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<br />IV. HYDRAULIC ANALYSIS
<br />
<br />Hydraulic ~haracteristics of the flood plain were evaluated to
<br />determine water surface elevation for peak flows resulting from the
<br />5-,10-,25-, 50-,100-,and500-yearflOOdS. Thewatersurface
<br />elevations were computed using the U.5. Army Corps of Engineers'
<br />HEC-2 water surface profile computer program (U.S. Army, 1981), ~uCh of
<br />the cross-sectional data were provided in HEC.2 format by the City of
<br />Sterling. Corrections and additional cross sections were made from sub-
<br />sequent field surveys,
<br />Culvert and bridge geometries were field measured. Elevations for
<br />top of road crossings and downstream and upstream channel inverts were
<br />fieldsurveyecl, Roughness coefficients were selected after field investi-
<br />gation and analysis of ground and aerial photographs taken during field
<br />reconnaissance. Manning's rDughness coefficients are tabulated in the
<br />HEC-2 runs and supported by photographS 1n the Technical Addendum.
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<br />Results
<br />in Figures
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<br />FlOOd profiles are presented
<br />reaches as follows:
<br />1, Sand Creek and Local Drainage,
<br />2. Pioneer Drainage Ditch, dnd
<br />3. Pawnee Overflow
<br />
<br />P-l through P-7 for the 3 channel
<br />
<br />The water surface elevations are given in Tables 5 through 7. The extent
<br />of flooding is shown on the flOoded area 1l1d~.s. A detailed description of
<br />the hydraulic andlysis is incl"dp<l in thp Tprh"i~'d A"""~dl,rm (I_~~f, lQB3)
<br />along with the HEC-2 ~uns,
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