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<br />h)'Q"en.(30) Ploodpreparedne.s is sl.soouttlned in fl publication by
<br />the Hydrologic Engin"ering C"nt~r, .Corps of ~ngin"~r". (3'-)
<br />
<br />Detection. Fl,,"h flood detection in\tolves the sensing of physlcal
<br />phenomena sLic:h as beavy raiafall or rislGK "trea"flo'" bj LnHtr\l'"ent~ '"
<br />hy visual ?b"ervatiQn. The~e d~ta must then he succ:e6sfully tran"m!t-
<br />te<lt"allelTlefgenc:yoperation5centerorothe.co",,,,,,ndlocatlon"here
<br />the da'~ can be used in decisiomnaking. The condLtions under ",hich
<br />volunteer observers ~ill he a~tivi\ted sho~ld be determined, in the
<br />emergency plan along ",ith the means of activation. AutOmatic detecrion
<br />networksshouldoperatefull-timeduringthefloods<<asoo. The type of
<br />report" and procedure' for handling incoming data ,hould also be speci-
<br />fied in the eloergency plnn. SpecHlc al~ern..tfves for flash flood
<br />detection ~ill be diseu"sed later.
<br />
<br />f:lements needed for .~ f lood prepared"e~s ~hn indude >/;1rnlng,
<br />evacuation "nd rese"e, teOlporary da<>age reduction ~"sures, recovery,
<br />p~blic information, plan impl~mentation, and plan rnJintenance. Two
<br />repn.ts by the ~ashville DistrIct, Corps of ~ngineer" (1),(2) are
<br />examples of detailed warning disscmtna~ion and evacuation ?lans,
<br />In~1uding personnel, equipment, ..nd organi.ation required. Flood
<br />""rniog plans have bee.n published for ~wo ba,dns lQcated irl the Denver
<br />~tropolitan are".(6),(34)
<br />
<br />FLASH FLOOD WARNING
<br />
<br />Evaluation. The evaluation of a flaah flQod threat ~t the Local
<br />leveL Is based o~ interpretation of incoming data fro~ the flash flood
<br />detection networlt or on Warnings ha<led by the NWS. An infruttllcture
<br />of ~om~l1nity arrangeme~~s i8 neCe$"flry to effectively use hydrologic
<br />information. IncoOllng data ",ay consist of phone calls ",ith fragmentary
<br />information, trained volunteer ob~etver" telephoning to report rain or
<br />rising streams, or ptintollts of data from auto~ati~ insttuments. The
<br />de~t8ion process ~y be bas~d on past experien~e, consultation with the
<br />)iiOS, or graphs or t,,-bl,," pr",vid~d hy ~h" ~-"S. Th., ",Ost sophisticated
<br />"valuation is dOLl~ wIth min1""T1pl1ters preprogra",m..d "'ith a hydrologi~
<br />model of the hasin. The cini~omputer would provid~ predi~~ed flood
<br />dl,chHges hased on real-time lnpllc of r"infa11 or strearofl",~ d"ta from
<br />a"tomated seosot5. The sophistication of the decision process should
<br />be COm"lCnsutate .~1th the quality and spe~d of inco'llng d~t8.
<br />
<br />Flash floods .He diff.,rentiat.,d fro," other Hood, by the sho.t
<br />time between the c""sat1.ve even~, sl1~_h "" !leavy rdnfaLl, and the flood
<br />~eak. As the ,~vailable time for preflood a~tion beC01Il<!8 O'horter, the
<br />imponance vI ""rning increa~e~ and the l,"portanc~ of da""'>\~ reducti<,>n
<br />decreases. If the "'arnl~g time Is very .h<>rt all efforts shocold be
<br />directed to tbe sde~y of endangered persons -- with n<.> t1."", lost for
<br />~rotection of proper~y.
<br />
<br />Ot:TLINEOrFLASnrLOQDWARNING$YSTEM
<br />
<br />Forecast. The (~spo~si'>llity for pr~JicUng flaqh flQod" M,,,d "n
<br />3~.,w<;pheric condition. ha" been gl"~n co the Sa~ional Woath~r S~rvi~c
<br />(,i""S). 1:he ri';S {" <<lao r,;sron"l~,~ For i."uin~ "arnh~". Th" N~S lU3
<br />
<br />prodd,,~ ".sist""c~ <<nd tech"tc~; e"'.,;a"c~ (r. e't~hlhILl_'.L!!- l"~"J. :-L"h
<br />
<br />[..~od "utnl~~ oVHe"'~ (~,WSI. The NHS is conc~rn"d ,dt':1 ~ 1aT~Q ~""..-
<br />,~r<lp':1icat "red. Priv"te O€ ,uaro logical consu t tant" C,1". 0'" ""P loyed :<>
<br />,'t"ov\dc' for~~a.L' for ~pe~tfiG l.){,ati""". For~c,l.'lng c., dhcl1,s<'d
<br />la,~~ M " l",rt M tl"ah flood det~~tl"n.
<br />
<br />h"u~nc~ "f W~~~l"!:. Tn.. 'JWS ha" n<,,,n charged b" 1"" ~tth th~
<br />respon,tbllity fo~ issuinll wcathet ~arnings. War"ing" should be isslIed
<br />~j, or oo~[di"-at~d "'ith, tho ,,,'W8. The ~"^'S tssl1es ~'arnin,;s ""l~n it con-
<br />,dJers the", "ecessary, rcgi\rdl~ss "f ...he,lIer "'ar~bg" ~y cth~~S ~r~
<br />h,~"..d. The drc"l.1ti.,o "f t",o o~ ,nor~ ",,,~"i~~s w11i CN3t~ p,,~l!'
<br />co~f<l~t"n 3,,-d may ~c ",ors" th"'~ ~" wa[~in3 .'It nil. (tnt~rvl~" ~ith
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