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<br />Since the potential levee alignment was located outside <br />the floodway, it was expected that any increase in the <br />lOa-year flood elevations would be less than 1 foot. As <br />shown in Table 4 of the main text, -the actual increase was <br />much less. Because the loa-year flood depths in the area <br />landward of the levee were shallOlN, the leveE~ extension did <br />not cause much loss in the left ban]e conveyance. <br /> <br />The lOa-year flood elevations developed by the <br />NEWDIKE.DAT file were used to establish the levee heights for <br />laO-year flood protection. At most cross sections, this was <br />done by adding 3 feet to the lOa-year flood water surface <br />elevation computed with the levee encroachments in place. In <br />the area of sections 42 and 43, a more consE~rvative approach <br />was used. Because of the curvature of the channel in this <br />area, the water surface elevations on the left overbank of <br />these cross sections could be significantly higher than <br />computed for the entire cross secti,:;.n. At cross section 43. <br />the lOa-year flood water computed a"t_ section 44 was used with <br />3 feet of freeboard. At section 42, the lOO--year elevation <br />at section 43 was used with 4 feet of freeboard added. <br /> <br />Once a final levee alignment is determined, -the <br />NEWDIKE.DAT file should be modified to run with that <br />alignment. Modification of the left bank alignment of <br />sections 42 and 43 would more accurately mOdE!l the water <br />surface elevations in that area. A sensitivity analysis <br />should also be conducted to determine the efl:ect of varying <br />the channel and overbank roughness values ("n" values) on the <br />computed water surface elevations. <br />