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<br />Fig1J~e 2 il1ustntes the seque"ce or events in a flash flood
<br />"'atning at Poud~e Patl<, based on ~ai"hll obsetv..~ions. In "ost ca.ses,
<br />tt is e>:pected that th"t" ...ould be a ),1.'5 forec"-st. A p~ealen could be
<br />activated at vsrious poi"ts, such as afte~ 0.5 inches of rsin had
<br />fallen. It is as""",ed ~hat a ""'as"~e"",nt of heavy rain for 15 minutes
<br />would b<! ~equiud to establhh ctedibility of detection. In figu~e 2,
<br />anothet 15 Minutes were allowed fat data transllission, inte~p~etatian,
<br />and hsuance of a warning -- ..ith 20 ",inutes fo~ diue<ttination af the
<br />warning ..ithin Poudn Pa~k. The time "vailable fo~ evacuation is,
<br />thus, 55 minutes. This asSUmes an efficie"t wa~ni"g ""d communication
<br />system.
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<br />For flash flood warning using an upatream ala~m gage set at 4,000
<br />c.f.s., the sequence. of eVents 1s displayed in Hgure 3, Inthhcas..,
<br />..arning is more deflnite., "0 10 ",inutes wss allo..ed for datatrans",ts-
<br />sion and decision 1Il&king and 1511l1nutu fot disse",l"atio" "'Uhin th..
<br />local c01lllllunity, Fo~" nearby stor"" le95 ...aming' tl"", -ts 3val1able
<br />using.trealllflowratherthanta1nfallas"..arning1"dicaeor..
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<br />L1v..s have. b<!..n sav..d in flood. ..1th only a few ",1nutu wa~"1ng,
<br />Howev"t. th.. evacuation ti=e ~o~ld he .cduced if co~nication. arc
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<br />hamp..red. Warnings =, need ",", tssu..d to oth..r areas " <>, '"=
<br />tillle. ", ,,- M day ",ould affect ~..adin".s. '"' flood sho.." " 6
<br />p.llI., for """"pIe, could OcCUt aC J p.m, ,. , p.m.
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<br />The dissemination task is slso affected by the d1st~ibutio" of
<br />population. The mor. dispersed th.. populat1o", ehe OlQfe ..ffon it
<br />takes to reach the sa.... number of peojlle. Hit lsassu..edone
<br />notificatio" or "'contact"" 10 needed for each COOll'lUnit)', One co"tact fo~
<br />eseh g~oup of t",o o~ ~ore ~esid."e"s, a"d o"e c,,"tact for eac~ isolated
<br />~es1de"ee, it would requi~e 24 contacts ",ithin th.. typi~al avaihbl..
<br />time of shout Z hou~. to "'am those in the teaCh from Ru"ti~ do"',,-
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<br />VOLUME I fiGURE 2
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