Laserfiche WebLink
<br />Federal Emergency Management Agency - Letter of Map Revision <br />Two-Mile Canyon Creek - Boulder, Colorado <br />Page 4 <br /> <br />41.0 FLOODPLAIN MANAGEMENT APPLICATIONS <br /> <br />4.1 Flood!)lain Boundaries <br /> <br />Two-Mile Canyon Creek floodplain boundaries were delineated using topographic <br />maps at a scale of 1" = 200' with a contour interval of 2 ti~et (Reference 4). <br /> <br />The 100-year and 500-year floodplain bowldaries and thl~ floodway are shollm on the <br />Flood Boundary and Floodway Map (Exhibit 1). In cases where the lOO"year and <br />500-year floodplain boundaries are clOSI: together, only the 100-year floodplain <br />boundary has been shown. Small areas within the flo~dp1ain boundaries may lie <br />above the flood elevations but cannot be shown due to limitations of the map scale <br />and/or lack of detailed topographic data. <br /> <br />Floodplain boundaries for Goose Creek were taken from the Flood Hazard Area <br />Delineation (FHAD) prepared by Greenhome & O'Mara, Inc. (Reference 5). <br /> <br />4.2 Floodways <br /> <br />The floodway presented in this study was computed on the basis of equal conveyance <br />reduction from each side of the floodplain. <br /> <br />The area between the floodway and 100-year floodplain boundaries is termed the <br />floodway fringe. The floodway fringe encompasses the portion of the floodplain that <br />could be completely obstructed without increasing the water surface elevation of the <br />100-year flood by more than 1.0 foot at: any point, in accordance with Federal <br />Emergency Management Agency Regulations (please refer to Table 2). <br /> <br />5.0 OTHER STUDIES <br /> <br />To ensure the reliability of this restudy, the results have been compared to the current FIS <br />and Flood Hazard Boundary Maps. It appears that the significant differences are a direct <br />result of cross section placement and the inadequate cross sections used in the current <br />regulatory FIS. The reasonableness of this study was also visually verified by field <br />observations made by City of Boulder personnellwd Love & Associates, Inc. <br /> <br />6.0 REFERENCES <br /> <br />1. U.S. Department of Agriculture, Soil Conservation Service, Soil Surv~lf <br />Boulder County Area. Colorado. January 1975. <br /> <br />2. Federal Emergency Management Agency, Flood llw.JLance Study. CWlf <br />Boulder. Colorado: Boulder County. CQlQml1.2, revised August 4, 1988. <br /> <br />3. U.S. Army Corps of Engineers, Hydrologic Engineering Center, Hlli::':1. <br />Water Surface Profiles Generalized Comp_uter PrOllIllll1!, Davis, California, <br />February 1991. <br /> <br />4. Genge Aerial Surveys, TQpo~l\Phic and Planimetric Mn~, Scale 1" = 200', <br />Contour Interval = 2 feet, Boulder, Colorado (flown October 1981). <br />