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<br />,oed elevations On the brlose approaChes are lower and overtopped by <br />lesser tloods than the brldg€ deckS. All crossings on 11eir 3ulc~ <br />and "",'r.yon the other strmlms utilize plpos and culverts toconv ey <br />strenm f lows. These structures are loc~te(, in the c~.anneI5 and <br />;onerellyhavocapacltiesequal to or l()s<;thllntheupstrellr/lChan- <br />oel. Excopt for Hellard Stroot on ~':clntro Gulch whiCh would not be;, <br />inundated by ~ Standard Project Flood, all streets w~ld be inundated <br />by discharges Of lessthanthelnter'llediataRegional FlooJ,withsOl1le <br />being flOO<Jed even by minor flows whICh <:an Cdused disruption of <br />traffic. <br /> <br /> <br />Obstructions to Flood Flow <br />Theoostructions to flow are thor:'lany i>ridges, CLJlverts, <br />and pipes located on Graup 2 streams_ "/elr3ulch has 5 culverts in <br />the study roach th~t aro ~dequato only for passing minor flocd dis- <br />cha~ges. The box cu Ivert on I'iajswort~ 30u lavard, a major traft ic <br />artery, is only c"pablo of pil%lr>g modo~<,te floods ilnd would bo a <br />serious restriction to high flryd5. Effects of the i>rldS0 a~d culverts <br />wore fu Ily consi do~cd, and bQck'~ater cond i tlo~s ilre 5~own on the <br />water surfaco proflle~. Th~ channu I c<J~"c ities cou Id i>e fu~thcr <br />ros.rrTcted by an accumul",tionof debriSilnd silt. In the lngi'll I, <br />STreet area, alOOf) La~ewo<yj GLJlch, local lnh'r..~ts hav" fill..d j~ th" <br />flOOd plain, resTricTing ovc~i>ank tlOWS and causing a rise In the <br />upstreamwi'ltersurtilCe. Sovoral smilll dams havo hll"!"Iconstructea on <br />these streams by loca I I nterests. They o~ Iy provide minor flood <br />control, but cause n backing-up of the flood flnws. <br />Head los5es fhrDugh the bridges wer"cOf',>,ut"d by the <br />method descri bed i ~ "i"ydrau I ies of ElrTdge \\'aterways," i>y the Divl sion <br />of Hyd..-au I ic rle'iearch, Buro~u of PUi> I ic RO<lds, 19.60. Woen bridges <br />a~d Jpproach rOJos were ove~toppcd, toe rOJd em~ankmenh w",re con- <br />slder"d a~ broad-crested welr~. The backwater effocts ~r" shown on <br />t.'1e wJter surface prof Ilos, p 13tos 21 th~ough 23 of thi s ~eport. <br /> <br />SrO'.thand Iltterindra;naqewilYS increase floodlnq as woll as being <br />unsIghtly_ <br /> <br /> <br />~ <br /> <br />LclkowoocJGulc'1 <br />TOP - Vi~w UrSt..-Cilm from Harlan Street. <br />8OTTCf.1 - V lew do'~nstr03m from Sho~I(.~n Slv.J. <br /> <br />3' <br /> <br />.,j <br />