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<br />2. ~';eitht~r the T?f 1 no-c the CD:.-f r,~?ort offers .celiable guidelines for (J.y,.. <br />e~tl~ati~g ~~8l1 basin floods. <br /> <br />3. The b2St 2sti~ates obt~i~dble for Cascade Creek and Portland Creek ~~. <br />Are frc~ the SCS ?rocedure. <br /> <br />:~ollc~~'ing t~12 ?r~:;ci?12s above, the recommendations below provide flc,;~?s <br />',,'hich C3.n be l:S02d to estimate flood stages. <br /> <br />1. ~~sins ~8r3er th2TI 30 square miles. The curves given on Figure 6 can <br />be Esed to esti.1Oilte 10, 50, 100 and 500 yee.r peak discharges for <br />bilsins b2t~een 2~out 30 and 1,000 square miles. They could be <br />2xtr;'1.polated dmvT!.h'ard to about 10 square miles with decreasing <br />reliability. The curves are generally cOffi;?romises between those <br />presented in References 1 and 2 but reflect the slopes of the <br />curves ~rcpared by the USGS in Reference 1. <br /> <br />2. R.~tl"nd. Creek, "nd C2scade Creek. The calculated values pres2nted <br />earlier 2re reco;::;:lended for use. Although a SOO-year value cailllot <br />be calculated directly from SCS data, an estimate can be ~ade from <br />the assumption that the ratio of 500 to 100 year floods of Reference <br />1 will also hold for Cascade and Portland Creeks. This yields the <br />follo~ing table of disch3rges: <br /> <br />L;3LE 3 <br /> <br />PC,'J( 'JISC'L'3.GES <br /> <br />C-:,sc2de. <br />Cl-2ek <br /> <br />?ortl,md <br />Creek <br /> <br />10 year <br />50 ';ear <br />100 year <br />500 year <br /> <br />270 <br />~80 <br /> <br />590 <br />1050 <br />1325 <br />1760 <br /> <br />606 <br /> <br />806 <br /> <br />~2liability of ZStiD2tcs <br /> <br />~'~"e ::ser or thi::i rc:~G["t r:-,ust ,.)2 c:.~"cr2 that t:-,2 :-el::'cJility of hydr.:-lo;s:ca.l <br /> <br />. <br /> <br />C <br /> <br />..-3t~~.ct02S \'E..C:'>::'S -.,":2.':':;.Ly. ~.:3:':::-.~-=2S ~2;;2j C:1. 2ct\..:-3,1 r22UrG2d c.\-,"':::ts 2.:-2- <br />..:s..~;.~ly I.{'li::e :-21i_2'Jle. ?r2(::..ctic:1s of uj......0;:f 2-~-Q"C1ts cc:ntaL....E:J in th:.s <br />r~?ort r2?r2s2~t ~est ~sti~at25 of flc~s likely to occur within certai~ <br />-~:-:2 _r2:":'25. ~':::-:(:~e2.s.::?:"l 2.ct1.:31 2st:::-:2ted ':;:.11..:2. ~ay vary considerably <br />n ~~ti~r~ c~3e~~Ed ~alues, t~2 ?~2dic~2d fl~~s qre ~211 ~ithin li~21y <br />_' :..:~.; '5 or fL: ,~. :c::~d C2:1. ::2 t:>:;',;..,....L:'=.J CO ,>:'::Jr i:1. a ....';C:,sc:.....:1ble pEriod of <br />"2. <br /> <br /> <br />:~e ~2St 2ata ~2~e ~sed in the ?r2?aration of this report is that cont~i~- <br />"-: leI ,~'I 1. S:.::il,l, t~2 :-E;:::-,:::s:::~on ~q'Jati.c-::s cev,=:loped for the Scu:=.hern <br />-~~-.-3.t.-:..:lU ::,'siC::1 '':::'2 ~.:::,e :....,lc:c.-:-_~,~~:'s:re::.8 :..:und n,:;',.e stafi.dard ,~r!"crs, <br />.;:--:'3':(25 of ~:-:?2":':~c,1 v3.rL~JiliL~"'., ra:l:;ing from 47 to 65 p~rcent. Esti- <br /> <br />o <br />