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<br />r.!.'_E_C(~El'5_~
<br />
<br />shown on plates 3, 4, 5, and 6. 'o'/lIte~ surtace p~of i los, employi nq thQ
<br />Standll~d Step MeT nod , show the deptl1 of 1 loodin ~ in the o;;l>ann<>1 and the
<br />el"'\fat ion 01 the wate~ su~ldces O\fer the adjacent 1 I ood pia in. Head
<br />losses at bridge'" wen. cDillpute~ us i ng d~ta in "Hydrau I iC5 of [}r- idge
<br />l1atorw",ys" published by the U. S. D"partmont of Cbmrnerce. Thewater
<br />surface p~oflles are shown on plates 7 and 8. The c~os~ ~ectlons on
<br />plates 9, 10, II, and 12 III ust~ate the strwm ctli'lnnel and va II ev cond it ions
<br />~y showing QrooM ele\fatlons and depths of ove~bank floodill~. Reterer>ee
<br />paints are used to locate flOOd elevations at Intervals alo~ the stream.
<br />r.;umb"~ad r"fe~<:n.;;e points coin.;; Ide with su~"eyed c~oss soct ion,; used in
<br />the study and they are 10Cilted on both the "FloodedA....eas" plates and t he
<br />"Proflle"plates. Tablo41Ists....eferen.;;eDolntdatalncludingelevations
<br />of thestroambed and the InterrnediateRoqlo"'-ll and Standard ProjoctFloods.
<br />Thaflcodoutlineswe....erroduced by matching flood heightswithcorr eSDcrtdinq
<br />elevations M tho surveyed cross so<:tlons ~nd on U. S. Gooiooical S<Jrvey
<br />7 1/2 minut" qu,~dra"9l!l maps. These outl ines are ....'!asonaole ....ather tlKtn
<br />pre<;:ise. For any specific situation, "hereoxtremeaccuracy isnooded,
<br />it wi II be neces""rv to take the appropriate f load elev~t ions from thE>
<br />protiles or referenco data end locate by ~uryay its cor....espondinq ele"atlon
<br />onthalloodDleln.
<br />
<br />The fre'1uency <)f rocurr"nC'-' of a curt"in SiH' flooe, or the
<br />prollilbi I ity 01 Its hilpPGnin'l, can 00 i Ilustreted with ~r"l<lWn 110'. data.
<br />Th<) flood of June 1%5, '.ith a P""~ d i <;t:harqe <)1 3,480 cub ic feet oer
<br />seconeattheGre€leY'1dqo.would occur on the averaqeonce """ryII vears.
<br />fhe averaqe annual peakdiSCharqe at the <")ilqe is8l3cubicfeetDersecond.
<br />rho Intermediate Reqlonal and Stilnda~d Project Flood flows are SnOW" In
<br />Tablo5. Floodsllven larger than the Standard Projoct Flood could occur
<br />but conditions necessa....y to brinq about SJCh en event ara extromelv ....e~".
<br />
<br />HAZARO_s...QF_~LARG[ F~
<br />Theextentofdamaqecausedbyaflooddependsonthetopo-
<br />q....aphyof t10 area llooded, deDth and duration of Ilooding, velocity 01
<br />flo'., rat" of I'"iso, and dcveloprnonts in tho flood plain. An Intormediate
<br />Regional or $tanJlIrd Project Flood on thl' Cache Ie POud....o River wooid
<br />result in the inundation of residential,COMmercial,and industrial pro-
<br />pertiesinthestudydroa. Oeeofloodw"terflowinqathiqhvelocityand
<br />car~y'~ flo.,ting oeDris ..aula c~eat" conditions hazardous to persons and
<br />""h icl!!s ilttemptinq to cross I loaded ~rea~. In q!!nera I, flood ."..ter two
<br />or more f'Jet deep and flowing dt a "iliaci tv of t~re" or more f"..t per
<br />s'JCO~d coulj <lil~lly ,.."'ilp <:In ilGult ~er501l off ~is feet, thus cr,,~ting
<br />del In ite danger of Injurv O~ drowni n'1. nap id I y ri sinq and s\o'ift I y t 10wl n<l
<br />floodw..termaytrappersonsinhDille5thilTareultimatclydestroycd,0r
<br />in vehicles that are ulti"",tely sut>morqcdor floatod. Wat"rlin<lscaobl!
<br />rupturl!obyJopositsofdebrisa"dthofo.ceof floodwatl!rs. Lla"",<:"Iod
<br />SaniT,]rY'Xlw"r I ines and 5C"'J'l" t.eatm""r plants could rosult in t~e
<br />p<.>lluti[m of tlo<.>dw"ters creating health ~alards. Isoliltion oi area5
<br />by 11000 water would c~e"te hazards in terms ot medlc,,1 or tire emerqencie5.
<br />
<br />F....0111"heupstreamllmitsottnestudyToaoout 11th Avenue
<br />tho Intermcd lata f{ogrona I and Standa....d projnct Floods cover an area ; n~
<br />clud Inq q....il\fe! pits, oqr icultura I land, v,"cent land, ta....m bu i id In<J~, ~a I 1-
<br />road tracks, h ighwaV5, 151 and Grove Park and same reside~t ial bui Id inqs.
<br />Thodvera'lelloodplainwidth is Ilboot 4,000 leet intl1isr"iICh. From 11th
<br />Avenue downstream to U. S. Hiqhway ~5 the Intermediate RegIonal and Standard
<br />P....oject Fioods cover an a.Od with an average width of aoout 3,800 leet and
<br />include residentla I, corrmercia I. I ndustria I, ~nd vacant landS. The left
<br />bank is mostly undeveloped while the right benk contains ",ost.of the
<br />developed areas. (lownstr<:am irom Hiqh~.dY (15 the munic ipal se~aqo d I spas" I
<br />o IJnt, gravel Ods, vacant I and, aqr leu Itu.ai iand, Ieee lots, ~~d f,lrm5
<br />are suoject to llooJinq. The flood plai" width in I,isrcach)v"r,]qos
<br />
<br />Flooded ure,] ,]nd n=d O(lmages - Areas that would be
<br />i I oed ed by t rlQ I f~F '" nd SPF 0 n the C,]cne I a POud....e 1(, ver ; '" Gree I ey ilr"
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