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The floodways for the Uncompahgre River and for MontrOse Arroyo upstream of East Niagara Road were computed on the basis of equal- conveyance reduction from each side of the flood plain. No flood- way was computed for Montrose Arroyo downstream of East Niagara Road because of extensive flow diversions. For any channel modification or fill in the sheetflow areas, a detailed review of the improvement should be undertaken to deter- mine the effects downstream. The results of these computations were tabulated at selected cross sections for each stream segment for which a floodway was computed (Table 4). As shown on the Flood Boundary and Floodway Map (Exhibit 2), the floodway boundaries were computed at cross sections. Between cross sections, the boundaries were interpolated. In caSes where the fl00dway and 100-year flood plain boundaries are either close to- gether or collinear. only the floodway boundary has been shown. The area between the fl00dway and 100-year flood plain boundaries is termed the floodway fringe. The floodway fringe encompasses the portion of the flood plain that could be completely obstructed without increasing the water-surface elevation of the 100-year flood by more than 1.0 foot at any point. Typical relationships between the floodway and the floodway fringe and their significance to flood plain development are shown in Figure 2. I- 100-YfAR FLOOD PLAIN -, FLQODWA Y FRINGE FLOODWA Y FLOODWAY FRINGE STREAM CHANNEL FLOOD ELEVATION WHEN CONFINED WITHIN FLOOD\'VAV AREA OF FLOOD PLAIN THAT COULD BE USED FOR DeVELOPMENT BY RAISING GROUND FLOOD ELEVATION BEFORE ENCROACHMENT ON FLOOD PLAIN LINE AB IS THE FLOOD ELEVATION BEFORE ENCROACHMENT. LINE CD IS THE FLOOD ELEVATION AFTER ENCROACHMENT. .SURCHARGE IS NOTTO EXCEED 1.0 FOOT (FEMA REQUIREMENTI OR LESSER AMOUNT IF SPECIFIED BY STATE. Figure 2. Fl00dway Schematic 16