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<br />the floodway and 100-year floodplain boundaries are ei ther close <br />together or collinear, only the floodway boundary has been shown. <br /> <br />No floodway has been computed for Boulder Creek (Reference 21), <br />Arapahoe Avenue Overflow, and Dry Creek. However, the City of <br />Boulder and UDFCD regulate a floodway which is more restrictive <br />than the floodway required by FEMA. Contact the City of Boulder <br />or UDFCD for this floodway information. Because Twomile Creek has <br />been designated as an area of shallow flooding, a floodway is <br />inappropriate; therefore, no floodway has been shown in this <br />study. <br /> <br />,,",, <br /> <br />The area between the floodway and 100-year floodplain boundaries <br />is termed the floodway fringe. The floodway fringe encompasses <br />the portion of the floodplain that could be completely obstructed <br />without increasing the water-surface elevation of the 100-year <br />flood by more than 1.0 foot at any point. Typical relationships <br />between the floodway and the floodway fringe and their <br />significance to floodplain development are shown in Figure 6. <br /> <br />~ <br /> <br />I ( <br /> <br />lOO-YEAR FLOODPLAIN <br /> <br />-I <br /> <br />~ FLOODWAY <br />FRINGE <br /> <br />. <br /> <br />FLOODWAY <br /> <br />FLOODWAY <br />FRINGE <br /> <br />STREAM _ <br />CHANNEL <br /> <br />FLOOD ELEVATION WHEN <br />CONFINED WITHIN FLOODWAY <br /> <br /> <br />ENCROACHMENT <br /> <br />ENCROACHMENT <br /> <br />AREA OF FLOODPLAIN THAT COULD BE USED <br />FOR DEVELOPMENT BY RAISING GROUND <br /> <br /> <br /> <br />FLOOD ELEVATION BEFORE <br />ENCROACHMENT ON FLOODPLAIN <br /> <br />j.Jj~ <br /> <br />LINE 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 /> <br />,l., <br /> <br />Figure 6. Floodway Schematic <br /> <br />26 <br />