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\ \ 't 10\(' ~ FLOOD PLAIN CONDITIONS Copies were obtained from Gingery Associates of the actual HEC-2 computer runs that were the basis for the Flood Plain and Floodway defined in the Basalt Flood Insurance Study. These computer runs were analyzed to determine a realistic location of the Floodway on the Hyde Park side of the River (Southwest side). Figure 3 (Sheet one of two, 24" x 36" sheets) is a 1" = 100', 5' conto~ interval, topographic map of the site illustrating the location of the 4 cross-sections utilized by previous flood plain studies. Figure 4 (Sheet two of two, 24" x 36" sheets) shows the 4 cross-sections together with the calculated 100-year flood plain levels and the floodway elevation and floodway li~its. The cross-sections on Figure 4 illustrate that the flood plain area outside the floodway, which is defined as flood fringe, consists of several low areas that meander across the site. The Floodway Analysis reveals that the entire IOO-year discharge of the Roaring Fork River could be cOnfined to an area far smaller than the defined flood plain with a very small increase in water surface or velocity of flow in the main channel and adjacent overflow area, except in the immediate vicinity of the Emma Road bridge. A realistic location for the Floodway limit through Hyde Park is shown on both Figures 3 and 4, together with the required elevation of building pads to maintain elevations at least I foot above the floodway water surface elevation. DEVELOPMENT OF PROPERTY The shape of the Hyde Park parcel is such that simply filling the site to a level .above th9 floodway elevation is not practical. Such filling would protect the site itself, but would direct flow to the west, away from the Roaring Fork River. It will be necessary to fill portions of the site, while maintaining a flow path through the site for a portion of the Flood Fringe area flow. The general concept for this approach is illustrated on Figure 3. The details of the plan will require detailed site topography. Final street grades, building siting, and overlot grading will require thorough design to implement the concept. IMPACT ON ADJACENT PROPERTY Implementation of the concepts illustrated on Figures 3 and 4 will reduce the flood damage potential to existing properties located northwest of the site. The entire 100-year flood flow of the Roaring Fork River can be passed by the Emma Road Bridge if it can be delivered to that point. Presently, the IOO-year flood would be spread across a wide area when it reaches the Emma Road, resulting in flooding of the housing units located nortllwest of the Hyde Park Parcel. The proposed site grading for Hyde Park would return much -2-