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become t~apped oc i5olate~ in overbank Jceas ~eSJ Iti ng ir f loo.di nJ deD~hs greater than t~ose soown on tne flood profi les. Floodi ng i 5 a Iso i ndi cat,"d in three "ceas pro~ected by s"la! I light Iy sodded s~n~ a1a gra.~e I I e-VE>es. T~e f re i I I evees ~t these locati 01S ",ra not <}x- pect<}d to '~ith5tar.C the e'^Osive f()~ce Of ~ major flood, ~~d will ~I"..ost cer~~inly fail, floo~ing ~r.,""s beyond. From the confluence with IJbnument C~eek to Acadumy Bouleva~d, Cottonwood is contained in the daap channel, wlth al rosldenti~1 anl"S well abovo; the fl=d elevlltior.~. At Academy Road, however, the I nsutflcient structure C1;Ipac1ty wi II C1;luse appro~lm1;ltely 1,125 cubic feet per secondot Interm€ldiateRegiol\<lland2,560cubic feet per second of the Standard Project floodflO\o/ to overtop the boulev1;Ird and flow westerly down Brookwood Drive and Imperial DrIve -totn.. dralnaaeway west of Price Drivewnere It wIll be Intercepte d and return<}d to Cottonwood Creek. In this area, many residential properties wi II be flooded by both major floods. Along Academy 6oulevard,tnewaterovertoppingtheroadwaywlll flood several coo- merclal properties and upstream of the Boulevard many residential propertlesonbotnbanksotth..stre1;lmwillexperlencatlooding. Manyrasldentlal properties 00 the north sidenearStatlon 95-+00 will be inundated froo tn" expected failure of the gravel Mdsand levee. The failure of anotner lav<}<} near Station 121+50 will resultlna diversion ot 85D cubic teet per second of the Intermediate Regional Flood and 2,!50 cubic feat per second of tn" Standard Project flood waters down Boysenberry Drive to 8rookwood Drive and down 8rookwood to return to the crock ~ar Station 95+00. The rernal nder of Cottonwood Creek t loo~s agrlcu Iture I land, but tt IseKtre_ly lmportantthat future development of tne valley does not Include the areas that wi II be inunda-rod. From Station 115+00 to Station 221+8D tnecreektloodSwldeareasof , pasture and range land, but does not endangar eny improved properties. AtoveStation221+80, 1""ecre<}k is again contained In a d"eplyerodac channel and wi I 1 rr"'~..nt no n"z<lrd to any res I denti a I proper1"les. Tt\c north Tributary to CoTtonwood Croek is eroded into a deep cnannel. The area is currently rangc land and the deep narrow valley is unsultablcfordevelopment. Floodlngshouldneverbaa prOblem in tne upper reaches of the Cottonwood and north tributary, if development is not permitt,,~ in the narrow valleys, and the stream crossing structures are adequately sized. Thesoutt\tributary to Cottonwood Creek traverses a heav. ily developed residential area along Dublin Boulevard below Academy Boulevard. In this reach of the triblJtary the streamtlows In the median of tne divided DublIn Boulevard. As can ba observod frem the flooced area maps, many residential propertie5will be tloodedalong Dublin. At tt\e intersection of Dublin and Wicklow Circle tha tribu- tarylssharp!ydlvertedtromitswE;sfarlycoursenortherly into Cottonwood Creek. Tnis diversion is made within a double 42 inch plpe culvert u1dar the west bOund lanes of Dublin. The culvert under Dub I in is not large enp~gr to accept a II the diSCharge trom ,"ither major flood, therefore, 777 cu~jc feet per second of tre intecnediate Regienal Flood and 1,473 cu~lc 'e<Jt per second fro," the Standard "'ro- j8Ct FlaoG 15 c~crlec ','ost ~lon9 D.w I i r oou ''''I~rd. The F lood~ater5 will contlm.e we~t.'<lrd along ~blin B<!ulev.,rd, 200 feat p'Jst Y\t6.1ne ''',ay, ,^.hert) it 'di I I .un '.'itn s~eet t'/?8 flow ;r ~ south.,rly direct;on into a s",~11 tributary of f10nument Cnwf',. Thelnrcrnediateflegional Flood will bocootained in tre double 9' X g' CJlvert under Acade~y Boulevacd, but St~ndard Project FIGod wi II overtop tne roadway. TIl," remainder of the south trlbut"rv fro", Academy Boulevard east Is currently undevelopec, ex- c;~pt fQr~ tennis cll;b neM$tatI0l185+QO w.1ic~..'ill ~~ve itscwtside tennis courts f loodec, but no ddm.age ~hou Id be incurred to the bul Id- ings. Velocities, RaTes of Rise, and Duration Table 3 includes the flood cna~acteristics along ,~tto~wooJ Cree~ and its trlbu~aries. The J~tu or Table 3 indi- cates ~Y8r~gec ~xlmy~ concitiocs with hci~hts of ~;5e. rates of 17 "