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This revision relied on mapping developed in 1977 by Nelson, Haley, Patterson, and Quirk, Inc., for the Comprehensive Drainage and Flood Study for Florence, Colorado, (Reference 20). Nelson, Haley, Patterson, and Quirk mapped a portion of the revised study area using aerial photography to produce orthophoto topographic mapping at a scale of 1"=100' with 2-foot contour intervals and showing all planimetric features such as streets and major structures. This mapping provided by the City of Florence covers the area that ends approximately 800 feet upstream of Minnequa Canal. Consequently, the FIS study reach extends approximately three-quarter mile upstream of the limit of the orthophoto topographic mapping coverage provided by the City. For the reach of Oak Creek that lies beyond the mapping coverage of the City, the flood plains were plotted on a U.S. Geological Survey Digital Orthophotographic Quarter Quadrangle (DOQQ) map. Elevations are referenced to NGVD 29. Elevation Reference Marks (ERMs) shown on the FIRM represent those used during the preparation of this and previous Flood Insurance Studies. The elevations associated with each ERM were obtained and/or developed during FIS production to establish vertical control for determination of flood elevations and floodplain boundaries shown on the FIRM. Users should be aware that these ERM elevations may have changed since the publication of this FIS. To obtain up-to-date elevation information on National Geodetic Survey (NGS) ERMs shown on this map, please contact the Information Services Branch of the NGS at (301) 713-3242, or visit their website at www.nqs.noaa.qov. Map users should seek verification of non-NGS ERM monument elevations when using these elevations for construction or floodplain management purposes. Cross sections 3+30 to 58+14 are a composite of data from the mapping provided by the city and channel data surveyed by Valley Survey under contract to the Ci ty of Florence. The field-surveyed cross sections (65+04 to 99+89) in the upstream reach were placed on the DOQQ map using field coordinates provided by Valley Survey. AS part of this revision, the format of the map panels has changed. Previously, flood-hazard information was shown on both the Flood Insurance Rate Map and Flood Boundary and Floodway Map. In the new format, all base flood elevations, cross sections, zone designations, and floodplain and floodway boundary delineations are shown on the Flood Insurance Rate Map and the Flood Boundary and Floodway Map has been eliminated. Some of the flood insurance zone designations were changed to reflect the new format. Areas previously shown as numbered Zone A were changed to Zone AE. Areas previously shown as Zone B were changed to Zone X (shaded). Areas previously shown as Zone C were changed to Zone X (unshaded). In addition, all Flood Insurance Zone Data Tables were removed from the Flood Insurance Study report and all zone designations and reach determinations were removed from the profile panels. 15