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-~-- --- Erosion of So~th bank of Bear Creek in Denver, May 1957 Channel capBcities vary from avea to avea along Beer and Clear Creeks. In some reaches of Bear Creek, flcrws of abo~t 200 cubic feet per sacond cause ovcrflcrw and annual flooding can be expected. In other reaches of Bear Creek, flows of about 7,600 cubic feet per second ave required to cause flooding. A discharge of this magnitude has about a 1 percent chance of occurring in sny year. Discharges of sbout 740 cubic feet per aecond ~ill cause flooding io some reaches of Clear Creek snd can be expected to occur about 1 year out of 2. In other veachcs of Clear Creek, discharges of about 25,200 cubic feet per aecond are required to cause flooding. A discharge of this magnitude has sbout a 1 percent chance of occurring in anyone year. . It should be recognized that increased channel capacity at isolated reaches does not necessarily insure agsinst flood riak in those reaches. Flood. stages in reaches having inadequate channel capacity ",ay cause flood~ ing which could spread overland to avess where channel capAcity is adequate. ~ostructions nt bridges or other channel locations may also cause flooding in areas Which normally have a relntively lo~ flood riSk. For this reaSOn it is advisable to study the flood outlinas illuatrated in this report to determ~ne areaa of potential flood hazard. FLOOD HISTORY Since 1876, 22 majQr and minor floods have been recorded in the Bear Creek basin. ConsUerablepropertydsIlISgehaabeenreportedand4Sl1ves have been lost to the rampaging waters ot Besr Creek. Since 1864, 12 floods have been reported in the Clesr Creek basin. Data obtained from the gaging station above Golden indicates that the 1888 :tlood had the greatest discharge of record. Tbeattached1ll9pa show the extellt of the floodplains on Bear and ClearCreeka under present conditions and the areas that could be inundate d by floods with a 1 percent chance of occurrence in any year. The tabulations on each map show probable ~ater surface elevations at selected locations for floods with 20, 4, 2 and 1 percent chance of occurring in anyone year. FLOOD DAMAGES The passage of flood waters thrOugh any area causes destruction and deaolation and often death. Small, harmless, bubbling, mountain streams become raging torrents that aweep a~ay everything in their paths. Homes, commercial buildings, bridges, roadS, public utilities, vehicles, and other properties suffer damage. Rapidly rising and moving ~nters have taken the lives of people who were trapped in buildinga, automobiles or :tields. PBstures, croplands, and gravel operations are damaged by deposits of silt and debris. Tourist travel is disrupted by road and other damsge and i"'poses financial loss on the economy of the ares. Damages in varying amounts result from all floods. Flooding of ooly a road causes damage end inconvenience. The 3rsphic effect of flQoding in deVeloped end undeveloped sreas is sh~.n below. L...!;.' l'~:L"~l /""""""" "'-:,.1/ I:." - 'I _ ~ , NO'U,W'''''V'''''___ nEYHOPED HOOD PlAIN UNOEVHOP~O HOOD PLAIN TYPICAL VAllEY CROSS.SECTlON