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<br />HYDRAULIC ANALYSIS <br /> <br />lntroduction: <br /> <br />Using t..'1e flood discharges as defined in the hydrologic (lna1ysis, water <br />surface profiles for Parachute Creek and the Colorado River were calculated with <br />the use of the U.S Army Corps of gngin~rs HEe2 computer pcogram (ref. 3). The <br />Sacramento District of the Corps performed the HEC2 analysis of the Colorado <br />River and the SCS performed the original and revised calculations far Parachute <br />Creek. J. E. Langford and Associates performed the revised 500-year flood <br />profile calculations for the overbank .llea of Parachute Creek in the Town. <br />Output listings for all runs are contained in a Technical Addendum on file with <br />theCN:::S. <br /> <br />Cross sectional data was abtilined from photograJm'etric mapping of the area <br />provided by Analytical Surveys, Inc. (ref. 4). Field investigations for the <br />Parachute Creek analysis were originally performed by the SCS in 1982 aoo 1983. <br />These included Treasurements of bridges aoo verification of channel aoo overbank <br />roughness coefficients (Manning's .n~ values). Field investigations including <br />mea5ur~ntofbridges.,.;ereperfornedbytheCorpsfortheColoradoRiverin <br />1985. <br /> <br />AdditionalrreasurernentsaftheD&RGrailroodbridgeoverParachuteCreek <br />were obtained in 1986 byJ. E. Langford and Associates at the request of the <br />Town. 'nIe cross sectional are" at the railroad bridge was found to 00 367 <br />square feet, some 24% greater than the area lJsed by the SCS in the oriqinal IIOC2 <br />model for the bridge, see Figure 2. Additionally, cross sections 242 and 243 <br /> <br />wc~c ~~rv~lcC fo~ ~~c Ta~T. i~ 1986. Thece ~re plotted in Fig~tc 3 togc~~cr <br /> <br />withtheSCSdigitiledcrosS-$ectionsfor~arison. <br />ra.ilcoad bridge area is ~~e principal reason the Town <br />to the SCS report. <br /> <br />'Il1edifferenceinthe <br />,~uested the modificati~) <br /> <br />Other factors that contribute to dLffetences ootween the oriqinal SCS <br />hydraulic analysis and the reviSed analysis contained in this re90rt are <br /> <br />10 <br />