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<br />~ates of the SOD-year flow are b~sed on extrapolations of mathemat- <br />ir:.:1l frequency distribnttons \,'[,.;,-=-11 represent tne best fit aV3i12ble <br />:0):' th2 data. The user ..,:I1Ou1<.1 be ,';T,,:are, 1!G\\'(:' vcr , that such estimates <br />~lst be vie~ed as very approximate. <br /> <br />5:-::aJ.1 '-='i:lsin estiT::;,lt..~S dre generally less reliable than those for large <br />~asins. This is a gellerally accepted problem among hydrologists in <br />ar,~as ~here little data is dvailable. The estinates presented are <br />~ased on widely accepted techniques developed by the U. S. Soil Conser- <br />vation Service. It should be recognized, however, that the data avail- <br />a~le to predict fl~oding from steep, rocky slopes such as the ones in <br />'i'!estinn are very f2~J. The observed vallIe of 2000 cfs at Skyrocket Creek <br />jl,lSt north of OlLr:.y i:.; :'-',)ce than t,:.;'ice the SOQ-year estL-,lates for Cas- <br />cade Cr2ek, a ~~t~r;::2d of about the S2~e size as Skyrocket. On the <br />other hand, the ICO-year estimate for Portland Creek, a watershed of only <br />2.82 "~uare ~il~s is 1325 cfs, 2bout the same as the IOO-year USGS and <br />l.~D~'f 2sti;-:~at2s for ;{ :)0 S'-i~;3.l:"e TTlile T'.-::lter:3hL;~d. <br /> <br />~n confronting qlJcstiors ri!isi!d by the r~11ge of estisates, or ~hen dif- <br />:~:cent e;r,gineers <.jrrlve 2t diff"'::'cc;:1t csti~.;.-;,t2S, the d2cisior:.~;:ak2r should <br />l'e aware that the estimates are pres~nted dS the best estimates that can <br />}e arrived at in the absence of ~ong term observed data at the locations <br />0f i~t2rest. They are a~2~~at2 for flGod~ay pla~ning, zoning and the <br />,~~~~n of flood cont~ol ~or~s. <br /> <br />. <br /> <br />r' <br />I <br /> <br />l~ <br />