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~ Ill. 7 VI[I-8 Post.Flood Activities Notification of State and Federal Ag~nci.es Pr~s ident FederdlDisasterAssistdnceAdministrdtion F~d~ral Emergency Mdndgem~nt Ag~ncy Corps of Engineers United StdteS Geologicdl Survey Gov~rnor UrDdn Drdindge dnd FloOd Control District OllpartmentofHousingdndUrtlanDevelo,.nent State Geologicdl Surv~y relief groups CHANNEL ALTERNATIVES Chdnnel alterndtives were "valuated only for ReaCh 1, and wer,: considered on Iy in con~unct ion witn br1dge improyement, at Foro Str\l.:t and >/asninglon Av\!nue since th~se urid'ol.es ~,,~ntlally control the amount and d~~th of flooo flow tnrougn tne reach. Tne "xist ing cnanne I and bridg"s in Reach I nay\! adequat~ ca~ac ity for ap- pro~imately 6,200 cfs, or near ly tn.: 50-year flood flow of 8,000 cf,. An a lternat ive baSda on an improyed 50-year des ign cnann~l was not cons idered because the difference in costs between a 50-yedr and IOO-year design cnann~l tnrougn Reacn 1 u.e minimal aM r~s;dual lOO-year flood damage lo'Oula remain with a ~O.year design. Th~ Ur~an Dr~inage and FlOOd Contra 1 Oistrict current ly maintains an ar2a wide f load detect ion system ut i 1 izing the GRO w~ather Center. In add it ion, imp1.ementdtionof a flood \oIarning syste<nfor Lena Gulcn i,t!xpected to begin duriny 1132 UMer the comoined participation of the Oistrict, Jeff.erson County, tne CIties of IrInedt Ridye an:l Lakewoad and Consolidated Mutual '4ater Company. Under the proposed system, 4 Situation Information Center (SIC ) for data co llect ion and ana lys is lo'Ould DC establ ished at the GRD '~e4ther Center. Tile ::>IC, ur lIdS~ stat ion, ill the single most cost 1.1 i "am of the flood '~arn1ng system because it incorporates the compJter and data terminal, printer, receiver,mapdiSplaj,radioanddllery.encygenerdtor. Grass-Lined Cnannel Agrdss_linedchannel maybethernost appealing of tnecnannel alternatiyes becauseof1tsnatural dppearanceand its adaptability to park and recreation schemes. Kawever, due to th.e relatively flat 4:L side slopes of a grass- 1 hIed cnanne I, tne requ i reo r ight.of-waj widt" i, 1 aryer than for cha~ne 15 with lined side slopes. rne City of Golden and Jefferson County can add Clear Creek to th.e sy stemoy buyiny into thll SIC and establishing the necessary rain and stre drngagesand observer , ites. Other features include pr~pdredness plan deve lopment dnd maintenance, public information programs, inStitutional organization and equipment maintenance. Rock.Lined Cnannel fner<.lCK-llnedcnann,,1 is a struct.ural <llternativewhlch increasestnllexis- t ing Channel capac ity ana reduces flood damages, but requi~es less r\ght_of_ way to an toe grass_lined channel. Slhce tne rOCK.l ined cn<!,mel i~ construct- ed of rock riprap III aced a long the inyert and side slop.es (2~ 1/2: 1 r.ecommend- ed max.) of tile channel it can witnstand higher ve loc i ties and gr~ater de;lths than the grdss-lined channel. fn" MJ.ster Ordin~ge Plan for Lower Ch~~r Creek (Ref~rcnce 34) included an est irn~t" tor ~s taD 11 snment of a f iouu warP' i rIg sy; t~nl for i.ower ::~ CJr Creek. fnis estirnate was rev1eweo and mOdifieo to include the Clear Creek Youngfield through Golden sludy ared. Since tne costs for establishing d flOOd warning system wou10 re~1ist ;ca11y oe Shdr.ed by the loc~l governlnents within tll" basin, tne cost presentee in tnls study represents theestimat2d )Jart ion of tl1~ total system cost wnich I'/OlJ10 b~ app I iCdb]~ to tne Cle~r Cr.eek _ !ou~gfielo Uwough Golden study area. structural-lrId11ed Ch~nnel rne structural-walled chdnnel iSdstructural alternativewn;cnincreasesthe existing Ch<lnnel capacity t~ereoy reliuci"g fio"d ..amage:;, ~r." req~~rcs 1~S5 r i<jht~of-woY than eith.er the \lrdss-1 ined or rock.l ineo chdnnel dlternatives. rne s tructura l-wa ll.ed cnanne 1 is constructed wi tn ~ ert i ca 1 concrete 'IIa 11 s with a rOCk-lined invert. fhis CMnnel, like the rOCk-lined channel, ciln be d"s igned for h ign"r ~e 1 oc i t ie5 dnd gre~ter deptns Of f low than th" gras,- 1 ined chan~e I.