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TABLE 1. <br />Drainage area (sq. miles) <br />Average annual precip.(in.) <br />Stream length (miles) <br />Elevation difference (ft) <br />Runoff lag time (hours) + <br />Stream slope (ft/mile) <br />SCS runoff curve number <br />Basin Characteristics <br />Waldo Canyon East tributary <br />1.48 .25 <br />20 20 <br />2.93 .95 <br />2080 680 <br />.39 .17 <br />71 0 ~ : 71 5 . -. ~7 d~-~ P <br />65 65 -~. ~~„~ <br />* elev. difference along main channel <br />+ as defined in USBR, Design of Small Dams (1974) <br />of the canyon side slopes and also along the defined channels. <br />The "effective" slope along the channels is not as great as that <br />indicated on the map because a field inspection revealed that the <br />channel consists of a series of "shoots and pools". That is <br />where the channel gradient consists of a series of "shoots" or <br />drops over outcrops of weather resistant granite from 0.5 to 4 <br />feet in height. Between these drops, the "pool" portion of the <br />channel has a nominal 1/2 to 1 percent slope that is normal for <br />many streams. The surface materials of the basin consist of <br />highly weathered granite that is not really a soil but rather a <br />coarse silt and sand. h• ~ttcial co~nring of tYfe <br />watershed results in ls~~'r°1ace runott than if the pi~ent <br />material had weathered to a coaplets soil such ae clay .• <br />The results of the HEC1 computer analysis of inputing the 100- <br />year, 24-hour design precipitation (Miller, et al., 1973) <br />indicate that t r discharges are: Maldo Canyon above the <br />conflue~, # tributarryy, 850 cubic feet per.~o <br />(cfs)~i -feet (AF1; East tributary above the <br />confluence -' , 1,45 c~j 26 AF; Waldo Canyon at' <br />Highway Um' - ale, 180AF. <br />These computed discharge rates are high unit runoff rates (cfs/ <br />sq. mile). The reasonable question needs to be asked and <br />reviewed relative to how comparative are these runoff rates in <br />terms of observed flows and other computed discharges in the <br />region. Exhibit G-1 is a plot of several maximum observed floods <br />as well as the estimated 100-year discharges for the reaches of <br />Fountain Creek in and around Manitou Springs (US Army Corps of <br />Engineers, 1974). The computed Waldo Canyon 100-year discharge, <br />durtace Nater Reaponsaa: Summit Pit Application page 3 <br />