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<br />. <br /> <br />3-hour period. Peak discharge estimates for this event were <br /> <br /> <br />41,500 cubic feet per second at a site just upstream from West <br /> <br /> <br />Kiowa Creek, 19,700 cubic feet per second at Kiowa, and 24,900 <br /> <br /> <br />cubic feet per second near Bennett. Of 69 floodwater retarding <br /> <br /> <br />structures built by the SCS in the Kiowa Creek basin, 30 were <br /> <br /> <br />filled to capacity and in some cases emergency spillway flow <br /> <br />depths were as high as 35 feet. <br /> <br />DischarRe Probability at WiRgins. The discharge-probability <br /> <br /> <br />curve for Kiowa Creek at Wiggins was based on the regional criteria <br /> <br /> <br />presented in the Interim Review Report for Bijou Creek, dated <br /> <br /> <br />October 1970, together with Snyder's unit hydro graph constants and <br /> <br />the diffusion routing technique discussed on page 59 of this report. <br /> <br />The discharge-probability curve at Wiggins shown on plate 64 <br /> <br /> <br />was computed from the following regional data. <br /> <br /> <br />log mean discharge = 2.12 + 0.531 (log drainage area) <br /> <br /> <br />standard deviation 0.6 <br /> <br /> <br />skew co~fficient = 0 <br /> <br /> <br />An expected probability adjustment based on average length of <br /> <br /> <br />record of 25 years are applied to this curve. The above regional <br /> <br /> <br />data were developed from discharge records of tributaries with <br /> <br /> <br />relatively narrow flood plains. The Kiowa Creek basin has similar <br /> <br /> <br />characteristics to a point about 4 miles upstream from Wiggins. <br /> <br /> <br />At this point, however, the Kiowa Creek flood plain widens out <br /> <br /> <br />cQnsiderably. In order to compensate for the attenuating effects <br /> <br /> <br />of this storage, a flood routing analysis was made through this <br /> <br /> <br />reach. An estimated 100-year flood hydrograph was developed for <br /> <br /> <br />the upstream end of the reach using a synthetic unit hydrograph <br /> <br />and the 100-year peak discharge from the regional-probability <br /> <br />. <br /> <br />49 <br />