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<br />. <br />. <br /> <br />IV. <br /> <br />. <br /> <br />. <br />I <br />. <br /> <br />V. <br /> <br />. <br /> <br />. <br />. <br /> <br />. <br /> <br />. <br /> <br />VI. <br /> <br />,. <br />. <br /> <br />. <br />. <br />. <br /> <br />. <br />. <br /> <br />. <br /> <br />HAPPING <br /> <br />The hydraulics ,snd floodplain maps are based on 40 scale, 1-foot contour <br /> <br />mapping developed by field survey completed in Hay 1990. This mapping is <br /> <br /> <br />based on USGS Datum data and matches the previous mapping used for the FIS <br /> <br /> <br />Study. Happing for the upstream and downstream ties to the existing FIS is <br /> <br /> <br />the original work maps used for the existing Flood Insurance Study and is at <br /> <br />400 scale with 10-foot contour intervals (Figure B). A certified letter is <br /> <br /> <br />included in the Appendix verifying benchmark ties for the mapping. <br /> <br />HYDROLOGY <br /> <br />The flows used for this CLOHR are taken from the current FIS HEC-2 data. A <br />summary of the flows is as follows: <br /> <br />CUB CREEK <br /> <br />Location <br /> <br />Dischar2e. cubic feet Der second (cfs) <br /> <br />10-YR <br /> <br />50-YR <br /> <br />100-YR <br /> <br />500-YR <br /> <br />Above confluence with <br />Little Cub Creek <br /> <br />570 <br /> <br />2120 <br /> <br />3520 <br /> <br />10,400 <br /> <br />HYDRAULICS FOR lllPROVEHENTS <br /> <br />All hydraulics were completed using the U.S. Army Corp of Engineers HEC-2 step- <br /> <br /> <br />backwater program. Starting water surface elevations at Station 2155 (FIS <br /> <br /> <br />Section Q, HEC-2 Section 99) all match the FIS Section Q elevations from the <br /> <br /> <br />FIS profile as noted below: <br /> <br />Flood Event <br />10-Year <br />50-Year <br />100-Year <br />500-Year <br /> <br />Startin2 Vater Surface Elevation (FIS Section 0) <br />7096,5 <br />7101.3 <br />7102.5 <br />7108.3 <br /> <br />3 <br />