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<br />VI-4 <br /> <br />'11-5 <br /> <br />Urb<lniZdtion of <I onindge basIn modifi~s tn.: n<ltural hydrologic response of <br />that bdsin, usudlly in am<inner to incredse the rate and volume of runoff. <br />If floodplain ldnds ar.:develop.:o, th.:drainageworks implemented typiCally <br />reduce the historical floodplain stor<lge c<lp<lcity. As <I result, tn~ upstre~~ <br /><lnd do..nstredl11 flOOd o<lmage pot.:ntial may be compound eo , unless eff.:ctive <br />stormwater management metnoas <Ire implementea. <br /> <br />Reach 1 (Upstream Golden City Limit to Tucker GulCh) <br /> <br />PROBLEM AREAS <br />FlOOd probl~ aredS along Clear CreeK include il1adequate bridge structur~s, <br />inundation of majOr stre"ts, ana residential, corrmercidl and industrial <br />structures locdted within the floodpl ain. fhe e~ ist ing channel has the capa- <br />city to contain the lO-year flood throughout the stuoy area, and, with the <br />exception of the channel witnin lhe City of Golden and through the Coors Com- <br />plex, the.:xistil1gChannel cancol1tain the 50-year and lQO_yearfloods, as- <br />sumil1g nodeoris blockage. rhe effect of debris blockage hds not been con- <br />sid.:r~d in the cdlculation of water >urfdce profiles becdus.: of toe unc.:rtain <br />character of such an occurrence. <br /> <br />1. .OO-yedr floodwaters flow from beneath the oridge at U.S. is a t hi~n ~e lo~ <br />city d~d o~erflow tn.: di~e wniCh separates ~Iear Cr.:ek frum the raw water <br />~onds for the Goloen Olat.:r Tredtment ~lant. fhe dike ldcks ri~rd~ pro- <br />tectio~ against high ~elocity flow and would be washed out during a maJor <br />floodevel1t. At the tr.:atmentplant, thefilterouilding 1s subJect to <br />l.~ feet of flooding by the lOO-yedr e~ent. <br /> <br />2. Between the Water freatment Pldnt a~d Wasnil1gton Ayenue tOO-year f lood~ <br />waters s~read out lO dn dverage of 600 f.:et to inunoate Lions Park, the <br />res ide~tidl neighborhood belween 9th dnd 10th Streets dnd the recreat ion <br />center, tne Library and the City Municilldl Builoiny. <br /> <br />3. AtOlashingtonStret!t, the existing bridye structure lackstneca ,;>acitytO <br />convey tne lOD-yedr flow and is overtopped to a depth of 2 feet. <br /> <br />Becduse of the Sleep grddlent, or slope, of th" Clear CreeK cnannel, flood- <br />waters In t~e channel zone would trave I at hign ,.elocit ie~ on tne on.ler of E <br />to 13 feet per second. fnroughout most of the ~tudj ar~a, fJooc no.. along <br />Clear Cree~ trdvels at or near critical condit.ions. Vdrhtlol1s in channel <br />dlignment, roughness, cross section, slope, minor deposits of sediment or <br />deDris may CdUSe sign1ficant fluctuations in deptn of flow. fhuS, the <br />dCCumU I at ion of oebris, whi Ie imllOSS io Ie to ~redict, Cdn significant ly wor,en <br />tile t!~ tt!"t and de"th of floud i ng. <br /> <br />~. ine extent Df flooo ing in the ar€a ::>etwe:on Ford Street and Oldsnlngton <br />Avenue i> contro Il.:d oy the ca~dc ity of tile FOrd Str.:et bridge. For tne <br />lOO-fe<lrflood dischdrg<o of 12,428cf"only 7,illlOcfsflows thrlwgh tne <br />Orloge whi I e th~ r~maining d ischdrge overflo'lIs southWird dl1a eastward <br />across Foro 3tre.:t. ril~ Mi tCh€ll Scnoo 1 and severdl cOIII'T1ercial struc- <br />tures are affected oy 100-fedr flooding in tnis drea. <br /> <br />E:~.~n ~^hting ~nd pot~nt:J' ~r:lb!~. ~re~s hdve t>~,,!n iliE'ntifi,"d in t~~ study <br />ared i1nd are indiCdted on Figur.: ;]-1. A r"ach by redch d.:script ion of tn<,>~ <br />proule:n dr~dS follow,. <br /> <br />:.. UDwnstr~am of ford Stl"e~t, tne major port ion of tn~ ov",rflow reJoins th.: <br />ctldnrlel f lOW in the area of the Agricultural ~itch h2Jdgat~ anc d i'l~n; iOI1 <br />chdnnel. fhe r.,-naining o.~rflow trdvels to t~~ soutn of tn~ Coors '~~1l- <br />n~ss Len,er <JUW'L 12th Str~..t d(,.J thr~"gr. t,~c br~'~~rj p~rki~i. lot. Tn;;> <br />mOO ~ 1 e hom.: pa~K a 1 on9 the north s id~ of the creeK downstredm of cord <br />Street is inundatea oy tne lOO-yeM flood. ~oile ~omes 10Cdteu in the <br />