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<br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />I <br />I <br />I <br /> <br />I <br />I <br /> <br />I <br /> <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />2nd cross-section: section 8,0, at downstream end of <br />cul vert:. <br /> <br />3rd cross-section: Section 9.0, at upstream end of <br />cul vert:. <br /> <br />4th cross-section: section 9.5, at toe of first drop. <br /> <br />5th cross-section: Section 10.0, at top of first drop. <br /> <br />6th cross-section: section 10,5, at toe of second drop. <br /> <br />7th cross-section: section 11.0, at top of second drop. <br /> <br />8th cross-section: section 12.0, 150' upstream of second <br />drop, <br /> <br />Sections 9.5, 10,0, 10.5, 11.0 and 12.0 are equivalent to <br />Sections 9.5, 10.0, 10,5, 11,0 and 12.0 in the submittal <br />for the request of LOMR in March 1982. Also, Section <br />12,0 is identified as cross-section "E" on the Flood <br />Insurance Rate Map. <br /> <br />statiohs and elevations for Sections 7.0 through 10.0 are <br />from as-built survey. <br /> <br />stations and elevations for Sections 10.5 through 12.0 <br />are from the March 1982 submittal (there have been no <br />changes to the concrete channel since then). <br /> <br />The approximate lOa-year water surface elevation at <br />Section 7.0 (first cross-section) is 5362.0. This value <br />is taken from the Flood Insurance Rate Map. <br /> <br />4 . <br /> <br />Manning'S "n" Coefficients <br /> <br />Manning'S roughness values used are as follows: <br /> <br />n = 0.015 concrete channel <br /> <br />n = 0,013 concrete box culvert <br /> <br />n 0.040 over bank areas, good vegetation <br /> <br />5, <br /> <br />Computations <br /> <br />Copies of the HEC-2 input, output and summary tables are <br />included in Appendix B, <br /> <br />The proposed lOa-year flood plain with the profile of the <br />lOa-year flood is shown on the drawings, included in the <br />back pocket of this report, <br /> <br />-3- <br />