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FLOOD SITUATI8~ is generally open and frM ot buildings and tre;,s; thc exceptions "...e at Larorte and In the arca of the College Avenue ~rldqe ",here "here are numorousrosldentialandcornmerclalbulldi"9s. Sources of Data and Records Flo; records 'orthB study reachot the Cache laPoudrc River are availablo from a IJ. S. rt)olosical $urveywater stage recorder gage locatoo 8.5 miles nort"'est of Fort Collins. The drainagearN at the gago is 1,055 square l'1i les, and its location "",rks '~here the river leaves the mountain canyons and enters the high plains toroqrarhv. FIDOdda"""gereductionmeasuros.Thereareno'I<::o;J control struct~res on the Cnehe la Doudre ~iver in the study roech. There are two dams on the ~Iorh Fork C<lche I" Poudre River. The Halligan Dan and Reservoir, located ahout24niles northwest of FortCoillns, was bull1- In 1910 for Irrigation storage and Is o;ned by t~e *>rth Poudre I rr i gat r on Compa ny . The ~,'i I ton S"""" n D3/"I and Roser~o I r, b u I I t by the city of R"eeleyln 1947 for munIcipal water supolv, Islocotedabout o~e mIle upstream from the North Fork confluence with the Cache 10 ~oudre River. The flood control effect of either dam Is considered negligible inthls study. There is no specific F"egulatlonordlnance aoplled to the flood plain 10 the study reach at the present tiMe, although local govern- ment can regulate to scme extent by control of building permits. The cIty of Fort Collins I\as acquired some tlood nrone lands for "opensoaco" uses, such as parks. Thore Is no evidence of flood proofIng 01 existing stru~tures In the flood olnin. The Larimer-Weld RegIonal Planning Commission proviced tho cross sect I on su rvey deta w h I eh "a S ~J sed to compute hvd rau I i c pro- fIles and to define flOOded area Ilnits. The cross section surveys wera made by photogrammetrlc met-hods in 1972. The aerial phctogrenhs <lsed as ~ b...s" fcr tho f lcodcd nrea "'''05 'lIere f 1000n I r J'J Iy 1969. Flood Season and Flood CharacteristIcs Annual peak f 10;5 c~ tho CaChe 1a POLJdro River I n t~e studv rwch norm"lly occur In thp r"rl<X1 ill'l throu1h ~,,,..hrthf'r, ~it~ llbout70pereentoceurrlng in June. Alt(;ouqhmostfleo<1srosultlrO<" IntDnso raInfall In the basin, snC>I"'fllt runoff is n lactor "nd fhe'",orst r<>tentla I f 100::: ing condItion Is that of heavy rilln5 at a timf' '~~en snOl'- noltrunoft Is hIghest, In Mlv or June. FactorsAffectlngFloadlngand Itslnpnct OtherfactorsandthBlrl"'racts-FortColllnshilsnot hao a large llood in the memory of most proscn~ resIdents of the clty ~nd thl s lact nay hava caused ~ comp Isconev nr laCk of awareness 01 potentIa I flooding by residents nMr the river. Local officials are eager to have the flood pl"ln defined as an I~portant aid to luture planning. Other f~ctor5 lor reduction of f load hazard are flood warning, f I cod emergency plans, and the anchOring of matorial stored on the flood plain. Cbstructlons to flood flcws - uridges Jcross the Channel, raised embankments at roads ane ra i I rOilds, trees and other ve~etation, Ilousesandotherbull<Jinss,an<Jloneesarenlloostructioostcflo.,alon(l the Cac~.e I.,. POlldre River I~ the study reach. There are 13 hridqes In the study roach; fhreorallroachrid,!"snnd ten roadbridqes. Sev"ral roadway and ra Ilway orrbankments cross tho llooC ria i ~ "nd in sOf''''' cases ,;uCh 00 struct Ions cause pond I ns of 'Iood f Io;~, on the tJrs+ream s; dn, resulting In higher'.1ater<;lJrt"c<,s. The 11(}().j "lain 1rthestudvr,'ach Flood warnl~ and forecasting - The Niltional OceanIc ano Atnospheric Administration, ~atlonal Weather Service provldos a general alert to the da~ger of Ilnsh flooding on the ~ac~e I" Pouor" River in tho I., ,