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<br />POII'iT ()IC <br />11IFllr~(',\Tl()"J <br /> <br />'-~7 <br /> <br />, ~ F'QW <br />~'?;;"",.",'- L <br />A,z " <br />0({?---~ '-- <br />. c" ''... <br />-/~/"' ,~.---...,,"-.... ~ <br />""",/ ..... <br />"-1'- '... <br />'. '(-~, <br />cc~\:~;- <br />~>~ <br />-..."i~~ Vi-" <br />'~'. r <br />,:~,:c~ " <br />Vf11 ""'" <br />~, . <br />~!\M~\~: <br />~J~.,-r[, <br />ooo7SrL...i, <br />.,~, <br />)-\ ,-! <br />~~-1\\ ;/ <br />F /I'--:';(---'"i\r <br />",,:~l,,:,"r <br />~_r 1- <br />Jf" '---'-',',:r <br />~'_/\ /<~ <br /> <br />. ~~-=~ it:', <br />"~V~:(. <br />.-' \ _-' -. L <br />..;'\ J-- \'~ <br />~./ <br />,~0Q ../ <br />. .../' <br />....-....y~ <br />~ <br /> <br />DlRECTlC\ <br /> <br />FIGURE 4 <br /> <br />fLOW HYDRAULICS CO\1PUTED BY <br />fEMiI \lULTI.CHANNEL METHOD <br /> <br />" <br />'..., <br /> <br />HII\O SPRINGS WASH NEAR <br />Lilt: c; HLli\ , NIT <br /> <br />MVLTI-CHAN~,H ANALYST" <br /> <br />DEPTH = 1 5 'T <br />VEL -= 6 FPS <br />WIDTH -= 3700 F"T <br /> <br />CO;-"'TOlTR r~TERVAL ,. ,~O FT <br /> <br />1:'01' <br /> <br />r:RAPH1C SCAL,S <br />o 6001200 2400 <br /> <br />IflU' <br /> <br />.~- <br /> <br />''''0'' <br /> <br />I <br />/ <br />! <br /> <br /> <br />SINGLE CHMII";EL AN/,l,Y:"lS <br /> <br />DEPTH ",35F1' <br />VF;L ~ 10 FPS <br />WIDTH "GOO FT <br /> <br />) <br /> <br />IY)(l ~ <br />" <br /> <br />,---- <br /> <br />FEMA (1985) published guideline',s outlining the combined single <br />and multi-channel approach for analyzing alluvial fan flood studies <br />in the document, "Flood Insurance study Guidelines and <br />Specifications for Study Contractors." These guidelines can be a <br />useful tool to help delineate alluvial fan flood hazards, but sound <br />engineering judgement is required in their application. <br /> <br />4.3 Assumptions and Limitations <br /> <br />The prediction <br />fans using FEMA's <br />Discussion of the <br />follow: <br /> <br />of single channel flow hydraulics on alluvial <br />method is based on several assumptions. <br />most important assumptions and limitations <br /> <br />* The FEMA method assumes an equal <br />probability and random distribution of the <br />channel location across a given contour. <br />The flow is assumed to be concentrated in <br />an identifiable channel and the channel <br />migrates over the fan during flood event. <br /> <br />The FEMA method is limited in its application to very <br />idealized undeveloped, uniform topog-raphy, alluvial fans. Local <br /> <br />12 <br />