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<br />100000 <br /> <br />PMF <br /> <br />.-.-............'.'.'.'.'.'.'.'.'.'.'.'.'.'.'.'.'.'.'.,.,.,.,.,.,.,.'.'.'.'.'.'.'-........... <br /> <br />10000 <br /> <br />100 <br /> <br />Gage (58 years) <br /> <br /> <br />\----.-::~ <br />~// --' \ <br /> <br /> <br />.....;............ <br />.....7.... <br />" <br /> <br /> <br />intervals <br /> <br />~ <br />- <br />'" <br />E <br /> <br />1000 <br /> <br />m <br />Cl <br />~ <br />l\l <br />.c <br />" <br />" <br />'tl <br /> <br />>< <br />l\l <br />" <br />Q. <br /> <br /> <br />Max paleoflood <br /> <br />10 <br /> <br />1 <br />1 <br /> <br />10 <br /> <br />100 1000 <br />Recurrence interval, years <br /> <br />10000 <br /> <br />100000 <br /> <br />Figure 5, Flood-frequency relations for Cherry Creek near Franktown (06712000) with paleoflood <br />data (shown as a rectangle, which reflects ranges for the magnitude and age of the paleoflood) with <br />95-percent confidence limits, The PMF cslimate for this site (from fig, 4) is shown for comparison. <br /> <br />The causes for the smaller floods in Cherry Creek basin, while not well understood. probably is <br />explained by several factors, First. the highest elevation of the Palmer Divide (-2.350 m; relief of <br />about 1.035 m on the south side of the Divide) is located at the headwaters of Cherry Creek (north, <br />draining basin) and may substantially deplete the available moisture for producing extremely large <br />rainfall amounts (or rain-shadow effect), Second. localized relief (bulles and ridges with about 7S to <br />100 m of reliet) also appears to affect location of maximum rainfall amounts, which historical <br />dramatically decrease within a distance of about 3 to 6 km (fig. I), and supports paleoflood study <br />results, In addition. high infiltration rates for soils in much of Cherry Creek basin and over thirty <br />flood retarding structures built by the U.S. Soil Conservation Service contribute to reduced flood <br />runoff. Spatial variability of extreme rainfall affects not only peak discharge but also the volume of <br />flood runoff. which in turn affects flood-control Storage requirements, <br /> <br />8 <br />