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<br />The duplicate effective I-foot rise floodway analysis was conducted and the results, as
<br />summarized in Table 3,2, were compared to published floodway results, At all cross sections the
<br />duplicate effective flood way water surface elevations matched the reported values,
<br />
<br />Table 3,2 Summary of Duplicate Effective Floodway Results,
<br />
<br />FIRM HEC-2 Base Flood Elevation Floodway WSEL
<br />Cross Change in WSEL'
<br />Panel ID Section (ft, NGVD) (ft, NGVD)
<br /> 16430 4993,5 4993,5 0,0
<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
<br /> 18168 4993,5 4993,5 0,0
<br /> 18240 4993,5 4993,5 0,0
<br />BH 18625 4993,5 4993,5 0,0
<br />BI 19337 4994,8 4994,8 0,0
<br /> 19830 4997,3 4997,3 0,0
<br />BJ 19880 4997,7 4997,7 0,0
<br />BK 20315 4999,3 4999,3 0,0
<br />
<br />, Change in WSEL = Floodway WSEL - BFE
<br />
<br />Compared to the I DO-year water surface profile, no increase in water surface elevations
<br />is indicated for the flood way analysis through the BNRR detention pond area, This was the
<br />intention of the effective floodway analysis for this reach, as encroachment into the lOO-year
<br />floodplain would constitute a reduction in the storage volume available in the detention pond,
<br />Since the available storage volume is critical to the operation of the BNRR detention pond, the
<br />flood way was defined to include the entire 100-year floodplain, Inspection of the effective HEC-2
<br />floodway model revealed that encroachments were generally defined at the limits of the 100-year
<br />floodplain, It appears that the intent in the effective floodway model was to set the encroachment
<br />stations at the unencroached start and end stations, rounded to the nearest foot. The one exception
<br />to this rule involves the left encroachment at Cross Section 19830 where the 100-year floodplain
<br />analysis utilized Arthur Ditch for conveyance, At this location, the floodway analysis encroached
<br />the left end of the cross section so as to preclude the ditch, This encroachment does not adversely
<br />impact the operation of the BNRR pond, as the ponded water surface elevation is lower than the
<br />existing ground elevations along this portion of the cross section, HEC-2 output for the duplicate
<br />effective floodplain and flood way analyses is provided in Section B to the Technical Addendum,
<br />
<br />L'OPEN"cocsrtDl",cocsrtUl t'ema-LOMR linal-rpl.\\pd
<br />
<br />II
<br />
<br />ANdERSON CONsulTiNG ENGiNEERS, INC.
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