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<br />INTRODUCTION <br /> <br />The purpose of this report is to provide the technical information necessary to <br />revise the existing floodway conveyance area mapping for Goose Creek in the <br />vicinity of North Broadway Shopping Center and the Boulder Medical Center. <br /> <br />PREVIOUS FLOOD STUDIES <br /> <br />This portion of Goose Creek has been studied by several different engineering firms <br />for several different purposes. These previous studies were reviewed in detail prior <br />to beginning this analysis. The following Table 1" summarizes the previous studies. <br /> <br />Table 1 <br />Summary of I'rev::m:,s <br />Flood Studies <br /> <br />Firm <br /> <br />Type of Stud;L_~____~,~~____~_,__,_.J2i.\jg <br /> <br />Greiner IMSM <br />Wright Water Engineers <br />David J. Love & Associates <br />Grcenhorne & O'Mara <br />David J. Love & Associates <br /> <br />FEMA Flood Insurance Study <br />Floodway for Boulder Com. Hosp. <br />Floodplain for Kaiser Permanente <br />Floodway for City of Boulder <br />Product 4 for City of Boulder <br /> <br />Apr. 1983 <br />Sep. 1985 <br />Aug. 1986 <br />May 1987 <br />Mar. 1988 <br /> <br />These studies all have been based on the same topographic information as was <br />provided by the original Greiner/MSM study. In the first of these studies, the <br />Greiner/MSM study, all flow was assumed to turn al: the corn{!r of Broadway and <br />Balsam and go south of the North Broadway Shopping Center and the Boulder <br />Medical Center. This basic assumption was not changed in the Wright Water <br />Engineers analysis. The initial David J. Love & Associates analysis modified the <br />locations of the cross-sections used in the HEC2 analysis. The base modeling <br />assumptions from the initial David J. Love & Associates analysis were unchanged in <br />thE~ subsequent studies by Greenhorne & O'Mara, and David J. Love & Associates. <br />These assumptions result in the 100-year floodplain encompassing the North <br />Broadway Shopping Center and the Boulder Medical Center. <br /> <br />The modeling approach used in the David J. Love &: Associates analyses assumes <br />that an increased friction factor can represent the impact of ex:isting structures in the <br />floodplain. Figure 1, the currently accepted mapping, indicates that the most <br />significant flow portion of the flood, as represented by the flood way area, !;oes <br />through the existing North Broadway Shopping Center and the Boulder Medical <br />Center buildings. While this type of modeling approach may yield a reasonable <br />estimate of the flow depth it clearly should not be uS2d to define the location of <br />specific flood conveyance areas. <br /> <br />For comparison purposes a copy of the existing David f. Love & Associates HEe2 <br />analysis is included in Appendix A. <br /> <br />1 <br />