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<br />NOAA is bounded to the west by the continental divide and covers all of Eastern Colorado. The <br /> <br />Front Range portion of the Eastern Colorado region may actually be contained in a separate <br /> <br />region not recognized by the NOAA atlas due to the orographic affect as indicated by Jarrett and <br /> <br />11/ <br /> <br />Costa (1983,1988) and Jarrett (1990, 1993). Also, it is difficult to delineate boundaries between )/ <br /> <br /> <br />homogeneous regions when there. is a lack of raingages such as in the Front Range of Colorado. <br /> <br />It has been shown by Jarrett (1987,1993) that variations in elevation and basin aspect in <br /> <br />the Rocky Mountains of Colorado can produce distinctive climatic effects related to flooding. <br /> <br />Jarrett plotted maximum unit discharge for streamflow-gaging stations against gage elevation for <br /> <br />the Rocky Mountain states and found that above an elevation limit of2,300 meters, high flows <br /> <br />are snowmelt dominated. Below 2,300 meters, maximum unit discharges in Colorado can be as <br /> <br />high as 38 m3/s!km2 , exhibiting the ability of convective storms to produce destructive flash <br /> <br />floods (Jarrett, 1993). The plains of Eastern Colorado are subject to intense thunderstorms, such <br /> <br />as the 1965 events, that produced approximately 10 inches in 3 to 4 hours on areas near Palmer <br /> <br />Lake, Larkspur, and Castle Rock, and on the divide between the Arkansas and South Platte <br /> <br />Rivers southeast of Elbert (Matthai, 1969). Summer thunderstorm activity becomes less <br /> <br />pronounced as one moves from the plains to the mountains. A high gradient of isopluviallines iJl <br /> <br />evident in any rainfall atlas (NOAA Atlas 2) describing spatial rainfall starting at the base of the <br /> <br />foothills and continuing to a level of approximately 2,300 meters as described previously by <br /> <br />Jarrett (1987). <br /> <br />The importance of defining a meteorologically and climatologically homogeneous region <br /> <br />in applying ~ suitable frequency distribution that most closely represents the true distribution is <br /> <br />iterated by Schaefer (1990): <br /> <br />. <br />"The selection and verification of homogeneous regions, the identification of the regional <br /> <br />/ <br />