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<br />General <br /> <br />4. Flood Dike Restoration - Plan and Profile <br />- Contour interval: I foot <br />- Scale: 1" = 30" <br />- Datum: Verbal confirmation from DGR at mean sea level <br />- Map Date: July 28, 1994 <br />- Bench Mark: Top/Operating nut fire hydrant, East side of North 3rd Street, South of <br />Swimming pool <br />- Map oflevee on Boone Street with sandbags on top <br />- Levee rebuilt after flood to level of sandbags (approximately two feet) <br /> <br />One Aerial photo used <br /> <br />I. Aerial photo of Rock Rapids Iowa <br />- Scale: approximately I" = 1000' <br />- Map Date: April 3, 1990 <br /> <br />Mapping Overlays <br /> <br />. The FIRM map was overlaid onto the Topa map of and the 100 year and 500 year <br />flood boundaries were plotted along with the water surface elevations and lettered <br />cross sections. (Light table and pencil) <br /> <br />Mapping Variations and Constraints <br /> <br />. The water surface elevations of the FIRM map did not correlate with the contours and <br />spot elevation of the Topo map. <br />. Any non-lettered cross section was not located on the FIS work map (or any other <br />mapping) and could not be determined on the Topographic map due to variations in <br />the map elevations. <br />. Variations in contour elevations between Topa map and the FIS map. Differences <br />range from 0 to 10 feet with the Topo map of Rock Rapids always being the greater <br />of the two elevations. <br />. The FIRM map has extended cross sections not showing begining or ending of the <br />actual surveyed section. <br />. The FIS surveyed sections do not correlate well with the quad elevations. <br /> <br />Since City surveyed the cross sections for the FIS, then the city should be able to tie <br />into the same datum for levee construction. Variations in mapping will not allow us <br />to determine levee heights and widths (Assumed hase height of 3 feet for lOO-yr <br />protection site A). <br /> <br />General - page 2 <br />