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<br />1
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<br />
<br />however, the contamination thre~t to danesti~ weter supplies cannot
<br />be illu.trated with similar e~se.
<br />
<br />main ch~nnal, except where flows Dan return through th~ main frBe-
<br />~~y undorpasses. High velocities and vari~ble depth ~ondition8 G~n
<br />be expected in the vicinity of thess embankment openings.
<br />
<br />Floonod Are~s and FIQnrl D~~~~~
<br />The ~re~~ ~long Monwmont Craek flooded by the St~ndard
<br />P~ojoct Flood, Intermediate Rsgianal Flood, and the May 1935 flood
<br />of re~ord are shown on Platns :3 through 7. OBpths of flow for any
<br />give~ stroaM lOGotion c~n be eatimntad from the high water profiles
<br />shown on Plntes e through 12. Plates 12 and 13 show sslected cross
<br />sections of the creek that are typical of the 40. s5ctions surveyed
<br />in th~ Mc~u~e~t Creek .tudy r~ach; ell cro~s sectio~ locatio~s arS
<br />sha~ o~ ths floodso area a~d profile plateB. Stream characteris-
<br />tics detarmin~d fram topagr~phic ~aps, ~sriel photographs, a~d v~l-
<br />l~y CrD3~ $ection~ ~ers u~ed to comp~te and define th~ flaod situ~-
<br />tion.
<br />
<br />Flaadw~ter p]pv~tio~s determined in any perticuler cross
<br />,,~r;tiol\ ~n,~ are not alw~yc ir\di~~tive of th,~ depth" ~dually at.
<br />t~ined. Oft"n, floodUJ~ter~ becnme i~ulated ",'d ent.apped in OVA~-
<br />b~nk ~re'>S r,,~ulting in flooding depthe 9~e~t,,~ th"" thO>ls "hown an
<br />thflhiqh""terp!:cfU"a.
<br />,j.u lnter"..ediilto HBgion~1 Flood w"'Jld h~ genp~~lly "00-
<br />tain~d in the ~ell_cnt~enched ~Qnunsnt C!:sek dhanne~. Ihe greater
<br />5tanda!:d Project Flood would overflow a oli~htly lar~er "re" than
<br />that coverBd by the hi~toric ~"y 1935 fload, thu~ c"u~in'J greeter
<br />flood dnmages than p!:evi~~oly experisncod.
<br />Flo"o1w"te!:s bre~ching ths ~"d bank "~ar th.. M""llIT'ent
<br />~aLloy Park o~i"miog pool ~ill !:each to Pi no Streot until neer the
<br />"r,?~ 0f iIi~~t Atj"" Street. The fluw ~o'~ld ~h"n oxpond farther
<br />~sst, cros~ing 5p!:vce and Walnut Str~eta to near the int,,!:seetio"
<br />af Che"tn'~t a"d Pik~'. Pe~k ~venllo: the". continue south ,,10"9 the9a
<br />~t!:ed. into the lo..or flood pI "in. The p!:Q:rinent Interstate High_
<br />~"Y 25 ",,,,l1,,n,,mo,,t ~ill hold theae fl,,"dw~te~e iflol"tod frorr, tIle
<br />
<br />Velocities, Rates llf Rise, and Duration
<br />The accurrence of the lnter~ediate Regional or Standard
<br />Project Flood ~ould re~ult in the flood charaete~istice ~ho~ in
<br />Table 5. Thie dst" reflects the ave~aged maximum conditions with
<br />heights of riee, rates af rise, ~nd durations of floading me~sur~d
<br />above bankfull stage.
<br />flaodflow velocities depend upan the general waterway
<br />configuration, and the size, shape, and olope of streambsd and over-
<br />b~nk flow ~ress. Average velocities may range fram tho mBximwms
<br />appearing in Teble S to less th~~ 50 petcent of theso value.. On
<br />30 ~ay 1935, the flooding du~ation waS app~llxirnetely 4.5 hours ss
<br />cornpnr~d to the 9.0 and 10.5 hours estimated fo~ the Inte!:mediate
<br />Regional and Standard Project Flaod~, respectively, in the lowet
<br />reach which extends th~ough urban Coior~do Springs.
<br />
<br />Obstructione
<br />
<br />aJ.'u~h ""J J..l1d~ ..",~lll"'J do"n~t"e,,'" ouriny flo",;" oft""
<br />collect against bridgas or within any resttictBd flow are~, !:H~,r,ina
<br />tha ~aterw~y openings ~nd cth8~"ise impeding flocdflow. This
<br />crentes a damming effect ~nd. depending upon tha dog!:ae of ~log.
<br />ging, csuses g~aater b~ckwnter dcptho with inc~B~sed ova~b~nk flood_
<br />ing. Wate!: pressu~e. building ~gainst ambankments and b!:idges, Cnn
<br />then ~esult in serious erosion, stress damage, O!: total oestruction
<br />of the structu!:e involved. A p~onounced increase in flo~ velocities
<br />ususlly occurs oo~nstrea~ frD~ an obstruction, thu~ extending the
<br />flaod'sdamagapotentlal,Obsttuctlvenewoevelopm"ntendfutura
<br />land filllng in o!: ne~!: the stream's floodway Cdn be a major f~~tor
<br />in multiplying the ~dve~se effects described, One problo~ channel
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<br />2S
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