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It was decided for portions of the Dry Creek floodway to permit encroachment to a point where the maximum rise in the I-percent annual chance flood water-surface elevation would be no greater than 1.0 foot as computed in the Dry Creek report (Reference 1). A 0.5 foot floodway was computed for Spring Creek based on a combination of equal conveyance reduction and by setting the encroachment stations at specified locations. The results of these computations are tabulated at selected cross sections for each stream segment for which a floodway is computed (Table 4). As shown on the FIRM (Exhibit 2), the floodway boundaries were computed at cross sections. Between cross sections, the boundaries were interpolated. In cases where the floodway and I-percent annual chance flood plain boundaries are either close together or collinear, only the floodway boundary has been shown. The area between the floodway and I-percent annual chance floodplain boundaries is termed the floodway fringe. The floodway fringe encompasses the portion of the floodplain that could be completely obstructed without increasing the water-surface elevation of the I-percent annual chance flood by more than 1.0 foot at any point. Typical relationships between the floodway and the floodway fringe and their significance to floodplain development are shown in Figure 1. I- 100- YEAR FLOODPLAIN .1 FLOODWAY FRINGE II( FLOODWAY lOOOWAY FRINGE STREAM CHANNEL flOOD ELEVATION WHEN CONFINED WITHJN FlOODWAY ENCROACHMENT AREA OF FlOODPLAtN THAT COULD BE USED FOR DEVELOPMENT BY RAISING GROUND LINE AS IS THE FLOOD ELEVA nON BEFORE ENCROACHMENT. LINE CO IS THE FLOOD ELEVATION AFTER ENCROACHMENT. .SURCHARGE 15 NOT TO EXCEED 1.0 FOOT (FIA REQUIREMENT) OR LESSER AMOUNT If SPECIFIED BY STArE. Figure 1 - Floodway Schematic 44