Louisiana Flood Zone

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Frequently-anticipated questions:

What does this data set describe?

    Title: Louisiana Flood Zone
    The Q3 Flood Data are derived from the Flood Insurance Rate Maps (FIRMS) published by the Federal Emergency Management Agency (FEMA). The file is georeferenced to earth's surface using geographic projection and decimal degree coordinate system. The specifications for the horizontal control of Q3 Flood Data files are consistent with those required for mapping at a scale of 1:24000.

    The user is encouraged to refer to the 'Q3 FLOOD DATA SPECIFICATIONS' manual <http://msc.fema.gov/specs.shtml> and the 'Q3 FLOOD DATA USERS GUIDE' <http://msc.fema.gov/q3users.shtml> for complete information on the technical details of the Q3 data, its attributes, its uses, and limitations.

    This metadata document acts as a global metadata document for 37 individual parish 'Q3 Flood Zone' datasets. Not all Louisiana parishes have a Q3 Flood Zone dataset. The geographic bounds given in this document represents the geographic bounds of the entire state, rather the geographic bounds of any particular parish data set.

    The following list gives the list of parishes with Q3 data and the name of the corresponding shapefile.

    Parish name            Shapefile name
    -----------            --------------
    Acadia                 acadia
    Allen                  allen
    Ascension              ascension
    Assumption             assumption
    Avoyelles              avoyelles
    Bossier                bossier
    Calcasieu              calcasieu
    Cameron                cameron
    Catahoula              catahoula
    Concordia              concordia
    East Baton Rouge       ebatonrouge
    Franklin               franklin
    Grant                  grant
    Iberia                 iberia
    Iberville              iberville
    Jefferson              jefferson
    Lafayette              lafayette
    Lafourche              laFourche
    Livingston             livingston
    Madison                madison
    Natchitoches           natchitoches
    Orleans                orleans
    Ouachita               ouachita
    Plaquemines            plaquemines
    Pointe Coupee          pointecoupee
    Rapides                rapides
    St. Bernard            stbernard
    St. Charles            StCharles
    St. James              StJames
    St. John the Baptist   StJohnBaptist
    St. Landry             StLandry
    St. Martin             stmartin
    St. Mary               StMary
    St. Tammany            StTammany
    Tangipahoa             tangipahoa
    Terrebonne             terrebonne
    Vermilion              vermilion

  1. How should this data set be cited?

    Federal Emergency Management Agency, 1999, Louisiana Flood Zone.

    Online Links:

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -93.929665
    East_Bounding_Coordinate: -88.762901
    North_Bounding_Coordinate: 33.019950
    South_Bounding_Coordinate: 28.875240

  3. What does it look like?

    <URL:q3floodzone1.gif> (GIF)
    thumbnail graphic of East Baton Rouge parish data set

  4. Does the data set describe conditions during a particular time period?

    Calendar_Date: 1999
    Date the most current Q3 data were projected to geographic coordinates, NAD83 for release on the 'Louisiana GIS CD: A Digital Map of the State.'

  5. What is the general form of this data set?

    Geospatial_Data_Presentation_Form: vector digital data

  6. How does the data set represent geographic features?

    1. How are geographic features stored in the data set?

      This is a Vector data set. It contains the following vector data types (SDTS terminology):

      • G-polygon (24365)

    2. What coordinate system is used to represent geographic features?

      Horizontal positions are specified in geographic coordinates, that is, latitude and longitude. Latitudes are given to the nearest 0.000000. Longitudes are given to the nearest 0.000000. Latitude and longitude values are specified in Decimal degrees.

      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.

      Altitude_Resolution: 1.000000
      Explicit elevation coordinate included with horizontal coordinates

  7. How does the data set describe geographic features?


    Internal feature number. (Source: ESRI)

    Sequential unique whole numbers that are automatically generated.

    Feature geometry. (Source: ESRI)

    Coordinates defining the features.

    Feature geometry. (Source: ESRI)

    Coordinates defining the features.


    Area of feature in internal units squared. (Source: ESRI)

    Positive real numbers that are automatically generated.

















    added Parish field to indicate data source

    character data set

    These data sets contain all the attributes of the Q3 Flood Zone Data source dataset. All of those attributes and the codes that appear in them are defined in the source listed for Entity_and_Attribute_Detail_Citation. As part of LSU data processing three additional attributes were added: area_sqm (area of polygon in square meters), perim_m (perimeter of polygon in meters), and area_ac (area of polygon in acres).
    Q3 FLOOD DATA SPECIFICATIONS, Draft 1996, Federal Emergency Management Agency, Washington, D.C. <http://msc.fema.gov/specs.shtml>

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)

  2. Who also contributed to the data set?

    LOSCO gratefully acknowledges FEMA for providing the source data for production of this data set and LSU (Louisiana State University) for projecting these data to NAD83 coordinates. The Purpose, Logical_Consistency_Report and Completeness_Report part of these metadata came from metadata supplied with FEMA Q3 source data.

  3. To whom should users address questions about the data?

    Louisiana Oil Spill Coordinator's Office
    c/o David Gisclair
    Technical Assistance Program (TAP) Director
    Louisiana Oil Spill Coordinator's Office
    Baton Rouge, LA 70804

    (225) 219-5800 (voice)
    (225) 219-5802 (FAX)

Why was the data set created?

The FIRM is the basis for floodplain management, mitigation, and insurance activities for the National Flood Insurance Program (NFIP). Insurance applications include enforcement of the mandatory purchase requirement of the Flood Disaster Protection Act which "... requires the purchase of flood insurance by property owners who are being assisted by Federal programs or by Federally supervised, regulated or insured agencies or institutions in the acquisition or improvement of land facilities located or to be located in identified areas having special flood hazards" (Section 2 (b) (4) of the 1973 Flood Disaster Protection Act). In addition to the identification of Special Flood Hazard Areas, the risk zones shown on the FIRMs are the basis for the establishment of premium rates for flood coverage offered through the NFIP.

Q3 Flood Data files are intended to convey certain key features from the existing hard copy FIRM to provide users with automated flood risk data. Edge-matching errors, overlaps and deficiencies in coverage, and similar problems are not corrected during digitizing or post-processing. These data may be used to locate Special Flood Hazard Areas (SFHAs). More detailed information may be obtained from the paper FIRM.

How was the data set created?

  1. From what previous works were the data drawn?

    Q3 (source 1 of 1)
    Federal Emergency Management Agency, 199?, Q3 Flood Data, [Louisiana Parish Name].

    Type_of_Source_Media: computer file
    Source_Contribution: spatial and attribute information

  2. How were the data generated, processed, and modified?

    Date: 1999 (process 1 of 3)
    Q3 data for each parish was projected from geographic coordinates, NAD27 to geographic coordinates, NAD83 and converted to shapefile.

    Person who carried out this activity:

    LSU Department of Geography and Anthropology
    c/o Hampton Peele
    Louisiana State University
    Baton Rouge, LA 70803

    (225)388-3455 (voice)

    (process 2 of 3)
    Dataset copied.

    Data sources used in this process:

    • Server=dogbert.er.usgs.gov; Service=5151; User=usgs; Version=SDE.DEFAULT

    (process 3 of 3)
    merged all parish floodzone shapefiles to one representative shapefile and added parish field

    Person who carried out this activity:

    Chris Polloni
    US Geological Survey
    Computer Specialist
    384 Woods Hole Road
    Woods Hole, MA 02543-1598

    508-548-8700x2280 (voice)
    508-457-2310 (FAX)

How reliable are the data; what problems remain in the data set?

  1. How well have the observations been checked?

  2. How accurate are the geographic locations?

    Specifications for the digitizing of FIRMs to create the Q3 Flood Data are consistent with those requirements for mapping at a scale of 1:24000. Horizontal control of Q3 Flood Data was established using USGS quadrangle maps at 1:24000 or other standard scales. Users should assess the horizontal positional sources and the requirements of their application. With increased frequency, large-scale spatial data sets are becoming widely available for computer-based geographic information systems. Q3 Flood Data may be used in combination with other digital spatial data, however, users should be aware that scalar enlargements do not enhance the relative accuracy of the Q3 Flood Data (i.e. 1:24000).

  3. How accurate are the heights or depths?

  4. Where are the gaps in the data? What is missing?

    Data completeness for Q3 Flood Data files reflect the content of the source graphic. Features may have been eliminated or generalized on the source graphic, due to scale and legibility constraints. 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 analysis 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 analysis are used to generate flood risk data only for developed or developing areas of communities. For undeveloped 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 Q3 Flood Data coverages may be derived from DFIRM-DLGs, from FIRM- DLGs, from FIRMs digitized previously for emergency applications, or may be newly created files. In Q3 Flood Data derived from older data sets, certain items may not have been captured or may have been captured differently from the current Q3 Flood Data specifications. In some cases, preliminary FIRM data have been included in the Q3 Flood Data files. These data have been provided to the community for their review and comment and may be subject to change before their final publication date. In addition, in some cases areas designated as Flood Prone Areas on maps prepared by USGS and FIA have been included in the Q3 Flood Data files. These areas were delineated based on available information on past floods and are described by a unique attribute code that distinguishes them from areas of 1% annual chance of flooding derived from FIRMs. Flood Insurance Rate Maps continually undergo revisions and updates. Some of these revisions are effected by letter (Letter of Map Revision (LOMR), Letter of Map Amendment (LOMA)). Q3 Flood Data may not reflect the most current information or information that is not mappable at the publication scale of FIRM. To obtain the latest information, contact the address listed under distributor.

  5. How consistent are the relationships among the observations, including topology?

    Polygon and chain-node topology are present. Certain node-area-line relationships are collected or generated to satisfy topological requirements. Some of these requirements include: lines must begin and end at nodes, lines must connect to each other at nodes, lines do not extend through nodes, left and right areas are defined for each line segment and are consistent throughout the files, and the lines representing the limits of the file neatlines are free of gaps. Tests of logical consistency were performed by ARC/INFO software modules. Check plots were made to test for leaks in all internal polygons.

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?

Access_Constraints: none
Use_Constraints: none

  1. Who distributes the data set? (Distributor 1 of 1)

    Louisiana Oil Spill Coordinator's Office
    c/o David Gisclair
    Technical Assistance Program (TAP) Director
    Louisiana Oil Spill Coordinator's Office
    Baton Rouge, LA 70804

    (225) 219-5800 (voice)
    (225) 219-5802 (FAX)

  2. What's the catalog number I need to order this data set?

    Downloadable Data

  3. What legal disclaimers am I supposed to read?

    The data herein, including but not limited to geographic data, tabular data, analytical data, electronic data structures or files, are provided "as is" without warranty of any kind, either expressed or implied, or statutory, including, but not limited to, the implied warranties or merchantability and fitness for a particular purpose. The entire risk as to the quality and performance of the data is assumed by the user. No guarantee of accuracy is granted, nor is any responsibility for reliance thereon assumed. In no event shall the Louisiana Oil Spill Coordinator's Office (LOSCO) be liable for direct, indirect, incidental, consequential or special damages of any kind, including, but not limited to, loss of anticipated profits or benefits arising out of use of or reliance on the data. The LOSCO does not accept liability for any damages or misrepresentation caused by inaccuracies in the data or as a result of changes to the data caused by system transfers or other transformations or conversions, nor is there responsibility assumed to maintain the data in any manner or form.

    These data have been developed from the best available sources. Although efforts have been made to ensure that the data are accurate and reliable, errors and variable conditions originating from physical sources used to develop the data may be reflected in the data supplied. Users must be aware of these conditions and bear responsibility for the appropriate use of the information with respect to possible errors, scale, resolution, rectification, positional accuracy, development methodology, time period, environmental and climatic conditions and other circumstances specific to these data. The user is responsible for understanding the accuracy limitations of the data provided herein. The burden for determining fitness for use lies entirely with the user. The user should refer to the accompanying metadata notes for a description of the data and data development procedures.

    Although these data have been processed successfully on computers at the LOSCO, no guarantee, expressed or implied, is made by LOSCO regarding the use of these data on any other system, nor does the act of distribution constitute or imply any such warranty. Distribution of these data is intended for information purposes and should not be considered authoritative for navigational, engineering, legal and other site-specific uses.

  4. How can I download or order the data?

Who wrote the metadata?

Last modified: 08-Sep-2003

Metadata author:
3001, Inc.
c/o Mendi Johnson
GIS Analyst
3655 SW 2nd Ave., Suite 3C
Gainesville, FL 32607

(352) 379-3001 (voice)
(352) 377-4234 (FAX)

Metadata standard:
FGDC Content Standards for Digital Geospatial Metadata (FGDC-STD-001-1998)

Metadata extensions used:

Generated by mp version 2.7.3 on Mon Sep 08 13:58:49 2003