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<br />CO~WARISON OF ALT~RNATIVES
<br />Table 20 p.u<lents compara~ive data for the flash ftood detection
<br />
<br />31ternatives.
<br />
<br />Alternative 4 "'ould include an all-volunteer net",ork of
<br />
<br />ratn and st.eam gage observe.s.
<br />
<br />Alternative SA would include volunteer
<br />
<br />rai"lladstrealllgageobaervcrsaionathCOl.,inatcmandautomatic
<br />
<br />equipment
<br />gagcaand
<br />
<br />Alternative SB ~ould use automattc rain
<br />
<br />in remote IIreas.
<br />
<br />volunteer stream staff g"~e observers. Il,,,,,ever, becau<le (ala
<br />
<br />gages would be confined to ~he main stem bastn only volunteer staff
<br />gngeawouid bc on the North Fork. Top.ovtderedundlll\cyo"cheNorth
<br />Fo.k, alternative 5B ~a" cltminated and replaced by "iternative 5E by
<br />adding automatic acream gages along the lower reach of the ~orth Fork.
<br />Alternative SC would use vol<.lnteer ratn gage observers and automatic
<br />strearngages. Alternative 5D "'ould conaiat of an autoOlatic st..H1mgage
<br />n"t\olurk and a backup volunteer staff gage net",ork. Alternative is "'auld
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<br />basin ,,"d stream gages on the Xorth Fork.
<br />
<br />The Hrst and "nnllal CO!ltS aho..n tn tllble20 indicate thU th"six
<br />
<br />alternatl"es \oIo<.lld require about the.a"le level of tnvestment.
<br />
<br />Except
<br />
<br />for the stream gage alternati"e, 5~, all would provide .imllsr lead
<br />time for flash flood 'i<lrnittg. l.ead ti"'e~ indicated ~hould he taken as
<br />
<br />a~~roxi~~ions because ~tffero~t results coul~ ~c obt~i~ed vtt~
<br />
<br />differe~t hydrologic ~dels, 3torm locatio~", 4r ruinf~ll di"trib~-
<br />tions, For pr~dtctlons based on rainfall l~ad ttme ls defined as the
<br />interv~l from 15 ~lnute. into hea"y raln to ehe elme of approximat~
<br />bankful discharge wlth 20 ~lnute~ deducted for data tra,,"mtssion and
<br />
<br />Interpretation.
<br />
<br />For ~lternative 5D, lead tlme ts defined aa the
<br />
<br />Int~rval from the occurrence of flood at<ls:e <It an up~trea'" ~a,," to the
<br />ti~e o[ fLood seage at the potnt to bc ..arned, ~ith 10 ~i"ute" deducted
<br />fur d~t3 il\t~rprctatton.
<br />
<br />Visual verif\c"tj,,~ of flood-t~g ",~"ld provIde ","r~ confjdeno~ 1,..
<br />
<br />"'''"'lings.
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<br />Only t'"" Aut01llattc ~ltermHive, 6, ",ould nOt provld~ t:th,
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<br />Confirttlatton of .a(nL,~l ("die~t"d by the ~.'5 r~d"r COuld h~ prc,'iJed
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<br />by <Ill .':terndtiv,," ,,~c~pt 5D.
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