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<br />. To modify the computer model to eva.luate the 100--year flood <br />plain a:1d floodway for the existing' levee and also to evaluate the <br />10-, 50-, and 500-year flood events;' <br /> <br />. To model an extension of thE! existing levee alignment along <br /> <br />the left boundary of the existing floodway; <br /> <br />. To provide criteria to enable the new levee to be <br />considered effective according to t:hE! standards of the National <br />Flood I1surance Program (NFIP) and .to upgrade the existing levee to <br />NFIP standards; and <br /> <br />. To provide a report describing the results of the s.tudy as <br />well aG provide the technical backup material, including the <br />computer models, water surface profile plots, levee height profile, <br />and flo:>d plain inundation maps for t.he! different cases considered. <br /> <br />COMMUNITY DES(~R:rPTION <br /> <br />Rangely is located in Rio Blanco County, approximately 70 <br />miles north of Grand Junction, in northwestern Colorado. The <br />elevation is approximate!ly 5,200 feet. The main economic <br />activities in the Rangely area are ranching and oil production. <br /> <br />FLOOD PROBLEM DleSCRIPTION <br /> <br />The White River flows to the .,est along the northern boundary <br />of Ran~'ely on its way to the confluence with the Green River in <br />Utah. Floods on the White River mm resul.t from ice jams, rapid <br />snowmelt, rain on snow, or heavy thunderstorms. Accordi:n9 to the <br />current FIS for Rangely (Reference 1), t.hE! largest flood on record <br />on the White River occurred in February 1962 as a result of ice <br />jams. Another large ice-jam flood occurred in March 1955. In both <br />of these events, floodwaters reache!d Main street in places. In the <br />summer of 1910 or 1911, a thunderst:orm reportedly produced White <br />River flood stages almost to 1:he level of 1962. Another <br />thunderstorm in the 1920's also reportedly caused theWhi1:e River <br />to floed into Rangely. <br /> <br />2 <br />