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<br />Flood of June 195ti: Unusudlly n~dYY snowm~1t runoff r,"sul ted in
<br />the fdilur~ of th~ Geor~etown Dam locat~d about one mile downstream
<br />from Georgetown. Tne pedkdischarge passing tnegdgeaooveGolden
<br />wds5,250cubicfeetpersecond. SythetimethecrestreacheOtne
<br />gaging station near themoutn of Clear Creek, it was reduced to
<br />2,880 cuoic feet per second.
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<br />The flood prof il es for Reacnes 2 and J were ca 1 cu 1 ateD us ing the HEC-2 \<Ia t<!~
<br />Surface f>rofi le BaCKwater computer p~ogrdm dev<! lop.,Jd by the U. S. Army Corps
<br />of Engineers (Reference 24). Tnis computer p~ogram provides <In efficient
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<br />me<lns of determining flood depths a long a natu~al channe. ...nh varyIng hy-
<br />drauliC cnaracteristics and controls, such as constrictions, oridges and drop
<br />structures.
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<br />Flood of July 23-26, 1965: On July 23 and 24, during seyere storms
<br />over the he<ld'~aters of Clear Creek and Tucker Gulch, 4.5 inChes of
<br />rain was reported to have fallen in fuckerGulcn inan hour which
<br />causedflasnflooding in Golden. Flooding, however, extended only
<br />a Short distance downstream. !nGolden, flood wilters from fucker
<br />Gulch spread over about 17 b loc~s and causea an est imated $11~,OOO
<br />damage to 69 res idences, thre€ comercial enter~rises, thr~e rai 1-
<br />road bridges, four str~"t bridges ana ut i] ity lines. At ~eGrge-
<br />town, debr i s blocked tne channe 1 and d i ~ ert"d the wat"rs down a
<br />street, tnerebjcausing extensive erosion of the surface dnd the
<br />f loud ing of ~ev..ral oasements.
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<br />Tne basic data required for this program consists Of cross sectio nal channel
<br />shapes, roughness, and survey information about culverts and bridges. SCMrf
<br />and Associates prov ided aerial photography and Bell Mapping Company ~rovided
<br />topographic mapping at a scale of 1-inch equals 200-feet along witn d~tailed
<br />briag~ information. A fi~lo inv~stigation of tne study area was conducted by
<br />Gingery Assoc., lnc., to estimate Channel and overbank roughness factors.
<br />BaCKwater com~utations were done using the peak flows developed by the Corps
<br />of Engineers h,flro logy study which dr~ based on future bdsin development
<br />conditions.
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<br />FlOOd Prof i l~s
<br />Tn~ 10-year anD lOO_year flood profi les presented i~ t~~ FlooO HdlarO i\rea
<br />Oelinedtion $tuDywere utilizeD in thlS master plan witn the exception of
<br />R~dCh 1 betwe~n Ford Street dno waShington Avenue. in tnis .Ired a spec ial
<br />analysis was done to det~rmine the lOO-year and 50-year flood levels cr~ated
<br />by tn" Dr ldge structures, in, Iud ing the ma!jni tud~ and depth of flow whiCh
<br />leilves the chdnne 1, inundat ing adjac~nt aredS. The dna\y,;es in this reach
<br />involved dcomcination of computer and hand calculations to arrive at the
<br />Dest est1m.n~ for th~ ~u",oin"tio" uf f1<.l~ thrJygh e~ch ~r~c;e J:":j flow ove~
<br />and around each bridge. fn~ r~sult, were pr~sented to the UrDan Ora inag~ dnd
<br />FloodCont"ol Gistrict in tne form of a lett",r rO:'port whicn may be found in
<br />AppendixC.
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<br />PRINCI~lES OF FLOODPLAIN CONTROLS
<br />fhO:' ov~ral I purpose of floodplain controls is to:
<br />o Protect tne pub1 ic h~d lth, saf~ty, and generdl wclfar~.
<br />o Mil1imizeflood1o"es illaredS subJect to flooo nazarcs.
<br />o Promot~ the wis~ use of the floodplain.
<br />o Provide for tne pres..rvat ion of floodway> and flOOdplain stora~e areas in
<br />oro~r tv protect those downstream from incr~ased flooding.
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<br />Floodplain controls ar" criticdl fadar", in drainagerllaTldgement. Successful
<br />flaodplain CQntrols will pr€serve a redsonable path for flooDwaters oycon-
<br />trolling oeV\llOjJlll~"lin f1uud h"lilcJ at""S, prevent 10$~ of flo~j,il~ir. sto~-
<br />age volume and vr~v~"t the intrOductlon of structures, property or I and uses
<br />into th~ flood~loin whiCh would result in ddffiag..s.
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