprised of coastal barrier units along the Atlantic, Gulf of Mexico and Great Lakes coasts. These areas are depicted on a series of maps titled "John H. Chafee Coastal Barrier Resources System" that are enacted by Congress. Most new Federal expenditures and financial assistance (including flood insurance) are prohibited within the CBRS. Since its inception in 1982, the CBRS has since been amended by several acts of Congress, including the Coastal Barrier Improvement Act of 1990 (P.L. 101-591). With minor exception, only Congress, through new legislation, can modify the boundaries of the CBRS. The U.S. Fish and Wildlife Service (FWS) is responsible for maintaining the official maps of the CBRS and facilitating changes enacted by Congress. In cooperation with the Federal Emergency Management Agency, FWS digitized the CBRS boundaries from the official CBRS source maps for this area and adjusted them to fit the digital Flood Insurance Rate Map (FIRM). The process of fitting CBRS boundaries to the FIRM base map in some cases resulted in a slightly different configuration of the line as shown on the Congressionally-adopted source maps. The CBRS boundaries depicted on this FIRM are not the controlling CBRS boundaries adopted by Congress. The official CBRS maps used to determine whether or not an area is located within the CBRS are available for download at http://www.fws.gov. An official determination of whether or not an area is located within the CBRS can be obtained by contacting the FWS field office at the phone number shown on the body of the FIRM panel.

cited responsible party - publisher

organisation Name  U.S. Fish and Wildlife Service

Contact information

Address

, Washington, D.C.

cited responsible party - originator

organisation Name  U.S. Fish and Wildlife Service

source

source description  Source Contribution: The coastal analysis results in the delineation of the SFHA and designation of flood risk zones on the FIRM and in the FIS report. Details of the coastal analysis are documented in the FIS report. Steps involved in the process include selecting methods and/or models, modeling/performing required analysis, and mapping of floodplains and Limits of Moderate Wave Action.Source Type DVD-ROM

representative resolution scale:

Scale denominator: 6000

source citation

Title Coastal Analysis, Gloucester County, VA

publication  Date   2010-09-17

presentationForm  mapDigital

other Citation Details  In a coastal analysis the FIRM and the FIS are developed together, and care is taken to ensure that the elevations and other features included in the FIS agree with the information shown on the FIRM. The data input to the models (e.g. SWELs, wave heights, wave periods, and fetch lengths) are checked for consistency with the historical data. Boundary conditions are checked and compared with those adjacent studies to ensure reasonable agreement. The results of the erosion assessment are evaluated by comparing the eroded profile to past effects, in the form of profiles, photographs, or simply descriptions.

cited responsible party - publisher

organisation Name  Federal Emergency Management Agency

Contact information

Address

, Washington, D.C.

cited responsible party - originator

organisation Name  RAMPP

AbsoluteExternalPositionalAccuracy

name Of Measure Horizontal Positional Accuracy Report

evaluation Method Description  The DFIRM Database consists of community based vector files and associated attributes produced in conjunction with the hardcopy FEMA FIRM. The published effective FIRM and DFIRM 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 Specifications for Flood Hazard Mapping Partners. 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 FEMA's DFIRM database was also performed.

AbsoluteExternalPositionalAccuracy

name Of Measure Vertical Positional Accuracy Report

evaluation Method Description  The DFIRM Database consists of community based vector files and associated attributes produced in conjunction with the hardcopy 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 FISs and flood mapping process that produces these data are available in the Guidelines and Specifications for Flood Hazard Mapping Partners. Vertical 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 database was also performed.

Completeness Commission

evaluation Method Description  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 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.

Completeness Omission

evaluation Method Description  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 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.

ConceptualConsistency

measure Description  When FEMA revises an FIS, adjacent studies are checked to ensure agreement between flood elevations at the boundaries. Likewise flood elevations at the confluence of streams studied independently are checked to ensure agreement at the confluence. The FIRM and the FIS are developed together and care is taken to ensure that the elevations and other features shown on the flood profiles in the FIS agree with the information shown on the FIRM. However, the elevations as shown on the FIRM are rounded whole-foot elevations. They must be shown so that a profile recreated from the elevations on the FIRM will match the FIS profiles within one half of one foot.