DIGITAL FLOOD INSURANCE RATE MAP DATABASE, MATHEWS COUNTY, VIRGINIA

Resource lineage description

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, Mathews County, VA

publication  Date   2014-12-09

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

source

source description  Source Contribution: Spatial and Attribute information for S_GEN_STRUCT, S_PERM_BMK and S_FIRM_PANSource Type Digitized

representative resolution scale:

Scale denominator: 12000

source citation

Title MATHEWS COUNTY, VIRGINIA, Digital Flood Insurance Rate Map

publication  Date   2007-11-16

presentationForm  mapDigital

other Citation Details  Grid of FIRM panels created for this study

cited responsible party - publisher

organisation Name  Federal Emergency Management Agency

Contact information

Address

, Washington, D.C.

cited responsible party - originator

organisation Name  Federal Emergency Management Agency

source

source description  Source Contribution: Spatial and Attribute information for S_QUAD_INDEXSource Type ESRI Shapefile

representative resolution scale:

Scale denominator: 12000

source citation

Title Virginia Digital Orthophoto Quadrangle and Quarter Quadrangle Grids

publication  Date   1999-07-12

presentationForm  mapDigital

other Citation Details  The USGS produces a quadrangle grid for the state of Virginia. Each grid represents the topographic land area covered by 7.5 quadrangle maps. Quad names are assigned by the USGS. There are three attributes in the DBF file that are most commonly used for interpretation by VEDP, those are Name, Ohio_index, and Quadno.

cited responsible party - publisher

organisation Name  VEDP

Contact information

Address

, Richmond, Virginia

cited responsible party - originator

organisation Name  Publication_Date 19990712

source

source description  Source Contribution: Spatial and Attribute information for S_BASE_INDEXSource Type CD-ROM

representative resolution scale:

Scale denominator: 4800

source citation

Title Base map orthophotography for Mathews County, Virginia

publication  Date   2000-01-01

presentationForm  mapDigital

other Citation Details  These files were photogrammetrically compiled at a scale of 1"=400' from aerial photographs. The aerial imagery was collected by Spatial Data Consultants, Inc. of High Point, NC by contract with Mathews County Department of Planning and Zoning. The imagery was then provided to USACE, Norfolk District by Mathews County. Used to develop titling index (S_BASE_INDEX) for imagery raster catalog: Mathews_Imagery.dbf

cited responsible party - publisher

organisation Name  Spatial Data Consultants, Inc

Contact information

Address

, High Point, NC

cited responsible party - originator

organisation Name  Publication_Date 2000

source

source description  Source Contribution: Spatial and Attribute information for Political lines and areasSource Type digital

representative resolution scale:

Scale denominator: 12000

source citation

Title Mathews County, Virginia Data from Federal Sources

publication  Date   2001-01-01

presentationForm  mapDigital

other Citation Details  These sources include TIGER data from the US Census Bureau, National Geodetic Survey (NGS), and US Fish and Wildlife Service.

cited responsible party - publisher

organisation Name  U.S. Department of Commerce, U.S. Census Bureau, Geography Division

Contact information

Address

, Washington, DC

cited responsible party - originator

organisation Name  Publication_Date 2001

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: Spatial and Attribute information for S_TRNSPORT_LNSource Type Scanned raster

representative resolution scale:

Scale denominator: 24000

source citation

Title USGS Digital Raster Graphics (DRG) Data for Virginia

publication  Date   1997-01-01

presentationForm  mapDigital

other Citation Details  Road data originally compiled by Virginia Geographic Information Network.

cited responsible party - publisher

organisation Name  US Geological Survey

Contact information

Address

, Reston, Virginia

cited responsible party - originator

organisation Name  Publication_Date 1997

AbsoluteExternalPositionalAccuracy

name Of Measure Horizontal Positional Accuracy Report

evaluation Method Description  The DFIRM Database consists of countywide 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 countywide 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.