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<br />at the upstream face of the BNRR were obtained from the results of the effective SWMM model.
<br />For the duplicate effective HEC-2 models, the study reach was limited to the portion of Spring
<br />Creek from the upstream face of the BNRR (Cross Section 16430) to Cross Section 20315,
<br />approximately 500 feet upstream of the Arthur Ditch crossing of Spring Creek,
<br />As defined in the effective HEC-2 model provided by the City, the regulatory 100-year
<br />discharge through the current study reach ranges from 2, 135 to 2,555 cfs. Within the study reach,
<br />the duplicate effective models indicate channel roughness coefficients (Manning's n values)
<br />ranging from 0,030 to 0,045, with overbank roughness coefficients varying from 0.035 to O. 100,
<br />A copy of the two original FIS work maps which encompass the current study reach are included
<br />with this report.
<br />The duplicate effective floodplain analysis was conducted and the resulting base flood
<br />elevations compared to the published 100-year water surface profile, The duplicate effective 100-
<br />year water surface profile matched the published FIS profile at all cross sections, The duplicate
<br />effective 100-year water surface profile is summarized in Table 3,1. Copies of both the tabular
<br />listing and the graphical representation of the effective FIS flood profiles through the current study
<br />reach are provided in Appendix B, In addition, graphical representations of the duplicate effective
<br />cross sections through the study reach are provided in Appendix C.
<br />
<br />Table 3,1
<br />
<br />Comparison of 100- Year Water Surface Profiles for Duplicate and Corrected
<br />Effective Analyses,
<br />
<br /> 100- Year
<br /> HEC-2 Water Surface Elevation Difference
<br />FIRM Cross (ft, NGVD) in WSEL Location
<br />Panel ID
<br /> Section Duplicate Corrected (feet)
<br /> Effective Effective
<br /> 16430 4993,5 4993,5 0,0 upstream side of BNRR
<br /> embankment
<br />BF 17380 4993,5 4993,5 0,0
<br /> 18075 4993,5 4993,5 0,0
<br />BG 18135 4993,5 4993,5 0,0 downstream face of unnamed road
<br />(Bay Road)
<br /> 18168 4993,5 4993,5 0,0 upstream face of unnamed road
<br /> (Bay Road)
<br /> 18240 4993,5 4993,5 0,0
<br />BH 18625 4993,5 4993,5 0,0
<br />BI 19337 4994,8 4994,7 -0,1
<br /> 19830 4997,3 4997.4 0,1 downstream side of Arthur Ditch
<br />BJ 19880 4997,7 4997,7 0,0 upstream side of Arthur Ditch
<br />BK 20315 4999,3 4999,3 0,0
<br />
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<br />
<br />10
<br />
<br />ANdERSON CONsulTiNG ENGiNEERS, INC.
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