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<br />. <br /> <br />. <br /> <br />. <br /> <br />Existing Floodway Study <br /> <br />3 <br /> <br />!60.3(d) which apply in the areas where there was an adopted floodway. The distinction between <br />these different sub sections is important because the West half of Laku Landing did not have an <br />adopted flood way, but the East half did. <br /> <br />This document will show that the end project as well as any conditions that will exist during <br />construction will not cause any rise in the waters of a base flood discharge. Throughout this <br />document, the terms "base flood discharge", "intermediate regional flood", and "100 year flood" <br />will be used interchangeablly. <br /> <br />Scope of Study <br /> <br />The different sections of this document discuss: (a) the existing flood way study performed by <br />Simons Li & Associates, with modifications made by Baker Engineers, (b) the technical aspects, <br />both hydrological and topographical of the Laku Landing Development, (c) hydraulic analyses of <br />the proposed conditions, and (d) hydraulic analysis of construction conditions. <br /> <br />It has already been det"rnuned by FEMA, that no new cross sections need to be added, and <br />no new field surveys need to be taken for this study. Instead, we will analyze the Laku Landing <br />Development using the same methods that would have been used if Laku Landing existed in its <br />final form before the most recent Flood Insurance Study (FIS). Because of this, all modifications <br />to the existing FIS HEC-2 data, will be related to the cross section which intersects the lake area <br />of Laku Landing. <br /> <br />The exception to this is when examining the conditions that will exist between the time lake <br />construction begins and when it is finished. For the construction conditions, five additional cross <br />sections have been added to analyze in more detail what happens to flood waters traveling around <br />stockpiles. These additional cross sections have been added at the request of the Colorado Water <br />Conservation Board. <br /> <br />Existing Floodway Study <br /> <br />An interesting point concerning the current FIS study, is that for a portion of the river surrounding <br />Laku Landing, there is no overbank area and therefore, the entire cross section #139690 is considered <br />part of the river channel. For this reason, a single value for Manning's "n' roughness coefficient <br />is used to describe the entire cross section. In the case of cross section #139690, an "n' value of <br />0.062 was used, producing a 100 year flood water level of 4769.9 feet. Figure 3 depicts cross section <br /># 139690 in the existing FIS study. <br /> <br />The method used in computing values of Manning's "n' for the current FIS, according to Scott <br />Queen of Simons Li & Associates, was to compute the total surface area from the cross section <br />