Laserfiche WebLink
<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 />Discharge values were discussed in the hydrology section of this study. Most <br /> <br /> <br />of the cross-section data were hand-picked from topographic maps, with a scale of <br /> <br /> <br />one inch equals 200 feet and two-foot contour intervals. Dimensions of bridges and <br /> <br /> <br />hydraulic roughness coefficients ('n' values) were determined from field <br /> <br />investigations. Tables 2A and 2B show the estimated 'n' values for HEC- RAS cross- <br /> <br />sections of Mud gulch and Four-Mile Creek. <br /> <br />Channel roughness coefficients (Mannings 'n') for these computations were <br /> <br /> <br />assigned on the basis of field inspection of the flood plain area. The ranges of 'n' <br /> <br /> <br />\'alues for the channels and oyerbanks are summarized in Table 4. <br /> <br />TABLE 4 <br />Roughness Coefficients <br />, , <br />n <br />Channel 0.03 <br />Flood plain 0.025 - 0.08 <br /> <br />The flood profiles presented in this study are based on flow through <br /> <br />unobstructed hydraulic structures, such as bridges, dikes, dams, and levees. <br /> <br />Therefore, the results should be considered valid anI\' if these stnictures do not fail <br /> <br />and remain unobstructed. A detailed description of the hydraulic analysis is included <br /> <br />in the Technical Addendum. <br /> <br />16 <br />