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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />of June I, 2002 with a time interval of I min. HEC-HMS was then used to calculate the peak <br />flow for these specifications. For more information refer to the HEC-HMS User's Manual. <br /> <br />4.4 Hydraulic Analysis <br /> <br />The hydraulic analysis began by importing the Geometric Data import file, created with HEC- <br />GeoRAS as described above, into HEC-RAS through the geometric data view using the "Import <br />Geometric Data" button from the File pull-down menu. HEC-RAS, the Army Corp of Engineers <br />Hydrologic Engineering Center's River Analysis Systems, is capable of steady flow water <br />surface profile calculations for the 100-yr flood through computer modeling and normal depth <br />calculations. The basis for these calculations is the solution of the one dimensional energy <br />equation. For rapidly varied surface water flow, the momentum equation is utilized. <br /> <br />Once the geometric data was imported into HEC-RAS, the XS interpolation tool in the <br />Geometric Data view was used to interpolate cross-sections within the river reach that were <br />further than one thousand feet apart. Next, an estimation of channel and bankfull parameters <br />were designated from Manning's "n" values and locations of the tops of banks, both of which <br />were determined from field observations, engineering judgment, and photographs that were <br />taken during the surveying procedure. The photographs can be found on the attached CD. Then, <br />the structural and hydraulic conditions and weir, expansion, contraction, entrance loss, and exit <br />loss coefficients were entered. The height, width, and/or diameters of the bridges and/or culverts <br />were entered. Entrance and exit loss coefficients of 0.7 and 0.1 were entered in for the culverts <br /> <br />and a weir coefficient of2.6 Hi was entered in for all deck roadways. Expansion and <br /> <br />contraction coefficients of 0.3 and 0.5 were entered in for all upstream and downstream locations <br />of the cross-sections, 0.3 and 0.5 for all bridges, and 0.6 and 0.8 for all culverts respectfully. <br /> <br />Finally, the water surface elevations were calculated, the final results were confirmed to fall <br />within a reasonable range for the watershed, and the computer model warnings were assessed <br />and amended. Results were confirmed with other literature sources and professionals with <br />knowledge of similar areas and conditions. <br /> <br />21 <br />