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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />Le <br />/~I <br />V; <br /> <br />4'(?~ <br />7JY~ <br />/' \ <br /> <br />HEC-2 is a channel flow simulation model utilizing hydraulic data to compute the surface water profiles for <br />a giveR flood. The PIS HEC-2 model was duplicated by WRC and was used as the basis for the hydraulic <br />modeling in this report. <br /> <br />The hydraulic features of the Reach such as cross section dimensions and roughness values (Manning's "n") <br />are based upon data gathered for the PIS. The Reach is natural channel with the exception of the First St <br />bridge, diversion weir, and the whitewater bypass. The latter two features were not modeled in the PIS but <br />were incorporated into the HEC-2 models developed by WRC. WRC is not aware of any other channel <br />improvements in the Reach. <br /> <br />Table -2 presents computed water surface elevations for the 100 year flood event. The five cases presented <br />in this table show the individual and combined effects of the diversion weir and the encroachments. <br /> <br />".' ",;,;/TABDE,i,2. ,>", "",:,::, ,,", ""':':"" " "", '. ::, '.:"" <br />COMPUTED W A TERSURFACEEf.;EyA.TIONSF'Q'RTlfEJOO,. YEAR' ",:," <br />, ""'PLOODEVENT <br /> <br />* <br />PIS <br />Section <br /> <br />'. ,. . <br />HEC-2 <br />Section PIS 100- CASE CASE CASE CASE CASE <br />NQ. Year A B C D E <br />9 5332.8 5332.8 5332.8 5332.8 5332.8 5332.8 <br />7 5334 5334 5334 5334 5334 5334 <br />7.1 5334.4 5334.4 5334.4 5334.4 5334.4 5334.4 <br />6 5343.2 5343.2 5343.2 5343.2 5343.2 5343.2 <br />5 5347 5347 5347 5347 5347 5347 <br />4 5352.1 5352.1 5352.1 5352.1 5351.6 5351.6 <br />3 5352.9 5352.9 5352.9 5352.9 5354.2 5354.2 <br />2.3 NA NA NA 5353.4 NA 5354.7 <br />2.2 NA :Y~~ NA 5353.2 NA 5356 <br /> I > <br />2.1 NA NA NA 5353.8 NA 5359 <br />2 5354.3 5354.3 5354.3 5354.3 5356.2 5359.3 <br />1 5359.3 5359.3 5359.3 5359.3 5360.7 5361 <br /> <br />AD <br /> <br />AE <br /> <br />AF <br />AG <br />AH <br />AI <br /> <br />AJ <br /> <br />AK <br />AL <br /> <br />Case A - Duplicate effective model <br />Case B - Corrected duplicate effective model (all sections with encroachments) <br />Case C - Corrected model with City's diversion weir <br />Case D - Corrected model with encroachments at D&RGW and southern <br />channel bank (no weir) <br />Case E - Corrected model with weir and encroachments at D&RGW RR and <br />southern channel bank <br /> <br />* <br /> <br />See Exhibit B for section locations <br /> <br />3 <br />