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<br />Veloci1ies of flow - Ove~bank flow velocities woul~ not be <br />---------- <br /> <br /> <br />III <br />~ <br /> <br />'''' <br />~_o <br />IRF <br /> <br /> <br />great duri~ la~ge potential lloods because of the width 01 1he flood <br />plain and relatively flat prevaili~ flood pL~in slopes. Velocities <br />J~e much greater I nand nOar the St. Vra I n Creek c~anno I. a nd a ha~ard- <br />ous condition could exist where the main channel flows over o~ e~ound <br />a b~idge crossinq. Overbank velocities in the study reach would range <br />Irom I 10 3 fel'tper second. <br /> <br />", <br /> <br />l",,~ <br /> <br />Rate of ~i 50 iln~ duration of I loodi n<1 - Peak I I oed i rIQ dur in<J <br />---------------.---- .. <br />a largo potential flood caused by ~~infall runoff '-llona wouid occur <br />~ifhin a half day after the rain. Duration of flooding In this event <br />\</Ould last up to a Mlf day. The duratIon 01 flood i rig may be 5;'1nlf- <br />icantly lncreasedductoanextendod period of wetweatherarld snow- <br />mel t ~unotf. <br /> <br />Future Flood Hoights <br /> <br />Flqure 1&. Sewage treatment plant. <br /> <br />Qb~t!:.u~.t1..o~s - Du~inq flOQds, debris colloctinr, on bridgos <br />arid c~I-""rts could decrease their ca~~yinq c~p~city aM caJSO <:~0ater <br />~~ter depths (b~k~dte~ elle~t) uostred~ 01 th&se st~ucturB5. Since <br />tneoccurr&ncoand"'"Cl'Jntofdebrisar" indet<lrmi"'atefactors,onlv <br />the physic~1 characteristics 0' the structure~ were considerod In <br />creparin] proliles of tno Inte~mDdidte Regio~al ~nd Stann~~d Project <br />Floods. S Imi lar Iy, the I"lars 0" I loudw; a~oas show the b<lck-~,~ter <br /> <br />effec~ cf cts~ructive ~ridge~ an~ culve~ts, but do no~ relLect <br /> <br />i ncreasod water surface eievation that could be Ca-Jsed by deb~ is <br />collooding "ga.nst tiw structu~e5. o~ by deposition of 5;lt i~ +~e <br />strea". c~>ilnne i u nde~ st~uctures. T~e effect of Obstruct ions can be <br /> <br />seen io t~blo 5 by comparl~ the eleYd~icns up5t~e~m and downstroam <br /> <br />of structurlls. <br /> <br />n <br /> <br />" <br />