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<br />River Ba.;ins on the north; and by the Rio
<br />Grande, Los Pii'ul.'l. and rlorida River Basin'
<br />on the east. Elevationsnm>:e from ubout(j700
<br />feet in the lIerlTl<ft;u area to over l~.n/)Off'ft in
<br />the hi>:h""t headwater ar~as t>f th" Anima"
<br />Riv~r and II/tOO feet in the Hermo'a Crf'ek
<br />Ra~in. Hcrmo,a Cref'k flows on a wutheast.
<br />f'rly<:<mrse throughout the ,tudy reach,
<br />Climate in th~ Animas Rive,' Ba8in 18
<br />characterized uy short, moderately warm
<br />,ummcrs and long, cold winten;, Normal
<br />annual pr~cipitation ranges from over 50
<br />In~hc~ in the highest headwat.€r rCl{ion, tQ
<br />about lli inche;; in Anima" Vallcy. Kearly half
<br />of the normal annual amount in the low~r
<br />e1cvations,-",cur, as rain during the rnonth" of
<br />July through Octot.:r. The remainder. which
<br />occursMsnowduringwinterandraindurill1<
<br />'prinsr.isustlallydistributedQ.uit€equally
<br />during tht' other mnnth. of the year. In
<br />headwater regions. wintertime IJrccipitation
<br />u'uallyoccur" as ,now anri adPPp8nnwpack
<br />
<br />accumulaw,. Snowpaci<:s of around 12 feN.
<br />with a water conll'nt of about 60 inche~.have
<br />been rt'cordL'Il. Temperature ..xtrem~'" in ~he
<br />Animas Vftll~y have rangM from a Summer
<br />hi!<hof!l()Ou,awinterlnwofminu~2()o.
<br />Ve1>:el.:l.tion inthfbu,in'variHswitop.lfva-
<br />tion. Mu"h of Anima, Valley is dc,'owd to
<br />..~riculture and the prim..l w!I."tation ha~
<br />theref~r(' lwt'n larl!"elyoblit~rated. Ve\tt'~ation
<br />in the mountainous arpas consist<< of native
<br />"ras't'~, low brush. SOme Pondero'apine, and
<br />exten,i"e ol."nd, uf spruee. Doul!"la, fir. and
<br />an,en, 1~1rl<e areas of shffr. open rock face
<br />rx:~",r dl(lVe timb<.>rlin". On the lnwer rnrmntain
<br />SIOlX'H, "Cl<"t"tion inc1udt'8~cattert'd Htandeof
<br />pinon pine. junipt'r, and oak. and 5hrub~ such
<br />a" mountain maho~an)'. service bPrry, and
<br />g"~,,bru~h.
<br />Approximatp draina~e areas at variou~
<br />lorations in thp s1l1t1)' area arp shown in
<br />Table 1,
<br />
<br />frequently OCl'ur d"rin~ ::;..ptembn and
<br />(ktolwr. Rainfloods characteri,tically ha"e
<br />hi>:h peak flow, and motit'rate volum.. and
<br />duratit>n, Floodinl< is more sever.. wh,'n the
<br />Kl'Ound i. frozen and infiltration i, minimal.
<br />Fioodinl<from rapidly meltir.ll'snowcouldh<.>
<br />pxpt'l'll'd cJ\mnl{tht, periud from law \bytn
<br />,,,,rll' .)"Iy, Snowm,,]1 flwdinl< is charaClkr.
<br />il.t'd by moot'rate pellk flows, larw "olume,
<br />Ion>: duration, and marked diurnal !1",d"".
<br />
<br />tionufflow.So:"metin"",on"",meltrunuffmay
<br />heaul<nwnu.d hy min. !.iurini<th,' ,ummer,
<br />convective typ,-, dn",lbur,t "torm, ell" ,,~
<br />expcct(~1 to0Ccur in the H..rm",a area. The
<br />rainfallintensit)'ofl'loudlJur,t.tonnsis<j<lite
<br />hi!-(handth,'rp"lItinKrlJnoffist'bral'teriwd
<br />byhi!(h pt'<\kcii"dlarKt'"hurtduration,and
<br />,mall volume. HGwever, nG major cloudburst
<br />floUt! t'Vt'nts art> kr.own to ha,'eoc~urred in the
<br />etudyart'a,
<br />
<br />FLOOD HISTORY
<br />
<br />Ikcord, :;how that, since th,-' turn of the
<br />century. rain or ,r\owm,~lt floods occurred on
<br />the ,trl'am' under,tudy in lfJ09. 11,ZO.Z7"IJ,
<br />
<br />,1~, ,19. fi2. .~7, 70. and 7:{. Available peak
<br />dit'-Charl('e data for thesc fl",-,J~ are shown in
<br />Table 2.
<br />
<br />TABLE 2
<br />
<br />PEAK FLOWS OF HISTORICAL FLOODS
<br />
<br />TABLE 1
<br />
<br />FloodYur
<br />
<br />Peak Flow'
<br />(d,)
<br />
<br />APPROXIMATE DRAINAGE AREAS
<br />
<br />Stream/Location
<br />
<br />AJ\irnasRiwr"t (jahrs llridgp
<br />Hermos"Cr""k below the confluence
<br />"fHu"K.Cr....k
<br />Hermosa Creek a~ th., "near H"rmos,,"
<br />strt'amKaKe
<br />
<br />Ani",,,, RiH'" Iwl<J'~ th,' e()nflu~n('('
<br />of Ht'rm,,'a Crt,t'k
<br />
<br />NATURE OF FLOOD PROBLEMS
<br />
<br />Ft<>Ott!OK in tht, ~!ud}'ar,'al'a" re,ultfrom
<br />:arll'e frontal typ'-' rainstorm, app,'oat'h,nll
<br />fr"", th,' 'mahw'i'st, fro", ral';'.liy meltml('
<br />sr.nw. ~nd frt"r. locallzpd cinudbur,t "Wrr.l~.
<br />
<br />Animll$Jliver/ OllIe
<br />
<br />Hermosa Creek! Dale
<br />
<br />Approximate
<br />Drainage Area
<br />!"'I.ml)
<br />41:1
<br />
<br />IYfJ!I !O,(J(Hl Scplt'moorG
<br />1~ll ~:\.IHHl Ilttn!'.'r:.
<br />192() 9,100 ;'10.:>' 2Z 2,79,,1 :,1,,}, 23
<br />1927 ~O,OOO June 2~
<br /> 14.1}f~ Sq\\f,,,,IJ<,r W 2,H~ ;;,'pt~",lwr "
<br />1!l41 1O,;,(lO May 14 2, ~lliO \1a;, "
<br />I~H~ ~,n() May " 2,160 ~h,' \j.
<br />1 ~J.l!l !2,70t1 June " 2,~:(ll ,Iww 1 ~,
<br />l~hW ,<q"O .Jun,' " 2,~~O .Iune
<br />19:;7 9,:llitl .rune!1 2,~W JUn<' "
<br />1>170 1l,ll.Jtl N'ptt'mber'; ,
<br />\\\7:, 7,.j90 June " 2;11i0 \h\' 1 ~l
<br />
<br />p'
<br />
<br />172
<br />
<br />i\tH
<br />
<br />FlooJi~;: from lI:t'",'ral ""in cun I", ,>,\,"-'c'lnj
<br />fro", lmd.Jutl<. thr""Kh [I'~'cmb,'t'. btlt
<br />r<''-'~rd, ,hn'.\' that rainoL'lrIM pro<:l::,'inll:
<br />majo~ f]<lod; in ,otlthw,,';;~rl1 C(l]t>r".l{, nw,[
<br />
<br />A: ,~'" Ao,,,,,, 1:,,,; "' p""""" '" d 1I,';",,~, <''''',k ":,,, I{,.,"'c,,-,, ~,,".,". '0..'" I',;:, I '", """,' I".",,,,,,. '
<br />""... ,,," ~'". i'1 "l~."t "',
<br />F:,,~ ""L ""'"".",;",,
<br />
<br />"
<br />
<br />I
<br />
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