"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 the earth's surface using the Universal Transverse Mercator (UTM) projection and a zonal coordinate system (units in meters). Specifications for the horizontal control of Q3 Flood Data files are consistent with those required for mapping at a scale of 1:24000."
"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 (SFHAs), the risk zones shown on the FIRMs are the basis for the establishment of premium rates for flood insurance coverage offered through the NFIP.
"Q3 Flood Data files convey certain key features from the existing hard copy FIRM. Edge-matching errors, overlaps and deficiencies in coverage, and similar problems are not corrected during digitizing or post-processing. The Q3 Flood Data files are inteded to provide users with automated flood risk data that may be used to locate SFHAs. More detailed information may be obtained from the paper FIRM."
"None. Acknowledgment of FEMA would be appreciated in products derived from these data."
The following is extracted from FEMA metadata --
"Attribute Accuracy Report: The Q3 Flood Data are countywide vector files derived from FEMA FIRMs. The attribute definitions may be found in the "Q3 Flood Data Specifications". Attribute accuracy was tested by manual comparison of source graphic with hardcopy plots and a symbolized display on an interactive computer graphic system. Selected attributes that could not be visually verified were individually queried. In addition, an ARC/INFO Arc Macro Language (AML) software program was applied to the dataset to test the attributes against a master set of valid attributes for the specific data category and a complete set of valid attribute combinations. (See also Entity Attribute Information.)"
"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 the following: 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."
"Data completeness for Q3 Flood Data files reflects 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 hydrologic 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 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.
"Q3 Flood Data may be derived from DFIRM-DLGs, from FIRM-DLGs, or from FIRMs digitized previously for emergency applications, or they may be newly created. 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 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 of past floods and are described by a unique attribute code that distinguishes them from areas of 1% annual chance.
"FIRMs 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 the FIRM. To obtain the latest information, contact the address listed under distributor."
"Specifications for the digitizing of FIRMs to create 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 accuracy of the Q3 Flood Data with regard to the selected base map 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."
ESRI ArcToolbox was used to import the ArcInterchange (E00) file to a vector coverage (C18089).
ESRI ArcToolbox was used to convert the vector coverage to a shapefile (LAKECOQ3_POLYGON.SHP).
ESRI ArcToolbox was used to change the projection from NAD27 to NAD83.
In an editing session, ESRI ArcMap was used to delete all polygons whose values for the field named "ZONE" were equal to "X" or "UNDES."
All fields were deleted except for those named "ZONE," "FLOODWAY," and "SFHA." Among the fields that were deleted was "COBRA," for which all polygons had a value equal to "COBRA_OUT."
The shapefile was saved under the new name of "FLOODPLAINS_Q3_FEMA_LAKE_COUNTY."
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