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<br />()tJst~uctions - TM~e a~" 14 brid'1C>5, excludin'1 ~ f()(]t
<br />b~id'l'" c~ossin'1 tMe stn",", within the study ~""ch. T"" h~id'1es ce<nbined
<br />with tllO ~odd embankr1ents ilC~OSS the f 100<1 "Iii In l"flue'K:e floo:l Mtt"rns.
<br />^ ~OadwilY which Is elevilted a~ve the fl~d ~Ialn tends to obstr~t floorl
<br />flowSilna raises ilood sta'1e'i on theuostre,,", side of theroild. fh<,,,mount
<br />of obstruction is shown on the Droflles by the difference in ~~ter Surt"e
<br />clovat ion on tho upstreil'" ilM downst~e,"'" side 0f ","eh r<;fld. Plat" ') Shows
<br />a snee ia I roadway et feet wh"re tMe Co lorado .1M Sou thorn Ra i 1 rOild hilS ,~
<br />skewedratherthant>eroondlculdrcrossi"'lnf the flood nlaln. Eastnlth"
<br />r<lilrOildbrldqeatrefererlCeooTnt 10 the water on theuDSlreil'" ,ide of the
<br />r<l i I raad embankment Ilows at a hi qhor e I ovat Ion tha I' on the downstreilm ~ I de
<br />Of tho embankment. eros"> sect ian 2, shown on plate 9. furt~er ill ustrates
<br />thecoodition. The upstre<lm\<1tersurf,lceelevations are Qivcnin
<br />table 5, co~re5{)oM inCl to reference pOints lettered ^ throu~M E. ^ s Iml lar
<br />cor'll'l1tion exists o,Ht 01 U. S. Hi'1hw"y 85 aM north of St~te HIQnw,~v 253
<br />as shown on plate 5. Flood Qlcvatlonsare also qiven 10 table 5 forrefor<ln<:e
<br />letters H throuQh P. Flood waters on the r>Orth ~iQe of State Hiq~wav ~Ij, are
<br /><I.~"med i 0 the v;c;nlty 01 rMerence points H, 0 ~n~ runt i I the water r ISe5
<br />
<br /> Velocities " flow - I'eloclties 0' 3 feet 000 second wlt~
<br />depths 0' , leet OC more are considered dangerous. 0v"'rbn~ flow velocities
<br />;, 'co are~ hehmen '" uostrenm limits 0' the study .~ I'd the 11th Avenue
<br />
<br />bridge for tMe IRF and SPF ~VBra'1e about I.J and 2.0 tpet per secon~, rps-
<br />Doctively wnTlo ilvere'1B oV<lrb~nk velocities between 11th Avenue and U. S.
<br />Highway 85 for the II<FandSPFere 1.0 to 1.5Ieetpersecond,respectiv""ly.
<br />DO"n5troa'" from Hlq~w~y 85 the overt>~nk velac;ties ,wera'1C ilboLJt 1.5 and 2.0
<br />fe...t par secomj, for the IRFandSPF, respectively. Althou'lhtheaoove
<br />~vera'la voloc it ies do not ,'ppear h"lzardoos, loca Ilzed veloc it ies are oft",n
<br />two or three times qreater than the avera'1e v",locitles. Travel throuqn the
<br />I I cod t lows shoLJld bo avoidod exceot fo~ e:xtreme ernerQencTes.
<br />
<br />high enouq,o " overton ;" hlqhway. The ov,'rflow +heo Cr05S<JS '", hl'1~
<br />ground ~ho~u ", '", cross1atch<)<j symbol '0 rejoin ,"0 riv0r. qnw " th"
<br />crO'';~hatCh"d ~re<l would 00 ~1",llo" ,1S indlc"tcd ny too 'Sheet now" note "
<br />
<br />""to of r ise ,~nd dura't ion of flood inq - Flood pe"kS at
<br />Greelev C~n re5U It from either Intense ra i nfa II and a combi "at ion of
<br />raintall and sno_elt. Certain sto~m cO/'1blnations would oroduce two
<br />d 1st Inct f load peaks ~t c,reeley. For a Standard Project FIOO<J under the
<br />double peak co~dltians, ne rate of rise or peaklnq ti...e for the first
<br />peak would t;.oaoout '1 IIours lollowod 2-1/2 days laterbVil o>'MllerPl'ilk
<br />reSu Itinq frc<n mountil Tn runolf. TMe tat,~ I duratTon o' f laod Inq c:ould I~,t
<br />ebout 7 days.
<br />
<br />plate'. rMe crosshat,nod ,,,,"hol wns u,.e1 to show thn "vcrflow il()()1
<br />h"~drd since the 1 dfl;j is ~oove tn" 1100d el Mdt ions I istlld tor reference
<br />pOints 61, ~2 and 61 ~nd '~ould not otM<Jrwise ",",ooar to h~ve ~ flood ~~~dr~.
<br />.lur inq floods. ,jf'lbr I'. collect in'l on br Id,ws drnJ culverts coo Id ~"creas",
<br />their carryi nq capac i ty ilM c"us" 'lreater w,lt"r d()rth~ I ~Ilckw"tar affoct)
<br />u!l~tr"dm of I!le.,,' st"ucturos. 5i<lce tl'8 occurrence anct i\moun1 of d"brl 'c,
<br />dre i ndeterm i nnt" lilctors, onlv j'h,' r~y';;cill character I st ies of the struclLlres
<br />
<br />'o'cre ,::"nslj",cd i;, prcp;Jr'o'l ~rcfl,()~ of t~Q !c.cc-"'ec,,,~e '~e~:o';)! ,,~~ S+~"di!~~
<br />
<br />Project FlooGs. S imi I~rl v, tjle ""ps of Ilooded 'JredS show the b~ckw"ter
<br />cfioct ot ob~tructlvn brid'1C!<, ~~~ culverts, but do rot reflect i:'1Cn'~sed
<br />w.~t~r ,ud~ce "IOv,l'1'I"n that COlli:! b" c",,~cd ~v ~o~ri" c011,,~tToQ ,~n~I'st to"
<br />
<br />S1ructLlr"~, Or ~v 'j"rc'si't'"'' "I 5;lt I~ to" ,fr"~'" (:oi!n,,~1 ",.,jpr ~tr",~jLJr"~.
<br />
<br />7.8
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<br />n
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