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The vertical datum offset values us~ed for this countywide study are included in Table 3"Vertical Datum Conversion Factor Table". Table 3- Vertical Datum Conversion Factor Table a Floodin S~ ource Vertical Datum Offset (ft) Chicken Creek +4.0 Lost Canyon Creek +4.0 Mancos River through the Town of Mancos +4.0 Example: To convert Chicken Creek elevations to NAVD 88, 4.0 feet were added to the NGVD 29 elevations. The Base Flood Elevations (BFEs) shown on the FIRM represent whole-foot rounded values. For example, a BFE of 6,920.4 will appear as 6,920 on the FIRM and 6,920.6 will appear as 6,921. Therefore, users that wish to convert the elevations in this countywide s~tudy to NGVD29 should apply the stated conversion factor(s) to elevations shown on the Flood Profiles in the FIS report, which are shown to the nearest 0.1 foot. For more information on NAVD88, see Converting the National Flood Insurance Program to the North American Vertical Datum of 1988, FEMA Publication FIA- 20/June 1992, or contact the Vertical Network Branch, National Geodetic Survey, Coast and Geodetic Survey, National Oceanic and Atmospheric Administration, Rockville, Maryland 20910 (Internet address http:/www.ngs.noaa.gov). ! 4.0 FLOODPLAIN MANAGEMENT APPLICATIONS The NFIP encourages State and local governments to adopt sound floodplain management programs. To assist in this endeavor, each FIS provides 1-percent annual chance floodplain data, which may include a combination of the following: 10-percent, 2- percent, 1-percent, and 0.2-percent annual chance flood elevations; delineations of the 1- percent and 0.2-percent annual chance floodplains; and 1-percent annual chance floodway. This information is presented on the FIRM and in many components of the FIS, including F'lood Profiles, Floodway Data tables, and Summary of Stillwater Elevation tables. Users should reference the data presented in the FIS as well as additional information that may be available at the local community map repository before making flood elevation and/or floodplain boundary determinations. 4.1 Floodplain Boundaries To provide a national standard without regional discrimination, the 1-percent annual chance (100-year) flood has been adopted by FEMA as the base flood for floodplain management purposes. The 0.2-percent annual chance (500-year) flood is employed to indicate additional areas of flood risk in the community. For each stream studied by detailed methods, the 1-percent and 0.2-percent annual 15