Digital Flood Insurance Rate Map DATABASE, ST. HELENA PARISH, LOUISIANA, USA

Resource lineage description

source

source description  Source Contribution: S_Quad_Index. S_Firm_Pan. Information about the US Geological Survey (USGS) 7.5-Minute Series Topographic Quadrangle maps that cover the study area.Source Type online

representative resolution scale:

Scale denominator: 24000

source citation

Title USGS 7.5-Minute Series Topographic Maps

publication  Date   1989-01-01

presentationForm  DIGITAL VECTOR DATA

other Citation Details  USGS has mapped the county with 1:24000 scale topographic maps (also referred to as 7.5-minute quadrangles). The entire county was mapped by the late 1980s. From the raster topographic maps, a vector index of the USGS topographic maps with its corresponding tile identification number and name was created.

cited responsible party - publisher

organisation Name  U.S.Geological Survey

Contact information

Address

, Reston, VA

cited responsible party - originator

organisation Name  U.S.Geological Survey

source

source description  Source Contribution: Spatial and attribute information for S_TRNSPORT_LN.Source Type Online

representative resolution scale:

Scale denominator: 12000

source citation

Title U.S. Census Bureau 2009 TIGER/Line Files

publication  Date   2009-01-01

presentationForm  TIGER/LINE FILES

other Citation Details  None

cited responsible party - publisher

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

Contact information

Address

, Washington, DC

cited responsible party - originator

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

source

source description  Source Contribution: Spatial and attribute information for S_POL_AR, S_POL_LN.Source Type Online

representative resolution scale:

Scale denominator: 12000

source citation

Title U.S. Census Bureau 2009 TIGER/Line Files

publication  Date   2009-01-01

presentationForm  TIGER/LINE FILES

other Citation Details  None

cited responsible party - publisher

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

Contact information

Address

, Washington, DC

cited responsible party - originator

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

source

source description  Source Contribution: S_Perm_Bmk. Spatial and attribute information for permanent benchmarks.Source Type Online

representative resolution scale:

Scale denominator: 12000

source citation

Title Permanent Bench Mark Data Sheets

publication  Date   2009-01-01

presentationForm  DIGITAL VECTOR DATA

other Citation Details  Geodetic data comprise the results of geodetic surveys to determine among other things, latitude, longitude, height, scale, and orientation control. The NGS' final product is the geodetic data sheet. Geodetic data sheets are comprehensive summaries of all the published information for a given geodetic reference point, including: the geographic position and/or height based on the current reference datum, condition of the survey mark when it was last visited, a description of where the point is located and how to reach it, and an explanation of the terms used in the data sheet.

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 S_WTR_LN.Source Type Online

representative resolution scale:

Scale denominator: 12000

source citation

Title National Hydrology Dataset

publication  Date   2009-01-01

presentationForm  mapDigital

other Citation Details  None

cited responsible party - publisher

organisation Name  U.S. Geological Survey (USGS)

Contact information

Address

, Reston, VA

cited responsible party - originator

organisation Name  U.S. Geological Survey (USGS)

source

source description  Source Contribution: S_PLSS_AR and S_PLSS_Ln. Contains information about PLSS areas that are associated with the study area. This would include the attributes for the range, township, and section areas.Source Type Online

representative resolution scale:

Scale denominator: 12000

source citation

Title Bureau of Land Management Nation Integrated Land System

publication  Date   2009-01-01

presentationForm  mapDigital

other Citation Details  None

cited responsible party - publisher

organisation Name  United States Department of the Interior, Bureau of Land Management

Contact information

Address

, Washington DC

cited responsible party - originator

organisation Name  United States Department of the Interior, Bureau of Land Management

source

source description  Source Contribution: Spatial and attribute information for ORTHOPHOTOGRAPHY.Source Type Online

representative resolution scale:

Scale denominator: 12000

source citation

Title U.S. Department of Agriculture (USDA) on-line spatial deliver system

publication  Date   2009-01-01

presentationForm  ORTHO DIGITAL DATA

other Citation Details  None

cited responsible party - publisher

organisation Name  U.S. Department of Agriculture (USDA) on-line spatial deliver system

Contact information

Address

, Salt Lake City, UT

cited responsible party - originator

organisation Name  Customer Service Section, USDA Farm Service Agency

source

source description  Source Contribution: Spatial and attribute information for floodplain widths, BFEs, cross sections, and floodplain location.Source Type paper

representative resolution scale:

Scale denominator: 12000

source citation

Title Flood Insurance Study, ST. HELENA PARISH, LOUISIANA, USA

publication  Date   1991-09-27

presentationForm  mapDigital

other Citation Details  The source of authority for this Flood Insurance Study is the National Flood Insurance Act of 1968, as amended. The hydrologic and hydraulic analyses for this study were prepared by the New Orleans District of the U.S. Army Corps of Engineers (COE), for the Federal Emergency Management Agency (FEMA), under Inter-agency Agreement No. EMW-87-E-2509, Project Order No. 11. This study was completed in July 1990.

cited responsible party - publisher

organisation Name  Federal Emergency Management Agency

Contact information

Address

, Washington, DC

cited responsible party - originator

organisation Name  Federal Emergency Management Agency

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.