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<br />delineated for this report is shown as an approximate special flood <br />hazard area. <br /> <br />The Urban Drainage and Flood Control District published a report on <br />Niver Creek in February 1974 (Reference 8). The report contained two <br />100-year profiles, one reflected existing conditions and a fully <br />developed basin and the second reflected channel improvements with <br />discharges based on a fully developed basin. Since the publication, <br />some of the channel improvements have been made. Also, the present <br />report reflects only present basin development. Therefore, no <br />comparison can be made between profiles. <br /> <br />.. : <br /> <br />. <br /> <br />A recent report on Northfield Creek, prepared by Hogan & Olhausen for <br />the City of Thornton (Reference 26), was published in March 1976. When <br />compared, the 100-year discharges in this study were found to be <br />different from those determined for the present study. This difference <br />is due to the different methods used to determine the discharges. A <br />meeting was held on April 16, 1976, wi th the Urban Drainage & Flood <br />Control District, the City of Thornton, Hogan & Olhausen, and Gingery <br />Associates in order to resolve the difference in discharges. The main <br />reason for the discrepancy was because Hogan & Olhausen considered <br />residential areas as being 25 percent impervious while the present <br />study used a 50 percent impervious figure, the figure recommended by <br />the UDFCD in their Urban Storm Drainage Criteria Manual for use in the <br />Denver metropolitan area. At this meeting, a resolution was never <br />confirmed, therefore the Federal Insurance Administration was contacted <br />for a final ruling. ,The Federal Insurance Administration decided to <br />use the 50 percent impervious figure. <br /> <br />During the appeals process, approximate flood boundaries were adopted <br />from studies on First Creek (Reference 27) and Second and Third Creek <br />(Reference 28) and Grange Hall Creek (Reference 29). <br /> <br />The present Flood Insurance Study for the unincorporated areas of Adams <br />County is authoritative for purposes of the Flood Insurance Program, <br />and data presented herein supersede or are compatible with all previous <br />determinations. <br /> <br />7.0 LOCATION OF DATA <br /> <br />Survey, hydrologic,-. hydraulic, and other pertinent data used in this <br />study can be obtained by contacting the office of the Federal Insurance <br />Administration, Regional Director, Room 311, 909 17th Street, Denver, <br />Colorado 80202. <br /> <br />8.0 BIBLOGRAPHY AND REFERENCES <br /> <br />1. U.S. Geological Survey, Water Supply Paper 997, Floods in Colorado, <br />R. Follansbee and L.R. Sawyer, 1948 <br /> <br />2. Hotchkiss, Inc., Tra iectory of a Tragedy-Denver Area Flood, June <br />16th-17th, 1965, G.F. Meister and E.J. Haley, 1965. <br /> <br />33 <br />