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<br />I <br />I <br />" <br /> <br />lateral e~teot of tne Intermediate Regional and ~tandard Proje~t Floods, <br />are shown On Plates 19 and 20. <br /> <br />tor the Intermediate Regional and Standard Project Floods on the Colorado <br />and Gunnison Rivers In the study area. On the average, the water surface <br />elevation of the St"odard Project Flood would be about ono foot hlqher <br />than the Intermediate Regional Flood. <br /> <br />OBSTRUCTIONS <br /> <br />There are five bridges crossing the ColoradO River In the study <br />lire". Nonec! these bridges cause My serious obstruction to flood. <br />flow. All clluse II small rise In the wllter surface upstream. "I though <br />debrIs lodging agaInst tho pIers elln cause addItional rise in tho <br />watersurfi!lce, the likelihOOd of debrlsblockTng the waterway to any <br />oxtent Is very remote. There Is only one ~rldge crossIng the GunnIson <br />RIver In the study area and It has no pIers. No obstruction to flo~s <br />Isantlclpated. <br /> <br />TABLE 3 <br />RATES OF RISE AND DURATION OF FLOODINt, <br /> <br />Flood <br /> <br />Me"lmum Height <br />RIlteof of <br />Rise Rls/a) <br />ft!hr ft <br />COLORADO RIVER AT MILE <br /> <br />Time <br />off})) <br />RIse <br />"" <br /> <br />Ouretionof <br />0' <br />Crltlcel Sta~e(C) <br />"" <br /> <br />1063.75 <br /> <br />The magnitude ot flows for IntermedIate Regional or Standard Project <br />floods are shown In Table 2. During an Intermediate Regional Flood the <br />average velocity of flo~ would be about 7 to 9 feet per second In the maIn <br />channel and 2 to 3 teet per second In the overbank area of the Colorado <br />RIVer. On the Gunnison RIver average velocitIes would be about 5 to 6 <br />Feet per seoond I n the channe I ilnd a!>out 2 feet per second i n t'll~ overbank <br />area. Itlsel<l'ectedthatsllghtlyhlghervelocltlesot tlowwouldoccur <br />during a Standard Project flood. Water flo~ing at about 2 feet per second <br />or less wIll deposit debris and silt. <br /> <br />IntermedIate <br />Re910nal <br />Standard <br />Project <br /> <br />0.03 2.9 415 <br /> <br />'" <br /> <br />VELOCITIES OF FLO~ <br /> <br />0.04 3.4 444 <br />t,UNNISON RIVER AT MILE 2.05 <br /> <br />552 <br /> <br />Inte","edlate <br />Re910nal <br />Standard <br />Project <br /> <br />0.07 1.4 18 <br /> <br />" <br /> <br />0.07 2.0 36 <br /> <br />180 <br /> <br />(a! CMheal sta{}f/. Lowf/.. (beginning of o!.>el"hank f.QI.)) to "'<1.t'1.1!IlIm <br />t.oodf1ow twet. <br />(h) Time pO!Mod col"1'eep<Jnding to hBi(1ht of l"ie... <br />(0) Period of time .f1ooding is above moiti"". stage. <br /> <br />RATES OF RISE AND ~URATION OF FLOOOING <br /> <br />P~OTOGRAPHS. FUTURE FLOOD HEIGHTS <br /> <br />The Colorado <Ind Gunnison Rlvers IIremllJor str",,,,"s with IIIrgedrain- <br />agebeslnsabovethestudyarea. Tile stre..mch"nnels are large and well <br />defined. ~m,,11 VOlume runotl such as that prOduced by cloudburst sto","s <br />has a n~llglble et1"'ct On the streams and no eftect on floodIng. Flood- <br />f lo~s are prOduced by snowmel t, occasion" Ily IIugmented by rlli n. Hlqh <br />temperatures oyer an extended period, usually occurrIng In late May and <br />e"rly June, produce mexlmum , lo~s of large volume. Rllte5 of r Is" are <br />relati~,,1 y slow but dur"tlon of floodi n9 Is prolonged. TIIb Ie 3 gIves <br />thetyplc,,1 rate of rise, height of rise, anddurlltionof critical stage <br /> <br />The levelS that the IntermedIate R&qlonlllllnd Standard Project Floods <br />are eXDected to reach at vllrlous locations In the study are" are Indlcated <br /> <br />in the fol i"''''ir.q pMtogr~p~.s. <br /> <br />19 <br /> <br />" <br />.. <br />