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I I I I I I I I After the crosa,sectional dats vere received fro. FEKA, they vere coded into HEC-2 format and run vith the FIS discharges to compare vith the FIS for Malta. The nev IIOdel compared to within 0.2 foot of the profiles furnished vith the cross-sectional date from FEKA. I I I EXISTING CONDITIONS After the FIS IIOdal vas verified, the aodal discharges vere changed to those computed for the reconnaisaance study. 'lbe effective flow arees vere checked and changed slightly, especially around the U.S. Highway 2 and railroad bridges. 'lbe effective flow areas were adjusted to smooth out their outlines, but this had a negligible effect on the overall vater surface profiles. So.e alterations were IlAda in the way the three bridges were modeled, but the effects on the vater surface profiles vere negli- gible. The "n" values were increased fro. those used in the FIS to better match a high-vater mark set in 1986 for an event vith 14,800 c.f.s. (about a 25-year event). The channel "n" value was increased 15 percent to 0.052 to reflect the meandering of the Kilk River, and the overbank "n" value vas increased to 0.065 to reflect the light brush and trees present (Open- Channel Hydraulics, Chov, 1959, pp. 109-113). 'lbe 1986 high-vater IlArk elevation was taken downstream fro. the foresight levee; therefore, no adjustment vas necessary. I I .' I I I I I The existing foresight levee vas assumed to be inadequate and vas failed in all existing-conditions models. Existing-conditions vater surface profiles were computed and are shown on plate 2 vith the computed FIS vater surface profiles. The maxi_ difference between the FIS water surface profiles and the existing-conditions profiles vas 1.5 feet for the 10-year event and 1 foot for events above 10 years. The FIS water surface profiles and the existing-conditions profiles were similar enough that they were assumed to have the same flooded areas. Therefore, the flood boundaries shown in the FIS report were used for existing conditions and are shown on plate 3. 15