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flood heights to 1.0 foot, provided that hazardous velocities are not produced. <br /> The floodways in this report are presented to local agencies as minimum <br /> standards that can be adopted or that can be used as a basis for additional studies. <br /> The floodway presented in this study was computed on the basis of a maximum <br /> one-foot rise in water-surface elevation over the 1% A.C. water surface, for the <br /> encroached floodway. The results of these computations were tabulated at <br /> selected cross sections for Willow Creek within the City of Lamar and a nearby <br /> reach of the Arkansas River within Prowers County (Table 2). <br /> As shown on the FIRM, the floodway boundaries were determined at cross <br /> sections, and between cross sections the boundaries were interpolated. In cases <br /> where the floodway and 1% A.C. flood boundaries are close together or collinear, <br /> only the floodway boundary has been shown. Only the floodway boundaries for <br /> Willow Creek and the Arkansas River in the reaches previously described have <br /> been evaluated in this study. <br /> The area between the floodway and the boundary of the 1% A.C. flood is termed <br /> the floodway fringe. The floodway fringe thus encompasses the portion of the <br /> flood plain that could be completely obstructed without increasing the water- <br /> surface elevation of the 1% A.C. flood more than 1.0 foot at any point. Typical <br /> relationships between the floodway and the floodway fringe and their significance <br /> to floodplain development are shown in Figure 1. <br /> 100-YEAR FLOODPLAIN 01 <br /> FLOODWAY FLOODWAY LOODWAY <br /> FRINGE FRINGE <br /> STREAM <br /> CHANNEL <br /> FLOOD ELEVATION WHEN <br /> CONFINED WITHIN FLOODWAY <br /> ENCROACHMENT ENCROACHMENT <br /> •• SURCN=R-E• ......• <br /> q .W:ii:iii:iiC' B <br /> AREA OF FLOODPLAIN THAT COULD BE USED FOR FLOOD ELEVATION BEFORE <br /> DEVELOPMENT BY RAISING GROUND ENCROACHMENT ON FLOODPLAIN <br /> UNE AB IS THE FLOOD ELEVATION BEFORE ENCROACHMENT. <br /> LINE CD IS THE FLOOD ELEVATION AFTER ENCROACHMENT. <br /> 'SURCHARGE IS NOT TO EXCEED 1.0 FOOT(FIA REQUIREMENT)OR LESSER AMOUNT IF SPECIFIED BY STATE. <br /> Figure 1. Floodway Schematic <br /> 15 <br />