DIGITAL FLOOD INSURANCE RATE MAP DATABASE, UVALDE COUNTY, TEXAS

Resource lineage description

source

source description  Source Contribution: 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. (S_Perm_Bmk)Source Type digital vector data

source citation

Title Permanent Bench Mark Data Sheets

publication  Date   2004-01-01

cited responsible party - originator

organisation Name  National Geodetic Survey

source

source description  Source Contribution: Spatial and attribute information for political boundaries. (S_Pol_Ln, S_Pol_Ar)Source Type Digital vector data

source citation

Title "StratMapv2_CITY_POLY", "StratMapv2_COUNTY_POLY", "StratMapv2_Cultural_Poly", StratMapv2_Park_Poly"

publication  Date   2006-09-01

cited responsible party - originator

organisation Name  Texas Department of Transportation, Texas Parks and Wildlife.

source

source description  Source Contribution: The imagery is based on panchromatic black and white (or color infrared) NAPP or NAPP-like photography. From the raster DOQs, a vector index is created. (S_Base_Index)Source Type digital vector data

source citation

Title Aerial photograph index

publication  Date   2007-09-25

cited responsible party - originator

organisation Name  MAPVI (Contractor to FEMA)

source

source description  Source Contribution: Spatial and attribute information for the index of USGS 7.5-Minute Series Topographic Map boundaries. (S_Quad_Index)Source Type Digital raster data

source citation

Title USGS 7.5-Minute Series Topographic Maps

publication  Date   1999-01-01

cited responsible party - originator

organisation Name  U.S. Geological Survey

source

source description  Source Contribution: Water line and polygon geometry and attribute information. (S_Wtr_Ar, S_Wtr_Ln)Source Type digital vector data

source citation

Title National Hydrography Dataset - High Resolution

publication  Date   2002-11-27

cited responsible party - originator

organisation Name  U.S. Geological Survey (http://nhd.usgs.gov/)

source

source description  Source Contribution: This file was significantly altered, by MAPVI, from it's original format. Spatial and attribute information for the index of USGS 7.5-Minute Series Topographic Map boundaries. (S_FIRM_PAN)Source Type Digital vector data

source citation

Title Digital Orthophoto Quadrangle

publication  Date   1989-08-26

cited responsible party - originator

organisation Name  U.S. Geological Survey

source

source description  Source Contribution: Spatial and attribute information for cross sections and Zone A floodplains. (S_BFE, S_XS, S_FLD_HAZ_AR)Source Type paper map

source citation

Title Flood Insurance Rate Map, Uvalde County, TX

publication  Date   1996-08-16

cited responsible party - originator

organisation Name  Federal Emergency Management Agency

source

source description  Source Contribution: Spatial and attribute information for cross sections. (S_BFE, S_XS, S_FLD_HAZ_AR)Source Type paper map

source citation

Title Flood Insurance Rate Map, City of Uvalde, TX

publication  Date   1996-08-16

cited responsible party - originator

organisation Name  Federal Emergency Management Agency

source

source description  Source Contribution: Orthos were flown on November 6, 2004 and November 25, 2004 and obtained in the UTM coordinate system, 24-bit color infrared, 1 meter resolution at a scale of 1:24,000. The files were available free of charge through the TNRIS website and were downloaded as zipped SID files. MAPVI reprojected the orthophotos to the Texas State Plane Central Coordinate System, converted the SID files to TIF and converted the color images to black and white.Source Type digital raster data

source citation

Title NAIP Digital Ortho Photo Image

publication  Date   2005-12-09

cited responsible party - originator

organisation Name  USDA-FSA-APFO Aerial Photography Field Office

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.