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<br />FUTURE FLOODS
<br />
<br />100- AND SOO-YEAR FLOODS
<br />
<br />Alth,,"vh (lOIx.!, with maVrlit\ld.'" a~rl
<br />frcqu~ncie,similarl<Jth"sc',,!flood'lhathav,'
<br />ntcllrr~d in th~ pa,t rould recur in th~ flltuf('.
<br />di,eu,s;orLuffuturl' f1oOl.l, in th;sr"l"rt
<br />rl'iat"s principally IIJ those rle.sivnat<-<J as 100-
<br />and ,)()(I-year flo()d~. ." toO-y"ar f1(l(xl has a
<br />peak f1()W mavnitude with a 1 pere"nt~hance.
<br />()!beinJ'(cquall,'d()rexc,'edfdinanyj(ivt'n
<br />year, or a !r~4u~n")' of """urr~n"r of about
<br />"tlce in 100 yean; on the Inn" tt'rm a\'~rall:".
<br />Similarly, a r>0lJ.}'~ar f1(x~1 ha" a p~ak flow
<br />ma.o:nimde with a n.2 p~rrent "han('~ Df ~,.,ing
<br />equalled orcH,'~dl'd in an}' ~ive,,}"'ar, or"
<br />frequen"y of ()<;C\lrr~nc~ of nlKJut once in .500
<br />ypar" un the lon~ t~rm a\i"ra~(',
<br />St\ld;~s mad~ !ur this rt'p()rt ~h,)\,' that
<br />S<:'v"rt' f100d;n.o: in the'tudy urea "an result
<br />from late '\lmm~r-early fall general rain-
<br />,wrm', from ~prinK-early ,ummer ,n!=,wmelt.
<br />or f"'Jm "nowmelt run()ff au.o:menwd h)!
<br />J;:enoral min, I,_'hould hrnotedthat.du.,to
<br />diffl'reHc~", ill elevutioll, vej.(etati\"(' Ciwer,
<br />dir~etion of exp',"u,",', or other f"etHr,. th"
<br />tnwof fl"o<i rllnoffnitiealonOlwt,';hutary
<br />,,,','a may l\lJt hi' "r;1.ie,,: r"r HiI()lil~r tributary
<br />an'" ill tiweam,'iJasin,Sp"{'ifi,,ally,th,'mort'
<br />""'ve..,' fi<~"l, rw tl", Anima, Riv<'r w"uld
<br />r('-sult from ~"J\"""l raill Thf mor~ ".Hl't'
<br />f1n(jd, On Ht'rm()~1L Crt't'k would lx','xp~e\kd to
<br />,...",u]l frll'" "n"wm~lt.
<br />De",,)'minatinn ofl"',,k f1nwv"I,,,,,f,,,.thi~
<br />1"'I.lnn. "'as ba""j ")1 a frt'qu.'ney ,-",aly~i" of
<br />;tn'amflew datu r<'em'd,'d lJ;' tlw "at Durango"
<br />'llLd ""l~",,' T"""rTLa" 1li1~'" on th" AnltlW"
<br />
<br />R;VN snd thee "n,'ar H"rmo,u" f(ay;~ on
<br />1I,'rmosa CN'ek. The ana]ysi; t'tln,id('r('d 1-.
<br />:1.. Ir,-, snd;W-dsyflowvalut)"a,wella'l'~ak
<br />flnw "al\leo, Pc'uk flUWH at th" \'p;;tn'am limit
<br />of th~ study "~ach of th., Animas R;v~r we.....
<br />jud;tt'<l t(l b..-, "bout ~Qual to til<.\.<;<, at the
<br />D",'any;uy;al/:t', Thi,condu,ionwa,bh.wdona
<br />comparison ofp.!ak flow, at the Tueoma ar.d
<br />DuranW'l'Iages,characteristicall).'lowconeur-
<br />rent flow from lIerm(N' C,'"ek during jK'ak
<br />flow p~riods on thl' riv~r. and consid..rationof
<br />th.. lar~c vC)lum~ of owrbank ,t<)"ay;~ in
<br />Anim"" Valley,
<br />llrdrop:raphsforstreamfl()wroutinWlw~re
<br />devt'loPt'd from a cornpukr model uoinJ;: ba<in
<br />rainfall-roJl\nff"harackri.o;tics,or h}' us;np:a
<br />r,'cordeuflowhydrographofamajorhistorical
<br />flQ(J(1 event as a patt~rn. For ba.~in modelinp:
<br />purpo",'".unithydI'<Jgra\Jn8andrainfalll",,'es
<br />for the J!a)1;ffi water~heds were dPtermined
<br />from reproduction, of nnw during the Sep-
<br />tt'mbcr 1!)70 floou event, Th",e unit hydro-
<br />gl'uph;;wer"c"nvert"dtodimen,ionl~",Hum-
<br />mationg'ruph,(S-graph'J[oruseindevelopinll
<br />unit hrdl"<J~ravh, for' 'Jl\l<ap:ed watenh,,(h_
<br />C()mp'lr'ltivr 'to"ly ,h<Jwen c1<J>lc similarity
<br />b"tweentb~S-g-r"ph"dt'wlo]Jt'dfortnis"tudy
<br />and th"s~ for oth,'r hasin" with e'luivnll'nt
<br />characteri,;tic"
<br />Rainfall 100, raw.' werefoundt"h"hip:herin
<br />t\w Herm"'h(:r",,'k n",intha!\ in the Anin'a_
<br />Riwr Basin dUQ to oi~nifi('aTltlyhi~her ve~"ta.
<br />tivee<JVt'r.!~,"sraw;luo<'<ifor,tan<iardpreject
<br />flu"d(SPFI'e",npututionB w"n':
<br />
<br />Standard jJroj~dHtorm criteria developed
<br />for the late summer-fall mon:hs for th~
<br />wawr8hpds under study indkat,'(\ hR.,in
<br />a"erag~ value" rlf 7,.1 indw, f()r the Anima,
<br />Riv~r and K7 inches for Hermo,,, Crt"k,
<br />Since ~tandard project "torm "rit~ria w~r"
<br />available, it Wa~ jun.o:ed that enmvutatinn (Jt
<br />Sl'f'"s for the ha8ins would helpueterminethe
<br />rainfall f1{1oul"'tentisl as well ashydn,~r")Jh
<br />pattern, descriptiveo!Dthfr ram (]'K"I "vents,
<br />r'low"aluesfrnmthefrequencycurVt'"atk~y
<br />inu~x pninb were \l,~d t/l det('rmin~ the I,,'uk
<br />and volume of the I and 0.2 percent chance
<br />f1,w>ds, and the SI'F'~ W"Fe us~d UJ 8hap', the
<br />hytlrol\"ruphs. One exc~ption to this was the
<br />hydrol<raph of the 1 percent chanc-e f]ood on
<br />H~rmosa Creek, which Wa" <hapetl ~imilar to
<br />the hydrograph ofthl' 1941 "nowmelt f]<)()(!
<br />evt'nt.
<br />
<br />InilialWelllng
<br />LOSS
<br />(io,'h,)
<br />I.tlO
<br />
<br />BaSIn
<br />
<br />,\lLi'na' River
<br />Ih'rm,,,,,Cn,,'k
<br />
<br />,nlllt_allon
<br />(jnchesp('rilnur)
<br />0,15
<br />
<br />1,;;'-'
<br />
<br />(),2:1
<br />
<br />Ti'"' f;,__, \;", ,,", i", ,."""',.,,j ~",'" ,I". "'",, _~,",,', """I,j:,,,:;,,,', "~ "h"".' ""'oj," "cd I..\,L,,,I,,,;,..,; "'"1",,,,,,
<br />"""I",',_d,.",,,.,,,,,,i)"""''''''::''''I',j,',A,,,, ;:,_."re.: ,'"Im",,,.,,,-,,,.,,,,,,<I,,,,,,,,,",'k,,,, ,1"",,,,,,I.,,,,.I',J;o",,,,,,,,,,,,I'
<br />""",'''''"""''',,,,,
<br />
<br />"
<br />
<br />Peak flows thu,develDI'.oo for lhclOO-:<nd
<br />500-yearflood,{atea"hcro;8section ui'-<'<Iin
<br />thehvdraulieanal;"'H',madeforthis,tudylan'
<br />'hOW;' in Tuble:l. lnfDrmationon lO-and:>O,
<br />yea,' flmd ~vent-, was al:lt) dt'velr)ped in
<br />~onj"nctien with the hydruloj(t<" ot\ldie, made
<br />for thi, !'(,p<,rt. These flood evrnt., ()n tJ".
<br />Anima.s RiH'r wnl1td re,ultfrom J.[en"ral ,'ain,
<br />,nQwmelt, or a ('emhinati()n of "nnwmelt and
<br />I\",'neral rain. On H"rrno,aCrepk, theywo\lld
<br />!'f's\llt from snowm"ltor from aeombination of
<br />snowmeltuodRt'neralrain.Withth"ex,.~ption
<br />of ,howinv their flow' in Table.1 and their
<br />wawr "urface elevat;onson Plaws 1fi-:.l2,the
<br />lO_"nd~_yearf1oOlharenetfurthercovr",-~1
<br />in this rel"'rt,
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<br />/0
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