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<br />'.- <br /> <br />TECHNICAL A[1\)ENDUI1 <br /> <br />FOR <br /> <br />ARKANSAS RIVER, TIMPAS CREEK <br />Otero County, Colorado <br /> <br />Job Number 91336 <br /> <br />March, 1931 <br /> <br />PURPOSE <br /> <br />The purpose of this Technical J\ddendum is to supp ly, for future <br />reference, the technical back-up in format ion and documenta t ion <br />for the results presented in the related report text. <br /> <br />HYDROLOGIC ANALYSIS <br /> <br />.-... <br /> <br />The hydrological analysis for this report was performed by the <br />U. S. Army Corps of Engineers in 1978. Their analys is was based <br />on statistical analyses of streamflow records covering an 80-year <br />period at selected gaging stations operated by the U.S. <br />Geological Survey. <br /> <br />Peak flows <br />Consultants, <br />These flows <br />Addendum. <br /> <br />for the Arkansas River were supplied to MSM <br />Inc. by the Colorado Water Conservation Board. <br />are tabulated on pages 3 and 4 of this Technical <br /> <br />It is assumed that the Corps of Engineers Hydrology <br />area and the peak flows from the Colorado Water <br />Board are valid Jor the purposes of this study. <br /> <br />of the study <br />Conservation <br /> <br />HYDRAULIC ANALYSIS <br /> <br />Analyses of the, hydraulic characteristics of the streams in the <br />study area were carried out to provide estimates of the water <br />surface elevations of floods of the selected recurrence intervals <br />along each stream. The water surface elevations were computed <br />through use of the Corps of Engineers' HEC-2 step-backwater <br />computer program (Reference 1). Cross sections for the backwater <br />analyses of the Arkansas River and Timpas Creek were <br />field-surveyed at close intervals above and below bridges in <br />order to compute the significant backwater effects of these <br />structures. All bridges within the study reaches were also hand <br />measured to provide accurate geometric information. Additional <br />digitized cross sections were secured when the topographic maps <br />were compiled. (Reference 2). The locations of the field <br /> <br />- <br /> <br />