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<br />5210.3 feet m. s .1. Estimating bet:wee,n these two cross sections, <br />the 10o-year flood water surface el,avation at the end of the levee <br />would be approximately 5211.3 feet m.s..l. Floodwaters will back up <br />on the landward side of the levee at .thai: E~levation. <br /> <br />In addition to having the necessary height, a leve,e must meet <br />certain structural criteria to be considered effective. The <br />existing levee at Rangely would need Isome improvements to meet the <br />struct11ral criteria. For the purpose of evaluating the maximum <br />potential flood protection that could be provided by a levee on the <br />existi::lg alignment, 100-.year flood boundaries were determined <br />considaring the levee to be effec1:i.ve,. ~rh,a flood bounda.ries were <br />deline:ited using the computed flood water surface elevations and <br />topogr:iphic mapping at a scale of 1 inch equals 100 feet with a 2- <br />foot c"ntour interval. Plate 2 show's the 100-year flood boundaries <br />for tha case where only the original levee by the filtrat:ion plant <br />is considered effective and for i:h.e case where the entire~ existing <br />levee is considered effective. It: is evident that, to prevent the <br />levee from being outflanked and tl::> provide more complete, 100-year <br />flood protection, an exi:ension 1:0 .the existing leVeE! Ivould be <br />needed. <br /> <br />Hvdraulic Analvsis of potentiql Exi:e]}ded-1i.~ <br /> <br />To provide 100-year flood prcltection t:o the developed area of <br />Rangely east of White Avenue, a levee extension would have to be <br />built north of the developed arlaa and tied into high ground <br />outside the 100-year flood plain. Extending the levee to just <br />northwest of the intersection of Ce,dar and Raven Avenues would <br />provide protection to the area within t.he corporate limits and east <br />of White Avenue. <br /> <br />'Ihe levee extension would begin at some loca1:ioD on the <br />existing levee and be located outside of the current designated <br />floodway. The shortest length of new levee would come from an <br />aligmrent that continues west at the point where the existing levee <br />turns north. The farther out along the existing levee the levee <br />extens ion begins, the longer the lem~rth of the existing levee that <br />must be improved. For the pUrpOSE!S of this study, the alignment <br />choser was the shortest that would provide the necessary protec- <br /> <br />9 <br />