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<br />The composite rainfall pattern shows that rainfall totals exceeded ten inches over an area <br />approximately 12 miles long and two to three miles wide for a total area approaching 30 <br />square miles. <br /> <br />Historical Perspective <br /> <br />State and Regional perspective <br /> <br />Extreme rainfalls in excess often inches in 24 hours or less in Colorado are rare but not <br />unprecedented. Just two months prior to the Fort Collins storm, the Colorado Climate Center <br />completed a study of extreme precipitation in Colorado (McKee and Doesken, 1997) for the <br />Colorado Department ofNatura1 Resources, Division of Water Resources. This study <br />identified twelve events during the Twentieth Century that most likely produced ten or more <br />inches ofrain and caused extreme flooding along the east slope of the Rocky Mountains <br />(Table 6). This list included three storms in similar topographic regions outside of Colorado <br />such as the Rapid City, South Dakota, storm of June 9, 1972. <br /> <br />Table 6. <br />Chronological List of Extreme Rain Events on the "Front Range" <br />during the Twentieth Century (from McKee and Doesken, 1997) <br /> <br /> Maximum <br />Storm Date Precipitation <br />LivermoreIBoxelder May 20-21, 1904 8+ inches <br />Pueblcv'Penrose June 2-8, 1921 6 - lZ' <br />Savageton, Wyoming Sept. 27-29, 1923 17" <br />Cherry CreeklHale May 30-31, 1935 12-24" <br />Northern Colorado Front Range Sepl2-3, 1938 6 -10" <br />Rye (Southern Cola Front Range) May 18-20, 1955 6 -13" <br />Gibson Dam, Montana June 6-8, 1964 16" <br />Plum Creek June 16-17, 1965 14 - 16" <br />Big Elk MeadCMS May 4-8, 1969 6-14" <br />Rapid City, South Dakota June 9, 1972 15" <br />Big Thompson July 31, 1976 12' <br />Frijole Creek July 2-3, 1961 B - 16" <br />Fort Collins July 27-28, 1997 14.5" <br />Pawnee Creek JulY 29-30, 1997 15,1" <br /> <br />The Fort Collins storm was smaller in area than several of these earlier huge rains. For <br />example, the stormes) of June 1965 struck several portions of eastern Colorado and caused <br />widespread severe flooding. The Fort Collins storm, however, was of sufficient short-term <br />intensity, and the combined precipitation from the earlier rain episodes during the 24 hours <br />preceding the final downpour were sufficiently great, to place this storm on the list of most <br />extreme Front Range rain events of the century. Prior to the Fort Collins storm, it had been <br />16 years since the last giant rainstorm. The Frijole Creek storm occurred near Trinidad, <br /> <br />33 <br />